Contributions to Terrestrial Magnetism.--No. VII

PHILOSOPHICAL TRANSACTIONS. XVII. Contributions to Terrestrial Magnetism.—No. VII. By Lieut.-Colonel Edward Sabine, R.A., For. Sec. R.S. Received April 30,—Read May 14, 1846. Containing a Magnetic Survey of a considerable portion of the North American Continent. FROM the moment that the fact was known, that the locality of the maximum of the magnetic Force in a hemisphere is not coincident, as was previously supposed, with the locality where the dip of the needle is $90^\circ$, researches in terrestrial magnetism assumed an interest and importance greatly exceeding that which they before possessed; for it was obvious that the hypothesis which then generally prevailed regarding the distribution of the magnetic Force at the surface of the globe, and which had been based on a too-limited induction, was erroneous, and that even the broad outline of the general view of terrestrial magnetism had to be recast. The observations on which this discovery rested, (being those which I had had an opportunity of making in 1818, 1819 and 1820 within the Arctic Circle, and at New York in 1822,) were published in 1825*; they constituted, I may be permitted to say, an important feature in the views, which led the British Association in the year 1835 to request that a report should be prepared, in which the state of our knowledge in respect to the variations of the magnetic Force at different parts of the earth's surface should be reviewed, and, as is customary in the reports presented to that very useful institution, that those measures should be pointed out which appeared most desirable for the advancement of this branch of science. In the maps attached to the report†, the isodynamic lines on the surface of the globe were drawn simply in conformity with observations, and unmixed with hypothesis of any sort. The observations collected for that purpose were not those of any particular individual or of any single nation, but embodied the results obtained by all persons who up to that period had taken part in such researches, subjected to such amount of discussion * Pendulum and other Experiments, pp. 460–499. † Reports of the British Association for 1837. only as conveyed a knowledge of the modes of observation severally employed, and reduced the whole to a common unit. The observations thus combined gave for the highest isodynamic lines of the northern hemisphere, closed and irregularly elliptical curves, extending across the North American Continent nearly in a north-west and south-east direction, and having their central point, or the point of maximum of Force, approximately in $52^\circ$ north latitude, and $270^\circ$ east longitude*. To confirm this previously unsuspected characteristic of the magnetic system of the globe,—to establish beyond a question so remarkable a fact in Physical Geography,—to fix within narrow limits the geographical situation of the point of maximum corresponding to a particular epoch,—to ascertain with the precision of modern instruments and methods the intensity of the magnetic Force at its point of maximum,—and to assign the form and geographical localities of the isodynamic curves adjacent to that point,—were objects which presented themselves amongst the most important desiderata for our present knowledge, and as likely to have a peculiar value at a future period in respect to the Ætiology of the science; when, like the earlier determinations in astronomy, these researches might serve to elucidate the laws of those secular changes, which, in our present ignorance of the causes of the earth’s magnetism, seem even more mysterious than the apparently complex relations of contemporary phenomena. The report referred to contained accordingly a suggestion of the expediency of measures being taken to procure a magnetic survey of that portion of the North American Continent, which is comprised within the isodynamic line of $1^\circ8$ in the arbitrary scale. This suggestion was treated as second in importance only to the recommendation which it was the primary object of that report to urge, and which has since been carried into execution; viz. a magnetic survey of the high latitudes of the southern hemisphere by a British naval expedition. The extensive territory over which it would be necessary to travel, in order to execute the proposed survey in North America, forms a part of the British dominions on that Continent, and is annually traversed during the summer months by the boats of the Hudson’s Bay Company conveying merchandize. A navigation conducted on lakes and rivers is better suited for the safe transport of small and delicate instruments, than where the travelling has to be performed exclusively on land. The good offices which the Hudson’s Bay Company had contributed to the success of the geographical expeditions, undertaken by the British Government, for the purpose of tracing the American rivers and coasts of the polar sea, and their liberality in originating expeditions of the same nature, and in executing them at their own cost and by their own officers, justified the hope that assistance might be given by the Hudson’s Bay Company, which should render an undertaking feasible, which undoubtedly would not have been so without their aid. With this expectation, and having reason to believe that leave of absence from * Vide Map 2 of the Report referred to. military duty might be obtained, I applied in 1839 to the respected Chairman of the Hudson's Bay Company, Sir John Pelly, Bart., and received from him the assurance that a conveyance in the Company's boats from Montreal to York Factory, and back to Canada by a different route, would readily be granted me on my personal application; and I accordingly commenced the preparation of the instruments which I proposed to employ. The execution of this design was prevented by the appointment in that year of officers and detachments of the Royal Artillery to conduct the Colonial magnetic observatories: these were placed under my superintendence, and the publication of the observations made at them entrusted to me. The project of a North American magnetic survey, however, was not suffered to drop. Having ascertained from Sir John Pelly that a conveyance in the Company's boats would be granted to an officer of the magnetic observatory at Toronto, on a representation from the President and Council of the Royal Society of the scientific interest attached to the undertaking, the late Lord Vivian, then Master-General of the Ordnance,—always desirous to encourage the officers who had the honour to serve under his command in rendering, in times of peace, such public though not strictly professional services as their public education qualified them to perform,—was pleased to annex the survey in question to the duties of the Toronto Observatory, and to add for that purpose an officer and a non-commissioned officer to the establishment of the observatory. This addition was proposed to Lord Vivian, with the concurrence and approval of the Deputy Adjutant-General of the Royal Artillery, Major-General Sir Hew Dalrymple Ross, K.C.B.; and on Lord Vivian's recommendation, the Treasury granted extra pay to the officer and the non-commissioned officer, with £30l. for the purchase of instruments, and 50l. a year for three years for the contingencies of the survey. On the proposal of Sir John Herschel, Bart., Chairman of the Committee of Physics of the Royal Society, the President and Council of that body addressed the Hudson's Bay Company in recommendation of the proposed undertaking, and received a favourable reply. In the autumn of 1842, Lieut. (since Captain) Lefroy, of the Royal Artillery, who had been the director of the magnetic observatory at St. Helena, and was appointed to the Toronto Observatory with a special view to his employment on the survey, left England for America, accompanied by Bombardier (since Sergeant) Henry of the same corps, to join the brigade of canoes of the Hudson's Bay Company, which would leave Montreal early in the following spring; the interval was employed in the preparation and trial of instruments, and in connecting, by an excursion in the United States, the observations about to be made in the British territories, with those which were in progress in different parts of the Union. In January 1843 I waited on Sir George Simpson, by appointment, at the Hudson's Bay House, to arrange with him the route by which it would be convenient to the Hudson's Bay Company to convey Lieut. Lefroy, so as to enable him to fulfil the objects of his employment. It was proposed by Sir George Simpson that Lieut. Lefroy should be conveyed, with his assistant and instruments, in one of the regular canoes of the brigade from Montreal to York Factory, and that from thence he should be provided with a light canoe to proceed, independently of others, to Moose Fort, near the head of Hudson's Bay, from whence he should return to Toronto overland as soon as the winter travelling should commence. By this route a circuit would be made completely round the supposed point of maximum of the Force, and within the isodynamic curve of 1·8. It was stated by Sir George Simpson, that the progress of the Brigade would admit of two hours in each day being taken for observation; that four hours would be given at each of the Company's posts, and twenty-four hours on the term-days of May and June; and that directions should be given accordingly to the conductor of the Brigade. Lieut. Lefroy was provided with the following instruments: 1. An Inclinometer of nine French inches diameter, by Gambeey. This instrument is the property of Captain Robert Fitzroy, R.N., and is the same which was previously lent by him for the survey of the British Islands, and by his permission is still employed for the public service. The needles belonging to it were the same which had been used in the British Survey, when they were proved to be free from index error at all inclinations, by the observations of Captain Johnson, R.N. and myself in the Regent's Park, reported in the account of that survey. Two additional needles were fitted to this instrument for the purpose of determining variations of the total force by Dr. Lloyd's method: they were made in 1839 by the late Mr. Robinson, and had been laid by in the hope that their magnetism would become steady. 2. A Fox's Inclinometer of seven inches diameter, with one reversing needle, and two needles for observing variations of the total force by Mr. Fox's method. 3. A portable unifilar magnetometer, for measurements of the absolute horizontal force, of the construction described in Lieut. Riddell's instructions for the use of portable magnetical instruments. 4. An azimuth compass of the construction proposed by the Committee for the improvement of ships' compasses, and now in use in Her Majesty's Navy; the bowl was reduced in height to render it more portable. 5. A portable declinometer. 6. A portable bifilar magnetometer; and 7. A portable induction inclinometer. These three instruments were designed for observations on term-days, and for the observations of diurnal variation and of disturbances in case of detention at any of the Company's posts. Lieut. Lefroy was also furnished with a Dollond's repeating and reflecting circle and mercurial horizon, for determining geographical positions; with meteorological instruments, including an apparatus for measuring heights by the boiling-point of water; and with two pocket chronometers, which were kindly lent for the occasion by the Hydrographer of the Admiralty. Lieut. Lefroy met Sir George Simpson at Montreal towards the end of April 1843, and embarked with Bombardier Henry and the instruments on board one of the Company's canoes at La Chine, commencing his observations on the 24th of May, in the ascent of the Ottawa river. The weather being favourable observations were made daily, with not more than one or two exceptions, until the Brigade arrived at Fort William on the 29th of May. It was there proposed by Sir George Simpson, who had preceded the Brigade, that Lieut. Lefroy should be provided with a canoe to himself, and should follow the Brigade at his convenience, but be entirely independent of it. This arrangement was consequently adopted, and Lieut. Lefroy left Fort William furnished with a guide and a canoe at his exclusive disposal, to carry out the original design of proceeding to York Factory. At the Rat Portage, however, on the Lake of the Woods, on the 20th of June, an accident happened to Gambey's inclinometer, which was thrown down, the glass cover broken, and one of the Lloyd's needles injured; Lieut. Lefroy was induced by this accident to deviate from the direct course to York Factory, and to proceed to the Red River settlement, where the damage was repaired. Here he met Sir George Simpson, and being of opinion that he should best promote the objects of the Survey by passing a winter in the interior, instead of carrying out the plan at first proposed of returning to Canada from York Factory, he arranged with that gentleman that, after returning to Norway House from Hudson's Bay, he should proceed direct to Fort Chipewyan on Lake Athabasca, winter there, descend McKenzie's River in the spring to the Arctic Circle, visit the Company's posts on the Saskatchewan and Peace Rivers, and return to Toronto at the conclusion of the summer of 1844. By this arrangement a considerable extension was given to the survey, and an opportunity was afforded of making the observations of a fixed magnetic observatory during several months of winter at Athabasca, where the magnetic variations, both regular and irregular, are of great magnitude, and have particular interest: on the other hand, some expense was incurred which had not been originally contemplated or provided for. The plan thus formed was executed; and the present number of the Contributions contains the observations during this survey of two of the magnetic elements, viz. of the Inclination and of the Force; the Declination is reserved for a future occasion, because a considerable augmentation of materials is expected. The winter observations with the magnetometers will have an appropriate place in the publication which contains the observations at the Colonial Magnetic Observatories. I am much gratified in being able to add to the interest and value of this number of the Contributions, by including observations not previously published, communicated to me by several gentlemen of the United States. In acknowledging the liberality and disinterested view for the advancement of science, with which the results of laborious and extensive researches have thus been unreservedly placed at my disposal, in anticipation of the publications in which they will respectively appear, I have great pleasure in calling attention to this example of the cordiality and good feeling, which happily subsist amongst the individuals of different nations, who have a common bond of union in the cultivation of magnetical science. I am indebted to Major James D. Graham of the Corps of Topographical Engineers of the United States, (Commissioner for exploring the North-Eastern Boundary of the United States under the act of Congress of July 20th, 1840, Principal Astronomer and Head of the Scientific Corps on the part of the Government of the United States for the joint survey and demarcation of the Boundary under the Treaty of Washington,) for the results of observations of the Inclination made from 1841 to 1845 at thirty-eight stations, chiefly in the parts of the country in which the Boundary Commissioners have been engaged. These observations were made with an inclinometer by Gambey, with the exception of three stations, where an instrument of Troughton and Simms was employed*; they appear to have been made with extreme care, and the results are remarkably accordant and satisfactory. Major Graham's observations have a particular value, in placing beyond question the fact that the direction of the isoclinal lines in that part of the American Continent is to the northward of east, whilst in the whole range of country elsewhere comprehended in this survey, these lines have a direction more or less from the northward of west to the southward of east: the geographical position in which certain of the isoclinal lines attain their greatest southing is thus satisfactorily ascertained. Major Graham states that the results now communicated are abstracted from a paper which has been presented to the American Philosophical Society of Philadelphia, and which will be hereafter published in the Transactions of that Society. From Dr. Locke of Cincinnati I have received the result of a very extensive series of observations of the Inclination and Force, on which he has been engaged for eight years (1838 to 1845 inclusive), comprehending the determination of both elements at about 100 stations, distributed in longitude from the seaboard of the United States to the Mississippi River, and in latitude from $38^\circ$ to $48^\circ$. It is in fact a magnetic survey of the Inclination and Force over the north-western and north-eastern States of the Union, conducted by an individual on his own unaided resources, and is one of the many notable instances of private research elicited by the impulse and systematic direction which have been given of late years to the study of terrestrial magnetism. The full account of these observations is designed to be published in the Transactions of the American Philosophical Society; but in the mean time the results have been spontaneously communicated to me by Dr. Locke (with whom I had not previously the pleasure of being acquainted), with full permission to make such use of them as I might deem advantageous to science. The Inclinations were observed with an inclinometer made by the late Mr. Robinson, and the variations of the magnetic Force by a Hansteen's apparatus, in which the needles vibrate in a partial vacuum, according to the plan devised by Dr. Alexander Dallas Bache. To Dr. A.D. Bache, Director of the Coast Survey of the United States, and to James Renwick, Esq., late Commissioner for Surveying and Exploring the North-Eastern Boundary of the United States, I am indebted for observations of the Inclination and of the absolute horizontal Force, which have been made by direction of the Government. * These stations were the Military Academy, West Point, New York; near the monument for marking the source of the River St. Croix; and Park's Hill on the boundary of Maine and New Brunswick. of the United States at stations of the Coast Survey, and which will hereafter be published in the Government reports. In the mean time the results have been communicated to me by Dr. Bache, with the permission of the Government. I have also availed myself of the Inclinations observed in different parts of the United States, by Professor Loomis and M. Nicollet, published in the seventh and eighth volumes of the Transactions of the American Philosophical Society. The skill of these gentlemen as observers, and the scrupulous care with which their observations are recorded, are too well-known to require comment. In conformity with the plan adopted in former numbers of these Contributions, I shall now proceed to discuss the general results of the observations embodied in this memoir under the separate heads of Magnetic Force and Inclination; referring where necessary to the documents in the sequel. **Magnetic Force.** The statical observations of the total Force furnish determinations at 120 stations, at 73 of which Lloyd's needles were employed, and Fox's needles at 109 stations. The observations of the horizontal force, with the magnets of the portable magnetometers, furnish determinations at 57 stations. The statical and horizontal methods together comprise 140 stations: the observations are given, and the results deduced in § 11. To these we have to add 10 determinations made at 10 stations near New York by Mr. Renwick, with a portable unifilar; and the ratios of the horizontal force at 101 stations, chiefly in the United States, by Dr. Locke, with a Hansteen's apparatus in which the needles vibrated in a partial vacuum. The connection of Dr. Locke's observations with those of Lieut. Lefroy, has been established by means of eleven stations common to both series, enabling both to be expressed in a common unit. The general table, No. XLVIII., which concludes § 11, comprehends 288 determinations of the magnetic force at 234 stations. Of the determinations 32 are of the absolute horizontal force, in which the magnetic moments of the magnets employed were examined on the spot: 35 were obtained with the same magnets, and give also the absolute horizontal force, but the magnetic moments were computed for the stations from experiments of deflection at other stations: 101 are of the ratios of the horizontal force, observed with needles whose magnetism was proved to be constant by their having been frequently brought back and examined at a base station; and 120 are ratios of the total force obtained by the statical method, in which also the magnetism of the needles was proved by their having been brought back to a base station. The number of stations at which statical ratios only were obtained is 74; the number at which horizontal ratios only were observed is 85; the number of the stations of absolute horizontal determinations only (whether by vibrations and deflections, or by vibrations alone) is 29; and finally, there are 37 stations at which both absolute and relative determinations were made. As all the stations of relative determination have the observatory at Toronto as a common base, it becomes an object to investigate with more than ordinary care the value of the total magnetic Force at that observatory, both in the arbitrary scale and in absolute measure. In the present state of experimental methods and apparatus we must obtain the absolute Force from the observations of its horizontal component, combined with observations of the Inclination. At Toronto we have for this purpose the values of the horizontal component resulting from the regular monthly series, made in the observatory on the 16th, 17th and 18th of each month in the year 1845, with a suspended magnet of three inches, and a deflecting magnet of 3·67 inches, the same magnets being used throughout. The details of these observations will be printed in the volume of the proceedings at the Toronto Observatory for the year 1845; the results are as follows: January . 3·5377. April . 3·5351. July . . . 3·5413. October . . 3·5373. February . 3·5376. May . . 3·5388. August . . 3·5383. November . 3·5360. March . . 3·5375. June . . 3·5421. September . 3·5373. December . 3·5379. The mean of the twelve months is 3·5380; and the mean of the Inclinations observed on the days in each month, nearest to those on which the Force was observed, is 75° 15'5': hence we have for the total force in absolute measure, 13·904. The magnets employed in the preceding determination were those of the Observatory unifilar. In September of the same year (1845), a very careful series of observations were made with the magnets Nos. 30, 31 and 17, of the unifilar magnetometer which had been employed on the survey; the particulars are given in the following Table: **Table I.—Observations on the absolute Horizontal Force made at Toronto with the Survey bars, Nos. 30, 31 and 17, in September 1845, reduced to the mean reading of the Bifilar Magnetometer for the day of observation.** | Date | Bars. | Distances. | Bifilar. | Deflections. | Vibrations. | Corresponding bifilar. | |------|-------|------------|----------|--------------|-------------|------------------------| | | | | Mean of the day. | At the observation. | Angles. | Therm. | Times. | Therm. | Sc. div. | Therm. | Suspension. | Value of m. | Value of X. | | Sept. 19. | 30 | feet. | 1·0257 | 568·9 | 64·0 | 564·2 | 65·0 | 11 26 26 | 61·5 | s. | 4·8666 | 61·6 | 558·2 | 64·4 | s. | -3806 | 3·5311 | | 19. | 30 | 1·0257 | 569·7 | 64·9 | 8 37 49 | 61·8 | 4·0136 | 62·7 | 565·2 | 65·9 | s. | -3805 | 3·5315 | | 19. | 30 | 1·2957 | 572·0 | 64·7 | 6 40 47 | 61·9 | s. | s. | s. | s. | s. | -3806 | 3·5311 | | 19. | 30 | 1·3257 | 571·7 | 65·2 | 5 16 35 | 61·5 | s. | s. | s. | s. | s. | -3806 | 3·5313 | | 20. | 31 | 1·0257 | 575·5 | 60·2 | 569·9 | 62·1 | 9 54 19 | 61·3 | 4·3292 | 60·0 | 558·3 | 61·9 | s. | -3305 | 3·5353 | | 20. | 31 | 1·1257 | 571·2 | 62·1 | 7 29 4 | 61·3 | 5·2409 | 62·0 | 575·9 | 62·4 | s. | -3306 | 3·5347 | | 20. | 31 | 1·2257 | 569·6 | 62·1 | 5 47 35 | 61·5 | s. | s. | s. | s. | s. | -3305 | 3·5354 | | 20. | 31 | 1·3257 | 569·3 | 62·0 | 4 34 53 | 61·7 | s. | s. | s. | s. | s. | -3306 | 3·5340 | | 22. | 17 | 1·1517 | 589·2 | 56·3 | 592·6 | 57·2 | 13 26 57 | 55·8 | 4·4196 | 57·6 | 592·8 | 57·9 | s. | -6291 | 3·5390 | | 22. | 17 | 1·4517 | 591·6 | 57·1 | 6 39 38 | 56·2 | 4·4149 | 56·0 | 584·7 | 55·8 | s. | -6290 | 3·5396 | | 24. | 17 | 1·1517 | 573·1 | 57·4 | 586·8 | 57·0 | 13 26 2 | 57·5 | 4·4138 | 56·5 | 581·1 | 56·7 | s. | -6287 | 3·5362 | | 24. | 17 | 1·4517 | 587·0 | 57·0 | 6 39 11 | 57·5 | s. | s. | s. | s. | s. | -6279 | 3·5404 | The 2nd observation of vibration of bar 17 entered on the 22nd was made on the 23rd, but is reduced to the mean bifilar reading of the 22nd. When s. is inserted in the column entitled "suspension," it implies that the magnet was suspended in a stirrup; otherwise the magnet was suspended without a stirrup. The value of $\pi^2K$ for bar 30 is 21·580 without the stirrup, and 31·745 with the stirrup; for bar 31, 21·853 without the stirrup, and 32·004 with the stirrup. The mean result of this series is $3^\circ 53' 50''$; and the Inclination from observations made on the same days $75^\circ 15' 8''$: hence we have the total force $13^\circ 89' 7''$. Finally, we have another series made with Nos. 30 and 31 in April 1846, and on this occasion unusual care was bestowed on the observations both of the Force and of the Inclination, preparatory to a repetition with the same instruments at Woolwich, for the purpose of making the comparison between Woolwich and Toronto as relatively correct as possible. The particulars of these observations are contained in the following Tables: **Table II.—Observations on the absolute Horizontal Force made at Toronto with the Survey bars Nos. 30 and 31, in April 1846, reduced to the mean reading of the Bifilar Magnetometer for the day of observation.** | Date | Bars | Distances | Bifilar. | Deflections. | Vibrations. | Corresponding bifilar. | Value of m. | Value of X. | |--------|------|-----------|---------|--------------|-------------|------------------------|-------------|-------------| | | | | Mean of the day. | At the observation. | Angles. | Times. | Therm. | Sc. div. | Therm. | Sc. div. | Therm. | Value of m. | Value of X. | | April | 6 | 31 | 1-026 | 579-5 | 55° 5 | 572-6 | 56° 3 | 10 27-9 | 56° 2 | 4-2061 | 50 | 581-0 | 54° 5 | 0-349 | 3-538 | | | 6 | 31 | 1-126 | 600-9 | 57° 0 | 576-5 | 56° 2 | 11 28-0 | 48° 5 | 4-0084 | 50 | 573-2 | 54° 5 | 0-349 | 3-535 | | | 7 | 30 | 1-026 | 580-5 | 55° 4 | 576-5 | 56° 2 | 11 28-0 | 48° 5 | 4-0084 | 50 | 573-2 | 54° 5 | 0-380 | 3-530 | | | 7 | 30 | 1-126 | 573-8 | 56° 5 | 56° 8 | 8 39-4 | 48° 8 | 4-0114 | 50 | 578-7 | 56° 6 | 0-380 | 3-530 | | | 8 | 31 | 1-026 | 592-4 | 51° 7 | 581-6 | 52° 2 | 10 28-8 | 48° 7 | 5-0985 | 50 | 586-7 | 51° 6 | 0-348 | 3-535 | | | 8 | 31 | 1-126 | 584-0 | 52° 1 | 7 54-9 | 48° 3 | | | | | | | 0-348 | 3-535 | | | 8 | 31 | 1-226 | 586-2 | 52° 1 | 6 8-0 | 48° 3 | 5-0995 | 50 | 592-3 | 52° 7 | 0-348 | 3-533 | | | 9 | 30 | 1-026 | 595-6 | 51° 2 | 581-7 | 52° 8 | 11 23-3 | 61° 2 | 4-8685 | 50 | 588-2 | 51° 2 | 0-379 | 3-532 | | | 9 | 30 | 1-126 | 583-2 | 52° 7 | 8 36-0 | 62° 0 | | | | | | | 0-379 | 3-531 | | | 9 | 30 | 1-226 | 582-5 | 52° 6 | 6 39-4 | 62° 5 | 4-8749 | 50 | 594-9 | 53° 6 | 0-379 | 3-531 | **Table III.—Observations of the Inclination made on the Pedestal of the Telescope used in the Observations of Vibration, and intended for comparison with a Base series of observations of the absolute Horizontal Force. April, 1846.** | Date | Observer. | Poles direct. | Poles reversed. | Mean Inclination. | |--------|-----------|---------------|------------------|-------------------| | | | a. | a'. | a''. | a'''. | Mean. | b. | b'. | b''. | b'''. | Mean. | | April | L. | 74 55-8 | 75 42-9 | 75 29-1 | 74 43-6 | 75 12-8 | 75 4-8 | 75 31-6 | 75 33-1 | 75 2-8 | 75 18-1 | 75 14-5 | | | H. | 75 3-8 | 75 45-6 | 75 32-8 | 75 1-7 | 75 21-0 | 75 2-2 | 75 30-9 | 75 27-6 | 74 46-2 | 74 11-7 | 75 16-3 | | 7 A.M. | L. | 75 4-3 | 75 34-8 | 75 34-8 | 75 4-0 | 75 19-4 | 75 47-4 | 75 41-8 | 75 31-4 | 74 44-4 | 75 18-7 | 75 16-5 | | | H. | 75 4-3 | 75 31-2 | 75 24-9 | 75 48-1 | 75 12-1 | 75 1-4 | 75 45-3 | 75 33-2 | 75 1-4 | 75 20-3 | 75 16-2 | | 8 A.M. | Y. | 74 54-9 | 75 41-1 | 75 24-0 | 74 38-2 | 75 9-5 | 75 3-5 | 75 27-7 | 75 39-7 | 74 56-3 | 75 16-8 | 75 13-1 | | | H. | 75 3-7 | 75 43-1 | 75 33-9 | 75 0-8 | 75 20-4 | 75 1-1 | 75 29-1 | 75 31-3 | 74 44-5 | 75 11-5 | 75 16-0 | | 9 A.M. | L. | 75 6-3 | 75 31-6 | 75 30-2 | 75 1-0 | 75 19-3 | 75 2-4 | 75 37-2 | 75 39-3 | 75 2-6 | 75 20-3 | 75 18-8 | | | H. | 75 6-3 | 75 31-6 | 75 30-2 | 75 1-0 | 75 19-3 | 75 2-4 | 75 37-2 | 75 39-3 | 75 2-6 | 75 20-3 | 75 18-8 | | 11 A.M.| W. | 74 56-2 | 75 38-4 | 75 21-2 | 74 46-0 | 75 10-4 | 75 3-0 | 75 30-8 | 75 31-0 | 75 2-2 | 75 16-7 | 75 13-6 | | 13 A.M.| H. | 75 3-2 | 75 39-7 | 75 34-1 | 75 3-3 | 75 20-1 | 75 0-5 | 75 29-3 | 75 28-4 | 75 45-6 | 75 10-9 | 75 15-5 | Mean Inclination, corresponding to the series of absolute horizontal Force........... 75 15-65 The instrument employed was Gambey's circle. Needle 1 was used for all the a.m. observations, and Needle 2 for all the p.m. observations, with the exception of the a.m. observation on the 13th, for which 2 was employed. The observers were, L. Lieut. Lefroy; Y. Lieut. Younghusband; H. Sergeant Henry; W. Sergeant Walker. MDCCXLVI. The mean of this series of the Force is $3.5330$, and of the Inclination $75^\circ 15'65$; hence we have the total Force $13.887$. The three determinations are as follows: - By the observatory magnets in the twelve months of 1845 . . . $13.904$ - By the three survey magnets in September 1845 . . . . . . $13.897$ - By two of the three survey magnets in April 1846 . . . . . . $13.887$ Whence we have the total Force in absolute measure at Toronto = $13.896$. For the value of the total Force in the arbitrary scale, we have, 1. A determination of the absolute Horizontal Force at Woolwich in June 1846, made by Captain Lefroy with the survey magnets Nos. 30 and 31, as shown in the following Table: **Table IV.**—Observations of the absolute Horizontal Force, made at Woolwich with the Survey bars Nos. 30 and 31. The corresponding readings of the Bifilar at Greenwich, kindly communicated by Mr. Airy, are inserted for reference. The times of vibration are entered as reduced to the common temperature of $80^\circ$, and corrected for torsion and rate: the angles of deflection are entered as observed. | Date | Bar. | Distance. | Deflection. | Vibration. | Values of m. | Values of X. | |----------|------|-----------|-------------|------------|--------------|--------------| | | | | Angles. | Therm. | Bifilar at | | | | | | | | Greenwich. | | | | | | Times. | Therm. | Bifilar at | | | | | | | | Greenwich. | | | 1846. | | | | | | | | June 8. | 30 | 1.026 | 10° 43'5" | 75°7" | 4.7621 | 80 | 0.01897 | 0.375 | 3.725 | | 8. | 30 | 1.126 | 8° 6'0" | 76°0" | 0.01938 | 80 | | 0.375 | 3.725 | | 8. | 30 | 1.226 | 6° 15'8" | 79°3" | 3.9287 | 80 | 0.01973 | 0.375 | 3.726 | | 11. | 31 | 1.026 | 9° 47'9" | 85°2" | 4.9944 | 80 | 0.01872 | 0.344 | 3.730 | | 11. | 31 | 1.126 | 7° 23'7" | 85°8" | 0.01977 | 80 | | 0.344 | 3.732 | | 11. | 31 | 1.226 | 5° 43'0" | 84°5" | 4.1204 | 80 | 0.02112 | 0.344 | 3.732 | | 12. | 31 | 1.026 | 9° 45'6" | 89°0" | 0.01888 | 4.1240 | 80 | 0.01826 | 0.344 | 3.727 | | 12. | 31 | 1.126 | 7° 22'4" | 91°0" | 4.9975 | 80 | 0.02221 | 0.344 | 3.727 | The mean is $3.7284$; and the mean of eight observations of the Inclination, made also between the 8th and 12th of June, with the same needles of Gambeys Inclinometer which had been employed to give the Inclination at Toronto, was $68^\circ 57'9$; hence we have the total force in absolute measure at Woolwich = $10.388$. We have therefore the total magnetic Force at Toronto to that at Woolwich as $13.896$ to $10.388$; or as $1.338 : 1$: and taking $1.372$ as the Force at Woolwich expressed in the arbitrary scale, we have the corresponding value at Toronto $1.835$. 2°. A statical determination of the ratio of the Force at Toronto and Woolwich by Mr. Fox's apparatus, conveyed by Lieut. Lefroy in 1842 from Woolwich to Toronto; the particulars will be found under their proper dates in the general detail of the observations in § 11; the result was $1.340$ at Toronto to unity at Woolwich; or $1.838$ to $1.372$. 3°. A second statical determination with the same apparatus, which Captain Lefroy, having occasion to return to England in the spring of 1846, brought with him from Toronto to Woolwich for that purpose. The particulars are contained in the subjoined Table; the ratio resulting from them is identical with that obtained by the absolute method, viz. 1·835 to 1·372. **Table V.—Observations with Fox's Circle to determine the relative Intensity of the Magnetic Force between Toronto and Woolwich. Needle C. \( q = 0.0017 \).** | Station | 1846 | Angles of deflection. | Thermometer. | Intensity. | |-------------|---------------|-----------------------|--------------|------------| | | | 1·5 grs. | 2·0 grs. | 2·5 grs. | 3·0 grs. | Woolwich = 1·372 | | Toronto | March 28 | 19° 59′ 2″ | 27° 44′ 7″ | 35° 19′ 7″ | 44° 18′ 5″ | 42° 6′ | 1·835 | | | March 31 | 20° 02′ 8″ | 27° 37′ 7″ | 35° 11′ 0″ | 44° 13′ 5″ | 57° 3′ | | | | April 2 | 19° 59′ 5″ | 27° 39′ 6″ | 35° 13′ 5″ | 44° 18′ 0″ | 69° 0′ | | | Woolwich | May 26 | 27° 03′ 2″ | 38° 34′ 6″ | 50° 41′ 7″ | 69° 42′ 5″ | 68° 4′ | 1·372 | | | May 28 | 27° 14′ 5″ | 38° 33′ 8″ | 50° 53′ 2″ | 69° 30′ 3″ | | | We have therefore three determinations of the total Force at Toronto expressed in the arbitrary scale, which are as follows: - By the statical method in 1842 . . . . . . . . . 1·838 - By the absolute method in 1845–46 . . . . . . . 1·835 - By the statical method in 1846 . . . . . . . . . 1·835 I have therefore concluded on taking 1·836 as the value in the arbitrary scale of the total Force at Toronto; and as all the relative determinations discussed in this memoir were either originally made in reference to Toronto as a base station, or have become connected with it by subsequent comparison, they form one series, and the values expressed in this scale, in the general table, No. XLVIII., are all dependent on 1·836 as the Force at Toronto; and will all require to be increased or diminished should future investigations show that 1·836 has been incorrectly adopted. Having then the values of the total Force at Toronto, 1·836 in the arbitrary scale, and 13·896 in absolute measure, arbitrary values are convertible into absolute by the factor \( \frac{13·896}{1·836} \), and absolute into arbitrary by \( \frac{1·836}{13·896} \). The absolute values of the total Force in the general table, No. XLVIII., have been thus computed in all cases when the original determination was a ratio, either total or horizontal; when the original determination was of the absolute horizontal Force, the absolute total Force computed therefrom is the product of the horizontal component and the secant of the observed Inclination. The simplest form, in which an approximate representation of the isodynamic ovals round the point of maximum, and within a limited distance of it, may be computed from observations distributed in the space included by those lines, appears to be that of concentric and similar ellipses. The representation will not be strictly just, because the curves which include the two points of maximum in a hemisphere are of the nature of lemniscates, and not of true ellipses, and the curves of higher intensity inclosed within them partake of the same form. I have taken for a calculation of this nature all the observations by the statical methods of Lloyd and Fox in which the resulting value of the Force equals or exceeds $1^\circ38$; with the exception of two stations, viz. the Little Rock Portage and Pierre au Calumet, where a comparison of the values, both of the Inclination and Force, with those at adjacent stations, shows that a great disturbing influence prevailed: and I have included the three stations at the foot of the Rocky Mountains, viz. Forts Vermilion, Dunvegan and Edmonton, where the intensity is less than $1^\circ38$, but the position important; as well as Toronto, where the value of the force is just beyond the limit (being $1^\circ36$), but has the advantage of having been remarkably well determined. The number of stations in this combination is seventy-eight, and double weight has been given to four, viz. Norway House, Cumberland House, Shamatawa and York Factory, on account of the repetition of the observations. These stations furnish therefore eighty-two equations of condition of the form described in the following Note, for which I am indebted to Archibald Smith, Esq., of Lincoln's-Inn, Fellow of Trinity College, Cambridge. --- "Note on the calculation of the Isodynamic Curves and the Focus of greatest intensity in North America. "These isodynamic curves consist of a series of ovals surrounding the point of greatest intensity. "The method of combining the observations at different stations which was used in the Magnetic Survey of Great Britain*, and which proceeded on the assumption that the isodynamic lines were nearly straight, cannot therefore be applied. The most simple assumption which will give an approximate result, and admit of all the observations within a given limited space being combined in the calculation, appears to be the following:— "Let a place near the centre of the region which is to be included in the calculations, be taken as the central station and origin of coordinates. Let $y_1$ and $y_2$, &c. be the differences of the latitudes of the several stations (which may be called $s_1$, $s_2$, &c.), and that of the central station: "Let $x_1$, $x_2$, &c. be the differences, multiplied respectively by the cosines of the latitudes of $s_1$, $s_2$, &c., of the longitudes of $s_1$, $s_2$, &c., and that of the central station. * See Reports of the British Association for 1838. "The position of a station of observation is thus determined by a distance in geographical miles measured along the meridian which passes through the central station, and a distance in geographical miles measured along that parallel of latitude which passes through the station of observation. "Let \( z \) be the magnetic element whose value is to be determined, which in this case is the total intensity, and let \( z_1, z_2, \&c. \) represent the values observed at \( s_1, s_2, \&c. \) "Assume that \( z \) may be expressed by the formula \[ z = ax^2 + bxy + cy^2 + dx + ey + f. \] "This amounts to assuming that the isodynamic curves may be represented by a series of similar and similarly situated concentric ellipses, on a plane projection of the sphere, in which parallels of latitude are represented by equidistant horizontal straight lines, the meridian passing through the central station by a vertical straight line, and the other meridians by curved lines which all intersect in the projection of the poles, and each of which intersects the projection of the equator at right angles at a distance from the central meridian proportional to the difference of its longitude and that of the central meridian, (and equal to the projection of a corresponding number of degrees of latitude,) and intersects the other parallels of latitude at distances from the central meridian, which are to the last-mentioned distance as the cosines of the latitude of the respective parallels of latitude are to unity. "Each station gives an equation of the form \[ \begin{align*} z_1 &= ax_1^2 + bx_1y_1 + cy_1^2 + dx_1 + ey_1 + f \\ z_2 &= ax_2^2 + bx_2y_2 + cy_2^2 + dx_2 + ey_2 + f \\ &\vdots \\ z_n &= ax_n^2 + bx_ny_n + cy_n^2 + dx_n + ey_n + f. \end{align*} \] "These equations being properly weighted are then combined by the method of least squares, and the values of the constants \( a, b, c, d, e \) and \( f \) are to be determined by elimination. One test of the applicability of this method is, that the resulting curves should be ellipses and not hyperbolas; \( a \) and \( c \) must therefore have the same signs, and \( 4ac \) must be greater than \( b^2 \). "Having determined the constants \( a, b, \&c. \), the coordinates \( \bar{x}, \bar{y} \) of the common centre of the ellipses, which is also the place of the greatest intensity, are given by the equations \[ 2a\bar{x} + b\bar{y} + d = 0, \] \[ b\bar{x} + 2c\bar{y} + e = 0, \] which give \[ \bar{x} = \frac{be - 2cd}{4ac - b^2}. \quad \ldots \quad (1.) \] \[ \bar{y} = \frac{bd - 2ae}{4ac - b^2}. \quad \ldots \quad (2.) \] The maximum value of the intensity is \[ \bar{z} = f + \frac{bde - cd^2 - ae^2}{4ac - b^2}. \quad \ldots \quad \ldots \quad \ldots \quad \ldots \quad \ldots \quad (3.) \] "If $\theta$ be the angle which either axis of the ellipses makes with the parallels of latitude, we have $$\tan 2\theta = \frac{b}{a-c}.$$ (4.) "This expression is ambiguous, giving two directions at right angles to each other, and does not determine which of these directions is that of the major axis. This will generally be apparent from the observations themselves; and it may be determined by this consideration, that if the numerical value of $a$ be greater than that of $c$, the inclination of the major axis to the parallel of latitude is greater than $45^\circ$; if less, less. "The values of the semi-axes of the isodynamic ellipse for which the intensity has the value $z$, are given by the two values of the expression $$\text{semi-axis} = \sqrt{\frac{2(z-\bar{z})}{a+c \pm \sqrt{(a-c)^2 + b^2}}}.$$ (5.) "The proportions of the semi-axes are $$a+c \pm \sqrt{(a-c)^2 + b^2} : 4ac - b^2.$$ (6.) "The simplest method of drawing the isodynamic ellipses will be to lay down the parallels of latitude and meridians in the manner above described; the isodynamic curves are true ellipses on that projection and may be easily constructed, and the points at which they intersect the meridians and parallels of latitude may then be laid down on any other map." A. S. Lincoln's Inn. I have taken the intersection of the latitude of $53^\circ$ with the meridian of $260^\circ$ as the origin of coordinates; the values of $x_1, x_2, \&c., y_1, y_2, \&c.$, were taken in units each of ten geographical miles; and, for convenience in calculation, the excess above $1.798$ has been taken at the value of $z$, the observed force at each station, and the decimals regarded as integers; the eighty-two equations thus furnished of the form described in Mr. Smith's Note have been combined by the method of least squares, to obtain the most probable values of the constants $a, b, c, d, e$ and $f$, the calculations having been performed by Sergeant McGrath and Corporal Hendley of the Royal Artillery, independently of each other, and agreeing; the six final equations were: $$\begin{align*} + & 5081 = +134394a - 69949b + 48449c + 1632d - 660e + 82f \\ - & 37298 = -3779899a + 2198523b - 1142033c - 69949d + 48449e - 660f \\ + & 98527 = +7136612a - 3779899b + 2198523c + 134394d - 69949e + 1632f \\ + & 2603880 = +177659938a - 96701976b + 57677688c + 2198523d - 1142033e + 48449f \\ - & 3570819 = -323660394a + 177659938b - 96701976c - 3779899d + 2198523e - 69949f \\ + & 6822989 = +622718413a - 323660394b + 177659938c + 7136612d - 3779899e + 134394f. \end{align*}$$ From these equations the values of the constants were obtained by elimination as follows: \[ \begin{align*} a &= -0.1138 \\ b &= -0.02522 \\ c &= -0.0356 \\ d &= +0.5633 \\ e &= +0.4485 \\ f &= +72.54. \end{align*} \] With these constants we obtain \[ \bar{z} = 79.9; \text{ and the Force at the point of maximum } = (1.798 + 0.0799) = 1.878: \] \[ \bar{x} = +29.38; \text{ whence the difference of longitude between the origin of coordinates } \] and the point of maximum \(= (+293.8 \text{ miles } \times \sec 52^\circ 19' = +481') = +8^\circ 01': \] \[ \bar{y} = -4.07; \text{ whence the difference of latitude between the origin and the point } \] of maximum \(= -40'.7. \] The geographical position of the maximum therefore is \(52^\circ 19' \text{ N.}, \text{ and } 268^\circ 01' \text{ E.}\) The angle which the major axes make with the parallel of geographical latitude is \[ \frac{180 - 46^\circ 10'}{2} = 66^\circ 55'; \] and the values of the semi-axes of the ellipse of 1.875 are 223 and 85 geographical miles respectively. The line of 1.875 has been drawn first on a map on a plane projection, and then transferred to the map on the polar projection which accompanies this memoir. The lines more distant from the maximum, viz. those of 1.850 and 1.800, have been drawn by the hand without the employment of calculation, and in such accordance with the observations as could be judged by the eye. The intensities entered in the map, and by which the lines have been drawn, are those of 192 stations. They include all the stations at which the total Force has been computed in the arbitrary scale, and inserted in the general table, No. XLVIII., except at 15 stations, where there is reason to believe that local disturbance prevailed to a considerable amount. The values of the total Force are derived from horizontal and statical ratios in the United States, and from statical ratios only in the countries to the north, where the Inclination became so great as to introduce an element of much uncertainty in the deduction of the total Force from its horizontal component. The intensities at four stations on the western side of the continent, on the shores of the Pacific, are introduced from the observations of Sir Edward Belcher, discussed in the IVth number of these Contributions. The line of 1.7, distinguished by a different character from that in which the other lines are drawn, is taken from the map (already referred to) in the Reports of the British Association for 1837, and is introduced into the present map for the purpose of affording a more ready means of comparing the form and geographical position of this line, with those of the lines inclosed within it, which are now for the first time delineated from observations, all of which have been made subsequently to the period when the map from which the line of 1.7 is taken was published. The accordance of the earlier and more recent observations is thus distinctly brought into view; and it will be perceived that the modifications, if any, which the line of 1.7 will require, will be very slight. With respect to the geographical position of the point of maximum of the Force, as it has been now computed from seventy-eight stations visited in 1843 and 1844, and surrounding the maximum in all directions, the coincidence with the central point of the closed curve of $1^\circ 7'$, as drawn in the map of 1837, could scarcely have been more perfect. Materials for the extension of the isodynamic lines to the north and east of the present survey will shortly be supplied,—to the north by the Expedition under Sir John Franklin,—and to the east by Lieut. Moore of the Royal Navy, whose magnetic observations in Her Majesty's ship Terror form an important portion of the Survey accomplished by the Expedition under Sir James Ross; and whose subsequent observations in the Pagoda, in conjunction with those of Lieut. Clerk, R.A., in the completion of that survey, will form the VIIIth number of the Contributions. Under the direction of the Lords of the Admiralty, Lieut. Moore has proceeded in the present summer to Hudson's Bay, in one of the vessels of the Hudson's Bay Company in which a passage has been kindly granted him, for the purpose of obtaining a suite of determinations intermediate between those which form the subject of the present communication, and those which are now in progress by the officers of the Arctic Expedition. The magnetic lines surrounding the one of the two points of maximum intensity which is on British territory, will thus be completely delineated: and I may be permitted to express a hope, founded on the unsparing liberality of the Russian Government in other branches of magnetical research, that the lines which surround the other point of maximum intensity in the northern hemisphere, which is within the Russian dominions, may ere long be determined with an equal completeness. The geographical longitude of the Siberian maximum is approximately known from the observations of Hansteen, Due and Erman; but an equally correct knowledge of its latitude appears to require an extension of the researches to the shores of the Polar Ocean. The intensity of the magnetic Force at its point of maximum in North America is $1^\circ 878$ in the arbitrary scale; or $14^\circ 21'$ in absolute measure, of which the units are,—of mass a grain, of time a second, and of space a foot, in British weights and measures. The intensity of the Force near the corresponding point in the southern hemisphere may be taken approximately, from a group composed of the daily determinations made by Sir James Ross's Expedition from the 19th to the 27th of March 1841, between the latitudes of $-58^\circ$ and $-64^\circ 26'$, and longitudes of $128^\circ 40'$ E. and $148^\circ 20'$ E., the track of the Expedition when crossing the southern isodynamic ellipse of $2^\circ 000$ about midway between the extremities of its principal axis. The mean of the results of this group is $2^\circ 059$, or in round numbers, $2^\circ 06$ in lat. $-64^\circ$ and long. $137^\circ 5$, or in absolute measure $15^\circ 60$. Neither the position of this maximum, nor the value of the Force, can be regarded as determined with as much precision as we may consider those at the northern maximum now to be; but we may conclude with certainty, that at the present magnetic epoch the Force at the southern maximum is consider- ably greater in amount than at the northern, and that its position is in a somewhat higher geographical latitude than the corresponding point in the north; as is also apparently the southern point of $90^\circ$ of Inclination; and probably also the position of the minor maximum of Force. If however we take a general view of the isodynamic lines in the two hemispheres, we see reason to believe that the difference under notice is rather a consequence of a different distribution of Force, than of an actual disparity in the magnetic charge of the two hemispheres. The two points of maximum in the south being nearer together at the present epoch (i.e. their shortest distance apart being less) than in the north, the intensity of the Force at both is raised, and a greater inequality is produced in the intensity on opposite sides of the southern hemisphere, than is the case in the northern hemisphere. The progress of secular change, as it may be inferred from the comparison of the earlier and more recent observations of the Declination and Inclination, is tending to bring the two points of maximum in each hemisphere nearer to each other; whilst this progressive approximation continues, we may expect that the Force in each hemisphere will become more and more unequally distributed, and that the intensity at each of the four points of maximum will augment. The increase or decrease of the distance in geographical longitude between the two points of maximum in a hemisphere appears to be chiefly occasioned by the rapid secular change in respect to locality (or the rapid movement in translation) which the phenomena of the minor system undergo. The minor maximum was probably at its greatest elongation ($180^\circ$ of geographical longitude) from the major maximum in the northern hemisphere, some time in the last century. At that epoch therefore the distribution of Force in that hemisphere made its nearest approach to equality; the opposite geographical longitudes had the minimum of dissimilarity in their respective intensities, and the values of the Force at the major and minor maxima were respectively lower than at any other epoch. In this conclusion I have omitted the subordinate consideration of the influence which the distribution of the Force in the southern hemisphere exercises on the northern intensities, which is distinctly perceptible even in the middle magnetic latitudes, and adds to the complication of the phenomena of progressive motion occasioned by secular change. The influence of the one hemisphere becomes of course more and more effective on the phenomena of the other, as the line which separates the magnetic hemispheres is approached: it is this circumstance which renders the phenomena in the equatorial regions of the globe so much more complicated than elsewhere, so much more difficult to disentangle, and consequently so much less suited to conduct readily to a comprehension of laws. It has been justly said that meteorological phenomena should be studied, in the first instance, in the tropical rather than in the temperate zones, because they present themselves under a simpler aspect: the contrary is true in respect to the magnetical phenomena, both in the distribution of the Force at a particular epoch, and in the order and succession of secular changes, which nowhere appear so complicated as in the lower magnetic latitudes, where they cannot be understood unless the magnetic state of both hemispheres is taken into the account. The coincidence of two or more points of maxima, (whether in the same or in different hemispheres,) under one and the same geographical meridian, may constitute magnetic epochs, which in the future history of the science may create an interest which can be very little conceived at present. The first conjunction of this kind, which our present purely empirical knowledge permits us to anticipate, is that of the two minor maxima, which, if the same progress of translation should continue that appears to have taken place in the last two and a half centuries, will hereafter be found on the same geographical meridian, and on the same side of the globe. Accompanying the movement of the two minor maxima of Force, the remarkable closed systems of the Declination lines, which are now found respectively in Siberia and in the Southern Pacific, by a movement of translation corresponding to that which they have undergone in the last two centuries, will also be found hereafter in the same geographical meridian, and will then doubtless have experienced a considerable modification of their form. If we connect the two points of $90^\circ$ of Inclination, the one in the northern and the other in the southern hemisphere, by an arc of a great circle crossing the terrestrial equator in the Atlantic Ocean, and if we examine the Inclination and Force along this arc, we shall find that the portions in which the Force decreases whilst the Inclination increases, amount to nearly a third of the whole distance between the points of $90^\circ$ thus measured along the surface of the globe. Not only therefore is the once-supposed law, according to which the magnetic Force should everywhere increase in a certain expressed ratio with the increase of the magnetic latitude, inapplicable to the phenomena, but the modification which has latterly been substituted,—“the law,” as it has been lately expressed, “of the general increase of the magnetic Force with the magnetic latitude,”—seems scarcely justified by the facts; and it may be doubted whether this expression is not more likely to mislead, by perpetuating the erroneous hypothesis in which it first took its rise, than to be of advantage as an empirical law, where the exceptions are so considerable. It is obvious that a too hasty generalization from observations made in those regions of the globe where the Force decreases with the increase of the dip, (as for example in the twenty degrees of latitude, or thereabouts, in North America, comprised between the point of maximum of the Force, and the point of $90^\circ$ of Inclination,) might have appeared to justify an inference which would have been the direct contrary of the above-mentioned law. There is in fact no such connection between the Inclination and the Force as will justify the one being spoken of as an immediate function of the other, or will sanction a general statement, that the increase of the one is to be looked for from the increase of the other, or vice versa. I have generally preferred, in these Contributions, the employment of the expres- sions "line of no Inclination" and "position or point where the Inclination is 90°," to the more technical designations of "magnetic equator" and "magnetic pole," because I have noticed that, since it has been known that the locality of the dip of 90° is not that of the maximum of Force, and that the line of no Inclination is not that of least intensity, an ambiguity has prevailed in the use of the technical expressions, which has frequently been prejudicial to a clear understanding of the passages in which those terms are employed. It would not be difficult to show, in the recent writings even of persons actively engaged in the advancement of magnetical science, instances in which the term "magnetic pole" is used, where it can have no other meaning than that of a point of greatest intensity; and other instances in which the meaning is doubtful in itself, and is not cleared by the context. The line of no dip is also frequently confounded with that of least intensity, although they represent different phenomena, and occupy different positions on the globe. By some authors the terms "pole of intensity" and "pole of verticity" have been introduced, by which ambiguity is indeed avoided; but, whilst the term "pole" is retained, it must be admitted that in one of the two instances at least, it is used in a sense which (whatever may have been its earlier signification) is inconsistent with modern definition from high authority (that of M. Gauss), and with that general understanding of its meaning, which has grown up under the hypothesis, imagined by some natural philosophers and now known to be erroneous, that the magnetism of the globe is analogous to that of a sphere of soft iron rendered magnetic by induction. The points of maximum of Force have also been called "foci" or "centres of Force," terms however which have not been suffered to pass without objection. In papers strictly limited as these Contributions are to investigations into the facts of terrestrial magnetism, I have thought it preferable to employ expressions, which although they may have the real disadvantage of appearing somewhat awkward, especially when they come to be frequently repeated, are subject to no ambiguity, and are obviously unconnected with any hypothesis. In advocating the consideration which, in a general view of the earth's magnetism, appears to be due to the points in each hemisphere which form the centres of the systems of isodynamic lines, and are themselves points of greatest Force,—and to the circle or curve which encompasses the earth and unites the points in each geographical meridian where the magnetic force is weakest,—I am far from desiring an undue importance to be attached to them, over the points where the needle is vertical (or its inclination is 90°,) and over the line where the direction of the needle is horizontal (or is parallel to the surface of the earth). No general view of terrestrial magnetism is just, or is agreeable to our present knowledge, of which the characteristic features of both phenomena, both of the Inclination and of the Force, do not form a part. In purely magnetical relations indeed,—and remembering that as yet there is no connection established between polar and gravitating forces,—the points of the earth's surface, where the action of the magnetic forces is most intense, have, as it appears to me, an importance beyond those where the magnetic direction, the resultant of those forces, may happen to coincide with the direction of the gravitating force. In like manner, I consider that the line of least intensity, (or the line on which in every meridian the magnetic Force, having progressively diminished from the high latitudes of the one hemisphere, attains a minimum, and commences a progressive increase to the high latitudes of the other hemisphere,) deserves to be considered as the separating line between the northern and southern magnetic hemispheres, more properly than does the line in which the resultant direction of the magnetic forces happens to be perpendicular to the direction of the gravitating force. It may be a question whether this association of the phenomena of independent forces may not have been too exclusively dwelt upon, and have thus become in some respects prejudicial to the advancement of terrestrial magnetism; but the view of the philosopher is imperfect, who, in the contemplation to which he subjects the magnetic phenomena, in the hope of being conducted by the sure path of induction to a knowledge of their laws, omits to give a due consideration, either to those relations which have the advantage of being purely magnetical, or to those coincidences or contrasts which the magnetic phenomena may present in respect to the phenomena of gravitation, or to those of any other of the great physical agents at the surface of our planet. **Magnetic Inclination.** The observations of the Inclination made in Lieut. Lefroy's survey are contained in §12. The number of determinations amounts to 179 (including 8 by Lieut. Younghusband, R.A. with the same instruments, and 5 by Dr. Rae, an officer of the Hudson's Bay establishment, furnished with an Inclinometer by Barrow), and the number of stations to 162. The general table, which includes the Inclinations observed by gentlemen of the United States, contains 450 determinations made at 335 stations. These were all observed between the years 1835 and 1846, and by far the greater number between 1839 and 1846. I have not attempted to introduce a correction for secular change, as the difference of epoch is small, and the rate of secular change is far from being even approximately known: without doubt also it varies in different parts of the wide district comprehended in this survey. At Toronto, its amount is so extremely small as to be scarcely appreciable by means of the most careful and multiplied observations continued for several years. The earliest observation of the Inclination in the United States, from which a satisfactory conclusion in respect to secular change may be derived, appears by Mr. Loomis's investigation*, to have been made by myself in 1822, in the garden of the Lunatic Asylum, near New York. By comparing the result which I then obtained (73° 05') with those of Locke, Lefroy and Renwick, at the same spot in 1841, 1842 and 1844 (72° 42'5), we find a diminution in twenty years amounting to 22'5, or rather more than 1' an- * Silliman's Journal, 1842, Art. IX. I believe that I may also claim the credit of having made in the same year the earliest determination of the magnetic force in the United States. nually. We may therefore presume from these instances, that the error in strict comparability, arising from the omission of a correction for secular change in the observations combined in this survey, the greater part of which differ not more than one or two years from a mean epoch, must be within the limits of the ordinary errors of observation, including of course those of station error. The method of computing the direction of the isoclinal lines, and the geographical distance between adjacent isoclinals representing certain differences in the amount of the Inclination, by a combination of the observations distributed over a limited district of the earth's surface, was first proposed by Dr. Lloyd in the Magnetic Survey of Ireland: it is simple and convenient when the lines conform to the conditions of being straight, parallel, and equidistant; but the problem becomes complicated and the calculation laborious in proportion as these conditions are departed from, and the number of indeterminate constants increases; until at length both complication and labour become excessive. In the parts of the continent of North America under consideration in this memoir, the variation of the isoclinal lines from the simple form above described is considerable: they are not straight lines on any projection; they are not parallel, nor are they equidistant. I endeavoured, nevertheless, to make the method of calculation answer, by breaking up the whole survey into several districts, and computing for each the coefficients of latitude and longitude, together with a central dip: but when districts were taken sufficiently small to satisfy approximately the required conditions of straightness, parallelism and equidistance, irregularities of observation arising from station error and other causes became significant, and materially influenced the results of the combination. I found myself obliged therefore finally to revert to the graphical method which I employed for the isoclinal lines of the British Survey, and which may be described as follows. The observations are first entered in a Mercator's map on a sufficiently large scale, a small cross being made to mark the spot of observation in its proper latitude and longitude, with the value of the Inclination written by its side. The isoclinal lines corresponding to degrees are then drawn roughly by the eye as the observations appear to direct. Lines are next drawn through each place of observation perpendicular to the direction of the isoclinal lines at the spot, and distances are set off on them corresponding to the value in geographical miles of the number of minutes which the observed dip is either above or below the full degree to which it is nearest. The value in geographical miles corresponding to the odd minutes is computed proportionally to the distance between the two isoclinals on either side of the place of observation; and it is set off, from the cross which marked the station, towards the isoclinal of the full degree which is nearest to the observation. A cross is then made in a different coloured ink, to mark the spot where the observation places its nearest isoclinal line; it is obvious that if there were no irregularities in the observations, the isoclinal lines would run continuously through these new points. Finally, the original rough draft of the lines is revised in reference to these points, and such corrections are made in the tracing of the lines as may appear to be required. Observations which, from station error or otherwise, cause their mark to fall amongst those of a different degree from themselves, are given a distinctive sign, so that they do not mislead, whilst at the same time they are kept in view. The number of stations where local influences of this magnitude were found to prevail, amounts to eleven in the 335 stations at which the Inclination is determined in this memoir. By this process each isoclinal line is deduced independently of those on either side of it, and distinctive features in each are shown, whether resulting from the general system or from district anomalies. The northern observations of Lieut. Lefroy extend so far to the westward that they overlap the meridians of some of the stations of Sir Edward Belcher, reported in the IVth Number of these Contributions. I have therefore included the four following stations of Sir Edward Belcher in this Map, and the isoclinal lines of $70^\circ$ and $76^\circ$ are thus carried across the whole continent of America from sea to sea. | Latitude | Longitude | Inclination | |----------|-----------|-------------| | Port Etches | $60^\circ 21'$ | $213^\circ 19'$ | $76^\circ 02'9''$ | | Sitka | $57^\circ 03'$ | $224^\circ 36'$ | $75^\circ 49'1''$ | | Baker's Bay | $46^\circ 17'$ | $235^\circ 58'$ | $69^\circ 26'7''$ | | Fort Vancouver | $45^\circ 37'$ | $237^\circ 24'$ | $69^\circ 22'2''$ | The lines drawn on the Mercator's map have been transferred to the map on the polar projection which accompanies this memoir; and for the purpose of more readily computing the inclination at any geographical position within the limits of the survey, corresponding to the observations combined in drawing the lines, the following Tables have been formed, which show the value of the Inclination at the intersection of every degree of latitude, with every fifth degree of longitude between the longitudes of $231^\circ$ and $261^\circ$, and with every $2\frac{1}{2}$ degrees between those of $261^\circ$ and $291^\circ$. The use of these Tables seems too obvious to need an explanation; by the usual process of interpolation, the Inclination due to any geographical locality within the bounds of the survey may be obtained by a very light calculation: a formula which should give the same result would necessarily consist of a considerable number of terms, and would therefore be of less practical utility. PART OF PEACE RIVER LAID DOWN BY CAPTAIN LEFROY FROM A FIELD SKETCH The dotted line denotes the course of the River by Arrowsmith's Map. 243° 244° 245° 246° Curriebo R. R. Boniface Vernilion Fort Falls of Peace R. Old Fort Basil R. Bear R. Iroquois River of 1850 and 1800 are drawn from the observations inserted in the Map; the point of Maximum of 1700 and 1600 are from earlier observations than those now given; and are taken from the The Force at the stations marked thus *, was determined by the absolute Maximum of Force is from the calculation in pp. 250-251; the dotted ellipse of 1875 is from the map accompanying Lieut. Col. Sabine's memoir on the variations of the magnetic needle by the absolute method; at all the other stations by relative methods. Table VI.—Showing the values of the Inclination at the intersection of each degree of latitude from 38° to 48°, with every $2\frac{1}{2}$° of longitude from 268° 30' to 291°. | Lat. | Longitudes | |------|------------| | | 268° 30'. | 271°. | 273° 30'. | 276°. | 278° 30'. | 281°. | 283° 30'. | 286°. | 288° 30'. | 291°. | | 38 | 68 46 | 69 01 | 69 21 | 69 40 | 69 57 | 70 14 | 70 22 | | | | | 39 | 69 43 | 69 57 | 70 17 | 70 36 | 70 52 | 71 09 | 71 16 | 71 18 | | | | 40 | 70 39 | 70 53 | 71 13 | 71 31 | 71 47 | 72 03 | 72 09 | 72 11 | | | | 41 | 71 34 | 71 48 | 72 08 | 72 26 | 72 42 | 72 57 | 73 01 | 73 03 | 73 08 | | | 42 | 72 28 | 72 43 | 73 03 | 73 21 | 73 36 | 73 50 | 73 53 | 73 54 | 73 58 | | | 43 | 73 21 | 73 37 | 73 57 | 74 15 | 74 30 | 74 42 | 74 44 | 74 45 | 74 47 | | | 44 | 74 13 | 74 30 | 74 51 | 75 09 | 75 22 | 75 32 | 75 34 | 75 34 | | | | 45 | 75 04 | 75 22 | 75 44 | 76 02 | 76 13 | 76 21 | 76 22 | 76 21 | 76 20 | 76 12 | | 46 | 75 54 | 76 13 | 76 36 | 76 50 | 77 02 | 77 07 | 77 06 | 77 09 | 77 06 | 76 57 | | 47 | 76 43 | 77 03 | 77 23 | 77 37 | 77 45 | 77 49 | 77 50 | 77 53 | 77 44 | 77 36 | | 48 | 77 32 | 77 54 | 78 08 | 78 22 | | | | | | | Table VII.—Showing the values of the Inclination at the intersection of each degree of latitude from 47° to 66°, with every 5° of longitude from 231° to 261°, and with every $2\frac{1}{2}$° of longitude from 261° to 268° 30'. | Lat. | Longitudes | |------|------------| | | 231°. | 236°. | 241°. | 246°. | 251°. | 256°. | 261°. | 263° 30'. | 266°. | 268° 30'. | | 47 | 70 09 | | | | | | | | | | | 48 | | | | | | | | | | | | 49 | | | | | | | | | | | | 50 | | | | | | | | | | | | 51 | | | | | | | | | | | | 52 | | | | | | | | | | | | 53 | | | | | | | | | | | | 54 | | | | | | | | | | | | 55 | | | | | | | | | | | | 56 | | | | | | | | | | | | 57 | | | | | | | | | | | | 58 | | | | | | | | | | | | 59 | | | | | | | | | | | | 60 | | | | | | | | | | | | 61 | | | | | | | | | | | | 62 | | | | | | | | | | | | 63 | | | | | | | | | | | | 64 | | | | | | | | | | | | 65 | | | | | | | | | | | | 66 | | | | | | | | | | | To give some idea of the degree of correctness with which these tables (particularly in the portion of the survey which is most likely to be referred to) may be considered to represent the observations from which they are derived, and to give consequently the true Inclinations corresponding to geographical positions, I have formed groups in localities where observations are much clustered, and have compared the tabular Inclination corresponding to the mean latitude and longitude, with that re- sulting from the mean of the observed Inclinations: the comparison shows as follows: **Table VIII.** | Group | Long. | Lat. | No. of observations | Mean of the observed Inclinations | Computed tabular Inclinations | Tabular in excess or defect | |-------|-------|------|---------------------|----------------------------------|-------------------------------|-----------------------------| | 1 | 269° 26' | 42° 28' | 14 | 73° 00'1" | 72° 59" | -1 | | 2 | 269° 59' | 38° 49' | 8 | 69° 38'7" | 69° 41" | +2 | | 3 | 275° 36' | 38° 30' | 6 | 70° 06'1" | 70° 05" | -1 | | 4 | 275° 19' | 46° 21' | 10 | 77° 05'2" | 77° 06" | +1 | | 5 | 278° 30' | 41° 18' | 15 | 72° 59'0" | 72° 59" | 0 | | 6 | 285° 58' | 40° 59' | 11 | 73° 01'3" | 73° 02" | +1 | | 7 | 288° 49' | 42° 13' | 11 | 74° 11'1" | 74° 09" | -2 | | 8 | 291° 20' | 46° 06' | 12 | 77° 01'4" | 77° 00" | -1 | The tabular inclination corresponding to the geographical position of Toronto is 75° 13'5". Dr. Locke's observation in 1843 was 75° 13'4". The needles of the observatory gave a mean inclination for that year amounting to 75° 16'. The mean of the last year (1845) is 75° 15'5". So far as the absence of station error is an object in the choice of a situation for a magnetic Observatory, the site of the Toronto Observatory appears to have been happily chosen. Taking single stations, there are seven at which the tabular dip differs more than 1° from the observed; at five of these the observed is in excess of the tabular, and at two in defect. The five are,—Kingston in Canada; Otter Island on Lake Superior; two stations 500 feet distant from each other in the Magnetic Inlet, and one on the adjacent isthmus on the south side of Lake Superior. The two in defect are Chat Falls on the Ottawa River; and the Portage Ecarteré, near Lake Superior, towards the height of land which separates the waters which flow into Lake Superior from those which flow towards Lake Winnipeg. At all these stations the observations of the magnetic Force, as well as those of the Inclination, manifest the existence of local disturbing influence. At Chat Falls the Inclination is in defect and the Force in excess; at Otter Island the contrary is the case, the Inclination being in excess and the Force in defect. At Portage Ecarteré, both Inclination and Force are in defect; and at the three other stations both elements are in excess. Besides the seven stations where the station error appears to exceed 1°, there are four (Isle d'Urval and Kingsey in Canada; Pierre au Calumet on the Elk River; and the Eagle River, in the same mineral district on the south side of Lake Superior as the magnetic inlet) at which the observations appear to be affected by station error to an amount which is less than 1°, but is still considerable. At each of these four stations the observed dip is in excess. The Inclinations at the eleven stations which have been thus named, are omitted in the map accompanying this memoir: they are eleven out of 335 stations. Of the remaining 324 stations there are some at which local disturbance of a less amount may be inferred; but all these are inserted in the map. Four of the eleven omitted stations are in a district, rich in minerals, on the south side of Lake Superior, near the 272nd geographical meridian: in each of these four instances the effect of the disturbance has been to increase the Inclination, but there are other stations in the same district where the observed Inclination does not materially differ from that which is due to the geographical position; and there is one station (United States Agency) where it is some minutes in defect. In the cases referred to, the influence of the disturbing causes is rather to produce irregu- larity at individual stations, than a systematic derangement of the general direction of the magnetic lines, similar to the highly interesting phenomenon in the northern part of Bohemia, recently investigated by M. KREIL*; from which investigation we learn that a more systematic relation may exist in some localities between geological and magnetical phenomena than had been previously apprehended. But instances of disturbance even at individual stations in the countries included in this survey are so unusually rare, that we should the less expect to find districts exhibiting a systematic affection: of such I can perceive no traces; the direction of the lines conforms to the general magnetic system of the globe, and appears to suffer no material inter- ruption; such district anomalies either do not exist, or the observations have not brought them to light. Determinations of Latitude and Longitude. The geographical positions of the stations visited by Lieut. LEROY in 1843 and 1844 are given in Table IX., with the authorities on which they depend: the latitudes and longitudes entered in the column headed 'observed' were either determined by his own observations, or reduced by himself by courses and distances from neigh- bouring stations of observation: to distinguish those stations at which the latitude or longitude was observed on the spot, a mark is inserted in the adjoining column: the mark ⊙ indicates latitude observed by meridian altitude of the sun; the mark * by altitudes of Polaris: in the column of longitudes, the mark ⊙ indicates chrono- metrical longitudes deduced from observations of the sun's altitude; and the mark * from altitudes of a star: where no mark is inserted, the latitude or longitude was deduced by observation of courses and distances from the adjacent stations. The chronometrical longitudes are dependent upon the longitudes of the following prin- cipal stations, as given by Sir JOHN FRANKLIN, Captain BAYFIELD, and others: viz. Fort William . . . 89° 27' BAYFIELD. 89° 16' FRANKLIN. 89° 23' TIARKS. 89° 22' Mean Sault St. Mary . . . 84° 34' BAYFIELD. * Magnetische und Geographische Ortsbestimmungen in Böhmen; Prag. 1846. MDCCXLVI. Fort Frances . . . . 93° 28'6" Franklin. Fort Alexander . . . 96° 21'4" Franklin. Norway House . . . 98° 7'1" Taylor*. York Factory . . . 92° 26'0" Franklin. Cumberland House . . 102° 19'4" Franklin. Mean of two determinations. Carlton House . . . 106° 12'7" Franklin. Isle à la Crosse . . . 107° 53'8" Franklin. Mean of two determinations. Athabasca . . . . 111° 18'7" Franklin. Mean of two determinations. Fort Simpson . . . 121° 25'0" Franklin. Mean of two determinations. These longitudes were determined with a greater number of chronometers than were carried by Lieut. Lefroy, and in some instances are the mean of determinations made by Sir John Franklin in his two journeys; the stations were selected therefore as points of departure; observations were made there with peculiar care, and the longitudes of intermediate stations, taken en route, were calculated from them successively. From July 1843 to September 1844 Lieut. Lefroy had the use of one chronometer only, (the other having met with an accident,) and it was found too irregular in its going to be relied on for long periods. The longitude was determined by lunar distances at certain stations, which are given in the Table. Wherever a station of observation is common to Sir John Franklin and Lieut. Lefroy, the latitude or longitude determined by the former officer is inserted for comparison in the column headed "from other determinations," which also contains values taken by measurement from the maps which accompany the narrative of his journeys. Lieut. Lefroy's observations along Peace River, and from thence by Lesser Slave Lake to the Saskatchewan, a line which was not taken by Sir John Franklin, are the first, it is believed, that have been published since those of Sir Alex. Mackenzie, and materially correct the course of that river, as laid down on the best maps. * Late Hudson's Bay Company's surveyor. This longitude is the mean of five observations of Jupiter's satellites, the extreme difference amongst them being 11' 10". ### Table IX. General Table of the Latitudes and Longitudes of the Stations visited by Lieut. Lefroy in 1843 and 1844. | Station | Observed Latitude | Observed Longitude | From other determinations Latitude | From other determinations Longitude | Remarks | |----------------------------------------------|-------------------|--------------------|------------------------------------|-------------------------------------|---------| | Montreal | 45° 31' (a.) | 286° 25' (a.) | | | (a.) From a map in the Quart-Master General's office in Canada. | | Isle d'Urval | 45° 24' (a.) | 286° 14' (a.) | | | | | La Combes | 45° 32' (a.) | 285° 51' (a.) | | | | | Island in the Ottawa River | 45° 36' 4" | 285° 33" | | | | | Entrance of Grenville Canal | 45° 36' 0" | 285° 28" | | | | | Chatham | 45° 36' 2" | | | | | | P'te aux Chênes | 284° 48" | | | | | | Alfred Township | 45° 37' (b.) | 285° 05' (b.) | | | (b.) from a map published for the Canada Company in 1829. | | Foxes Point | 45° 32' (b.) | 284° 26' (b.) | | | | | Templeton's Farm | 45° 29' (b.) | | | | | | Point Aylmer | 45° 15' | 284° 02" | | | | | Chat Portage | 45° 26' (b.) | 283° 28' (b.) | | | | | Fort Portage | 45° 36' | 283° 07" | | | | | Décharge d'Argile | 45° 39' 6" | | | | | | Grand Calumet | 45° 45" | 283° 20" | | | | | Fort Coulange | 45° 54' 9" | 282° 56" | | | | | Pointe Baptême | 46° 06' (c.) | 282° 34' (c.) | | | (c.) From Wylde's Map, 1843. | | Portage des deux Joachims | 46° 12" | 281° 41" | | | | | Roche Capitaine | 46° 17' 2" | 281° 42" | | | | | Trou Portage | 46° 15' 0" | 281° 27" | | | | | Matawa | 46° 18' 0" | 281° 20" | | | | | Little River, 1st Portage | 46° 18' 5" | 281° 17" | | | | | Lake Temisque | 46° 18' 0" | | | | | | Lac du Grand Vase, South side | 46° 18' 5" | 280° 34" | | | | | Portage du Grand Vase | 46° 19' 5" | 280° 26" | | | | | Lake Nipissing | 46° 14' 0" | 280° 01" | | | | | French River | 45° 58' 0" | 279° 25" | | | | | Riccolet Falls | 45° 57' 0" | 278° 59" | | | | | P'te au Croix | 45° 55' 5" | 278° 42" | | | | | Lake Huron | 46° 00" | 278° 10" | | | | | La Cloche | 46° 07' | 277° 32" | | | | | Snake Island | 46° 10" | 277° 10" | | | | | Cranberry Bay | 46° 11" | 276° 57" | | | | | Near Mississauga | 46° 08' | 276° 50" | | | | | Tessalon Point | 46° 16" | 276° 29" | | | | | St. Mary's River | 46° 20' | 276° 04" | | | | | Sault St. Mary | 46° 30' 7" | | | | | | Pointe aux Pins | 46° 29' 3" | | | | | | Pointe au Crêpe | 275° 02" | | | | | | Gargantua | 47° 37' 2" | 274° 49" | | | | | Fort Michipicoton | 47° 56' 0" | 274° 53" | | | | | Near Chienne River, one mile E. | 47° 52' 0" | 274° 36" | | | | | Otter Island | 48° 07' (B.) | 373° 45' (B.) | | | | | One mile below White River | 48° 31' 6" | 273° 27" | | | | | White River | 48° 33' 3" | 273° 27" | | | | | Fort Pic | 48° 38' 0" | 273° 29" | | | | | Terreplatte | 48° 49' 0" | 272° 15" | | | | | Near Thunder Bay | 48° 20' 3" | | | | | | Near Pointe Tonnerre | 48° 19' 0" (B.) | 270° 58' (B.) | | | | | Fort William | 48° 23' 6" | | | | | | Portage Ecarté | 48° 25' (B.) | 270° 15' (B.) | | | | | Portage de l'Isle | 48° 26' (F.) | | | | | | Bad Portage | 48° 29' (F.) | | | | | Mean 270° 38 | Station | Observed Latitude | Observed Longitude | From other determinations Latitude | From other determinations Longitude | Remarks | |-------------------------------|-------------------|--------------------|------------------------------------|-------------------------------------|----------------------------------------------| | Chien Portage | 48° 47' 0" | 270° 20' | 48° 39' (F.) | 270° 26' (F.) | | | Chien Lake | 48° 50' 9" | | 48° 57' (F.) | 269° 59' (F.) | (F.) Captain Sir John Franklin, R.N. | | Prairie Portage | 48° 35' 0" | 269° 52' | 48° 53' (F.) | 269° 57' (F.) | | | Savannah Portage | 48° 35' 0" | 268° 27' | | 268° 33' (F.) | | | French Portage | 48° 35' 0" | | | 268° 33' (F.) | | | Portage des Morts | 48° 34' 5" | | | 267° 50' | | | Portage des deux Rivières | 48° 34' 5" | | | 267° 33' | | | Lac à la Crosse | 48° 34' 5" | | | 267° 33' | | | Lac à la Crosse | 48° 34' 5" | | | 267° 33' | | | 2nd Portage from Lac à la Crosse | 48° 14' 6" | | | 267° 33' | | | Sturgeon Lake | 48° 27' | | | 267° 26' (F.) | | | Sturgeon Lake | 48° 28' | | | 267° 26' (F.) | | | Portage | 48° 29' | | | 267° 19' | | | Lac la Pluie | 48° 32' 5" | | | 267° 04' | | | Fort Francis | 48° 37' 2" | | | 48° 36' (F.) | 266° 31' (F.) | | Rainy River | 48° 47' 7" | | | 265° 29' | | | Lake of the Woods | 49° 05' 0" | | | 264° 59' | | | Lake of the Woods | 49° 19' 0" | | | 265° 18' | | | Lake of the Woods | 49° 28' 7" | | | 265° 20' | | | Lake of the Woods | 49° 28' 0" | | | 265° 20' | | | Rat Portage | 49° 46' 5" | | | 265° 21' | 49° 45' (F.) 265° 33' (F.) | | Winnipeg River | 50° 10' 1" | | | 264° 50' | | | Burnt Portage | 50° 19' 0" | | | 264° 24' | | | Slave Portage | 50° 10' 6" | | | 264° 23' | | | Barrier Portage | 50° 06' 0" | | | 264° 27' | | | Portage in Pinnaway River | 50° 12' 0" | | | 263° 57' | | | Cap Lake | 50° 20' 8" | | | | | | Fort Alexander | 50° 37' 1" | | | | | | Lake Winnipeg | 50° 27' 3" | | | 263° 22' | | | Upper Fort Garry | 49° 53' 1" | | | 262° 57' | | | Mouth of Red River | 50° 19' 0" | | | 263° 19' | | | Lake Winnipeg, West side | 51° 03' 6" | | | 263° 15' | | | Lake Winnipeg, East side | 51° 04' 0" | | | 263° 39' | | | Ox Island | 51° 16' 5" | | | 263° 32' | | | Lake Winnipeg | 51° 34' 0" | | | 263° 18' | | | Lake Winnipeg | 51° 38' 0" | | | 263° 12' | | | Lake Winnipeg | 51° 44' 5" | | | 263° 12' | | | Lake Winnipeg | 51° 45' 3" | | | 263° 07' | | | Lake Winnipeg | 52° 21' 0" | | | 262° 51' | | | Lake Winnipeg | 52° 22' 6" | | | 262° 51' | | | Lake Winnipeg | 52° 29' 0" | | | 262° 47' | | | Poplar Point | 52° 56' 0" | | | | | | Old Norway House | | | | 53° 41' 6' (F.) 261° 59' (F.) | | | Norway House | 53° 58' 9" | | | 261° 53' (e.) | | | Blackwater River | 54° 18' 8" | | | | | | Carpenter's Lake | 54° 14' 0" | | | 262° 22' | | | Hairy Lake | 54° 20' 0" | | | 262° 50' | | | Echiamamis | 54° 21' 0" | | | 262° 55' | | | Painted Stone Portage | 54° 22' 3" | | | | | | Whitefall Portage | | | | 54° 24' (F.) 263° 29' (F.) | | | Holey Lake, East side | 54° 56' 0" | | | 264° 18' | | | Half mile below the Crooked Spout | 54° 43' 9" | | | | | | Oxford House | 54° 56' 4" | | | 264° 30' | | | Rapid below Oxford House | 54° 52' 8" | | | 264° 32' (F.) | | | Knife Portage | 54° 53' 2" | | | | | | North side of Knee Lake | | | | 264° 49' | 54° 51' (F.) | (e.) From five observations of Jupiter's satellites by the late Mr. Taylor. | Station | Observed Latitude | Longitude | From other determinations Latitude | Longitude | Remarks | |-------------------------------|-------------------|-----------|------------------------------------|-----------|--------------------------| | Long Portage, Jack's River | 55°15'0" | ○ | 265°35' | ○ | 55°14(F.) | | Creek Portage | 55°24'6" | ○ | | | 265°38(F.) | | Morgan's Portage | 55°29'0" | ○ | 266°08' | | 265°57(F.) | | White Earth Portage | 55°26'0" | ○ | 265°57' | ○ | 265°57(F.) | | White Earth Portage | | ○ | 266°10' | ○ | 265°33(F.) | | Shamatawa | 56°21'0" | ○ | 267°04' | | 267°00(F.) | | Five miles below Shamatawa | 56°25'7" | ○ | | | | | York Factory | 57°00'1" | ○ | | | 57°00'1 | | Lake Winnipeg | | ○ | 260°55' | ○ | | | Ditto, near first Rocky Point | 53°31 | ○ | 260°48' | | | | Saskatchewan River | 53°11 | ○ | | | | | Grand Rapid | | ○ | 260°32' | ○ | 53°08(F.) | | Cross Lake, East side | 53°10'2" | ○ | 260°28' | ○ | 260°23(F.) | | Hare Island, Cedar Lake | 53°12'0" | ○ | | | | | Island in Cedar Lake | 53°18'0" | ○ | 259°48' | ○ | | | Devil's Drum Island | | ○ | 259°15' | ○ | 53°19(F.) | | Four miles above the Pas | 53°48 | * | 258°32' | ○ | 258°37(F.) | | Cumberland House | | ○ | | | 53°57(F.) | | Pine Island Lake | 54°14'3" | ○ | | | | | Crooked Rapid | 54°24'7" | ○ | | | | | Beaver Lake | 54°26'0" | ○ | 257°50' | ○ | | | Half a mile north of Haye's River | 54°44'0" | ○ | 257°21' | ○ | | | Carp Portage | 54°47'2" | ○ | | | | | Pine Portage | | ○ | | | 55°04(F.) | | Frog Portage | | ○ | | | 55°27(F.) | | Little Rock Portage | 55°34'3" | ○ | 255°26' | ○ | 255°27(F.) | | Great Devil's Portage, East end | 55°40'1" | ○ | 254°55' | ○ | 255°12(F.) | | Portage des Écres | 55°43'0" | * | | | | | Trout Portage | 55°42'5" | ○ | 254°31' | ○ | | | Harrier Portage | 55°35'8" | ○ | | | | | Half a mile above Cardinal Rapid | 55°39'1" | * | | | | | Half a mile below Rapide qui ne parle pas | 55°43'5" | ○ | 254°10' | ○ | | | Canoe Portage | 55°42'7" | ○ | | | | | Pine Portage | 55°43'2" | ○ | | | 254°04(F.) | | Snake Point | 55°51'0" | ○ | 253°15' | ○ | | | Snake Rapid | 55°45'7" | ○ | | | | | Portage Sonnante | | ○ | 252°34' | ○ | 55°54(F.) | | Isle à la Crosse | | ○ | | | 55°25(F.) | | Buffaloe Lake | 56°04 | ○ | | | | | Long Portage on River de la Loche | 56°14'9" | ○ | 250°42' | ○ | | | Portage de la Loche, East end | 56°34'5" | * | 250°16' | ○ | | | Portage de la Loche, West end | 56°43'4" | * | 250°08' | ○ | 56°43(F.) | | Portage Terre Blanche | 56°41'7" | ○ | | | | | Portage Gros Roche | 56°43'5" | ○ | 249°51' | ○ | 56°42(F.) | | Cascade Portage | 56°42'5" | ○ | 249°41' | ○ | 56°39(F.) | | Clearwater River | | ○ | | | | | Pine Island, Elk River | 56°58'0" | * | 248°13' | ○ | 57°24(F.) | | Pierre au Calumet | | ○ | | | 58°07(F.) | | Pte Brulée | | ○ | | | 58°43(F.) | | Athabasca | | ○ | | | | | Fort Good Hope | | ○ | | | 66°16(S.) | | Rapide sans Sault | 65°48 | ○ | | | | | Fort Norman | | ○ | | | 64°31(F.) | | Fort Simpson | 61°51'7" | ○ | | | | | Pte Brulée | 61°10'0" | ○ | 240°51' | ○ | | (S.) Observed by Simpson. | Station | Observed Latitude | Observed Longitude | From other determinations Latitude | From other determinations Longitude | Remarks | |-------------------------------|-------------------|--------------------|------------------------------------|-------------------------------------|---------------------------------------------| | Yellow Knife River | 61° 12'3 | 0° | 0° | 0° | | | Sandy Point | 61° 20'0 | 242° 00 | | | | | Little Lake | 61° 25'7 | | | | | | Big Island (Fishery) | 61° 11'7 | 243° 22 | | | | | Big Island, East end | 61° 07'7 | | | | | | Hay River | 60° 48 | 244° 49 | 60° 51(F.) | 244° 42(F.) | | | Near Hay River | 60° 49 | | | | | | Fort Resolution | 61° 10 | | | | | | Buffaloe River | 60° 34 | 246° 48 | | | | | Portage Grand Detour | 60° 22 | 247° 00 | | | | | In ditto, First Lake | 60° 20'6 | | | | | | Salt River (Slave River) | 60° 02'2 | 247° 45 | 60° 06(F.) | 247° 38(F.) | | | Slave River | 60° 02'2 | | | | | | Pelican Portage | 58° 55 | 248° 09 | 59° 58(F.) | 248° 09(F.) | | | Peace River | 58° 58 | 247° 50 | | | | | Point Providence | 59° 10'1 | | | | | | Peace River | 58° 58 | 247° 01 | | | | | Poplar Island | 58° 39 | 246° 03 | | | | | Falls of Peace River | 58° 24'2 | 245° 06 | | | | | Fort Vermilion | 58° 24'7 | 243° 55 | | | | | Peace River | 57° 57'0 | 243° 00 | | | | | Peace River | 57° 50'7 | | | | | | Peace River | 57° 19'0 | 243° 32 | | | | | Peace River | 57° 12'3 | | | | | | Opposite River Cadotte | 56° 47'0 | 242° 58 | | | | | Peace River | 56° 42'0 | | | | | | Fort Dunvegan | 55° 55'6 | 241° 35 | | | | | Riviere de Prairie | 55° 50'1 | | | | | | Fort at Lesser Slave Lake | 55° 32'8 | 244° 07 | | | | | Cranberry Point | 55° 29'5 | 244° 54 | | | | | Point Dejala | 55° 26'5 | 244° 59 | | | | | On Lesser Slave Lake | 55° 15'6 | | | | | | Junction of the Slave and Elk R. | 55° 13'0 | 246° 10 | | | | | Elk River, opposite Pembina River | 54° 45'7 | | | | | | Elk River | 54° 43'0 | 246° 00 | | | | | Fort Assiniboine | 54° 19'7 | 245° 32 | | | | | Paddle River | 54° 09'8 | 245° 59 | | | | | Pembina River | 54° 08'0 | 246° 06 | | | | | Edmonton | 53° 31'1 | 247° 08 | | | | | Saskatchewan River | 54° 04'8 | 248° 16 | | | | | Saskatchewan River | 53° 50'0 | 249° 30 | | | | | Fort Pitt | 53° 34'0 | 250° 41 | | | | | Saskatchewan River | 53° 07'0 | 251° 30 | | | | | Saskatchewan River | 52° 23'2 | 252° 56 | | | | | Carlton House | 52° 51(F.) | 253° 47(F.) | | | | | Saskatchewan River | 255° 12 | 53° 16(F.) | | | | *By 2 sets of lunar distances, (C from sun west 241° 41'. *By 4 sets of lunar distances, 2 (C from *E., and 2 (C from W. 244° 06'. § 11. Lieut. Lefroy's Observations of the Magnetic Force. These observations were of two kinds; those which were designed to determine the absolute value of the horizontal component of the force; and those which had for their object to determine the ratio of the total force at different stations. For the absolute determinations magnets of small dimensions were employed in portable apparatus, which will be hereafter described. The observations to determine the relative values of the total force were made with two needles on Dr. Lloyd's statical principle, used in Gambev's circle, and with two needles on Mr. Fox's principle, used in a circle of seven inches diameter. The Lloyd's needles were distinguished as L. A. and L. B.: the Fox's as F. A. and F. C. Experiments to determine the coefficient in the temperature corrections of these needles were made at Toronto in the first three months of 1843. The observations at high temperatures were made in the detached building of the observatory, which was heated for the purpose by a copper stove: those at low temperatures were made partly in the same room and partly in the open air outside the building. In Tables X. and XI., in which these experiments are recorded, \( v \) denotes the angle of deflection with a constant weight at the temperature \( t \), in the experiments at low temperatures; \( \theta \) the inclination; and \( \phi \) the total force, which is \( \frac{\cos v}{\sin (\theta - v)} \) with Dr. Lloyd's needles, and \( \sin v \) with Mr. Fox's; \( v' \), \( \theta' \) and \( \phi' \) denote the corresponding values in the experiments at high temperatures. Then, \( q \) being the coefficient, \( \phi = \phi' (1 - q(t - t')) \); and \( q = \frac{\phi - \phi'}{\phi'(t - t')} \). Table X. Abstract of the Observations made at Toronto to ascertain the value of \( q \) for the needles L. A. and L. B. L. A. | Low temperatures | High temperatures | |------------------|-------------------| | 1842 and 1843 | | | Dec. 10. | Jan. 9. | | 29° | 66° | | 31° | 66° | | 32° | 66° | | 35° | 66° | | 38° | 66° | | Feb. 1. | Feb. 1. | | 25° | 62° | | 25° | 62° | | 27° | 62° | | 37° | 62° | | 25° | 62° | | 27° | 62° | Hence for L. A. \( q = 0.000016 \). ### Table XI. Abstract of the Observations made with Needle F. A. and F. C. to determine the Coefficient for the temperature correction. #### Needle F. A. | Weight | 1843. | Low temperatures. | High temperatures. | Weight | 1843. | Low temperatures. | High temperatures. | |--------|-------|-------------------|--------------------|--------|-------|-------------------|--------------------| | | | t. | v. | t'. | v'. | t. | v. | t'. | v'. | | Jan. | 4 | 26·0 | 21 09·9 | 60·8 | 21 17·2 | Jan. | 4 | 26·2 | 56·2·2 | 61·5 | 27 11·8 | | | 4 | 28·0 | 21 08·9 | 56·8 | 21 20·3 | 4 | 27·4 | 26 45·9 | 57·1 | 27 18·1 | | | 12 | 35·2 | 21 12·3 | 74·2 | 21 19·5 | 12 | 35·5 | 27 04·2 | 74·8 | 27 05·7 | | | 12 | 35·5 | 21 21·8 | 82·4 | 21 25·6 | 12 | 35·4 | 27 00·3 | 80·0 | 27 11·3 | | | 14 | 30·6 | 21 09·5 | 71·5 | 21 32·1 | 14 | 29·5 | 26 53·1 | 70·5 | 27 12·9 | | | 14 | 27·0 | 21 12·6 | 61·2 | 21 20·8 | 14 | 26·0 | 26 58·8 | 62·1 | 27 02·1 | | | 16 | 33·5 | 21 10·0 | 72·7 | 21 25·9 | 16 | 32·5 | 27 08·4 | 74·8 | 27 18·1 | | Means. | | 30·8 | 21 12·1 | 67·4 | 21 23·1 | Means. | | 30·4 | 26 57·6 | 68·7 | 27 11·4 | | Jan. | 4 | 26·7 | 33 05·0 | 61·2 | 33 17·2 | Jan. | 12 | 34·9 | 46 45·4 | 74·4 | 46 52·5 | | | 4 | 26·2 | 33 02·8 | 58·8 | 33 18·5 | 12 | 34·0 | 46 42·1 | 80·3 | 47 05·6 | | | 12 | 35·5 | 33 21·6 | 75·9 | 33 26·0 | 16 | 34·5 | 46 41·4 | 82·0 | 47 15·4 | | | 12 | 35·0 | 33 15·2 | 83·4 | 33 25·8 | Means. | | 31·7 | 33 11·1 | 71·5 | 33 20·6 | | | 12 | 34·2 | 33 14·8 | 78·2 | 33 15·6 | Means. | | 34·4 | 46 43·0 | 78·9 | 47 04·5 | Hence, giving the observations with 4·0 grains, half the weight of the observations with each of the other three weights, we have $q = 0.000164$. ### Needle F. C. | Weights | 1843. Low temperatures. | High temperatures. | Weights | 1843. Low temperatures. | High temperatures. | |---------|------------------------|--------------------|---------|------------------------|--------------------| | | t. | v. | t'. | v'. | t. | v. | t'. | v'. | | Feb. | 2. | 24·7 | 26·32 | 83·0 | 26·36 | Feb. | 2. | 28·0 | 34·06 | 88·0 | 34·53 | | | 3. | 32·7 | 26·47 | 83·5 | 26·49 | | 3. | 30·7 | 34·19 | 87·4 | 34·33 | | | 3. | 31·0 | 26·38 | 67·8 | 27·16 | | 3. | 29·5 | 33·54 | 70·1 | 34·24 | | | 6. | 29·0 | 26·54 | 82·0 | 26·58 | | 6. | 29·0 | 34·16 | 79·2 | 34·30 | | | 6. | 28·1 | 26·45 | 64·6 | 26·55 | | 6. | 28·2 | 34·15 | 64·0 | 34·30 | | | 4. | 28·2 | 26·42 | 64·5 | 26·42 | | 4. | 31·4 | 34·21 | 65·0 | 34·18 | | Means | 28·9 | 26·43 | 72·9 | 26·52·7 | Means | 29·5 | 34·12 | 75·6 | 34·28 | | Feb. | 2. | 24·0 | 42·45 | 89·0 | 42·43 | Feb. | 6. | 28·5 | 19·39 | 82·1 | 20·12·0 | | | 3. | 29·1 | 42·31 | 87·2 | 42·38 | | 6. | 27·5 | 19·46 | 65·3 | 20·03·0 | | | 3. | 28·5 | 42·37 | 70·5 | 42·35 | | Means | 28·0 | 19·42·5 | 78·7 | 20·07·5 | | | 6. | 29·0 | 42·41 | 73·0 | 42·40 | | | | | | | | | 6. | 28·1 | 42·43 | 62·2 | 42·47 | | | | | | | | | 4. | 33·7 | 42·42 | 65·0 | 42·56 | | | | | | | | Means | 28·7 | 42·39·8 | 72·8 | 42·43·2 | Means | 28·0 | 19·42·5 | 78·7 | 20·07·5 | Hence, giving the observations with 1·5 gr. one-third the weight of those with each of the other weights, \( q = 0.00013 \); or, if we reject the observations with 3 grains, which are much more irregular than the others, \( q = 0.000175 \). The value which has been employed is 0.00016 for both needles F. A. and F. C. It will perhaps be most convenient to give a brief history of each needle during the period comprised by the observations discussed in this memoir; beginning with F. A. of Mr. Fox's apparatus, as having been the most extensively employed. The observations with this needle commenced at Woolwich, as a base station, on the 7th of July 1842. In the transport in which Lieut. Lefroy made his passage to Canada in July and August, it was employed to give determinations of the Inclination and Force on all days when the weather permitted. The greater part of these determinations belong to a part of the globe which is not now under consideration, and will not therefore be discussed on the present occasion; but a continuation of the series at some stations in Lower Canada, and at several in the United States which Lieut. Lefroy visited on his way to Toronto, for the purpose of connecting the base stations of other observers with his own future base station at Toronto, will be found in Table XII. The deflections obtained with this needle at Toronto on the 26th of October 1842, with the same weights which had been used at Woolwich in July, gave for the ratio of the total force at Toronto 1·3395 to 1 at Woolwich; or 1·838 to 1·372 in terms of the usual arbitrary scale. Two subsequent determinations, one with the same apparatus in 1846, and the other derived from absolute measures of the horizontal Force at Toronto and Woolwich, gave each 1·835 to 1·372; these determinations have been discussed in the introductory remarks, pages 244 to 247, the result of the discussion being that 1·836 has been finally adopted. MDCCCXLVI. On the 28th of October, the needle F. A. being put away in its case, a very powerful bar magnet was inadvertently laid on the top of the case for a few minutes. Observations made on the following day (the 29th), compared with those which had been made on the 26th, showed that the needle had sustained a sensible loss of magnetism by this accident. A new series therefore in the determinations with this needle was commenced on the 29th of October, referring to Toronto as a base station, at which the value of the force is expressed by $1.836$ as before. In November 1842, F. A. was employed by Lieut. Younghusband, R.A. at four stations in the states of Ohio and Michigan, and was brought back to Toronto in the same month: the abstract of these observations is given in Table XIII. In the first three months of 1843 the observations were made in high and low temperatures, by which the coefficient in the temperature correction was determined; and repetitions were made on different days in natural temperatures of the angles of deflection with several weights which were afterwards employed in the countries to the north. Towards the end of April Lieut. Lefroy embarked at La Chine in the canoes of the Hudson’s Bay Company, and commenced a course of observations, which was continued daily with very few intermissions until his arrival at Athabasca towards the end of September, at the conclusion of the season of navigation. The observations with F. A. were made by Lieut. Lefroy himself until the station of the 11th of May at the Trou Portage; and from thenceforward by Bombardier Henry, unless where specially noticed in the column of remarks in Tables XIV., XV. and XVI.; towards the end of July the performance of the needle was thought to be somewhat impaired, and in consequence, at York Factory, the terminations of the axles which worked in jewels, as well as the jewels themselves, were carefully examined with a microscope; the front axle was found in admirable order, but the polish of the back axle was not good on one side. The jewels were in good order; the front jewel was scratched on the face and round the edge of the cylindrical bore, probably by the end of the axle in mounting the needle, but the scratches did not appear to enter the bore or affect the bearing points; F. A. was continued in constant use until the end of the season, but its performance was occasionally sluggish and unsatisfactory in comparison with what it had formerly been, and led to its being only occasionally employed in the following year. On the return to Toronto at the close of 1844, the observations were repeated with the weights which had been used in the north; the performance of the needle on that occasion was considered to be a decided improvement on former ones, and the angles of deflection agreed within limits of ordinary error with the angles observed in 1843, before the journey to the north; showing that the magnetism of the needle had sustained no deterioration during the interval. The abstract of the observations with this needle from 1842 to the close of 1844, are given in Tables XIV., XV. and XVI. Needle F. C. had been kept in reserve at the different stations of the Survey whilst F. A. continued to give satisfactory results. Being examined at York Factory, the polish of the axle was found perfectly good, but the back axle had been injured in shape. A spare axle had been furnished with the apparatus, and appearing perfect both in shape and polish, it was fitted to F. C., and observations were made with this needle at Norway House on the 11th of August 1843, and were repeated at the same spot on the 7th of September 1844. The magnetism of the needle appeared steady, but from some undiscovered cause its performance at some other stations at which it was tried was sluggish and irregular, so that no satisfactory results were obtained with it at them. On the return to Toronto, the angles of deflection were observed with the same weights which had been used at Norway House in August 1843 and September 1844. These give an identical value for the increase of the magnetic force between Toronto and Norway House, to that obtained by the other needle of the apparatus F.A.; the particulars are given in Table XVII. In Mr. Fox's apparatus the angle of deflection with any particular weight is half the difference of the arcs shown with the weight first on the one hook, and then on the other hook. The experiment is repeated with the face of the circle both east and west, and the angle of deflection entered in the Table is the mean of the angles with the face of the circle east and west. L. A. and L. B. were the needles on Dr. Lloyd's statical principle fitted to the Gambeys circle; at Toronto, in January and February 1843, the observations were made with them in Table X., by which the coefficient in the temperature correction was determined; and angles of deflection with weights inserted in the hole most distant from the axle were observed for the purpose of supplying a base determination. On arriving at St. Helen's, however, the angles of deflection appeared inconveniently large, and the weights were shifted in each needle into the middle hole, and a new series of relative determinations commenced. The angles of deflection having been observed on the same day at St. Helen's with the weight both in the middle and in the outer hole, the second series become thereby connected with the former; but the advantage of the frequent repetition which had been made at Toronto as a base station was impaired, inasmuch as the connection of the second series commencing at St. Helen's is established by a single observation only in each position of the weights. On arriving at Fort William at the end of May, it was found necessary again to change the weights, because the view of the part of the circle opposite to which the needle rested was interrupted by the cross bar which supports the agate planes. In the case of L. B., the weight was now replaced in the hole in which it had been used at Toronto, and the connection of the subsequent observations with the original base station was thereby fully restored. In the case of L. A., a new weight appears to have been chosen, and as observations were made at Fort William both with the old and the new weight, the two series with this needle,—viz. before and after the change of the weight at Fort William,—have that station common to both. From the time of the embarkation in the Hudson's Bay Company's canoes at La Chine, on the 30th of April, L. A. was in constant and L. B. in occasional use. This continued until the 20th of June at Rat Portage, when the circle was accidentally thrown down, and the axle of L. A., which was mounted at the time for observation, was bent. The injury which the circle had received was repaired a few days afterwards at the Red River settlement; an endeavour was made to straighten the axle of the needle, and with so much success, that observations were occasionally made with it at subsequent stations; the same weight was used as before, but the angles of deflection were of course not comparable with the preceding ones. L. B. was now taken into daily use; and as in this needle the weight was the same as at Toronto and in the same position, the observations continued for some time forward to be directly referable to the base observations at Toronto. On arrival at York Factory the angles of deflection were again found to have become inconveniently large: a new weight was substituted, and continued in use until the 8th of August at Norway House, when the position of the weight was again changed, the angles of deflection in both positions being however observed: Norway House is thus a station common to three of the four series with this needle, and is itself directly connected with Toronto by one of the series. Observations with L. B. were continued to the close of the navigation in 1843, but were not resumed in 1844 with either of the Lloyd’s needles. Under the circumstances which have been narrated, the course which has appeared to be best suited for the deduction of the variations of the magnetic Force resulting from the observations with L. A. and L. B., has been to ascertain, in the first instance, with as much precision as possible, the ratio of the magnetic force at Norway House to that at Toronto, and to regard Norway House as a base station for those series with L. A. and L. B., which are directly connected with it. By this means the only remaining unconnected series with Lloyd’s needles is that with L. A. between St. Helen’s and Fort William; and this series has been connected with the others, by obtaining in a similar manner the value of the Force at Fort William as a base station from the observations with all the other needles. For the increase therefore of the total Force between Toronto and Norway House we have the following determinations by three independent methods: viz.— 1. **By Mr. Fox’s Method and Apparatus.** Needle F. A.—The first and apparently the best comparison with this needle is furnished by the angles of deflection observed with weights from two to four grains in natural temperatures at Toronto, on different days in January, March and April 1843, before Lieut. Lefroy’s departure to join the Hudson’s Bay Company’s boats, and the angles of deflection observed with the same weights at Norway House on the 13th July following; the observations will be found in Table XIV. From this comparison we have the force at Norway House = 1·0196 to 1 at Toronto. For a second comparison with this needle we may unite the whole of the deflec- tions observed with the weights at Toronto at different times between October 1842 and December 1844 (Tables XIII., XIV. and XVI.), and the whole of the deflections observed with the same weights at different times at Norway House, viz. on July 13, 1843; August 7, 8, 9, 1843; and September 7, 1844 (Tables XV. and XVI.). From this comparison we obtain the force at Norway House = 1·0171 to 1 at Toronto; and we may consider the mean of these two determinations, or 1·0184, as the result with F. A. Needle F. C.—By combining the angles of deflection observed with this needle at Norway House, with weights from 1·5 to 3·5 grains, on the 11th of August 1842 after the new axle had been applied to it, and repeated on the 7th of September 1844 with very small variation in the results,—with the angles observed with the same weights and the same axle at Toronto on the 14th and 17th of December 1844,—we obtain the Force at Norway House = 1·0184 to 1 at Toronto; which is precisely the same result as that deduced by needle F. A. The observations will be found in Table XVII. We may therefore regard 1·0184 as the ratio of the Force at Norway House to unity at Toronto by Mr. Fox’s method. 2. By Dr. Lloyd’s Method and Needles. L. A.—In consequence of the accident which befell this needle on the 20th of June 1843, on the route between Toronto and Norway House, the connection of the series was broken, and we can derive no aid from it for the present purpose. L. B.—With this needle we have the deflections in natural temperatures at Toronto, in January and February 1843, in Table X., and with the same weight at Norway House on the 12th of July in the same year, in Table XXII. From this comparison we obtain the force at Norway House = 1·0232 to 1 at Toronto. When Lieut. Lefroy visited Norway House in August of the same year, the observations with this weight do not appear to have been repeated; it had been considered expedient to change the weight employed in deflecting the needle at York Factory, and as the angles both with the old and new weights were observed at that station, and as nearly under the same circumstances as possible, we are furnished with the means of computing the equivalent value of \(\frac{\cos v}{\sin (v - \theta)}\) for either weight at any other station, where one of the weights only may have been employed. If then we compute this value for the old weight, from the angles with the new one which were observed at Norway House on the 7th, 8th and 11th of August 1843 (Table XXIII.), we obtain a second comparison with the original angles of deflection at Toronto, which gives the force at Norway House = 1·0185. The indirect process by which this last determination is obtained is to a certain degree a diminution of its value. On the other hand, it represents observations repeated on three different days at Norway House, whereas the first determination is from the observations of a single day only. Not feeling confident that either determination is entitled to a decided preference over the other, I have regarded the mean, 1·0208, as the most satisfactory result which I am able to derive from the observations with this needle at Toronto and Norway House; and therefore as the result by Dr. Lloyd's method. 3. By absolute measures of the Horizontal Force. The value of the horizontal force in absolute measure at Norway House is given by Lieut. Lefroy at 2·1742, derived from the experiments with two magnets in July 1843, and with three magnets in September 1844, Table XXXVIII. The Inclination observed at Norway House in 1843 and 1844 is 81° 09'·8. Hence the total magnetic force at Norway House = 14·15 in absolute measure. At Toronto we have the horizontal force 3·535 by the experiments with the three survey magnets in January, February and March 1845, Table XXXVIII. The Inclination at this period, taken to the nearest minute from the observations at the observatory, made twice in each week, is 75° 14'. Hence the total magnetic force at Toronto at that period was 13·87. If therefore the total force at Toronto be taken as unity, the ratio at Norway House is $\frac{14·15}{13·87} = 1·0205$. It is right to notice that the value of the total force at Norway House would be altered 0·027, and the ratio of the force at Toronto and Norway House ·0019 by a correction of 1' only in the observed dip; and that the uncertainty which must attach to a determination of the dip made with a single instrument, even under the most favourable circumstances, taking into account both the possibility of constant errors, and the probable observation error, can scarcely be deemed so small as 1'. Collecting then in one view the results of the three methods, we have the ratio of the total Force at Norway House as follows: - By Mr. Fox's method . . . 1·0184 to 1 at Toronto. - By Dr. Lloyd's method . . . 1·0208 to 1 at Toronto. - By absolute measure . . . 1·0205 to 1 at Toronto. As there do not appear sufficient grounds to assign a decided preference to any one of these results over the other two, and as, moreover, they are much more accordant with each other than might reasonably have been expected, we appear to be justified in taking 1·020 as probably a very near approximation to the true ratio of the total magnetic force at Norway House to unity at Toronto. If the Force at Toronto be taken at 1·836 in the arbitrary scale, then the value of the force at Norway House, in terms of the same scale, is 1·873: which has been considered the value whenever Norway House has been used as a base station. For the ratio of the total Force at Fort William we have the result of the two series of observations with F. A. at that station on the 29th of May 1843, one by Lieut. Lefroy and the other by Bombardier Henry, with the same weights which had been used at Toronto in the early part of the same year (Table XIV.); these give the value of the Force = 1·867. We have also the observations with L. B. on the same day (May 29th) at Fort William, included in the same series with the observations of the 12th of July at Norway House (Table XXII.); from these we have the Force at Fort William = 1·864. The mean of the two determinations is 1·8655; which has therefore been taken as the value whenever Fort William has been used as a base station. Tables XVIII. to XXIV. contain the several series with needles L. A. and L. B., arranged according to the base stations to which they respectively refer. The angles of deflection in these tables are always a mean of the angles in four different positions of the needle and circle; i.e. with the face of the circle turned towards the east and towards the west, and with the needle reversed on its supports so that each end should rest alternately on the opposite plane. Since Lieut. Lefroy's return to Canada from the Hudson's Bay territories, Gambev's circle has been supplied with a second pair of statical needles on Dr. Lloyd's principle. These needles were used in 1845 by Lieut. Younghusband, R.A., at four stations in Canada, and by Lieut. Lefroy at six stations in Canada and the United States; the observations are contained in Tables XXV. and XXVI. **Table XII.—Observations on the Magnetic Force with Fox's Needle F. A., made by Lieut. Lefroy in 1842 between Woolwich and Toronto.** | Station | 1842. | Angles of deflection with weights of | Temperature | Intensity | Remarks | |---------------|-------|-------------------------------------|-------------|-----------|---------| | | | 2·0 grs. | 2·5 grs. | 3·0 grs. | | | | Woolwich | July 7 | 27° 30' 0" | 35° 29' 1" | 44° 00' 9" | 53° 55" | 1·372 | Base station. | | Quebec | Sept. 1 | 20° 20' 1" | 25° 45' 8" | 31° 34' 5" | 74° | 1·829 | Royal Artillery Barracks. | | Three Rivers | | 20° 23' 0" | 25° 40' 8" | 31° 31' 4" | 66° | 1·828 | Mr. Bell's Garden. | | Sorel | | 20° 30' 8" | 25° 57' 6" | 31° 36' 1" | 61° | 1·817 | Bank E. of the Roman Catholic Church. | | Kingsley | | 20° 35' 8" | 26° 00' 3" | 31° 47' 8" | 60° | 1·810 | Captain Cox's Garden. | | Stanstead | | 20° 38' 6" | 26° 06' 1" | 32° 06' 1" | 60° | 1·801 | Garden of the Hotel near the Church. | | St. Helen's | | 20° 32' 5" | 25° 51' 7" | 31° 48' 3" | 59° | 1·813 | 100 yards S.S.W. of the Barracks. | | New York | | 21° 01' 6" | 26° 46' 0" | 32° 39' 2" | 71° | 1·771 | Lunatic Asylum, Manhattanville. | | Providence | | 20° 45' 8" | 26° 39' 1" | 32° 32' 2" | 75° | 1·783 | Steam-boat landing. | | Cambridge | Oct. 3 | 20° 50' 7" | 26° 34' 5" | 32° 30' 1" | 63° | 1·779 | Garden of the Observatory. | | Philadelphia | | 20° 31' 1" | 26° 19' 7" | 32° 22' 2" | 62° | 1·795 | Girard College. | | Baltimore | | 20° 51' 6" | 26° 22' 2" | 32° 26' 5" | 62° | 1·784 | Washington's Monument N. 42° E., distant 400 yards. | | Washington | | 20° 54' 8" | 26° 38' 1" | 32° 41' 1" | 63° | 1·774 | In the grounds west of the Capitol. | | Princeton | | 20° 53' 0" | 26° 23' 1" | 32° 18' 0" | 62° | 1·785 | Field 200 yards east of the College. | | Newhaven | | 20° 00' 5" | 26° 33' 5" | 32° 39' 4" | 67° | 1·775 | In an open space in Grove Street. | | West Point | | 20° 32' 8" | 26° 03' 6" | 31° 44' 5" | 54° | 1·809 | Professor Bartlett's Garden. | | Albany | | 20° 38' 9" | 26° 12' 0" | 32° 00' 5" | 55° | 1·799 | Hill between Orange and Patroon Streets. | | Toronto | | 20° 12' 3" | 25° 34' 8" | 31° 19' 7" | 57° | 1·838 | Magnetic Observatory. | **Note.—**The Force at Toronto having been finally taken at 1·836 (p. 244 to 247), the values given in this Table for the stations in Canada and the United States require to be diminished by '002, and have accordingly been so diminished in Table XXVII., in which the several determinations with the statical needles are collected in one view. ### Table XIII. Observations with Needle F. A., by Lieut. Younghusband, R.A., in November 1842. | Station | Angles of deflection with weights of | Temperature | Intensity | Remarks | |---------------|-------------------------------------|-------------|-----------|--------------------------| | | 1·5 gr. | 2·0 grs. | 2·5 grs. | | | | Toronto | Oct. 29. | 21 14·6 | 27 00·5 | 33 11·6 | 53 43 | 1·836 Base station. | | | Dec. 30. | 21 18·5 | 27 08·0 | 33 08·2 | | | | Cleveland | Nov. 3. | 21 34·4 | not observed | 33 58·3 | 56 1·807 | Inland from the Wharf. | | Detroit | 4. | 21 23·4 | 27 12·3 | 33 25·8 | 47 1·826 | 40 yards from the Wharf. | | S. Manitou Island | | 7. | 21 15·5 | 26 55·8 | 32 55·0 | 1·846 40 yards from the Wharf. | | Chicago | 15. | 21 26·7 | 27 14·1 | 33 26·4 | 47 1·823 | Dr. Eldridge's Garden. | | | 16. | 21 29·7 | 27 12·7 | 33 25·1 | 47 | | ### Table XIV. Observations on the Magnetic Force with Fox’s Needle F. A., between Toronto and Norway House, from January 1844 to July 1844. | Station | Angles of deflection with weights of | Temperature | Intensity | Remarks | |------------------|-------------------------------------|-------------|-----------|--------------------------| | | 2·0 grs. | 2·5 grs. | 3·0 grs. | 3·5 grs. | 4·0 grs. | Thermometer | Intensity. | | | | | | | | | Toronto = 1·836. | | Toronto | Jan. 4. | 21 09·9 | 26 52·2 | 33 05·0 | | | 26 | | | 4. | 21 08·8 | 26 45·9 | 33 02·8 | | | 27 | | | 12. | 21 12·3 | 27 04·2 | 33 21·6 | | | 46 45·4 | 36 | | | 12. | 21 21·8 | 27 00·3 | 33 15·2 | | | 46 42·1 | 35 | | | 12. | | | 33 14·8 | | | 34 | | | 14. | 21 09·4 | 26 53·1 | | | | 30 | | | 14. | 21 12·6 | 26 58·8 | | | | 27 | | | 16. | 21 10·0 | 27 08·4 | 33 07·4 | | | 46 41·4 | 34 | | March 8. | 21 14·7 | 27 16·6 | 32 59·7 | 39 34·4 | 46 42·5 | | 60 | | | 8. | 27 16·1 | 33 06·1 | | 46 42·1 | | 59 | | | 9. | 21 17·6 | 27 06·1 | 33 05·0 | | | 46 42·7 | 60 | | April 6. | 26 57·6 | 33 06·0 | 39 22·0 | 46 57·9 | | | 46 | | | 7. | 27 08·3 | 33 12·0 | 39 24·5 | 46 53·0 | | 59 | | Mean. | 21 13·0 | 27 02·3 | 33 08·7 | 39 27·0 | 46 45·9 | | 46 1·836 | Base station. | | St Helen’s | April 25. | 27 21·9 | 33 21·4 | 39 58·9 | | | 54 | 1·821 | | Isle d’Urval | 30. | 27 27·2 | 33 37·0 | 40 30·9 | 47 55·0 | | 47 | 1·805 | | La Combes | May 2. | 26 44·2 | 33 23·2 | 39 43·5 | 47 05·4 | | 48 | 1·833 | | Pte aux Chênes | 3. | 27 47·2 | 33 47·7 | 40 43·0 | 47 54·8 | | 56 | 1·800 | | Foxes Point | 4. | 27 10·3 | 32 56·0 | 39 35·2 | 46 42·2 | | 50 | 1·837 | | Chat Falls | 6. | 26 49·1 | 33 03·8 | 39 15·2 | 46 33·6 | | 53 | 1·846 | | Grand Calumet | 7. | 27 24·9 | 33 29·6 | 40 01·4 | 47 05·1 | | 74 | 1·826 | | Fort Coulonge | 8. | 26 47·2 | 33 01·8 | 39 31·0 | 47 10·5 | | 55 | 1·841 | | Pte Baptême | 9. | 27 22·2 | 33 24·1 | 40 00·2 | 47 13·4 | | 57 | 1·822 | | Deux Joachims Portage | 10. | 27 22·0 | 33 31·8 | 40 02·7 | 46 56·9 | | 74 | 1·827 | | Trou Portage | 11. | 27 07·5 | 33 12·6 | 39 36·7 | 46 48·3 | | 80 | 1·842 | | Little River | 12. | 21 10·7 | 27 10·1 | 32 47·6 | 39 49·6 | 46 23·2 | 78 | 1·836 | | L. du Grand Vase| 13. | 26 44·0 | 33 02·9 | 39 53·7 | 47 08·6 | | 72 | 1·843 | | Ricolet Falls | 15. | 26 21·0 | 32 55·8 | 38 31·4 | 45 44·2 | | 61 | 1·871 | | Pte au Croix | 16. | 26 14·6 | 32 52·7 | 39 40·6 | 46 35·4 | | 49 | 1·852 | ## OBSERVATIONS OF THE MAGNETIC FORCE. ### TABLE XIV. (Continued.) | Station | 1843 | Angles of deflection with weights of | Thermometer | Intensity. | |--------------------------|------|-------------------------------------|-------------|------------| | | | 2·0 grs. | 2·5 grs. | 3·0 grs. | 3·5 grs. | 4·0 grs. | Toronto = 1·836. | | Lake Huron | May 17 | 27 10·3 | 33 13·3 | 39 17·2 | 46 51·6 | 59 | 1·838 | | Snake Island | 18 | 27 39·5 | 33 13·0 | 39 58·2 | 46 33·7 | 68 | 1·829 | | Tessalon Point | 19 | 26 49·8 | 32 22·7 | 39 38·2 | 46 12·3 | 69 | 1·860 | | Pointe aux Pins | 20 | 26 37·2 | 32 09·3 | 39 29·2 | 46 16·4 | 70 | 1·867 | | Pte au Crêpe | 21 | 26 00·4 | 31 30·6 | 38 04·8 | 44 36·7 | 73 | 1·910 | | Fort Michipicoton | 23 | 26 29·5 | 32 56·9 | 38 57·8 | 46 37·1 | 40 | 1·851 | | Otter Island | 24 | 27 32·5 | 34 06·0 | 40 43·8 | 49 08·7 | 52 | 1·790 | | Pic Fort | 25 | 27 14·5 | 33 06·4 | 38 52·5 | 47 22·9 | 66 | 1·841 | | Terreplatte | 27 | 27 06·4 | 32 28·4 | 39 21·6 | 45 42·5 | 45 | 1·853 | | Pointe Tonnerre | 28 | 25 56·5 | 31 58·3 | 38 20·8 | 46 19·9 | 58 | 1·890 | | Fort William | 29 | 26 40·4 | 32 22·8 | 38 51·8 | 46 05·0 | 73 | 1·867 | | Portage Ecarté | June 2 | 26 38·6 | 32 40·8 | 39 26·8 | 46 14·9 | 48 | 1·852 | | Chien Portage | 3 | 26 31·9 | 32 27·7 | 38 45·1 | 45 43·9 | 47 | 1·868 | | Prairie Portage | 5 | 26 38·2 | 32 42·1 | 39 03·6 | 46 09·1 | 56 | 1·859 | | Savannah Portage | 6 | 26 42·6 | 32 39·8 | 38 51·2 | 45 52·9 | 65 | 1·866 | | French Portage | 7 | 26 40·3 | 32 42·3 | 39 00·5 | 46 04·5 | 60 | 1·861 | | Portage des deux Rivières| 8 | 26 32·0 | 32 32·1 | 39 04·0 | 46 04·2 | 57 | 1·864 | | Lac à la Crosse | 10 | 26 39·0 | 32 39·0 | 39 16·6 | 46 11·1 | 61 | 1·859 | | 2nd Portage from ditto | 11 | 26 53·4 | 32 53·9 | 39 07·7 | 46 16·3 | 69 | 1·855 | | Sturgeon Lake | 12 | 26 34·8 | 32 31·8 | 39 10·1 | 46 04·8 | 68 | 1·866 | | Lac la Pluie | 13 | 26 32·5 | 32 49·8 | 39 02·5 | 46 02·8 | 55 | 1·861 | | Fort Francis | 14 | 26 50·8 | 32 50·3 | 39 24·8 | 46 05·9 | 62 | 1·853 | | Rainy River | 16 | 26 16·3 | 32 03·0 | 38 22·0 | 45 26·3 | 64 | 1·890 | | Lake of the Woods | 17 | 26 36·6 | 32 36·8 | 38 59·6 | 45 52·2 | 67 | 1·871 | | Lake of the Woods | 18 | 26 44·4 | 32 48·0 | 38 58·8 | 46 20·0 | 82 | 1·864 | | Rat Portage | 20 | 26 48·2 | 32 47·2 | 39 18·5 | 46 07·6 | 67 | 1·858 | | Winnipeg River | 22 | 26 23·9 | 32 30·7 | 38 50·4 | 45 38·3 | 71 | 1·877 | | Slave Portage | 23 | 26 34·7 | 32 44·3 | 39 21·3 | 46 16·3 | 87 | 1·867 | | Fort Alexander | 25 | 26 50·5 | 32 47·4 | 39 35·3 | 46 05·7 | 78 | 1·857 | | Lake Winnipeg | 26 | 26 38·6 | 32 37·0 | 39 05·5 | 46 11·3 | 80 | 1·867 | | Upper Fort Garry | 29 | 26 39·4 | 32 38·9 | 39 17·5 | 46 12·2 | 72 | 1·861 | | Upper Fort Garry | July 3 | 26 51·2 | 32 40·8 | 39 13·7 | 46 07·7 | 84 | 1·861 | | Mouth of the Red River | 4 | 26 44·6 | 32 42·9 | 39 07·0 | 46 06·5 | 66 | 1·861 | | Lake Winnipeg | 5 | 26 42·8 | 32 42·2 | 39 07·2 | 46 20·9 | 66 | 1·859 | | Lake Winnipeg | 6 | 25 53·2 | 31 44·2 | 37 56·4 | 44 49·8 | 61 | 1·909 | | Lake Winnipeg | 7 | 26 19·9 | 31 46·1 | 38 02·5 | 44 46·0 | 69 | 1·904 | | Lake Winnipeg | 8 | 26 15·4 | 32 20·4 | 38 16·6 | 46 25·0 | 66 | 1·880 | | Lake Winnipeg | 10 | 26 08·9 | 33 04·3 | 38 47·3 | 46 28·9 | 65 | 1·862 | | Lake Winnipeg | 10 | 26 45·9 | 33 04·2 | 39 28·4 | 45 52·5 | 71 | 1·862 | | Norway House | 13 | 26 41·0 | 32 14·4 | 39 08·3 | 45 36·9 | 70 | 1·872 | Commencing with the 12th of May at Little River, these observations were made by Bombardier Henry, R.A., except where L. is inserted in the column of remarks. ### Table XV. Observations on the Magnetic Force with Fox's Needle F.A., between Norway House and Athabasca, from July 1843 to October 1843; observer, Bombardier Henry, R.A. | Station | 1843. | Angles of deflection with weights of | Thermometer. | Intensity. | Remarks | |--------------------------|-------|-------------------------------------|--------------|------------|---------| | | | 2° grs. | 2° grs. | 3° grs. | 3° grs. | 4° grs. | Toronto = 1°836. | | Norway House | | | | | | | | | July 13. | | 26 41°-0 | 32 14°-4 | 39 08°-3 | 45 36°-9 | 70 | | | Aug. 7 | | 20 45°-3 | 26 41°-9 | 32 45°-9 | 39 08°-9 | 45 57°-1 | 81 | | | | 20 59°-8 | 26 39°-3 | 33 17°-6 | 39 20°-0 | 45 56°-7 | 82 | | | | 20 35°-7 | 26 53°-2 | 32 56°-8 | 39 24°-1 | 46 31°-1 | 85 | | Mean | | 20 45°-6 | 26 44°-3 | 32 48°-7 | 39 15°-3 | 46 00°-5 | 79 | 1°873 | | | | | | | | | Base. | | Long Portage | July 20. | 26 52°-4 | 32 19°-4 | 38 48°-1 | 45 40°-4 | 64 | 1°880 | | Long Portage | Aug. 2. | 26 50°-0 | 32 22°-9 | 39 41°-9 | 45 45°-3 | 71 | 1°869 | | White Earth Portage | July 21. | 26 47°-0 | 32 00°-5 | 39 34°-2 | 46 58°-7 | 81 | 1°862 | | White Earth Portage | 31. | 27 11°-7 | 32 23°-1 | 38 46°-2 | 46 29°-2 | 59 | 1°857 | | Shamatawa | 22. | 26 43°-9 | 33 35°-2 | 39 56°-8 | 47 09°-6 | 63 | 1°875 | | Shamatawa | 23. | 26 32°-5 | 32 57°-5 | 38 19°-9 | 45 57°-7 | 70 | 1°870 | | York Factory | 24. | 26 57°-3 | 32 30°-3 | 39 05°-0 | 46 59°-1 | 70 | 1°861 | | York Factory | 25. | 27 13°-0 | 33 16°-5 | 39 44°-1 | 45 55°-0 | 56 | 1°869 | | Hill River | Aug. 1. | 26 42°-0 | 32 31°-6 | 39 06°-1 | 45 57°-0 | 66 | 1°879 | | Oxford House | 3. | 26 56°-6 | 32 01°-3 | 38 35°-4 | 45 11°-3 | 66 | 1°870 | | Windy Lake | 4. | 26 20°-4 | 32 30°-8 | 39 17°-8 | 46 07°-5 | 76 | 1°879 | | Whitefall Portage | 5. | 26 41°-4 | 32 32°-2 | 39 19°-3 | 45 45°-3 | 82 | 1°865 | | Hairy Lake | 6. | 21 00°-6 | 32 54°-1 | 39 18°-9 | 46 09°-9 | 73 | 1°869 | | Lake Winnipeg | 14. | 26 49°-7 | 32 51°-2 | 38 46°-0 | 46 05°-9 | 70 | 1°872 | | Grand Rapid | 15. | 26 54°-9 | 32 29°-6 | 38 47°-9 | 46 07°-6 | 67 | 1°874 | | Cross Lake | 16. | 26 38°-4 | 32 33°-8 | 38 51°-6 | 46 20°-7 | 68 | 1°875 | | Cedar Lake | 18. | 26 51°-0 | 32 22°-6 | 39 29°-0 | 46 15°-0 | 74 | 1°871 | | Cumberland House | 23. | 26 56°-9 | 32 35°-4 | 39 24°-4 | 46 12°-7 | 62 | 1°865 | | Cumberland House | 24. | 26 45°-4 | 32 33°-6 | 39 22°-4 | 46 12°-8 | 55 | 1°869 | | Beaver Lake | 26. | 26 42°-3 | 32 50°-4 | 38 37°-7 | 46 41°-1 | 64 | 1°871 | | Portage des Epinettes | 27. | 26 33°-3 | 32 35°-0 | 39 02°-4 | 46 18°-8 | 56 | 1°870 | | Frog Portage | 29. | 26 28°-6 | 33 17°-1 | 39 23°-4 | 46 49°-4 | 58 | 1°875 | | Little Rock Portage | 31. | 24 48°-0 | 30 28°-7 | 35 54°-1 | 43 01°-4 | 64 | 1°857 | | Great Devil's Portage | Sept. 1. | 26 43°-2 | 32 39°-6 | 39 11°-9 | 46 57°-0 | 72 | 1°858 | | Great Devil's Portage | 1. | 26 00°-3 | 32 42°-1 | 38 40°-0 | 46 32°-6 | 67 | 1°875 | | Pine Portage | 3. | 26 00°-3 | 32 42°-1 | 38 40°-0 | 46 32°-6 | 67 | 1°884 | | Snake Rapid | 4. | 26 22°-0 | 32 43°-3 | 38 40°-4 | 46 40°-0 | 54 | 1°874 | | Portage Sonnante | 7. | 26 39°-4 | 33 01°-2 | 39 12°-1 | 46 50°-1 | 52 | 1°858 | | Isle à la Crosse | 9. | 26 38°-2 | 33 12°-2 | 38 56°-8 | 47 20°-7 | 64 | 1°857 | | Isle à la Crosse | 9. | 26 42°-5 | 33 18°-2 | 38 57°-0 | 47 18°-6 | 70 | 1°854 | | Buffaloe Lake | 13. | 26 58°-5 | 33 16°-0 | 39 05°-0 | | 54 | 1°854 | | River de la Loche | 14. | 27 21°-7 | 34 04°-8 | 40 09°-0 | 47 20°-9 | 70 | 1°826 | | Portage de la Loche | 16. | 26 54°-4 | 33 11°-8 | 40 02°-8 | 48 14°-8 | 60 | 1°835 | | Clearwater River | 19. | 26 56°-6 | 33 13°-6 | 39 12°-9 | 46 30°-3 | 44 | 1°850 | | Pierre au Calumet | 20. | 25 20°-3 | 31 33°-6 | 37 14°-1 | 44 46°-6 | 55 | 1°938 | | Pointe Brulée | 21. | 27 16°-5 | 33 11°-5 | 38 32°-8 | 46 35°-8 | 43 | 1°852 | | Athabasca | 25. | 27 06°-0 | 33 43°-4 | 39 53°-8 | 47 39°-1 | 44 | 1°828 | | Athabasca | 25. | 27 03°-3 | 33 28°-0 | 39 58°-9 | 47 52°-3 | 44 | 1°828 | | Athabasca | Oct. 9. | 26 48°-7 | 33 45°-7 | 39 55°-5 | 47 34°-5 | 36 | ### Table XVI. Observations on the Magnetic Force with Fox’s Needle F. A., between Athabasca and Toronto, from July 12th, 1844, to December 17th, 1844: Observer, Bombardier Henry, R.A. | Station | 1844. | Angles of deflection with weights of | Temp. | Intensity. | |------------------|-------|-------------------------------------|-------|------------| | | | 2·5 grs. | 3·0 grs. | 3·5 grs. | 4·0 grs. | 4·5 grs. | Toronto=1·836. | | Toronto | Dec. 14. | 26 52·6 | 33 18·4 | 39 16·6 | 46 39·2 | 54 25·6 | 41 | | | Dec. 17. | 26 40·8 | 33 02·4 | 39 13·7 | 46 42·1 | 54 33·1 | 32 | | Mean. | | 26 46·7 | 33 10·4 | 39 15·2 | 46 45·5 | 54 29·3 | 36·5 | 1·836 | | Fort Vermilion | July 12. | 27 20·1 | 33 51·3 | 40 07·0 | 47 44·8 | 56 10·7 | 68 | 1·811 | | Fort Dunvegan | | 23 27 06·6 | 33 47·8 | 40 15·5 | 47 57·1 | 56 03·4 | 54 | 1·809 | | Fort Edmonton | Aug. 17. | 27 19·7 | 33 47·2 | 40 03·0 | 47 21·5 | 55 26·0 | 38 | 1·809 | | Cumberland House | | 30 26 37·0 | 32 56·8 | 38 59·0 | 46 24·9 | 54 06·2 | 61 | 1·853 | | Norway House | Sept. 7. | 26 22·9 | 32 54·3 | 38 53·6 | 46 29·2 | 54 09·6 | 60 | 1·858 | ### Table XVII. Observations on the Magnetic Force with Fox’s Needle F. C., between Norway House in August 1843, and Toronto in December 1844. | Station | 1844. | Angles of deflection with weights of | Temp. | Intensity. | |------------------|-------|-------------------------------------|-------|------------| | | | 1·5 gr. | 2·0 grs. | 2·5 grs. | 3·0 grs. | 3·5 grs. | Toronto=1·836. | | Toronto | Dec. 14. | 19 43·6 | 27 23·0 | 34 48·5 | 43 42·4 | 53 56·8 | 40 | | | Dec. 17. | 19 47·1 | 27 17·7 | 34 47·5 | 43 42·5 | 53 55·0 | 32 | | Mean. | | 19 45·3 | 27 20·4 | 34 48·0 | 43 42·4 | 53 55·9 | 36 | 1·836 | | Norway House | 1843. | Aug. 11. | 19 32·2 | 26 54·5 | 34 12·0 | 42 39·3 | 52 33·0 | 56 | | | 1844. | Sept. 7. | 19 33·8 | 26 50·3 | 34 20·0 | 43 09·4 | 52 11·3 | 56 | | Means. | | 19 33·0 | 26 52·4 | 34 16·0 | 42 54·3 | 52 22·1 | 56 | 1·870 | ### Table XVIII.—Observations on the Magnetic Force with Lloyd's Needle L. A., from St. Helen's (in Canada) to Fort William, in April and May 1843. | Station | 1843 | Angles of deflection | Temp. | Inclination | Intensity. | Remarks | |--------------------------|---------------|----------------------|-------|-------------|------------|---------| | | | | | | Toronto=1·836 | | | Fort William | May 29. | 9° 37'7" | 70° | | | | | | | 9° 41'1" | 56° | | | | | Mean.. | | 9° 39'4" | 63° | 78° 10° | 1·8655 | Base station. | | St. Helen's | April 25. | -15° 06'1" | 60° | 77° 05'5" | 1·826 | | | Isle d'Urval | 30. | -16° 26'9" | 45° | 77° 21'1" | 1·817 | | | La Combes | May 2. | -14° 35'6" | 49° | 76° 50'6" | 1·829 | | | Pte aux Chênes | 3. | -17° 10'0" | 49° | 76° 55'4" | 1·810 | | | Point Aylmer | 5. | -15° 05'8" | 52° | 76° 41'0" | 1·825 | | | Fort Coulange | 8. | -12° 13'8" | 53° | 77° 29'7" | 1·847 | | | Deux Joachims Portage | 10. | -14° 04'9" | 70° | 77° 03'8" | 1·834 | | | Trou Portage | 11. | -13° 24'5" | 87° | 77° 24'4" | 1·840 | | | Little River | 12. | -13° 12'6" | 69° | 77° 28'5" | 1·841 | | | L. du Grand Vase | 13. | -12° 05'2" | 86° | 77° 21'7" | 1·849 | | | Lake Nipissing | 14. | -13° 48'0" | 64° | 77° 09'5" | 1·836 | | | Ricolet Falls | 15. | -9° 15'7" | 60° | 76° 45'4" | 1·870 | | | Pte au Croix | 16. | -11° 41'0" | 50° | 76° 31'3" | 1·852 | | | Lake Huron | 17. | -12° 57'3" | 51° | 77° 05'6" | 1·843 | | | Snake Island | 18. | -13° 41'2" | 68° | 77° 05'5" | 1·837 | | | Tessalon Point | 19. | -12° 42'3" | 52° | 76° 59'3" | 1·844 | | | Pointe aux Pins | 20. | -11° 02'4" | 70° | 77° 13'4" | 1·858 | | | Pointe au Crêpe | 21. | -12° 47'4" | 63° | 77° 11'5" | 1·844 | | | Michipicoton | 23. | -10° 26'4" | 46° | 78° 06'3" | 1·859 | | | Otter Island | 24. | -18° 20'8" | 51° | 79° 43'6" | 1·812 | | | Pic Fort | 25. | -11° 46'6" | 58° | 78° 45'8" | 1·851 | | | Terreplatte | 27. | -11° 02'6" | 48° | 78° 53'6" | 1·855 | | | Pointe Tonnerre | 28. | -10° 02'7" | 55° | 78° 23'2" | 1·862 | | ### Table XIX.—Observations on the Magnetic Force with Lloyd's Needle L. A., between Fort William and Rat Portage (where the needle met with an accident) in the months of May and June 1843. | Station | 1843 | Angles of deflection | Temperature. | Inclination | Intensity. | Remarks | |--------------------------|---------------|----------------------|--------------|-------------|------------|---------| | | | | | | Toronto=1·836 | | | Fort William | May 29. | -17° 09'6" | 53° | | | | | | 29. | -17° 09'9" | 53° | | | | | Mean.. | | -17° 09'75" | 53° | 78° 10° | 1·8655 | Base station. | | Portage Ecarté | June 2. | -18° 38'2" | 52° | 77° 13'5" | 1·852 | | | Chien Portage | 3. | -17° 41'4" | 47° | 78° 26'8" | 1·863 | | | Prairie Portage | 5. | -18° 34'4" | 53° | 78° 26'2" | 1·857 | | | Savannah Portage | 6. | -16° 52'4" | 60° | 78° 21'8" | 1·869 | | | French Portage | 8. | -18° 01'6" | 60° | 78° 20'4" | 1·860 | | | Portage des deux Rivières.| 9. | -17° 41'8" | 58° | 77° 49'4" | 1·861 | | | Lac à la Crosse | 10. | -17° 41'9" | 58° | 77° 51'0" | 1·861 | | | 2nd Portage from the Lake.| 11. | -18° 27'5" | 72° | 77° 40'1" | 1·855 | | | Sturgeon Lake | 12. | -18° 08'2" | 66° | 77° 44'8" | 1·857 | | | Lac la Pluie | 13. | -18° 12'5" | 60° | 77° 47'9" | 1·857 | | | Fort Francis | 14. | -17° 48'3" | 63° | 77° 28'0" | 1·859 | | | Rainy River | 16. | -11° 20'6" | 66° | 77° 57'4" | 1·906 | | | Lake of the Woods | 17. | -17° 27'2" | 65° | 78° 03'7" | 1·863 | | | Lake of the Woods | 18. | -19° 51'6" | 79° | 78° 16'7" | 1·847 | | ### Table XX. Observations on the Magnetic Force with Lloyd's Needle L. A. (after the axle had been straightened), between Upper Fort Garry on the 3rd of July 1843, and Lake Winnipeg on the 14th of August 1843. | Station | 1843. | Angles of deflection. | Temperature. | Inclination. | Intensity. | Remarks | |------------------|-------|-----------------------|--------------|--------------|------------|---------| | Norway House | | | | | | | | | July 12. | -9 12·8 | 68 | | | | | | 13. | -9 31·9 | 76 | | | | | | Aug. 8. | -11 17·5 | 80 | | | | | | 9. | -11 49·4 | 84 | | | | | | 11. | -10 45·4 | 56 | | | | | | Mean | -10 31·4 | 73 | 81 09·8 | 1·873 | Base station. | | Upper Fort Garry | July 3. | -12 45·6 | 78 | 78 17·8 | 1·857 | | | Lake Winnipeg | 10. | -11 36·0 | 69 | 80 05·5 | 1·866 | | | Long Portage | 20. | -9 18·0 | 87 | 82 13·9 | 1·880 | | | Long Portage | Aug. 2. | -9 13·0 | 71 | | | | | York Factory | July 24.| -18 46·7 | 80 | | | | | York Factory | 25. | -18 07·7 | 73 | | | | | Oxford House | Aug. 3.| 11 48·0 | 60 | 82 38·8 | 1·869 | | | Windy Lake | 4. | 11 19·0 | 71 | 81 57·0 | 1·870 | | | Whitefall Portage| 5. | 13 47·0 | 79 | 81 47·9 | 1·858 | | | Old Norway House | 12. | 10 35·0 | 65 | 80 45·4 | 1·872 | | | Lake Winnipeg | 14. | 13 53·0 | 64 | 80 16·8 | 1·853 | | ### Table XXI. Observations on the Magnetic Force with Lloyd's Needle L. B., between St. Helen's in Canada on the 25th of April 1843, and Fort William on the 29th of May 1843. | Station | 1843. | Angles of deflection. | Temperature. | Inclination. | Intensity. | Remarks | |------------------|-------|-----------------------|--------------|--------------|------------|---------| | Fort William | May 29.| -3 25·9 | 80 | 78 16 | 1·8655 | Base station. | | St. Helen's | April 25.| -11 00·7 | 60 | 77 05·5 | 1·812 | | | Isle d'Urval | 30. | -13 15·2 | 45 | 77 21·1 | 1·796 | | | Foxes Point | May 4. | -9 05·0 | 51 | 76 35·3 | 1·827 | | | Chat Falls | 6. | -8 34·0 | 50 | 75 16·1 | 1·835 | | | Pointe aux Pins | 20. | -4 28·6 | 70 | 77 13·4 | 1·861 | | ### Table XXII. Observations on the Magnetic Force with Lloyd’s Needle L. B., between Williamsburg in Canada on the 20th of April 1843, and York Factory on the 25th of July 1843. | Station | 1843 | Angles of deflection | Temperature | Inclination | Intensity. | Remarks | |--------------------------|---------------|----------------------|-------------|-------------|------------|---------------| | Norway House | July 12 | -39° 16' 0" | 7° | 81° 09' 8" | 1·873 | Base station. | | Williamsburg | April 20 | -34° 23' 0" | 55 | 76° 30' 0" | 1·841 | | | St. Helen's | 25 | -36° 06' 7" | 52 | 77° 05' 0" | 1·831 | | | Fort William | May 29 | -34° 08' 1" | 55 | 78° 10' 0" | 1·864 | | | Fort William | 29 | -34° 03' 5" | 56 | 77° 28' 0" | 1·846 | | | Fort Francis | June 14 | -35° 18' 2" | 57 | 77° 57' 4" | 1·890 | | | Rainy River | 16 | -31° 08' 4" | 68 | 78° 17' 8" | 1·867 | | | Upper Fort Garry | July 3 | -34° 18' 5" | 78 | 78° 32' 6" | 1·866 | | | Mouth of the Red River | 4 | -34° 37' 5" | 64 | 79° 11' 8" | 1·866 | | | Lake Winnipeg | 5 | -35° 50' 3" | 70 | 79° 38' 0" | 1·915 | | | Lake Winnipeg | 6 | -30° 11' 1" | 59 | 79° 38' 0" | 1·904 | | | Lake Winnipeg | 7 | -31° 26' 5" | 67 | 79° 28' 3" | 1·869 | | | Lake Winnipeg | 10 | -37° 10' 1" | 66 | 80° 05' 5" | 1·869 | | | Long Portage | 20 | -41° 15' 7" | 87 | 82° 13' 9" | 1·881 | | | White Earth Portage | 21 | -47° 17' 0" | 84 | 83° 03' 0" | 1·857 | | | Shamatawa | 23 | -48° 22' 0" | 64 | 83° 36' 0" | 1·863 | | | York Factory | 24 | -50° 16' 6" | 85 | 83° 47' 0" | 1·853 | | | York Factory | 25 | -50° 44' 8" | 47 | 83° 47' 0" | 1·853 | | ### Table XXIII. Observations on the Magnetic Force with Lloyd’s Needle L. B., between York Factory on the 26th of July 1843, and Norway House on the 11th of August 1843. | Station | 1843 | Angles of deflection | Temperature | Inclination | Intensity. | Remarks | |--------------------------|---------------|----------------------|-------------|-------------|------------|---------------| | Norway House | Aug. 7 | +13° 39' 0" | 77° | 81° 09' 8" | 1·873 | Base station. | | | 8 | +12° 39' 0" | 81 | | | | | | 11 | +14° 45' 0" | 58 | | | | | Mean | +13° 41' 0" | 72 | 81° 09' 8" | 1·873 | | | | York Factory | July 26 | +19° 00' 2" | 75 | 83° 47' 0" | 1·861 | | | York Factory | 26 | +18° 55' 9" | 74 | 83° 36' 0" | 1·858 | | | Shamatawa | 28 | +17° 58' 0" | 65 | 83° 03' 0" | 1·855 | | | White Earth Portage | 31 | +15° 20' 0" | 58 | 82° 55' 0" | 1·867 | | | Hill River | Aug. 1 | +17° 41' 0" | 65 | 82° 13' 9" | 1·872 | | | Long Portage | 2 | +16° 21' 0" | 80 | 82° 38' 8" | 1·874 | | | Oxford House | 3 | +18° 16' 8" | 68 | 82° 38' 8" | 1·870 | | | Whitefall Portage | 5 | +14° 31' 8" | 78 | 81° 47' 9" | 1·870 | | | Hairy Lake | 6 | +11° 12' 2" | 75 | 81° 20' 9" | 1·857 | | ### Table XXIV. Observations on the Magnetic Force with Lloyd's Needle L.B., between Norway House on the 11th of August 1843, and Athabasca on the 20th of October 1843. | Station | 1843 | Angles of deflection | Temperature | Inclination | Intensity. Toronto = 1·836 | Remarks | |------------------------|---------------|----------------------|-------------|------------|---------------------------|---------| | Norway House ..........| Aug. 11 | -26° 12' 0" | 68 | | | | | | | -25° 17' 0" | 58 | | | | | Mean | | -25° 44' 5" | 63 | 81° 09' 8" | 1·873 | Base station. | | Old Norway House ......| Aug. 12 | -24° 28' 0" | 66 | 80° 45' 4" | 1·877 | | | Lake Winnipeg ..........| | -26° 26' 0" | 68 | 80° 16' 8" | 1·860 | | | Grand Rapid ...........| | -24° 02' 0" | 60 | 80° 21' 5" | 1·876 | | | Cross Lake ............| | -23° 59' 0" | 58 | 80° 28' 2" | 1·877 | | | Cumberland House ......| | -25° 24' 0" | 55 | 80° 30 | 1·868 | | | Cumberland House ......| | -25° 03' 0" | 55 | 80° 09' 8" | 1·845 | | | Isle à la Crosse ......| Sept. 9 | -28° 18' 0" | 55 | 80° 09' 8" | 1·845 | | | Isle à la Crosse ......| | -28° 20' 0" | 51 | 80° 09' 8" | 1·845 | | | Athabasca .............| Oct. 20 | -29° 33' 0" | 50 | 80° 09' 8" | 1·845 | | | Athabasca .............| | -30° 57' 0" | 50 | 80° 09' 8" | 1·845 | | | Athabasca .............| | -30° 41' 0" | 37 | 81° 37' 7" | 1·849 | | | Athabasca .............| | -30° 07' 0" | 32 | 81° 37' 7" | 1·849 | | ### Table XXV. Observations on the Magnetic Force at Stations in Canada with Lloyd's Needles L.C. and L.D., in June and July 1845, by Lieut. Younghusband, R.A. | Station | 1845 | Needle | Mean angle of deflection | Thermometer | Inclination | Intensity. Toronto = 1·836 | Remarks | |------------|------|--------|--------------------------|-------------|------------|---------------------------|---------| | Toronto | | | | | | | | | June 3. C. | | -17° 28' 2" | 62° | | | | | | 3. C. | | -17° 38' 6" | 68 | | | | | | 4. C. | | -17° 34' 8" | 64 | | | | | | 4. C. | | -17° 32' 7" | 69 | | | | | | 5. C. | | -17° 28' 4" | 61 | | | | | | July 7. C. | | -17° 35' 0" | 75 | | | | | | 7. C. | | -17° 32' 3" | 73 | | | | | | Mean.. C. | | -17° 32' 9" | 67 | 75° 13' 0" | 1·836 | | | | June 3. D. | | -13° 50' 4" | 64 | | | | | | 3. D. | | -13° 58' 9" | 67 | | | | | | 4. D. | | -13° 38' 9" | 66 | | | | | | 4. D. | | -13° 34' 7" | 68 | | | | | | 5. D. | | -13° 28' 5" | 63 | | | | | | July 7. D. | | -13° 44' 9" | 76 | | | | | | 7. D. | | -13° 35' 2" | 72 | | | | | | Mean.. D. | | -13° 41' 8" | 68 | 75° 13' 0" | 1·836 | | | | Brockville | | -20° 57' 1" | 72 | 76° 18' 9" | 1·812 | Garden at Rockfort. | | | Cornwall | | -16° 52' 1" | 83 | 76° 16' 4" | 1·822 | Orchard behind Chesleys. | | | Montreal | | -15° 17' 5" | 66 | 77° 08' 6" | 1·788 | Garden on the mountain. | | | Quebec | | -22° 39' 6" | 70 | 77° 08' 8" | 1·801 | Near Wolfe's monument. | | Corrections have been made for the variations of temperature; the coefficient q in these needles is '000052 for L.C. and '000058 for L.D. ### Table XXVI. Observations on the Magnetic Force at Stations in Canada, with Lloyd's Needles L. C. and L. D., in October and November 1845, by Lieut. Lefroy, R.A. | Station | 1845. | Needles | Mean angle of deflection. | Thermometer. | Inclination. | Intensity. | Remarks | |---------------|-------|---------|--------------------------|--------------|-------------|------------|--------------------------| | | | | | | | | Toronto = 1·836 | | Toronto | Oct. 17. | C. | -17 22·7 | 49 | | | | | | Nov. 3. | C. | -17 41·9 | 47 | | | | | | | C. | -17 28·2 | 48 | | | | | | | C. | -17 40·8 | 50 | | | | | | Mean.. | C. | -17 31·3 | 49 | 75 14·3 | 1·836 | Base station. | | | Oct. 17. | D. | -14 17·6 | 49 | | | | | | Nov. 3. | D. | -14 18·6 | 49 | 75 14·3 | 1·836 | | | | Mean.. | D. | -14 19·0 | 50 | 75 14·3 | 1·836 | | | Niagara | Oct. 18. | C. | -19 36·7 | 55 | 74 46·8 | 1·822 | In a field near the Falls. | | | | D. | -16 28·8 | 59 | 74 37·0 | 1·814 | 1½ mile distant from the Lake. | | Buffaloe | | C. | -20 19·0 | 44 | 73 30·0 | 1·822 | Garden of the Hon. J. Gordon. | | Amherstburg | | D. | -17 18·9 | 44 | 73 38·8 | 1·814 | Corner of Lafayette and Orleans Streets. | | Detroit | | C. | -19 09·1 | 54 | 74 15·8 | 1·825 | Garden near the Ferry. | | Port Sarnia | | D. | -16 25·3 | 49 | 75 48·0 | 1·828 | Garden at the foot of the Hill. | Corrections have been made for the variations of temperature. Table XXVII. contains the several determinations with the statical needles of Lloyd and Fox collected in one view, and exhibits a mean of the several statical determinations at each station. ## Table XXVII. Results of the Observations on the Magnetic Force with the Statical Needles in Canada and the Hudson's Bay Territories in 1842, 1843, 1844 and 1845. | Station | Lat. | Long. | L.A. | L.B. | F.A. | Mean. | Remarks | |------------------|------|-------|------|------|------|-------|---------| | **1842** | | | | | | | | | Quebec | 46° 49' | 288° 44' | | | 1·827 | 1·827 | | | Three Rivers | 46° 19' | 287° 24' | | | 1·826 | 1·826 | | | Sorel | 46° 02' | 287° 00' | | | 1·815 | 1·815 | | | Kingsley | 45° 48' | 287° 41' | | | 1·808 | 1·808 | | | Stanstead | 45° 02' | 287° 50' | | | 1·799 | 1·799 | | | St. Helen's | 45° 31' | 286° 25' | | | 1·811 | 1·811 | | | New York | 40° 49' | 285° 57' | | | 1·769 | 1·769 | | | Providence | 41° 50' | 288° 35' | | | 1·781 | 1·781 | | | Cambridge | 42° 22' | 288° 52' | | | 1·777 | 1·777 | | | Philadelphia | 39° 58' | 284° 50' | | | 1·793 | 1·793 | | | Baltimore | 39° 17' | 283° 23' | | | 1·782 | 1·782 | | | Washington | 38° 53' | 282° 59' | | | 1·772 | 1·772 | | | Princeton | 40° 22' | 285° 20' | | | 1·783 | 1·783 | | | Newhaven | 41° 18' | 287° 02' | | | 1·773 | 1·773 | | | West Point | 41° 24' | 285° 59' | | | 1·807 | 1·807 | | | Albany | 42° 39' | 286° 15' | | | 1·797 | 1·797 | | | Cleveland | 41° 30' | 278° 18' | | | 1·807 | 1·807 | | | Detroit | 42° 24' | 277° 00' | | | 1·826 | 1·826 | | | South Manitou Island | 45° 05' | 274° 22' | | | 1·846 | 1·846 | | | Chicago | 41° 53' | 272° 16' | | | 1·823 | 1·823 | | | **1843** | | | | | | | | | Toronto | 43° 39' | 280° 39' | | | 1·836 | 1·836 | | | St. Helen's | 45° 31' | 286° 25' | | | 1·826 | 1·826 | | | Isle d'Urval | 45° 24' | 286° 14' | | | 1·817 | 1·817 | | | La Combe | 45° 32' | 285° 51' | | | 1·829 | 1·829 | | | Pointe aux Chênes | 45° 37' | 285° 05' | | | 1·810 | 1·810 | | | Foxes Point | 45° 32' | 284° 26' | | | 1·827 | 1·827 | | | Point Aylmer | 45° 15' | 284° 02' | | | 1·825 | 1·825 | | | Chat Falls | 45° 26' | 283° 28' | | | 1·835 | 1·835 | | | Grand Calumet | 45° 45' | 283° 20' | | | 1·846 | 1·846 | | | Fort Coulonge | 45° 56' | 282° 56' | | | 1·847 | 1·847 | | | Pointe Baptême | 46° 06' | 282° 34' | | | 1·822 | 1·822 | | | Deux Joachim's Portage | 46° 12' | 281° 41' | | | 1·834 | 1·834 | | | Trou Portage | 46° 15' | 281° 27' | | | 1·840 | 1·840 | | | Little River | 46° 18' | 281° 17' | | | 1·841 | 1·841 | | | Lac du Grand Vase| 46° 18' | 280° 34' | | | 1·849 | 1·849 | | | Lake Nipissing | 46° 14' | 280° 01' | | | 1·836 | 1·836 | | | Ricolet Falls | 45° 57' | 278° 59' | | | 1·870 | 1·870 | | | Pointe au Croix | 45° 55' | 278° 42' | | | 1·852 | 1·852 | | | Lake Huron | 46° 00' | 278° 10' | | | 1·843 | 1·843 | | | Snake Island | 46° 18' | 277° 10' | | | 1·837 | 1·837 | | | Tessalon Point | 46° 16' | 276° 29' | | | 1·844 | 1·844 | | | Pointe aux Pins | 46° 29' | 275° 19' | | | 1·858 | 1·858 | | | Pointe au Crêpe | 46° 58' | 275° 02' | | | 1·844 | 1·844 | | | Fort Michipicoton| 47° 56' | 274° 55' | | | 1·859 | 1·859 | | | Otter Island | 48° 07' | 273° 45' | | | 1·812 | 1·812 | | | Pic Fort | 48° 38' | 273° 31' | | | 1·851 | 1·851 | | | Terreplatte | 48° 49' | 272° 15' | | | 1·855 | 1·855 | | | Pointe Tonnere | 48° 19' | 270° 58' | | | 1·862 | 1·862 | | | Fort William | 48° 24' | 270° 38' | | | 1·864 | 1·864 | | | Portage Ecarté | 48° 25' | 270° 15' | | | 1·852 | 1·852 | | | Chien Portage | 48° 39' | 270° 26' | | | 1·863 | 1·863 | | | Prairie Portage | 48° 57' | 269° 59' | | | 1·857 | 1·857 | | | Savannah Portage | 48° 53' | 269° 57' | | | 1·869 | 1·869 | | | French Portage | 48° 35' | 268° 53' | | | 1·860 | 1·860 | | | Portage des deux Rivières | 48° 35' | 268° 33' | | | 1·861 | 1·861 | | | L. à la Crosse | 48° 24' | 267° 50' | | | 1·861 | 1·861 | | | 2nd Portage from ditto | 48° 15' | 267° 36' | | | 1·855 | 1·855 | | | Sturgeon Lake | 48° 28' | 267° 27' | | | 1·857 | 1·857 | | | Lac la Pluie | 48° 32' | 267° 04' | | | 1·857 | 1·857 | | | Fort Francis | 48° 37' | 266° 31' | | | 1·859 | 1·859 | | | Rainy River | 48° 48' | 265° 29' | | | 1·906 | 1·906 | | MDCCLXXXVI. | Station | Lat. | Long. | L. A. | L. B. | F. A. | Mean. | Remarks | |-------------------------|------|-------|-------|-------|-------|-------|---------| | Lake of the Woods | 49°19' | 265°18' | 1·863 | | 1·871 | 1·867 | | | Lake of the Woods | 49°28' | 265°20' | 1·847 | | 1·864 | 1·856 | | | Rat Portage | 49°46' | 265°21' | | | 1·858 | 1·858 | | | Winnipeg River | 50°10' | 264°50' | | | 1·877 | 1·877 | | | Slave Portage | 50°11' | 264°23' | | | 1·867 | 1·867 | | | Fort Alexander | 50°37' | 263°39' | | | 1·857 | 1·857 | | | Lake Winnipeg | 50°27' | 263°22' | | | 1·867 | 1·867 | | | Upper Fort Garry | 49°53' | 262°57' | 1·857 | 1·867 | 1·861 | 1·862 | | | Mouth of the Red River | 50°19' | 263°19' | | | 1·866 | 1·861 | 1·863 | | | Lake Winnipeg | 51°04' | 263°15' | | | 1·866 | 1·859 | 1·862 | | | Lake Winnipeg | 51°38' | 263°12' | | | 1·915 | 1·909 | 1·912 | | | Lake Winnipeg | 51°45' | 263°07' | | | 1·904 | 1·904 | 1·904 | | | Lake Winnipeg | 52°23' | 262°51' | | | 1·880 | 1·880 | | | Lake Winnipeg | 52°29' | 262°47' | 1·866 | 1·869 | 1·862 | 1·865 | | | Norway House | 53°59' | 261°53' | 1·873 | | 1·873 | 1·873 | | | Long Portage | 55°15' | 265°35' | 1·880 | 1·877 | 1·880 | 1·879 | | | White Earth Portage | 55°26' | 265°57' | | | 1·855 | 1·856 | 1·862 | | | Shamatawa | 56°21' | 267°04' | | | 1·863 | 1·860 | 1·862 | 1·861 | | | York Factory | 57°00' | 267°34' | 1·848 | | 1·857 | 1·857 | 1·855 | | | Hill River | 55°22' | 266°00' | | | 1·867 | 1·875 | 1·871 | | | Oxford House | 54°56' | 264°30' | 1·869 | 1·874 | 1·889 | 1·880 | | | Windy Lake | 54°37' | 263°58' | 1·870 | | 1·870 | 1·870 | | | Whitefall Portage | 54°24' | 263°34' | 1·858 | | 1·870 | 1·879 | 1·871 | | | Hairy Lake | 54°20' | 262°50' | | | 1·857 | 1·861 | 1·859 | | | Old Norway House | 53°42' | 261°59' | 1·872 | | 1·877 | | 1·874 | | | Lake Winnipeg | 53°31' | 260°48' | 1·853 | | 1·860 | 1·872 | 1·864 | | | Grand Rapid | 53°08' | 260°32' | | | 1·876 | 1·874 | 1·875 | | | Cross Lake | 53°10' | 260°28' | | | 1·877 | 1·875 | 1·876 | | | Cedar Lake | 53°18' | 259°48' | | | 1·871 | 1·871 | | | Cumberland House | 53°57' | 257°41' | | | 1·868 | 1·866 | 1·867 | | | Beaver Lake | 54°26' | 257°50' | | | 1·869 | 1·869 | | | Portage des Epinettes | 55°04' | 257°18' | | | 1·871 | 1·871 | | | Frog Portage | 55°27' | 256°30' | | | 1·857 | 1·857 | | | Little Rock Portage | 55°34' | 255°26' | | | 1·995 | 1·995 | | | Great Devil's Portage | 55°40' | 255°12' | | | 1·875 | 1·875 | | | Pine Portage | 55°43' | 254°04' | | | 1·884 | 1·884 | | | Snake Rapid | 55°46' | 253°30' | | | 1·874 | 1·874 | | | Portage Sonnante | 55°54' | 252°24' | | | 1·858 | 1·858 | | | Isle à la Crosse | 55°25' | 252°06' | | | 1·845 | 1·857 | 1·851 | | | Buffaloe Lake | 56°04' | 251°20' | | | 1·854 | 1·854 | | | River de la Loche | 56°15' | 250°42' | | | 1·826 | 1·826 | | | Portage de la Loche | 56°34' | 250°16' | | | 1·835 | 1·835 | | | Clearwater River | 56°39' | 249°11' | | | 1·850 | 1·850 | | | Pierre au Calumet | 57°24' | 248°25' | | | 1·938 | 1·938 | | | Pointe Brulée | 58°07' | 248°35' | | | 1·852 | 1·852 | | | Athabasca | 58°43' | 248°42' | | | 1·849 | 1·828 | 1·838 | | | Fort Vermilion | 58°55' | 243°55' | | | 1·811 | 1·811 | | | Fort Dunvegan | 55°35' | 241°35' | | | 1·809 | 1·809 | | | Fort Edmonton | 53°31' | 247°08' | | | 1·809 | 1·809 | | | Cumberland House | 53°57' | 257°41' | | | 1·853 | 1·853 | | | Brockville | 44°35' | 284°15' | 1·811 | 1·813 | | 1·812 | | | Cornwall | 45°02' | 285°13' | 1·821 | 1·823 | | 1·822 | | | Montreal | 45°31' | 286°25' | 1·790 | 1·786 | | 1·788 | | | Quebec | 46°49' | 288°44' | 1·802 | 1·800 | | 1·801 | | | Niagara | 43°05' | 280°51' | 1·821 | 1·823 | | 1·822 | | | Buffaloe | 42°52' | 281°06' | 1·814 | 1·814 | | 1·814 | | | Amherstburg | 42°06' | 276°47' | 1·823 | 1·821 | | 1·822 | | | Detroit | 42°24' | 277°02' | 1·807 | 1·821 | | 1·814 | | | Port Sarnia | 42°58' | 277°26' | 1·825 | 1·824 | | 1·825 | | | Goderich | 43°45' | 278°08' | 1·828 | 1·828 | | 1·828 | | Report relative to the determinations of Absolute Horizontal Force, drawn up by Lieut. I. H. Lefroy, R.A., and transmitted from Canada in 1845. "The measurements of the absolute horizontal force, from September 1842 to March 1843, were made with a transportable magnetometer by Meyerstein of Göttingen, on the plan of Professor Weber, described in Taylor's Scientific Memoirs, Part VIII. The deflecting bar in this instrument was retained at right angles to the meridian, and the angles of deflection were measured upon a long scale carried by the telescope. "Two deflecting bars were supplied with the instrument, 0·4 inch in diameter and 3·9 and 3·75 inches in length respectively. The angle of deflection was first observed with the farthest end of the deflecting bar at the distance 1·5 foot on the deflection scale; secondly, with the same end at 1·7 foot; and finally with the nearer end at 1·7 foot, giving the following as the distances of the deflecting bar. The bars are distinguished by the letters and numbers marked upon them. | N. IX. feet. | N. 13. feet. | |-------------|-------------| | \( r = 1\cdot3437 \) | \( 1\cdot3371 \) | | \( r' = 1\cdot5437 \) | \( 1\cdot5371 \) | | \( r'' = 1\cdot8562 \) | \( 1\cdot8629 \) | "The third distance is as nearly in the ratio of 1·32 to the first as the graduation of the scale admitted. The angular value of one division of the scale was 1'011. "The following Table contains the weight and dimensions of the magnets and of the stirrup in which they were vibrated, together with those of the small cylindrical brass weights, numbered 5 and 6, used in determining the moment of inertia of the suspended mass. **Table XXVIII.** | Length. | Diameter. | Weight. | |---------|-----------|---------| | ft. | ft. | grs. | | Deflecting bar, N. IX. | 0·3125 | 0·0325 | 1024·4 | | Deflecting bar, N. 13. | 0·3257 | 0·0354 | 1092·4 | | Cylindrical weight, No. 5. | 0·1243 | 0·0342 | 417·9 | | Cylindrical weight, No. 6. | 0·1245 | 0·0342 | 418·2 | | Stirrup, between the points of suspension | 0·3902 | . . . . | 736·0 | "The moment of inertia was found by vibrating each bar with and without the cylindrical weights, and the values of the constant \( \pi^2K \) given by these experiments at various stations are included in the following Table, where \[ K' = \frac{1}{2}(l^2 + r^2)W = \log 1\cdot50454, \] and \[ K = K'\frac{T^2}{T_{v2} - T_2}. \] TABLE XXIX. | Station | Bar No. IX | Bar No. IX | Bar No. IX | |---------------|------------|------------|------------| | | Time of vibration. | Without weights. | With weights. | $\pi^2K$. | | | Time of vibration. | Without weights. | With weights. | $\pi^2K$. | | September | Quebec | s | s | 6·929 | 13·616 | 11·024 | s | s | 7·137 | 13·420 | 12·465 | | September | New York | Not observed. | | | | | s | s | 6·286 | 11·862 | 12·314 | | December | Toronto | 6·580 | 12·965 | 10·942 | 6·670 | 11·615 | 12·239 | | January | Toronto | 6·617 | 13·049 | 11·193 | 6·728 | 12·689 | 12·333 | | Means | log $2\cdot04348$ | 11·043 | log $2\cdot09124$ | 12·338 | "Subsequent experience has shown the insufficiency of so small a number of observations as the above, to determine the constant ($\pi^2K$) with the requisite degree of precision; but as an improved instrument was substituted in March 1843 for the original transportable magnetometer, and the latter was returned to England at the same time, no opportunity has been afforded for repeating the observations. "Experiments of Deflection.—The observed angles of deflection, multiplied by the ratio $\left(1 + \frac{H}{F}\right)$, are given for each station, without any further correction. "Experiments of Vibration.—The observed times of vibration have been corrected for the arc, and for torsion. A note was made of the apparent chord of the arc of vibration as seen through the theodolite, at the beginning and ending of each series, with a few omissions. A movement of the end of the bar through a space equal to its diameter, corresponded to an arc of 12°. When the arcs were not recorded, an approximate value has been taken, viz. for the initial arc 10°, and for the terminal arc 4°. The ratio of the torsion force $\frac{H}{F}$ was observed at one station only, viz. Philadelphia. The same value has been applied at other stations slightly modified for differences of intensity. "Temperature.—The value of the coefficient for changes of temperature was not ascertained. The experiments of vibration and deflection were usually made at short intervals apart, and when both bars were employed, as was generally the case, one was vibrated during the time that the other was in use as a deflector; consequently the correction will generally have been unimportant or counterbalanced on the mean of the two results. "Induced Magnetism.—No correction has been applied for changes in the magnetic moment of the bars, due to their different positions with respect to the earth's inducing force during the two parts of the experiment. This correction was not determined for the bars here employed. "Gauss's formula for three or more distances* has been employed for the calcula- * Scientific Memoirs, Part V. Art. II. tion of \( m \) and X (the values of the magnetic moment of the deflecting magnet and of the horizontal component of the force). The values of the absolute horizontal force are expressed in the units directed in the Report of the Committee of Physics of the Royal Society, 1840, pp. 21, 22. These values may be converted into their equivalents in the scale more frequently employed by the continental magneticians, by being multiplied by the factor 0·4609. Table XXX.—Abstract of the observations to determine the absolute value of the horizontal component of the Magnetic Force with a German transportable magnetometer. | Date | Station | Bar. | Angles of deflection. | Corrected time of one vibration. | Temperature. | Values of \( m \). | X. | |--------|---------------|------|-----------------------|---------------------------------|--------------|-------------------|----| | | | | \( u \) | \( u' \) | \( u'' \) | Deflection. | Vibration. | N. IX. | Observed. | Mean. | | 1842. | | | | | | | | N. IX. | | | | Sept. 7 | Quebec ... | N. IX. | 11 38·0 | 7 42·6 | 4 27·6 | 6·929 | 62 | 62 | .756 | 3·045 | 3·040 | | | | N. IX. | 12 30·3 | 8 16·9 | 4 40·6 | 7·137 | 62 | 63 | .798 | 3·035 | Near the R.A. Barracks | | Oct. 16 | Montreal ... | N. IX. | 11 54·9 | 7 48·1 | 4 23·0 | 7·201 | 62 | 62 | .776 | 3·064 | St. Helen's. [Tanjille. | | Oct. 25 | New York ... | N. IX. | 9 17·8 | 6 08·2 | 3 27·3 | 6·286 | 55 | 58 | .779 | 4·008 | Lun. Asylum, Manhat- | | Oct. 13 | Cambridge ... | N. IX. | 10 02·2 | 6 38·1 | 3 44·8 | 6·598 | 72 | 65 | .774 | 3·662 | Magnetic observatory. | | Oct. 13 | Philadelphia | N. IX. | 9 30·3 | 6 16·7 | 3 38·7 | 6·364 | 65 | 72 | .744 | 3·669 | Magnetic observatory. | | Nov. 12 | Chicago* | N. IX. | 9 04·3 | 6 00·3 | 3 23·5 | 6·765 | 29 | 43 | .788 | 4·106 | Magnetic observatory. | | Oct. 28 | Toronto† | N. IX. | 10 23·8 | 6 52·8 | 3 53·4 | 6·718 | 50 | 50 | .775 | 3·529 | Magnetic observatory. | | Dec. 19 | Toronto ... | N. IX. | 9 38·6 | 6 27·3 | 3 44·2 | 6·509 | 50 | 51 | .745 | 3·501 | Mean 3·532 | | Mar. 25 | Toronto ...... | N. IX. | 9 17·3 | 6 11·3 | 3 34·6 | 6·633 | 46 | 45 | .712 | 3·526 | Magnetic observatory. | | Mar. 27 | Toronto ...... | N. IX. | 9 21·9 | 6 12·4 | 3 35·3 | 6·621 | 42 | 42 | .711 | 3·545 | Mean 3·541 | | Mar. 28 | Toronto ...... | N. IX. | 9 19·0 | 6 10·7 | 3 34·2 | 6·623 | 49 | 46 | .710 | 3·551 | Magnetic observatory. | | Mar. 25 | Toronto ...... | N. IX. | 10 15·4 | 6 47·4 | 3 50·1 | 6·730 | 46 | 45 | .768 | 3·546 | Magnetic observatory. | | Mar. 27 | Toronto ...... | N. IX. | 10 15·9 | 6 47·9 | 3 50·4 | 6·725 | 42 | 41 | .772 | 3·536 | Magnetic observatory. | | Mar. 28 | Toronto ...... | N. IX. | 10 18·0 | 6 49·1 | 3 50·8 | 6·722 | 48 | 47 | .770 | 3·541 | Magnetic observatory. | "I proceed to the observations of absolute horizontal force made subsequently to March 1833 with a portable unifilar magnetometer, constructed on the principle proposed by Dr. Lamont, in which the deflecting bar is retained at right angles to the suspended bar, and the angles of deflection are read off upon the graduated circle of the base. The lengths of the suspended and deflecting bars were in the ratio of 1 * The observations at this station were made by Lieut. Younghusband, R.A. The bar was vibrated in a different stirrup from that commonly employed, and its moment of inertia was afterwards ascertained at Toronto, by vibration of each bar with and without weights: the following were the dimensions; \( l = 3·755 \) inches; \( r = 0·4095 \) inches; \( p = 418·0 \) grains; whence \( K' = (\frac{1}{2}l^2 + r^2)p = 20·594 \); and the following were the resulting values of \( \log \pi^2 K \), by a single set of vibrations with each bar: N. IX. = 2·13194; N. IX. = 2·17200. † The observations at Toronto in 1842 have been already published in the Toronto volume for 1840–42. The series in March 1843 was observed by Lieut. Younghusband. The horizontal intensity at Toronto having since been determined with superior instruments, these results are principally interesting for comparison with those obtained at other stations. to $1.224$, being $2.45$ inches and $3.00$ inches respectively; but in order to secure an independent check upon the results by these bars, a third deflector of $3.6$ inches in length, was also employed, at one distance of deflection only, at many of the stations of observation. It was found that the values of the absolute intensity given by the $3.6$ inch bar agreed very satisfactorily with those given by the $3.0$ inch bars, and in taking the general mean at each station, an equal weight has been allowed to the results by each bar. The observations were made in the manner described in the instructions for the use of portable instruments by Lieut. C. J. B. Riddell, R.A. The separate parts of each experiment were reduced to a common value of the horizontal force by corresponding observations with a portable bifilar magnetometer, which was previously placed in adjustment at all the stations where it is not otherwise stated; but as a small instrument mounted in the open air is exposed to accidents, and to be much affected by atmospheric changes, it has happened in some instances that breaks and interruptions have occurred in the series, and when the several parts of the experiments were not completed at once, (as at Dunvegan and Isle à la Crosse,) they could not be reduced to a common scale division; at some few stations, where time did not permit of the adjustment of a differential instrument, or other circumstances rendered it inconvenient, the bifilar was not employed. "Table XXXVIII. contains the corrected data of each experiment, viz.— "1. The angles of deflection at each distance, corrected to a temperature of the deflecting bar of $50^\circ$, and reduced to a mean value of the differential instrument. "2. The time of one vibration corrected for the rate of the chronometer, for torsion, and for arc, reduced to a common temperature of $50^\circ$, and to the mean value of the differential instrument. The uncorrected data are given in a separate Table, No. XXXIX. "Corrections for Temperature.—The following Table contains the values of the coefficient ($q$) for changes of temperature for each bar, as obtained by different experiments at Toronto. | 1845 | No. 30 | No. 31 | No. 17 | |------|-------|-------|-------| | January and February | -0.00226 | -0.00254 | -0.00362 | | | -0.00267 | -0.00218 | -0.00378 | | | -0.00218 | -0.00224 | -0.00371 | | | -0.00225 | -0.00266 | -0.00374 | | | -0.00205 | -0.00226 | -0.00374 | | Means | -0.00228 | -0.00234 | -0.00371 | "For bars 20, 23 and 29, employed at Athabasca and McKenzie's River, I have assumed a value for $q$, viz. -0.0023." "Experiments of Deflection.—If the lengths of the magnets are in the proportion of 1 to 1·224, each observed angle of deflection furnishes an approximate value of the ratio \( \frac{m}{X} \) by the formula \( \frac{m}{X} = \frac{1}{2} r^3 \sin u \); but as in the great majority of these observations, the value resulting from the larger distances is greater than that given by the lesser distances, it appears that the correction depending on the distribution of free magnetism in the deflected and suspended bars was not wholly inappreciable. The approximate results have therefore been divided by the coefficient \( \left(1 + \frac{P}{r^2}\right) \); the values of the constant \( P \) having been derived for each bar from observations at two distances of deflection by the approximate formula \( P = -\frac{r^2 r^{15} \sin u' - r^{12} r^5 \sin u}{r^{15} \sin u' - r^5 \sin u} \). These values of \( P \) are contained in Table XXXII., in which the values deduced from the observed angles of deflection at some of the latter stations of observation have been included, as well as those resulting from observations made for the purpose at Toronto. | Date | Station | No. 30. | No. 31. | No. 17. | |---------------|-----------------|---------|---------|---------| | 1844. September 25. | Rat Portage | ... | -0.0060 | | | | Fort Francis | ... | -0.0038 | | | October 11. | Fort William | -0.0054 | -0.0052 | | | November 4. | Sault St. Mary | -0.0076 | -0.0034 | | | 1845. January and February | Toronto | -0.0011 | -0.0063 | +0.0010 | | | Toronto | -0.0019 | -0.0035 | +0.0004 | | | Toronto | -0.0063 | -0.0045 | +0.0026 | | | Toronto | -0.0068 | | +0.0026 | | Means... | | -0.0048 | -0.0048 | +0.0016 | "The angle of deflection was first observed with the deflecting bar to the east of the suspended magnet, and then to the west; four reversals were commonly made in each position with bars 30 and 31, and five with bar 17, which was employed at one distance only; the mean angle is given in the general table; an intermediate distance was employed at Fort Simpson, viz. 1·1757 foot for each of the two bars, 30 and 31; the distances employed at all the other stations, including those for the spare bars 20, 23 and 29, and for the bars 30, 31 and 17, in the experiments at Toronto in January and March 1845, are contained in the following Table:" **Table XXXIII.** | Bar. | Length. | \( r \) | \( r' \) | \( r'' \) | \( r''' \) | |------|---------|--------|--------|--------|--------| | | in. | ft. | ft. | ft. | ft. | | 30 | 3·0 | 1·0257 | 1·3257 | | | | 31 | 3·0 | 1·0257 | 1·3257 | | | | 17 | 3·6 | 1·2514 | | | | | 20 | 3·6 hollow. | 1·2530 | | | | | 33 | 2·45 | 1·1019 | 1·4019 | | | | 29 | 2·0 | 0·9328 | 1·0828 | 1·3828 | | Experiments at Toronto. | | | | | | | |------|---------|--------|--------|--------|--------| | 30 | 3·0 | 1·0257 | 1·1757 | 1·3257 | | | 31 | 3·0 | 1·0257 | 1·1257 | 1·2257 | 1·3257 | | 17 | 3·6 | 1·1514 | 1·4514 | | | "Experiments of Vibration.—The bars were vibrated in the series of 1843 in a stirrup weighing 322 grains, and similar to the one employed in the observations with the German magnetometer: the moment of inertia was ascertained by vibration with and without cylindrical weights; it has since been re-determined in the method proposed by Dr. Lamont, employing accurately turned brass rings instead of weights, and the values obtained by the latter method have been applied in preference. The bars were vibrated throughout 1844, and at some of the stations of 1843, without any appendage, the suspension thread being attached by a very light wooden pin, set into the hole which is made in the centre of each for the purpose of fixing it in the stirrup: this method had the advantage of diminishing the time of vibration, and allowing the use of a suspension silk of almost insignificant torsion force; it was found to give greater regularity to the results. "The moment of inertia of each bar, when vibrated without any appendage, is given by the formula \( k = \frac{a^2 + b^2}{12} M \): it has also been determined by vibration with the brass rings, the results agreeing very nearly with those determined by measurement. "The dimensions and weights of the different magnets were as follows:— **Table XXXIV.** | Length. | Diameter. | Weight. | Breadth. | Thickness. | |---------|-----------|---------|----------|------------| | in. | in. | gr. | in. | in. | | Bar 30 | 3·017 | 0·292 | 415·3 | | | 31 | 3·017 | 0·300 | 416·7 | | | 17 | 3·635 | 0·314 | 572·5 | | | 20 hollow. | 3·672 | 0·320 | 252·3 | | | 23 | 2·446 | 0·300 | 337·0 | | | 29 | 1·977 | 0·290 | 271·2 | | | Ring No. 1 | ... | 2·986* | 289·19 | 0·195 | 0·078 | | 3 | | 3·644* | 358·78 | 0·195 | 0·078 | | Stirrup.| 2·970 | Between the points of suspension. | | Weight 5| 1·199 | 0·315 | | 419·9 | | 6 | 1·197 | 0·315 | | | *a Outer diameter.* "From these data we have the following values of $K'$: For ring No. 1. $K' = \frac{1}{2} (r^2 + r'^2) W = \log 0.87111$. No. 3. $K' = \frac{1}{2} (r^2 + r'^2) W = \log 0.59442$. For the stirrup with weights 5 and 6. $K' = \frac{1}{2} (l^2 + r^2) W = \log 0.80974$. The values of $K \left(= K' \frac{T^2}{T^2 - T_w^2} \right)$ for each magnet, determined by vibration with Dr. Lamont's rings, were as follows: **Table XXXV.** | With the stirrup. | Without the stirrup. | |-------------------|----------------------| | No. 30. | No. 31. | | 3.2091 | 3.2375 | | 3.2220 | 3.2477 | | 3.2169 | 3.2477 | | 3.2127 | 3.2371 | | 3.2212 | 3.2437 | | 3.2163 | 3.2427 | | No. 30. | No. 31. | |-------------------|----------------------| | 2.1867b | 2.2154b | | 2.1867b | 2.2141b | | 2.1866b | 2.2125b | | 2.1866b | 2.2145b | | 2.1867 | 2.2142 | | No. 17. | No. 20. | |-------------------|----------------------| | 4.3866a | 1.9806b | | 4.3827b | 1.9804a | | 4.3880b | 1.9805b | | 4.3803b | 1.9831b | | 4.3844 | 1.9812 | *a* Observed with ring No. 1. *b* Observed with ring No. 3. "The mean values of $K$ in Table XXV. give the following values of the constant $\log \pi^2 K$, which are compared with the approximate values previously obtained by vibration with weights, and by measurement. **Table XXXVI.** | Vibration. | Bars. | Log $\pi^2 K$. | |------------------|-------|-----------------| | | | With rings. | With weights. | | With the stirrup.| No. 30| 1.50167 | 1.49830 | | | 31 | 1.50521 | 1.50387 | | | | | By measurement.| | Without the stirrup | 30 | 1.33408* | 1.33826 | | | 31 | 1.33952 | 1.33995 | | | 17 | 1.63621 | 1.63872 | | | 20 | 1.29122 | 1.29176 | "Both methods of vibration, with the stirrup and without, were employed at several stations, for the sake of comparison, and the horizontal intensity has been deduced from the values of $m X$ resulting from each. In the following Table these stations *As this value differs materially from the value given by measurement, the bar was again vibrated Sept. 9, 1845, for the purpose of verification: the resulting value of $\pi^2 K$ was however nearly the same, viz. 1.33442.* are brought together for the purpose of showing by the agreement in the resulting values of X, the general accuracy of the constants, whether the bar was vibrated in the stirrup, or without it. **Table XXXVII.** | Date | Station | No. 30 | No. 31 | |------------|------------------|--------|--------| | | | Values of X. | Values of X. | | | | With stirrup | Without stirrup | Diff. ΔX. | ΔX/X | | | | With stirrup | Without stirrup | Diff. ΔX. | ΔX/X | | 1843. | Cross Lake | 2·348 | 2·361 | +·013 | +·006 | | August | Cumberland | 2·345 | 2·345 | ·000 | ·000 | | September 9| Isle à la Crosse | 2·387 | 2·397 | +·010 | +·004 | | October | Athabasca | 2·021 | 2·025 | +·004 | +·002 | | 1844. | Athabasca | 2·018 | 2·025 | +·007 | +·003 | | March | Fort Simpson | 1·936 | 1·961 | +·025 | +·013 | | May | Fort Good Hope | 1·666 | 1·675 | +·009 | +·005 | | 1845. | Toronto | 3·528 | 3·522 | −·006 | −·002 | | Jan. and Feb.| Toronto | 3·510 | 3·511 | −·001 | −·000 | | September | Toronto | 3·514 | 3·518 | −·004 | −·001 | "If we omit the observations at Fort Simpson, at which the difference between the values of X by the two methods of suspension is considerable with both bars, and must have been due to some other cause than a discrepancy between the constants, the mean difference in the values of X, irrespective of signs, is for No. 30. ·0029 = \(\frac{1}{345}\) of X, No. 31. ·0012 = \(\frac{1}{833}\) of X. "Experiments of Vibration.—Each time of vibration has been corrected for the rate of the chronometer, which was generally large, \(10^s\) to \(20^s\); and as the chronometer was usually worn in the pocket, under circumstances not favourable to its performance, the actual rate on any given day may have sometimes differed to a sensible amount from the mean rate applied. The arc of vibration was not recorded; but as a general rule it was reduced at the commencement to an apparent value of one diameter of the end of the magnet as seen through the theodolite, which is equivalent to \(12^\circ\). As the magnet carried no reflector, and there were no direct means of measuring the exact amount of the arc, an approximate correction has been applied, by assuming the mean value of the initial semi-arc \(360'\), and of the terminal semi-arc as \(200'\). The same circumstances prevented any direct measurement of the value of \(\frac{H}{F}\), but a mean value for each mode of suspension employed was ascertained at Toronto, by trying several suspension threads of the same number of fibres, and of the same silk, as were employed on the Survey." "The following were the mean values of $\frac{H}{F}$ so obtained: With stirrup. Without stirrup. No. 30. '0022 . . . . . '00024. 31. '0028 . . . . . '00030. 17. . . . . . '00031. "From the above mean values at Toronto, an approximate value has been obtained for each of the other stations by multiplying them by the ratio $\frac{T^2}{T_2}$ at each station. Thus the value applied at Fort Good Hope for the vibration in the stirrup, was for bar 30, '0046, and for bar 31, '0058. "Table XXXVIII. contains the particulars of all the experiments by which a complete determination of the absolute horizontal force was made; these have been corrected for the various circumstances referred to; and in Table XXXIX. the data are given which have been employed for the corrections in each experiment. Table XXXIX. is followed by a notice of such additional circumstances at any of the stations as may seem to require explanation. **Table XXXVIII.** Exhibiting the corrected data of each experiment for determining the Absolute Horizontal Force. The letter $s$ affixed to the time of vibration signifies that the bar was suspended in the stirrup. | Date | Station | Bar. | Angles of deflection | Time of one vibration | Values of m. | Values of X. | |------------|-----------------|------|----------------------|-----------------------|--------------|-------------| | Nov. 4, 1844 | Sault St. Mary | 30 | 13 52°5 | 4:2527 | 0:394 | 3:030 | | | | | | | 0:394 | 3:028 | | | | | | | 0:390 | 3:031 | | | | | | | 0:393 | 3:032 | | May 31, 1843 | Fort William | 30 | 17 01°7 | 4:9311 (s.) | 0:455 | 2:868 | | | | | | | 0:455 | 2:871 | | | | | | | 0:420 | 2:870 | | | | | | | 0:419 | 2:874 | | Oct. 11, 1844 | Fort William | 30 | 14 42°7 | 4:3471 | 0:396 | 2:880 | | | | | | | 0:396 | 2:880 | | | | | | | 0:352 | 2:882 | | | | | | | 0:353 | 2:878 | | June 14, 1843 | Fort Francis | 30 | 15 59°3 | 4:7821 | 0:455 | 3:049 | | | | | | | 0:456 | 3:046 | | | | | | | 0:418 | 3:051 | | | | | | | 0:418 | 3:047 | | Sept. 29, 1844 | Fort Francis | 30 | 13 55°6 | 4:2395 | 0:396 | 3:034 | | | | | | | 0:397 | 3:027 | | Date | Station | Bar. | Angles of deflection | Time of one vibration | Values of m. | Values of X. | |--------------|-------------------|-----|----------------------|-----------------------|-------------|-------------| | Sept. 29, 1844 | Fort Francis | 31 | 12 16-3 | 4·5242 | 0·351 | 3·044 | | 29, 1844 | Fort Francis | 31 | 5 39-5 | 4·7110 | 0·351 | 3·045 | | 29, 1844 | Fort Francis | 17 | 12 23-9 | 4·7110 | 0·640 | 3·046 | | 25, 1844 | Rat Portage | 30 | 14 48-7 | 4·3592 | 0·397 | 2·863 | | 25, 1844 | Rat Portage | 30 | 6 48-1 | 4·3592 | 0·396 | 2·865 | | 25, 1844 | Rat Portage | 31 | 13 00-7 | 4·6466 | 0·352 | 2·880 | | 25, 1844 | Rat Portage | 31 | 6 00-0 | 4·6466 | 0·351 | 2·879 | | 25, 1844 | Rat Portage | 17 | 13 11-1 | 4·8392 | 0·642 | 2·877 | | June 21, 1843| River Winnipeg | 30 | 16 34-9 | not observed | 0·395 | 2·941 | | 21, 1843 | River Winnipeg | 30 | 7 36-6 | | | 2·935 | | Sept. 19, 1844| Fort Alexander | 30 | 15 36-3 | 4·4898 | 0·397 | 2·710 | | 19, 1844 | Fort Alexander | 30 | 7 15-2 | 4·4898 | 0·397 | 2·702 | | 19, 1844 | Fort Alexander | 31 | 13 51-8 | 4·7943 | 0·351 | 2·706 | | 19, 1844 | Fort Alexander | 31 | 8 23-7 | 4·7943 | 0·352 | 2·704 | | 19, 1844 | Fort Alexander | 17 | 14 06-4 | 5·0090 | 0·641 | 2·689 | | June 30, 1843| Upper Fort Garry | 30 | 16 55-2 | 4·9748 (s.) | 0·450 | 2·851 | | 30, 1843 | Upper Fort Garry | 30 | 7 47-4 | | 0·451 | 2·846 | | 30, 1843 | Upper Fort Garry | 31 | 15 35-1 | 5·1938 | 0·416 | 2·851 | | 30, 1843 | Upper Fort Garry | 31 | 7 11-7 | | 0·417 | 2·848 | | July 14, 1843| Norway House | 30 | 19 20-0 | 6·1351 (s.) | 0·439 | 2·179 | | 14, 1843 | Norway House | 30 | 8 50-2 | | 0·441 | 2·169 | | 14, 1843 | Norway House | 31 | 21 49-6 | 5·7609 (s.) | 0·391 | 2·177 | | 14, 1843 | Norway House | 31 | 10 01-4 | | 0·390 | 2·179 | | Sept. 6, 1844| Norway House | 30 | 19 37-7 | 5·0058 | 0·396 | 2·176 | | 6, 1844 | Norway House | 30 | 9 00-7 | | 0·397 | 2·171 | | 6, 1844 | Norway House | 31 | 17 23-6 | 5·3569 | 0·351 | 2·168 | | 6, 1844 | Norway House | 31 | 7 57-5 | | 0·351 | 2·170 | | 6, 1844 | Norway House | 17 | 17 34-0 | 5·5516 | 0·644 | 2·180 | | July 26, 1843| York Factory | 30 | 32 09-9 | 6·9613 (s.) | 0·435 | 1·507 | | 26, 1843 | York Factory | 30 | 14 13-7 | | 0·434 | 1·510 | | 26, 1843 | York Factory | 31 | 28 45-5 | 7·2275 (s.) | 0·400 | 1·533 | | 26, 1843 | York Factory | 31 | 12 48-2 | | 0·398 | 1·537 | | Aug. 16, 1843| Cross Lake | 31 | 17 52-7 | 5·8808 (s.) | 0·391 | 2·348 | | 16, 1843 | Cross Lake | 31 | 8 11-9 | | 0·391 | 2·347 | | 16, 1843 | Cross Lake | 30 | 19 45-6 | 5·6034 (s.) | 0·430 | 2·349 | | 16, 1843 | Cross Lake | 30 | 9 02-5 | | 0·431 | 2·347 | | 16, 1843 | Cross Lake | 31 | 17 52-7 | 4·8516 | 0·393 | 2·348 | | 16, 1843 | Cross Lake | 31 | 8 11-9 | | 0·431 | 2·348 | | 16, 1843 | Cross Lake | 30 | 19 45-6 | 4·6167 | 0·431 | 2·361 | | 16, 1843 | Cross Lake | 30 | 9 02-3 | | 0·431 | 2·361 | | 23, 1843 | Cumberland House | 30 | 19 46-3 | 5·5994 (s.) | 0·431 | 2·347 | | 23, 1843 | Cumberland House | 30 | 9 05-0 | | 0·432 | 2·347 | | 23, 1843 | Cumberland House | 31 | 18 12-1 | 5·9089 (s.) | 0·394 | 2·327 | | 23, 1843 | Cumberland House | 31 | 8 10-7 | | 0·394 | 2·327 | | 23, 1843 | Cumberland House | 30 | 19 46-3 | 4·6163 | 0·431 | 2·347 | | 23, 1843 | Cumberland House | 30 | 8 05-0 | | 0·432 | 2·343 | | 23, 1843 | Cumberland House | 31 | 18 12-1 | 4·8845 | 0·394 | 2·326 | | 23, 1843 | Cumberland House | 31 | 8 10-7 | | 0·390 | 2·326 | | 26, 1844 | Carlton House | 30 | 15 28-1 | 4·4542 | 0·396 | 2·743 | | 26, 1844 | Carlton House | 30 | 7 06-5 | | 0·397 | 2·743 | | 26, 1844 | Carlton House | 31 | 13 33-8 | 4·7654 | 0·350 | 2·751 | | 26, 1844 | Carlton House | 31 | 6 15-7 | | 0·350 | 2·750 | | 17, 1844 | Edmonton House | 30 | 14 25-7 | 4·2948 | 0·397 | 2·943 | | 17, 1844 | Edmonton House | 30 | 6 39-6 | | 0·398 | 2·939 | | 17, 1844 | Edmonton House | 31 | 12 20-1 | 4·5935 | 0·350 | 2·956 | | 17, 1844 | Edmonton House | 31 | 5 51-1 | | 0·351 | 2·945 | | Sept. 9, 1843| Isle à la Crosse | 30 | 18 46-8 | 5·6434 (s.) | 0·417 | 2·390 | | 9, 1843 | Isle à la Crosse | 30 | 8 38-8 | | 0·418 | 2·382 | | 9, 1843 | Isle à la Crosse | 31 | 17 16-5 | 5·9081 (s.) | 0·384 | 2·386 | | 9, 1843 | Isle à la Crosse | 31 | 7 55-1 | | 0·384 | 2·387 | | Date | Station | Bar. | Angles of deflection | Time of one vibration | Values of m. | Values of X. | |--------------|-----------------------|-----|----------------------|----------------------|-------------|-------------| | Sept. 9, 1843 | Isle à la Crosse | 30 | 18° 46' 8" | 4·6589 | 0·419 | 2·402 | | | | | | | 0·420 | 2·392 | | | | | | | 0·384 | 2·386 | | | | | | | 0·384 | 2·386 | | Oct. 13, 1843| Athabasca | 30 | 22° 26' 8" | 6·1381 (s.) | 0·418 | 2·018 | | | | | | | 0·416 | 2·024 | | | | | | | 0·385 | 2·031 | | | | | | | 0·386 | 2·027 | | March 1, 1844| Athabasca | 30 | 22° 32' 1" | 6·1234 (s.) | 0·419 | 2·019 | | | | | | | 0·419 | 2·018 | | | | | | | 0·378 | 2·019 | | | | | | | 0·378 | 2·021 | | July 2, 1844 | Athabasca | 30 | 20° 10' 0" | 5·1507 | 0·399 | 2·039 | | | | | | | 0·399 | 2·041 | | | | | | | 0·356 | 2·044 | | | | | | | 0·357 | 2·040 | | Oct. 14, 1843| Athabasca | 20 | 15° 05' 5" | 4·3373 | 0·515 | 2·017 | | | | | | | 0·206 | 2·042 | | | | | | | 0·207 | 2·034 | | | | | | | 0·155 | 2·034 | | | | | | | 0·156 | 2·025 | | June 22, 1844| Fort Resolution | 30 | 24° 46' 9" | 5·5320 | 0·400 | 1·761 | | | | | | | 0·400 | 1·762 | | | | | | | 0·359 | 1·764 | | | | | | | 0·359 | 1·765 | | May 2, 1844 | Fort Simpson | 30 | 23° 06' 5" | 6·3133 (s.) | 1·412 | 1·935 | | | | | | | 1·412 | 1·936 | | | | | | | 1·411 | 1·939 | | | | | | | 0·368 | 1·944 | | | | | | | 0·367 | 1·948 | | | | | | | 0·368 | 1·945 | | | | | | | 0·417 | 1·960 | | | | | | | 0·416 | 1·964 | | | | | | | 0·372 | 1·961 | | | | | | | 0·372 | 1·970 | | | | | | | 0·372 | 1·968 | | | | | | | 0·686 | 1·959 | | | | | | | 0·686 | 1·952 | | Date | Station | Bar. | Angles of deflection | Time of one vibration | Values of m. | Values of X. | |--------------|--------------|------|----------------------|-----------------------|-------------|-------------| | June 12, 1844 | Fort Simpson | 30 | 22° 26'9" | 5·2323 | 0·401 | 1·952 | | | | | | | | 1·954 | | | | | | | | 1·952 | | May 28, 1844 | Fort Norman | 30 | 25° 36'5" | 5·4832 | 0·409 | 1·753 | | June 2, 1844 | Fort Norman | 31 | 22° 10'5" | 5·8403 | 0·362 | 1·768 | | May 29, 1844 | Fort Good Hope | 30 | 26° 44'2" | 6·8206 (s.) | 0·408 | 1·669 | | | | | | | | 1·666 | | | | | | | | 1·666 | | Jan. 22, 1845 | Toronto | 30 | 11° 56'0" | 4·7712 (s.) | 0·395 | 3·527 | | Feb. 3, 1845 | Toronto | 31 | 10° 32'4" | | | 3·533 | | | | | | | | 3·533 | | | | | | | | 3·533 | | March 11, 1845| Toronto | 31 | 10° 27'9" | 4·2051 | 0·349 | 3·543 | | | | | | | | 3·543 | | | | | | | | 3·543 | ### Table XXXIX. Exhibiting the uncorrected particulars of each experiment in Table XXXVIII. | Date | Station | Mean readings | Value of 1 sc. div. in parts of H. F. | Bar. | Experiments of Deflection | Experiments of Vibration | |------------|--------------------------|---------------|--------------------------------------|------|---------------------------|-------------------------| | | | Scale. | Therm. | | Bifilar. | Time of one vibration. | | | | Scale. | Therm. | | Scale. | Number. | | Nov. 4 | Sault St. Mary | 170·7 | 40·4 | 0·0025 | 30 | 18·5 | | May 31 | Fort William | 254·0 | 55·0 | 0·0057 | 30 | 17·1 | | Oct. 11 | Fort William | 208·0 | 60·0 | 0·0044 | 30 | 15·6 | | June 14 | Fort Francis | 208·0 | 49·0 | 0·0064 | 30 | 15·3 | | Sept. 19 | Fort Alexander | 208·0 | 69·5 | 0·0041 | 30 | 15·2 | | June 30 | Upper Fort Garry | 235·0 | 83·0 | 0·0086 | 30 | 15·1 | | July 14 | Norway House | 237·0 | 49·5 | 0·0018 | 30 | 15·0 | | Sept. 6 | Norway House | 222·0 | 74·0 | 0·0083 | 30 | 14·9 | | Aug. 16 | Cross Lake | 216·0 | 63·0 | 0·0034 | 30 | 14·8 | | Sept. 9 | Isle à la Crosse | 176·0 | 64·6 | 0·0037 | 30 | 14·7 | | Oct. 13 | Athabasca | 254·4 | 50·4 | 0·0037 | 30 | 14·6 | * Watch 5240. "Remarks referring to Table XXXIX. "Sault St. Mary, November 4, 1844.—The observations of vibration of No. 31 were accidentally omitted at this station, by the interruption occasioned by the sudden death of one of the voyageurs; the value of X given in the table was deduced from the experiments of deflection, by applying to the observed value of the ratio $\frac{m}{X}$ the known values of $m$, as given by the observations of September 6, 19, 25 and 29, and October 11, 1844, viz. 0·3; in the general mean it is allowed only half the weight of the complete observations. "Fort William, May 31, 1843, and October 11, 1844.—The reduction of the observed values of X to the mean of the bifilar readings is omitted in the observations of October 11, 1844: the magnetometer was observed, but the connection of the readings did not appear satisfactory. "Fort Francis, June 14, 1843, and September 29, 1844.—The bifilar was not adjusted for the observations of 1844; the value of X by No. 30 in 1844 differs considerably from the mean values by the two other bars, but not to a greater extent than might have been caused by actual changes of the force. "Rat Portage, September 25, 1844.—The unfavourable state of the weather obliged the observations to be made in a dwelling-house, which like all the dwelling-houses in that part of the north of America was constructed of wood, with scarcely any iron whatever; the floor was laid with trenails, and the lock on the door was a wooden one; hence it is considered that the observation is as unexceptionable as if made in the open air: the bifilar was not in adjustment. "Winnipeg River, June 21, 1843.—The value of X is deduced from observations of deflection only, employing the mean values of $m$ given by the complete observations of June 14 and June 30. "Upper Fort Garry, June 30, 1843.—The time of vibration of No. 30 was observed with the weights 5 and 6 attached*, but the second set without the weights could not be taken. The observed value of $T^a$ has been multiplied by 0·338, the value of the ratio $\frac{K}{K+K'}$ to obtain the value of $T^b$, and the square root of the product (4·9748) inserted in table No. XXXVIII.; a few vibrations (22) which were observed as a check, gave a mean value of 4·912. "Norway House, July 14, 1843, and September 6, 1844.—The value of $m$ of bar 31 in 1843, appears too small, being 0·012 less than the mean at the preceding and following stations; the value of X is slightly in excess of the mean of the other two bars (2·178 instead of 2·174), indicating the error to be probably in the experiment of deflection. The observations of 1843 are reduced to the mean of corresponding readings of the bifilar; those of 1844 are reduced to the mean of hourly readings continued for twenty-one hours. "York Factory.—The day of observation at this station, the 26th of July 1843, was one of very considerable magnetic disturbance, and in other respects unfavourable, being windy and showery; the tent which sheltered the bifilar magnetometer was blown down, and the glass tube of the instrument broken, rendering it for the time unserviceable. In consequence of this accident the time of vibration of No. 31 is not reduced to the same value of the horizontal force as the other parts of the experiments; and the mean values of X, by bars 30 and 31, differ to an amount which is very large, when compared with the small value of the horizontal component at the station, i.e. $\frac{1}{4}$th its whole amount. "Cross Lake, August 16, 1843.—This was the first occasion on which the bars were vibrated without the stirrup. The bifilar was not in adjustment. "Cumberland House.—The bars were vibrated in 1843, both with and without the stirrup, and the mean horizontal intensity is deduced from all the resulting values of X. The bars were vibrated again in August 1844 with the same mode of suspension, but the experiments of deflection were not made. "Carlton House, August 26, 1844.—The bifilar was not adjusted at this station; and as the experiments of deflection with No. 17 were omitted, the mean value of X is deduced from the observations with bars 30 and 31 only. * This was done at several of the stations; but the values of K so obtained have been superseded by the more accurate determination with the brass rings. "Edmonton, August 17, 1844.—The bifilar was adjusted, but the state of the weather prevented the continuance of the readings for so long as twenty-four hours, and the value of X is reduced to the mean of twelve hourly readings only. "Athabasca.—There are three separate determinations at this station with bars 30, 31 and 17, viz. in October 1843, and in March and July 1844; the two former at the beginning and termination of a series of hourly observations of the bifilar, &c., made during the winter of 1843, and the latter after my return to Athabasca, from Mackenzie's river. Three spare bars of various lengths, No. 23, 29 and 20, were also employed in October 1843; but as the results obtained from them were calculated with an assumed temperature coefficient, and their moments of inertia are less accurately known than those of bars 30, 31 and 17, to introduce the values of X given by them into the general mean would only vitiate more accurate results, and they are added for purposes of illustration only; the general mean at the station is the mean by all the observations with bars 30, 31 and 17, except one of bar 17, in which the accuracy of the observed times of vibration appeared doubtful, and which is not included in the Table. "Vermilion, July 12, 1844.—The bifilar was placed in adjustment, and the several parts of the observation are reduced to the mean of the corresponding readings. "Dunvegan, July 23, 1844.—The bifilar was placed in adjustment, and hourly readings taken on the 23rd and 24th of July, the term day of the month. The absolute intensity is reduced to the mean reading of the bifilar on the 23rd, which differs but little from the mean of thirty-two hourly observations. "Big Island, June 20, 1844.—The place of observation was a small fishing-station near the Big Island on Great Slave Lake, and named after it, but not actually upon it. The values of X are deduced from experiments of deflection only, applying the mean values of m given by the observations of June 12 and 23. The bifilar was not observed. "Fort Simpson, May 2 and June 12, 1844.—The experiments of May are reduced to the mean reading of the bifilar given by the hourly observations of nine days, from April 27 to May 8. Those of June are reduced to the mean of the readings taken during the experiments; the values of X obtained from the experiments with the spare bars 20 and 23 have not been included in the mean, for the reason given in the remarks on the observations at Athabasca. "Fort Good Hope.—The observation at this, the most northern station of the series, was made at midnight on the 29th and 30th of May, by the soft and beautiful twilight of that season and latitude. The night was calm, and free from any magnetic disturbance. The results are reduced to the mean of twenty hourly observations of the bifilar magnetometer. The value of X by the observation of No. 30, when vibrated in the stirrup, is apparently too small. The suspension thread broke after 100 vibrations had been observed, occupying only $11^\circ 20'$, being too short a time to give an accurate result in so high a magnetic latitude: in taking the general mean I have allowed it only half the weight of the other results."—J. H. Lefroy. Determination of the absolute Horizontal Force derived from the times of vibration of the magnets of the portable unifilar magnetometer in 1844. It has been seen by the preceding Table, No. XXXVIII., that there were sixteen stations at which observations of deflection as well as vibration were made with the magnets of the portable unifilar in 1844, and that at three of the stations they were made at two different epochs: there were also twenty-five other stations, visited in the same year, at which the times of vibration only of the magnets are derived; and in respect to these we have in the first instance to derive the magnetic moment of each magnet, at the several periods when the vibrations only were observed, from the deflections at the stations where both processes were completed; and having thus obtained a knowledge of the variations which the magnetism of the bars may have undergone from time to time in the course of the year, we shall be enabled to derive the values of the absolute horizontal force at those stations also, or at least at a great part of them, where the vibrations alone are observed. The observations, which include the deflections as well as vibrations, have been discussed by Captain Lefroy in the preceding pages; and we are thus furnished with nineteen determinations of the magnetic moment of No. 30, seventeen of No. 31, and fourteen of No. 17, at different times in the course of the year. The values of $m$ (the magnetic moment) of No. 30 at the stations at which the deflections are observed, were as follows, viz.— | Station | Date | $m$ | |--------------------------|---------------|-------| | Athabasca | March 2, 1844 | .4207 | | Fort Simpson | May 2, 1844 | .4166 | | Fort Good Hope | May 29, 1844 | .4106 | | Fort Norman | June 2, 1844 | .4091 | | Fort Simpson | June 12, 1844 | .4018 | | Fort Resolution | June 24, 1844 | .4002 | | Athabasca | July 2, 1844 | .3988 | | Fort Vermilion | July 11, 1844 | .4005 | | Fort Dunvegan | July 24, 1844 | .3992 | | Fort Edmonton | Aug. 18, 1844 | .3978 | | Carlton House | Aug. 26, 1844 | .3965 | | Norway House | Sept. 4, 1844 | .3967 | | Fort Alexander | Sept. 20, 1844| .3962 | | Rat Portage | Sept. 25, 1844| .3964 | | Fort Francis | Sept. 29, 1844| .3962 | | Fort William | Oct. 10, 1844 | .3962 | | Sault St. Mary | Nov. 5, 1844 | .3940 | | Toronto (with the stirrup)| January 1845 | .3947 | | Toronto (without the stirrup) | Jan. 29, 1845 | .3931 | An inspection of these values shows that the magnetism of No. 30 was not constant during the period under consideration, but that a progressive loss took place, which was considerable in amount between March and June, but became much smaller and more regular between June 1844 and January 1845. The whole of the twenty-five stations at which the times of vibration only were observed, are comprised between Fort Dunvegan on the 24th of July, 1844, and Toronto on January 29, 1845, or during the period when the loss of magnetism of No. 30 was small and tolerably regular; we may therefore assume for this portion of the year the most simple hypothesis of an uniform loss in equal intervals of time, without incurring the risk of any material error. If \( x \) be the magnetic moment at Toronto on January 29, 1845, \( a \) the interval of time in days between the date of the observations at any anterior station and the 29th of January, and \( y \) the change of \( m \) corresponding to a single day, each of the stations where observations of deflection were made will furnish an equation of the form, \[ \text{observed value of } m = x + ay; \] and by the method of least squares we shall obtain the most probable values of \( m \) on the hypothesis of uniform loss. There are fifteen such equations furnished by No. 30, between June 12, 1844, and January 29, 1845; from these we obtain \( m = 3928 \), and \( y = 0.000317 \). Hence we have \( m \) at Toronto on January 29 = 3928; and on any earlier day between June 12, 1844, and January 29, 1845, \( m = 3928 + 0.000317a \). By the experiments with Dr. Lamont's rings, p. 293, the values of \( \pi^2K \), or the moment of inertia of each of the magnets 30, 31 and 17, multiplied by the square of the ratio of the circumference of a circle to its diameter, were determined as follows, viz.— | No. 30. | 21·581. | | No. 31. | 21·853. | | No. 17. | 43·272. | The absolute horizontal force at the stations where the observations of vibration only were made, are then deducible from the following expression, \[ X = \frac{\pi^2K}{mT^3}, \] in which \( T \) is the time of vibration and \( m \) computed as above. The values of \( m \) with magnet No. 31 at the stations where the deflections were observed were as follows: - Athabasca, March 2, 1844 . . . 3763. - Fort Simpson, May 2, 1844 . . . 3721. - Fort Good Hope, May 29, 1844 . . . 3641. - Fort Norman, June 2, 1844 . . . 3616. - Fort Simpson, June 12, 1844 . . . 3587. - Fort Resolution, June 24, 1844. . . 3592. - Athabasca, July 2, 1844 . . . 3568. - Fort Vermilion, July 11, 1844 . . . 3592. - Fort Dunvegan, July 24, 1844 . . . 3528. - Fort Edmonton, Aug. 18, 1844. . . 3507. - Carlton House, Aug. 26, 1844 . . . 3499. - Norway House, Sept. 4, 1844 . . . 3512. - Fort Alexander, Sept. 20, 1844 . . . 3517. - Rat Portage, Sept. 25, 1844 . . . 3515. - Fort Francis, Sept. 29, 1844 . . . 3506. - Fort William, October 10, 1844. . . 3522. - Toronto (with stirrup), Feb. 5, 1845. . . 3494. - Toronto (without stirrup), Feb. 5. . . 3494. In this case also the twenty-five stations at which the times of vibration only were observed, were all comprised in the interval between the 24th of July 1844 at Dunvegan, and the 5th of February 1845 at Toronto. The loss of magnetism of No. 31 in this interval appears to have been very small; and to have been progressive, although the evidence on this point is obscured by the occasional irregularities of observation. If we treat the observed values between Dunvegan and Toronto in the manner already described in discussing the observations with No. 30, we obtain $0.3495$ as the value of $m$ at Toronto on the 5th of February 1845, and $0.3495 + 0.00012a$ as its value on any anterior day in that interval. The values of $m$ with No. 17, derived from the deflections, are as follows: | Location | Date | Value | |---------------------------|---------------|---------| | Fort Simpson | May 2, 1844 | 0.6858 | | Fort Simpson | June 12, 1844 | 0.6738 | | Fort Resolution | June 24, 1844 | 0.6707 | | Athabasca | July 2, 1844 | 0.6691 | | Fort Vermilion | July 11, 1844 | 0.6678 | | Fort Dunvegan | July 24, 1844 | 0.6727 | | Fort Edmonton | Aug. 18, 1844 | 0.6702 | | Norway House | Sept. 4, 1844 | 0.6441 | | Fort Alexander | Sept. 20, 1844| 0.6414 | | Rat Portage | Sept. 25, 1844| 0.6423 | | Fort Francis | Sept. 29, 1844| 0.6401 | | Fort William | October 10, 1844| 0.6405 | | Sault St. Mary | Nov. 5, 1845 | 0.6393 | | Toronto | March 8, 1845 | 0.6368 | A cursory examination of these values suffices to show, that between September 4, 1844, at Norway House, and March 8, 1845, at Toronto, a small and progressive loss of magnetism was sustained; but that between the observations at Fort Edmonton on the 18th of August, and those at Norway House on the 4th of September, an irregular and very considerable loss occurred. A more careful examination of the times of vibration of this magnet, in comparison with those of No. 30 and 31, show that the period at which this loss took place was, after the observations at Devil's Drum Island on September 1, and before those at Norway House on the 4th of the same month. The stations therefore at which the observations of deflection were made with this magnet may be divided into two series; one antecedent to the loss thus sustained, and the other subsequent to it. For the latter series, viz. between Norway House on the 4th of September and Toronto in February 1845, the most probable values of $m$ have been obtained by the method of least squares in the manner already described; which gives for $m$ at Toronto, on the 8th of March 1845, $=0.6363$, and on anterior days $0.6363 + 0.00032a$. But we have still to provide for the observations of vibration made in July and August, and for this period the arithmetical mean of the observed values of $m$ between June 24 at Fort Resolution, and August 18 at Fort Edmonton, viz. $0.6700$, is perhaps the least exceptionable value that can be taken; the irregularities of the observed values during the period would scarcely justify a more precise deduction. When the values of $m$, resulting from the observations made with a magnet at several stations of a survey, give reason to infer that its magnetism has remained constant, it is obviously preferable to employ at each station a mean value of $m$ derived from the whole body of the observations, as irregularities of individual determinations afford a mutual compensation. When the loss of magnetism during the whole or a part of the survey has been small and progressive, a probable value of $m$, computed for the period of the loss in the manner described, may continue to be preferable at the stations where the individual values were observed. For other portions of a survey where the observed discrepancies are considerable, and where they present an alternation of increasing and decreasing values, an arithmetical mean may furnish the most probable value: but when the observed values at successive stations have varied to an amount which considerably exceeds what may reasonably be ascribed to observation error,—and whilst they manifest a progressive loss, afford no very decided indication of its regularity in correspondence with intervals of time,—a satisfactory combination may not be possible, and it may be safer to employ the individual values furnished at each station of observation. Thus the arithmetical mean of the four values obtained with No. 31, from June 12 at Fort Simpson to July 11 at Fort Vermilion, appears preferable to the values themselves, or to any other deduction that might be made for that period; and in the case of No. 17, the values observed on May 2 and June 12 are probably preferable to any others which could be assigned for the respective epochs, but their differences are too great to permit a value to be derived from them for any intermediate or an earlier period. The following Table contains the times of vibration of the three magnets, Nos. 30, 31 and 17, at the whole of the stations in 1844, with the values of $m$ either observed or deduced in the manner which has been described, and the absolute horizontal force computed by $X = \frac{\pi^2 K}{m T^2}$. **Table XL.** | Station | Date | Magnet. | Time of vibration. | Magnetic moment. | Horizontal force in absolute measure. | |------------------|------------|---------|--------------------|------------------|--------------------------------------| | Athabasca | March 1844.| 30 | 5-0328 | -4207 | 2-025 | | | | 31 | 5-3740 | -3763 | 2-011 | | | | 17 | 5-5204 | * | 2-018 | | Fort Simpson | May 2, 1844.| 30 | 5-1393 | -4166 | 1-961 | | | | 31 | 5-4691 | -3721 | 1-963 | | | | 17 | 5-6751 | -6858 | 1-959 | | Fort Good Hope | 29, 1844. | 30 | 5-6013 | -4106 | 1-67 | | | | 31 | 5-9763 | -3641 | 1-68 | | | | 17 | 6-1109 | * | 1-678 | | Fort Norman | June 2, 1844.| 30 | 5-4832 | -4091 | 1-755 | | | | 31 | 5-4803 | -3616 | 1-772 | | | | 17 | 5-9717 | * | 1-763 | | Fort Simpson | 12, 1844. | 30 | 5-2323 | -4018 | 1-963 | | | | 31 | 5-5993 | -3587 | 1-943 | | | | 17 | 5-7305 | -6738 | 1-956 | | Fort Resolution | 24, 1844. | 30 | 5-5320 | -3998 | 1-767 | | | | 31 | 5-8714 | -3585 | 1-768 | | | | 17 | 6-0479 | -6700 | 1-766 | | Athabasca | July 2, 1844.| 30 | 5-1507 | -3995 | 2-036 | | | | 31 | 5-4725 | -3585 | 2-035 | | | | 17 | 5-6326 | -6700 | 2-036 | | Fort Vermilion | 11, 1844. | 30 | 4-9000 | -3992 | 2-251 | | | | 31 | 5-1890 | -3585 | 2-264 | | | | 17 | 5-3771 | -6700 | 2-234 | * Values uncertain. | Station | Date | Magnet. | Time of vibration | Magnetic moment | Horizontal force in absolute measure | |-----------------------|------------|---------|------------------|-----------------|-------------------------------------| | Fort Dunvegan | July 24, 1844 | 30 | 4·4557 | 3988 | 2·726 | | | | 31 | 4·7671 | 3519 | 2·733 | | | | 17 | 4·8589 | 6700 | 2·736 | | Lesser Slave Lake | Aug. 5, 1844 | 30 | 4·4449 | 3985 | 2·744 | | | | 31 | 4·7706 | 3517 | 2·730 | | | | 17 | 4·8741 | 6700 | 2·718 | | | | 30 | 4·2948 | 3989 | 2·940 | | Fort Edmonton | 18, 1844 | 31 | 4·5939 | 3515 | 2·946 | | | | 17 | 4·6876 | 6700 | 2·939 | | | | 30 | 4·3747 | 3979 | 2·834 | | Saskatchewan | 20, 1844 | 31 | 4·6908 | 3515 | 2·826 | | | | 17 | 4·7792 | 6700 | 2·828 | | | | 30 | 4·4348 | 3979 | 2·758 | | Saskatchewan | 21, 1844 | 31 | 4·7706 | 3515 | 2·732 | | | | 17 | 4·8472 | 6700 | 2·749 | | | | 30 | 4·4167 | 3979 | 2·781 | | Fort Pitt | 22, 1844 | 31 | 4·7334 | 3515 | 2·775 | | | | 17 | 4·8223 | 6700 | 2·777 | | | | 30 | 4·3646 | 3978 | 2·848 | | Saskatchewan | 23, 1844 | 31 | 4·6798 | 3515 | 2·839 | | | | 17 | 4·7562 | 6700 | 2·847 | | | | 30 | 4·3520 | 3978 | 2·865 | | Saskatchewan | 24, 1844 | 31 | 4·6534 | 3515 | 2·871 | | | | 17 | 4·7525 | 6700 | 2·860 | | | | 30 | 4·4842 | 3977 | 2·735 | | Carlton House | 26, 1844 | 31 | 4·7654 | 3515 | 2·738 | | | | 17 | 4·8565 | 6700 | 2·738 | | | | 30 | 4·5560 | 3977 | 2·614 | | Saskatchewan | 27, 1844 | 31 | 4·8791 | 3515 | 2·612 | | | | 17 | 4·9668 | 6700 | 2·618 | | | | 30 | 4·7775 | 3976 | 2·378 | | Cumberland House | 29, 1844 | 31 | 5·1080 | 3515 | 2·383 | | | | 17 | 5·2235 | 6700 | 2·367 | | | | 30 | 4·7705 | 3975 | 2·385 | | Near the Pas | 31, 1844 | 31 | 5·1090 | 3514 | 2·383 | | | | 17 | 5·1978 | 6700 | 2·386 | | | | 30 | 4·7485 | 3975 | 2·408 | | Devil's Drum Island | Sept. 1, 1844 | 31 | 5·0968 | 3514 | 2·394 | | | | 17 | 5·1934 | 6700 | 2·395 | | | | 30 | 4·8097 | 3975 | 2·347 | | Grand Rapid | Sept. 2, 1844 | 31 | 5·1558 | 3514 | 2·340 | | | | 17 | 5·3157 | * | * | | | | 30 | 5·0058 | 3974 | 2·166 | | Norway House | 4, 1844 | 31 | 5·3569 | 3513 | 2·168 | | | | 17 | 5·5516 | 6441 | 2·180 | | | | 30 | 4·7613 | 3971 | 2·397 | | Lake Winnipeg | 14, 1844 | 31 | 5·2045 | 3512 | 2·397 | | | | 17 | 5·2997 | 6419 | 2·400 | | | | 30 | 4·4437 | 3971 | 2·754 | | Lake Winnipeg | 16, 1844 | 31 | 4·7457 | 3512 | 2·763 | | | | 17 | 4·9326 | 6418 | 2·771 | | | | 30 | 4·4662 | 3970 | 2·725 | | Lake Winnipeg | 17, 1844 | 31 | 4·7866 | 3512 | 2·716 | | | | 17 | 4·9768 | 6418 | 2·722 | | | | 30 | 4·5414 | 3970 | 2·636 | | Lake Winnipeg | 18, 1844 | 31 | 4·8576 | 3512 | 2·637 | | | | 17 | 5·0498 | 6418 | 2·644 | * Value uncertain. | Station | Date | Magnet. | Time of vibration | Magnetic moment | Horizontal force in absolute measure | |--------------------------|---------------|---------|------------------|-----------------|-------------------------------------| | Fort Alexander | Sept. 20, 1844 | 30 | 4·4898 | -3·970 | 2·697 | | | | 31 | 4·7943 | -3·511 | 2·708 | | | | 17 | 5·0090 | -6·417 | 2·688 | | Rat Portage | 25, 1844 | 30 | 4·3592 | -3·969 | 2·864 | | | | 31 | 4·6466 | -3·511 | 2·883 | | | | 17 | 4·8392 | -6·415 | 2·880 | | Fort Francis | 29, 1844 | 30 | 4·2395 | -3·967 | 3·027 | | | | 31 | 4·5242 | -3·510 | 3·042 | | | | 17 | 4·7110 | -6·414 | 3·040 | | Portage des 2 Rivières | Oct. 4, 1844 | 30 | 4·3170 | -3·965 | 2·921 | | | | 31 | 4·6034 | -3·510 | 2·938 | | | | 17 | 4·7976 | -6·413 | 2·932 | | Prairie Portage | 7, 1844 | 30 | 4·3838 | -3·964 | 2·834 | | | | 31 | 4·6720 | -3·510 | 2·853 | | | | 17 | 4·8705 | -6·412 | 2·845 | | Chien Portage | 9, 1844 | 30 | 4·3888 | -3·964 | 2·826 | | | | 31 | 4·6840 | -3·510 | 2·838 | | | | 17 | 4·8717 | -6·411 | 2·844 | | Fort William | 10, 1844 | 30 | 4·3474 | -3·963 | 2·882 | | | | 31 | 4·6387 | -3·509 | 2·894 | | | | 17 | 4·8517 | -6·411 | 2·868 | | Lake Superior | 14, 1844 | 30 | 4·1192 | -3·962 | 3·211 | | | | 31 | 4·3988 | -3·509 | 3·219 | | | | 17 | 4·5875 | -6·409 | 3·208 | | Fort Pic | 17, 1844 | 30 | 4·4726 | -3·961 | 2·724 | | | | 31 | 4·7741 | -3·508 | 2·733 | | | | 17 | 4·9833 | -6·408 | 2·725 | | White River | 21, 1844 | 30 | 4·4104 | -3·960 | 2·804 | | | | 31 | 4·7096 | -3·508 | 2·809 | | | | 17 | 4·9150 | -6·407 | 2·796 | | Fort Michipicoton | 30, 1844 | 30 | 4·3598 | -3·957 | 2·869 | | | | 31 | 4·6507 | -3·507 | 2·881 | | | | 17 | 4·8606 | -6·404 | 2·860 | | Gargantua | 31, 1844 | 30 | 4·1408 | -3·956 | 3·182 | | | | 31 | 4·4156 | -3·507 | 3·196 | | | | 17 | 4·6015 | -6·404 | 3·191 | | Sault St. Mary | Nov. 5, 1844 | 30 | 4·2527 | -3·954 | 3·018 | | | | 31 | not observed | | 3·026 | | La Cloche | 8, 1844 | 30 | 4·2058 | -3·953 | 3·087 | | | | 31 | 4·4774 | -3·506 | 3·109 | | | | 17 | 4·6495 | -6·401 | 3·127 | | Penetanguishene | 15, 1844 | 30 | 4·0551 | -3·951 | 3·323 | | | | 31 | 4·3324 | -3·505 | 3·322 | | | | 17 | 4·5047 | -6·397 | 3·326 | | Toronto | Jan. 29, 1845 | 30 | 3·9463 | -3·928 | 3·528 | | | Feb. 5, 1845 | 31 | 4·2041 | -3·495 | 3·538 | | | Mar. 8, 1845 | 17 | 4·3858 | -6·363 | 3·536 | Determination of the absolute Horizontal Force derived from the times of vibration of the magnets of the portable unifilar magnetometer in 1843. Besides the ten stations at which observations both of deflection and of vibration were made with Nos. 30 and 31 in 1843, which have been discussed in pp. 289–302, there were also thirteen stations at which the times of vibration only were observed, unaccompanied by observations of deflection: these stations were all comprised between Cumberland House on the 22nd of August and Athabasca on the 13th of October. The deflections observed at Cross Lake and Cumberland House on the 16th and 22nd of August, and at Athabasca on the 13th of October, indicate that the magnetic moment of both magnets sustained a considerable diminution in the interval; and from the only intermediate determination, made at Isle à la Crosse on the 9th of September, we may infer that the greater part at least, if not the whole of the loss, occurred in both magnets between August 23 and September 9. For the second portion of the interval therefore, or from September 9 to October 23, the arithmetical mean of the determinations at Isle à la Crosse and at Athabasca have been taken for the values of $m$, viz. ‘4138 for No. 30, and ‘3841 for No. 31. In regard to the previous interval, or that comprised between August 22 and September 9, the observations at Cumberland House and at Isle à la Crosse manifest that a very considerable change took place in the magnetic moment of both bars, but as intermediate observations of deflection are wholly wanting we have no direct evidence of the particular time when it occurred. A careful examination and comparison of the times of vibration at the intermediate stations makes it probable that the greater portion at least of the loss occurred in No. 31 between Cumberland House and Beaver Lake, and in No. 30 between Beaver Lake and the Portage des Epinettes; but as there is necessarily much uncertainty involved in any conclusion on this point, it has appeared the safest course to record the times of vibration at the stations between Cumberland House and Isle à la Crosse without an attempt to deduce the horizontal force from them. The times of vibration of No. 17 were also observed at the stations between Cumberland House and Athabasca, but no deflection experiments were made with it before the arrival at Athabasca; it appears by the observations of vibration that this bar unquestionably lost magnetism in the interval, but as there is no independent evidence to show at what particular time the loss took place, or whether it was of a sudden or of a progressive character, the times of vibration with this magnet have also been recorded, but no conclusion has been drawn from them in regard to the values of the horizontal force at any earlier station than at Athabasca. TABLE XLI. Absolute Horizontal Force deduced from the times of vibration of Nos. 30 and 31 in 1843. | Station | Date | Magnet. | Time of vibration | Magnetic moment | Horizontal force in absolute measure | |--------------------------|----------|---------|------------------|-----------------|-------------------------------------| | Isle à la Crosse | Sept. 9 | 30 | 4·6589 | .4138 | 2·403 | | | | 31 | 4·8838 | .3841 | 2·394 | | Buffaloe Lake | 13 | 30 | 4·7694 | .4138 | 2·283 | | | | 31 | 4·9986 | .3841 | 2·278 | | River de la Loche | 14 | 30 | 4·7101 | .4138 | 2·341 | | | | 31 | 4·9345 | .3841 | 2·332 | | Portage de la Loche | 16 | 30 | 4·7725 | .4138 | 2·280 | | | | 31 | 4·9968 | .3841 | 2·275 | | Clearwater River | 19 | 30 | 4·7822 | .4138 | 2·271 | | | | 31 | 5·0201 | .3841 | 2·262 | | Pierre au Calumet | 20 | 30 | 4·8867 | .4138 | 2·175 | | | | 31 | 5·1162 | .3841 | 2·172 | | Pointe Brulée | 21 | 30 | 5·0054 | .4138 | 2·073 | | | | 31 | 5·2482 | .3841 | 2·062 | | Athabasca | Oct. 13 | 30 | 5·0514 | .4138 | 2·035 | | | | 31 | 5·2816 | .3841 | 2·036 | TABLE XLII. Times of Vibration of Nos. 30, 31 and 17, between August 22 and October 13, recorded but not employed. | Station | 1843 | No. 30 | No. 31 | No. 17 | Station | Date | No. 17 | |--------------------------|----------|--------|--------|--------|--------------------------|----------|--------| | Cumberland House | Aug. 22 | .... | .... | 5·126 | Isle à la Crosse | Sept. | 5·116 | | Beaver Lake | 26 | 4·667 | 4·945 | 5·205 | Buffaloe Lake | 13 | 5·236 | | Portage des Epinettes | 28 | 4·689 | 5·007 | 5·272 | River de la Loche | 14 | 5·169 | | Frog Portage | 29 | 4·786 | 5·049 | 5·318 | Portage de la Loche | 16 | 5·231 | | Great Devil Portage | Sept. | 4·765 | 4·937 | 5·286 | Clearwater River | 19 | 5·253 | | Pine Portage | 3 | 4·786 | 5·011 | .... | Pierre au Calumet | 20 | 5·364 | | Snake Rapid | 4 | 4·760 | 4·983 | 5·231 | Pointe Brulée | 21 | 5·493 | | Portage Sonnante | 7 | 4·644 | 4·879 | 5·097 | | | | Collecting then in one view the results obtained by Lieut. Lefroy with the magnets of the German and unifilar magnetometers, and employing the Inclinations observed at the stations which will be found in the general table at the close of § 12, we have the values of the horizontal component, and of the total Force, severally as follows:— a. signifies by the German magnetometer; b. by the unifilar, where both deflections and vibrations have been observed; and c. when the times of vibration only of the magnets of the unifilar were observed. ## OBSERVATIONS OF THE MAGNETIC FORCE. ### TABLE XLIII. | Station | Date | Horizontal component | Mean horizontal component | Total force in absolute measure | Remarks | |------------------------|--------|----------------------|----------------------------|---------------------------------|--------------------------| | Quebec | 1842 | 3·040 a | 3·040 | 13·78 | | | Montreal | 1842 | 3·064 a | 3·064 | 13·78 | | | New York | 1842 | 4·008 a | 4·008 | 13·49 | | | Cambridge | 1842 | 3·665 a | 3·665 | 13·55 | | | Philadelphia | 1842 | 4·176 a | 4·176 | 13·50 | | | Chicago | 1842 | 4·106 a | 4·106 | 13·77 | | | Fort William | 1843 | 2·869 b | 2·875 | 13·91 | | | Fort William | 1844 | 2·881 b | | | | | Fort Francis | 1843 | 3·048 b | 3·044 | 14·18 | | | Fort Francis | 1844 | 3·040 b | | | | | Upper Fort Garry | 1843 | 2·849 b | 2·849 | 14·05 | | | Norway House | 1843 | 2·176 b | 2·173 | 14·18 | | | Norway House | 1844 | 2·171 b | | | | | York Factory | 1843 | 1·523 b | 1·523 | 14·07 | | | Cross Lake | 1843 | 2·352 b | 2·352 | 14·21 | | | Cumberland House | 1843 | 2·341 b | 2·358 | 14·12 | | | Cumberland House | 1844 | 2·376 b | | | | | Isle à la Crosse | 1843 | 2·394 c | 2·394 | 14·01 | | | Buffaloe Lake | 1843 | 2·278 c | 2·278 | 13·97 | | | River de la Loche | 1843 | 2·336 c | 2·336 | 13·90 | | | Portage de la Loche | 1843 | 2·278 c | 2·278 | 13·95 | | | Clearwater River | 1843 | 2·262 c | 2·262 | 13·85 | | | Pierre au Calumet | 1843 | 2·172 c | 2·172 | 14·33 | | | Pointe Brulée | 1843 | 2·067 c | 2·067 | 14·00 | | | Athabasca | 1843 | 2·036 b | | | | | Athabasca | 1844 | 2·018 b | 2·030 | 13·94 | | | Athabasca | 1844 | 2·036 b | | | | | Fort Simpson | 1844 | 1·961 b | 1·957 | 13·84 | | | Fort Simpson | 1844 | 1·954 b | | | | | Fort Good Hope | 1844 | 1·678 b | 1·678 | 13·64 | | | Fort Norman | 1844 | 1·763 b | 1·763 | 13·63 | | | Fort Resolution | 1844 | 1·767 b | 1·767 | 13·99 | | | Fort Vermilion | 1844 | 2·250 b | 2·250 | 14·07 | | | Fort Dunvegan | 1844 | 2·732 b | 2·732 | 14·03 | | | Lesser Slave Lake | 1844 | 2·731 b | 2·731 | 13·87 | | | Fort Edmonton | 1844 | 2·942 b | 2·942 | 14·04 | | | On the Saskatchewan | 1844 | 2·829 c | 2·829 | 13·71 | | | On the Saskatchewan | 1844 | 2·746 c | 2·746 | 13·84 | | | Fort Pitt | 1844 | 2·778 c | 2·778 | 14·15 | | | On the Saskatchewan | 1844 | 2·847 c | 2·847 | 14·24 | | | On the Saskatchewan | 1844 | 2·865 c | 2·865 | 14·09 | | | Carlton House | 1844 | 2·737 c | 2·737 | 13·74 | | | On the Saskatchewan | 1844 | 2·615 c | 2·615 | 13·94 | | | Near the Pas | 1844 | 2·386 c | 2·386 | 14·32 | | | Devil's Drum Island | 1844 | 2·399 c | 2·399 | 13·82 | | | Grand Rapid | 1844 | 2·343 c | 2·343 | 14·11 | | | Lake Winnipeg | 1844 | 2·398 c | 2·398 | 14·38 | | | Lake Winnipeg | 1844 | 2·763 c | 2·763 | 15·37 | | | Lake Winnipeg | 1844 | 2·721 c | 2·721 | 14·40 | | | Lake Winnipeg | 1844 | 2·639 c | 2·639 | 14·51 | | Lunatic Asylum. Observed by Lieut. Young-Husband, R.A. ### Table XLIII. (Continued). | Station | Date | Horizontal component | Mean horizontal component | Total force in absolute measure | Remarks | |--------------------|------|----------------------|----------------------------|---------------------------------|---------| | Fort Alexander | 1844.| 2·698 b. | 2·698 | 14·08 | | | Rat Portage | 1844.| 2·876 b. | 2·876 | 13·97 | | | Portage des deux Rivières | 1844.| 2·930 c. | 2·930 | 13·89 | | | Prairie Portage | 1844.| 2·844 c. | 2·844 | 14·18 | | | Portage du Chien | 1844.| 2·836 c. | 2·836 | 14·17 | | | Lake Superior | 1844.| 3·213 c. | 3·213 | 15·89 | | | Pic Fort | 1844.| 2·725 c. | 2·725 | 13·84 | | | White River | 1844.| 2·803 c. | 2·803 | 14·12 | | | Fort Michipicoton | 1844.| 2·870 c. | 2·870 | 13·93 | | | Gargantua | 1844.| 3·190 c. | 3·190 | 15·26 | | | Sault St. Mary | 1844.| 3·026 c. | 3·026 | 13·98 | | | La Cloche | 1844.| 3·108 c. | 3·108 | 13·64 | | | Penetanguishene | 1844.| 3·326 c. | 3·326 | 14·08 | | | Toronto | 1842.| 3·537 a. | | | | | | 1843.| | | | | | | 1845.| 3·537 b. | 3·535 | 13·90 | | | | 1845.| 3·535 b. | | | | | | 1846.| 3·533 b. | | | | | Woolwich | 1846.| 3·729 b. | 3·729 | 10·39 | | **Values of the Magnetic Force at Dr. Locke's stations.** Dr. Locke's determinations were of the ratios of the horizontal component of the Force to its value at Cincinnati taken as a base station: it is therefore requisite to establish, in the first instance, the relative values of the magnetic Force at Cincinnati and Toronto on the best evidence that the observations furnish. For this comparison we have—1°. Dr. Locke's observations with Hansteen's apparatus, at Toronto on the 20th of June, and at Cincinnati on the 4th of July 1844, combined with observations of the Inclination on the same days. The observations of horizontal Force give the ratio '7784 at Toronto to unity at Cincinnati, and those of Inclination 70° 25'0 at Cincinnati, and 75° 13'4 at Toronto. Whence, if we take the total Force at Toronto in the arbitrary scale as 1·836, its value at Cincinnati is 1·795. 2°. Dr. Locke's determination of the ratios of the horizontal force at New York, Cambridge, and Philadelphia, to unity at Cincinnati, with the Inclination at each station, combined with Lieut. Lefroy's determination of the ratios of the horizontal force at the same three stations to the force at Toronto, all which were observed with the magnets of the German transportable magnetometer. The place of observation at New York, Cambridge and Philadelphia, was the same with both observers; viz. the Lunatic Asylum at Manhattanville near New York, and the magnetic observatories at Cambridge and Philadelphia. The particulars of this comparison are as follows:— ### Table XLIV. | Station | Date | Dr. Locke | Lieut. Lefroy | Lieut. Lefroy | |---------------|--------|-----------|--------------|--------------| | | | Ratio of the horizontal force to 1 at Cincinnati. | Inclination observed at Cincinnati. | Horizontal force observed at the stations in the first column. | Horizontal force deduced at Cincinnati. | Horizontal force observed at Toronto. | Inclination observed at Toronto. | Total force at Cincinnati to 1·836 at Toronto. | | New York | 1841. | '8828 | 70° 26'2 | (1842.) | (1842.) | (1842.) | (1842.) | Mean ........... 1·791 | | | 1844. | '8811 | 70° 25'0 | | | | | Mean ........... 1·797 | | Cambridge | Mean | '8819 | 70° 25'6 | 4·008 | 4·544 | 3·537 | 75° 16'0 | Mean ........... 1·792 | | Philadelphia | 1841. | '9175 | 70° 26'2 | 3·665 | 4·558 | 3·537 | 75° 16'0 | Mean ........... 1·794 | Whence we have the total force at Cincinnati = 1·794. 3°. Dr. Locke's determination of the ratios of the horizontal force at Baltimore, Washington, Princeton, Newhaven, Albany and Sault St. Mary, to unity at Cincinnati, and his observations of the Inclination at those stations, combined with the ratios of the total force to 1·836 at Toronto, determined by Lieut. Lefroy at the same six stations. The particulars of the comparison are as follows: ### Table XLV. | Station | Dates | Ratio of the horizontal force to 1 at Cincinnati. | Inclination observed at the stations in column 1. | Total force at Cincinnati to 1·836 at Toronto. | |-----------------|-------|--------------------------------------------------|--------------------------------------------------|--------------------------------------------------| | | | Dr. Locke | Dr. Locke | By observations at the stations in column 1. | Deduced for Cincinnati. | | Baltimore | 1841. | '9370 | 71° 34'1 | 70° 26'2 | 1·782 | 1·796 | | Washington | 1844. | '9483 | 71° 13'4 | 70° 25'0 | 1·772 | 1·795 | | Princeton | 1844. | '8833 | 72° 40'4 | 70° 25'0 | 1·783 | 1·794 | | Newhaven | 1842. | '8385 | 73° 29'8 | 70° 26'2 | 1·773 | 1·794 | | Albany | 1844. | '7876 | 74° 40'2 | 70° 25'0 | 1·797 | 1·800 | | Sault St. Mary | 1843. | '6695 | 77° 30'2 | 70° 25'5 | 1·862 | 1·796 | Mean ........... 1·796 Whence we have the total force at Cincinnati = 1·796. Collecting in one view the results of the three comparisons, we have— 1°. By the direct comparison of the horizontal force at Cincinnati and Toronto, by Dr. Locke ........................................ 1·795 2°. By three intermediate stations, at which the ratios of the horizontal force were determined by Dr. Locke to the force at Cincinnati, and by Lieut. Lefroy to the force at Toronto ........................................ 1·794 3°. By six intermediate stations, at which the ratios of the horizontal force were determined to the force at Cincinnati by Dr. Locke, and the ratios of the total force to its value at Toronto, by Lieut. Lefroy ........................................ 1·796 The total force at Cincinnati, the base station of Dr. Locke's survey, has therefore been taken = 1.795; and the final column in the following Table has been computed accordingly; employing for that purpose the Inclinations observed at the same stations by Dr. Locke, contained in § 12, where also the geographical positions of the stations are given. **Table XLVI. — Values of the Magnetic Force at the stations of Dr. Locke's survey.** | Station | Date | Ratios of the horizontal force to unity at Cincinnati | Ratios of the total force to unity at Cincinnati | Ratios of the horizontal force to unity at Cincinnati | Ratios of the total force to unity at Cincinnati | |------------------|--------|------------------------------------------------------|-------------------------------------------------|------------------------------------------------------|-------------------------------------------------| | Cincinnati | 1838. | 1-0000 | 1-795 | 1842 | .9057 | | Dayton | 1838. | .9582 | 1-0032 | 1842 | .9845 | | Dayton | 1840. | .9544 | .9991 | 1842 | .9767 | | Springfield | 1838. | .9494 | .9978 | 1842 | .9917 | | Urbana | 1838. | .9533 | 1-0122 | 1842 | .9917 | | Columbus | 1838. | .9666 | .9967 | 1843 | .9850 | | Columbus | 1845. | .9644 | .9957 | 1843 | .9850 | | St. Louis | 1839. | 1-0430 | .9973 | 1843 | .9850 | | Davenport | 1839. | .9385 | 1-0120 | 1843 | .9850 | | Lostgrove | 1839. | .9360 | 1-0154 | 1843 | .9850 | | Wabashinecon River| 1839. | .9302 | 1-0206 | 1843 | .9850 | | Iron Ore Bed | 1839. | .9085 | 1-0302 | 1843 | .9850 | | Brown's Settlement| 1839. | .9181 | 1-0129 | 1843 | .9850 | | Mahoqueta River | 1839. | .9034 | 1-0178 | 1843 | .9850 | | Harpers Ferry | 1839. | .9144 | 1-0238 | 1843 | .9850 | | White Water River| 1839. | .8627 | 1-0165 | 1843 | .9850 | | Mahoqueta River* | 1839. | .8897 | 1-0093 | 1843 | .9850 | | Dubuques Town | 1839. | .8805 | 1-0130 | 1843 | .9850 | | Little Mahoqueta | 1839. | .8813 | 1-0160 | 1843 | .9850 | | Turkey River | 1839. | .8732 | 1-0091 | 1843 | .9850 | | Prairie du Chien | 1839. | .8763 | 1-0187 | 1843 | .9850 | | Blue Mound | 1839. | .8540 | 1-0174 | 1843 | .9850 | | Madison | 1839. | .8521 | 1-0378 | 1843 | .9850 | | Mineral Point | 1839. | .8686 | 1-0137 | 1843 | .9850 | | Hamilton | 1840. | .9383 | 1-0035 | 1843 | .9850 | | Piqua | 1840. | .9461 | 1-0026 | 1843 | .9850 | | Lebanon | 1840. | .9720 | 1-0011 | 1843 | .9850 | | Mason | 1840. | .9770 | .9989 | 1843 | .9850 | | Williamstown | 1840. | 1-0122 | .9932 | 1843 | .9850 | | Lexington | 1840. | 1-0102 | .9954 | 1843 | .9850 | | Clay's Ferry | 1840. | 1-0203 | .9993 | 1843 | .9850 | | Frankfort | 1840. | .9151 | 1-087 | 1843 | .9850 | | Louisville | 1840. | .9254 | .9965 | 1843 | .9850 | | Mount Vernon | 1840. | .9065 | .9913 | 1843 | .9850 | | New Harmony | 1840. | .9581 | .9989 | 1843 | .9850 | | Princeton | 1840. | .9047 | .9923 | 1843 | .9850 | | Vincennes | 1840. | .9260 | .9983 | 1843 | .9850 | | Paoli | 1840. | .9313 | .9880 | 1843 | .9850 | | Philadelphia | 1841. | .9174 | .9943 | 1843 | .9850 | | Philadelphia | 1842. | .9178 | .9955 | 1843 | .9850 | | Pittsburgh | 1841. | .9151 | .9918 | 1843 | .9850 | | Pittsburgh | 1842. | .8907 | 1-0041 | 1843 | .9850 | | Pittsburgh | 1845. | .8869 | 1-0034 | 1843 | .9850 | | Chambersburgh | 1842. | .9216 | .9964 | 1843 | .9850 | | Mount St. Mary's | 1842. | .9319 | .9977 | 1843 | .9850 | | Baltimore | 1841. | .9370 | .9935 | 1843 | .9850 | | Baltimore† | 1841. | .9319 | .9914 | 1843 | .9850 | | Trenton | 1841. | .9246 | .9978 | 1843 | .9850 | | Newark | 1841. | .8785 | .9957 | 1843 | .9850 | | Newark | 1844. | .8758 | .9925 | 1843 | .9850 | | New York‡ | 1841. | .8835 | .9943 | 1843 | .9850 | | New York‡ | 1841. | .8617 | .9944 | 1843 | .9850 | | New York‡ | 1841. | .8828 | .9918 | 1843 | .9850 | | New York‡ | 1844. | .8811 | .9924 | 1843 | .9850 | | New York‡ | 1841. | .9003 | .9942 | 1843 | .9850 | | Newhaven | 1842. | .8385 | .9884 | 1843 | .9850 | * North Branch. † St. Mary's College. ‡ Columbia College. § Lunatic Asylum, Manhattanville. ¶ Mr. Bond's Magnetic Observatory. ** At these four stations, which are all within one mile of each other, considerable local disturbance obviously exists. †† Magnetic Observatory. ‡‡ Grounds of the Capitol, mean of the east and west sides. §§ Pott's Wood. ¶¶ Rock Hills (trap). **** In the woods. Values of the Magnetic Force at Mr. Renwick's Stations. Mr. Renwick's observations consisted partly of determinations of the absolute horizontal force with a portable unifilar magnetometer, and partly of determinations of its ratios, by means of the times of vibrations of the magnet of the unifilar, of which the magnetism is assumed to have been constant. The absolute values of the total force are derived from the horizontal component obtained by both classes of observations, by applying the Inclinations observed at the same stations, which will be found in the General Table of Inclinations in the sequel, where also the geographical positions of Mr. Renwick's stations are given. The particulars of the magnetic determinations will be contained in the official publication of the United States Government: the results now communicated have been computed by Mr. Renwick. Table XLVII. Results of the Observations on the Magnetic Force made by Mr. Renwick in 1844. | Station | Absolute horizontal force | Absolute total force | Remarks | |--------------------------|---------------------------|----------------------|-----------------------| | Stonington | 3°7479 | 13°133 | | | Bridgeport | 3°7380 | 13°050 | | | Greenport | 3°8501 | 13°142 | | | Saybrook | 3°5636 | 13°388 | | | New York (Columbia College) | 4°1317 | 13°883 | | | New York (Old Lunatic Asylum) | 4°0913 | 13°849 | | | Sandy Hook | 4°1270 | 13°824 | Vibrations only | | Yale College | 3°8758 | 13°514 | | | Stamford | 3°9429 | 13°512 | | | Oyster Bay | 3°9526 | 13°506 | | The determinations of the magnetic force which have been discussed in the preceding pages, are collected in one view in the following General Table, No. XLVIII.; which exhibits the names of the stations, their geographical positions, the observers, and the intensities of the Force; the latter are placed in separate columns according to the nature of the determination in each case, the relative values of the total Force being placed in the one column, and the absolute values of the horizontal component in another; the former are expressed in the arbitrary scale, and are dependent on 1°836 as the force at Toronto; the latter are expressed in British units. A final column is added for the purpose of showing the total Force in absolute measure corresponding to the determinations in the two preceding columns: when the deduction is from the horizontal component, the values in the final column are the horizontal force multiplied by the secant of the observed Inclination; when from the ratios of the total Force, they have been computed by multiplying the respective ratios by $\frac{13°896}{1°836}$. The number of separate results in the Table is 289, of which 222 are relative, and 67 are absolute determinations. The number of stations at which the force has been obtained by these observations is 234. Seventeen of the results at fifteen stations present discordances much exceeding the ordinary limits; in most of these cases similar discrepancies occur in the observations of the Inclination also, whence it may be inferred that they are occasioned by station-error. Setting aside these seventeen results, there remain 272 independent determinations at 219 stations distributed over a portion of the earth's surface, extending in latitude above twenty-eight degrees, and in longitude above fifty degrees. At thirty-five of Captain Lefroy's stations, results were obtained both by the magnets of the unifilar magnetometer, and by the statical needles. Omitting Pierre au Calumet, where much local disturbance prevailed, there are thirty-four stations at which the values of the total Force in absolute measure derived from the two methods admit of being compared; when this is done it is found that the values obtained by the horizontal method are in excess at fifteen stations, and in defect at an equal number, the results being identical at the remaining four stations. The sum of the differences in excess is $1.95$, and in defect $1.22$; the difference of these two numbers divided by 34 (the number of stations), gives $0.0215$ as the average excess of the absolute determinations, or about $0.0015$ of the whole force. As the two methods of experimenting are perfectly independent of each other, having no single element in common, such an agreement is a very satisfactory confirmation of the general merits of both, and testifies, far more than any verbal expressions, in praise of the unremitting care with which the observations were conducted and executed. The sum of the differences in excess and defect, taken without reference to signs, is $3.17$, which divided by 34 gives an average difference at each station of $0.09$ between the two methods. As in all probability the differences which appear in the results of the two methods in such very high magnetic latitudes are chiefly attributable to observation-error in the Inclinations, of which the secants are employed in the deduction of the total Force from the horizontal components, it may be proper to notice that an error of $0.09$ in the total Force is equivalent, when the Inclination is $80^\circ$, to an observation-error of less than $4'$ in the Inclination: and when all the circumstances are considered under which the observations of Inclination were made, an average error of $4'$ in determinations, which rarely admitted of confirmation on a second day, will by no means appear an extraordinary amount. As a considerable portion of the statical determinations of the Force, and of the observations of Inclination, were entrusted to Bombardier Henry, I may take this occasion to insert, as I have great pleasure in doing, the following extract from a communication from Captain Lefroy:—"During the twenty months which I passed in the Hudson's Bay Territories, Bombardier Henry was my only English assistant: his excellent conduct and cheerful endurance at times of considerable inconvenience and hardships, did as much credit to his character as a non-commissioned officer of artillery, as the interest with which he devoted himself to the observations entrusted to him did to his zeal and intelligence." ### Table XLVIII. General Table of the Observations of the Magnetic Force. | Station | Lat. | Long. | Observer | Relative scale. Toronto = 1°336. | Magnetic force. In absolute measure. | |--------------------------|------|-------|----------|---------------------------------|-------------------------------------| | | | | | | Horizontal | Total | | **Between the latitudes of 38° and 40°.** | | | | | | | | St. Louis | 38° 38' | 269° 56' | Locke. | 1°790 | ... | 13°55 | | New Harmony | 38° 11' | 272° 12' | Locke. | 1°778 | ... | 13°46 | | Mount Vernon | 37° 59' | 272° 13' | Locke. | 1°779 | ... | 13°47 | | Princeton | 38° 23' | 272° 30' | Locke. | 1°781 | ... | 13°48 | | Vincennes | 38° 43' | 272° 35' | Locke. | 1°792 | ... | 13°56 | | Paoli | 38° 05' | 273° 25' | Locke. | 1°775 | ... | 13°44 | | Louisville | 38° 03' | 274° 30' | Locke. | 1°788 | ... | 13°53 | | Richmond | 39° 49' | 275° 13' | Locke. | 1°799 | ... | 13°61 | | Frankfort | 38° 14' | 275° 20' | Locke. | 1°774 | ... | 13°43 | | Oxford | 39° 30' | 275° 22' | Locke. | 1°805 | ... | 13°66 | | Hamilton | 39° 23' | 275° 28' | Locke. | 1°801 | ... | 13°63 | | Williamstown | 38° 36' | 275° 38' | Locke. | 1°783 | ... | 13°50 | | Cincinnati | 39° 06' | 275° 38' | Locke. | 1°795 | ... | 13°59 | | Dayton | 39° 44' | 275° 43' | Locke. | 1°797 | ... | 13°60 | | Clay's Ferry | 37° 54' | 275° 42' | Locke. | 1°775 | ... | 13°43 | | Lexington | 38° 06' | 275° 42' | Locke. | 1°769 | ... | 13°38 | | Mason | 39° 22' | 275° 47' | Locke. | 1°793 | ... | 13°57 | | Carrollton | 39° 38' | 275° 51' | Locke. | 1°800 | ... | 13°62 | | Lebanon | 39° 26' | 275° 54' | Locke. | 1°797 | ... | 13°60 | | Springfield | 39° 54' | 276° 09' | Locke. | 1°791 | ... | 13°55 | | Columbus | 39° 57' | 276° 57' | Locke. | 1°788 | ... | 13°53 | | Marietta Island | 39° 25' | 278° 32' | Locke. | 1°800 | ... | 13°62 | | Near Marietta Island | ? | ? | Locke. | 1°795 | ... | 13°58 | | Chambersburg | 39° 55' | 282° 20' | Locke. | 1°788 | ... | 13°53 | | Mount St. Mary's | 39° 41' | 282° 42' | Locke. | 1°790 | ... | 13°55 | | Mount Vernon | 38° 41' | 282° 53' | Locke. | 1°782 | ... | 13°49 | | Georgetown | 38° 53' | 282° 57' | Locke. | 1°768 | ... | 13°38 | | Washington | 38° 53' | 282° 59' | Locke. | 1°773* | ... | 13°42 | | Washington | 38° 53' | 282° 59' | Lefroy. | 1°772* | ... | 13°41 | | Washington | 38° 54' | 282° 59' | Locke. | 1°800† | ... | 13°62 | | Washington | 38° 54' | 282° 59' | Lefroy. | 1°798† | ... | 13°61 | | Baltimore | 39° 17' | 283° 22' | Locke. | 1°779 | ... | 13°47 | | Baltimore | 39° 17' | 283° 23' | Locke. | 1°784 | ... | 13°50 | | Baltimore | 39° 17' | 283° 23' | Lefroy. | 1°782 | ... | 13°49 | | Philadelphia | 39° 58' | 284° 50' | Locke. | 1°784‡ | ... | 13°50 | | Philadelphia | 39° 58' | 284° 50' | Lefroy. | 1°793‡ | ... | 13°57 | | Philadelphia | 39° 58' | 284° 50' | Lefroy. | 4°176‡ | ... | 13°50 | **Between the latitudes of 40° and 45°.** | Station | Lat. | Long. | Observer | Relative scale. Toronto = 1°336. | Magnetic force. In absolute measure. | |--------------------------|------|-------|----------|---------------------------------|-------------------------------------| | Prairie du Chien | 43° 01' | 268° 51' | Locke. | 1°828 | ... | 13°83 | | Brown's Settlement | 42° 02' | 268° 54' | Locke. | 1°818 | ... | 13°76 | | Mahoqueta River | 42° 14' | 269° 03' | Locke. | 1°818 | ... | 13°76 | | North branch of ditto | 42° 23' | 269° 08' | Locke. | 1°811 | ... | 13°71 | | Turkey River | 42° 42' | 269° 12' | Locke. | 1°811 | ... | 13°71 | | Iron Ore Bed | 41° 55' | 269° 20' | Locke. | 1°849§ | ... | 13°99 | | White Water River | 42° 18' | 269° 22' | Locke. | 1°824 | ... | 13°80 | * Grounds of the Capitol. † Magnetic Observatory. The Inclinations observed at the Magnetic Observatory and in the grounds of the Capitol, differ also about one-third of a degree; the results at the observatory are omitted in the map. ‡ Magnetic Observatory. § Local influence; omitted in the map. MDCCXLVI. ### Table XLVIII. (Continued.) | Station | Lat. | Long. | Observer | Magnetic force | |--------------------------|------|-------|----------------|----------------| | | | | | Relative scale | In absolute measure | | | | | | Toronto = 1°836 | Horizontal | Total | | Between the latitudes of 40° and 45° (continued). | | | | | | | | Little Mahoqueta River | 42° 31 | 269° 29 | Locke. | 1°823 | ... | 13°80 | | Davenport | 41° 30 | 269° 34 | Locke. | 1°818 | ... | 13°76 | | Wabasepinnecon River | 41° 44 | 269° 37 | Locke. | 1°832 | ... | 13°86 | | Dubuque Town | 42° 29 | 269° 37 | Locke. | 1°818 | ... | 13°76 | | Farmer's Creek | 42° 13 | 269° 37 | Locke. | 1°836 | ... | 13°90 | | Lostgrove | 41° 39 | 269° 51 | Locke. | 1°822 | ... | 13°79 | | Mineral Point | 42° 50 | 270° 06 | Locke. | 1°819 | ... | 13°76 | | Blue Mound | 43° 01 | 270° 22 | Locke. | 1°826 | ... | 13°82 | | Madison | 43° 04 | 270° 54 | Locke. | 1°862† | ... | 14°09 | | Chicago | 41° 53 | 272° 16 | Younghusband. | 1°823 | ... | 13°80 | | Chicago | 41° 53 | 272° 16 | Younghusband. | 4°106 | ... | 13°77 | | St. Mary's | 40° 32 | 275° 41 | Locke. | 1°805 | ... | 13°66 | | Piqua | 40° 06 | 275° 47 | Locke. | 1°799 | ... | 13°61 | | Urbana | 40° 05 | 276° 12 | Locke. | 1°816 | ... | 13°74 | | Ann Arbor | 42° 18 | 276° 15 | Locke. | 1°828 | ... | 13°84 | | Amherstburg | 42° 06 | 276° 47 | Lefroy. | 1°822 | ... | 13°79 | | Detroit | 42° 25 | 277° 04 | Lefroy. | 1°814 | ... | 13°72 | | Detroit | 42° 25 | 277° 04 | Locke. | 1°815 | ... | 13°73 | | Detroit | 42° 25 | 277° 04 | Younghusband. | 1°826 | ... | 13°82 | | Port Sarnia | 42° 58 | 277° 26 | Lefroy. | 1°825 | ... | 13°81 | | Huron | 41° 26 | 277° 33 | Locke. | 1°817 | ... | 13°75 | | Goderich | 43° 45 | 278° 03 | Lefroy. | 1°828 | ... | 13°84 | | Cleveland | 41° 30 | 278° 18 | Locke. | 1°824 | ... | 13°80 | | Cleveland | 41° 30 | 278° 18 | Younghusband. | 1°807 | ... | 13°67 | | Ashtabula | 41° 52 | 279° 08 | Locke. | 1°855† | ... | 14°04 | | Warren | 41° 16 | 279° 11 | Locke. | 1°805 | ... | 13°66 | | Wheeling | 40° 08 | 279° 13 | Locke. | 1°813 | ... | 13°72 | | Wellsville | 40° 38 | 279° 16 | Locke. | 1°794 | ... | 13°58 | | Pittsburg | 40° 32 | 279° 58 | Locke. | 1°803 | ... | 13°65 | | Penetanguishene | 44° 49 | 279° 59 | Lefroy. | 3°326 | ... | 14°08 | | Toronto | 43° 39 | 280° 39 | Lefroy. | 1°836 | ... | 13°90 | | Toronto | 43° 39 | 280° 39 | Locke. | 1°836 | ... | 13°90 | | Toronto | 43° 39 | 280° 39 | Lefroy. | 3°535 | ... | 13°90 | | Near Toronto | 43° 39 | 280° 41 | Locke. | 1°835 | ... | 13°89 | | Niagara | 43° 05 | 280° 51 | Lefroy. | 1°822 | ... | 13°79 | | Buffaloe | 42° 53 | 281° 06 | Lefroy. | 1°814 | ... | 13°73 | | Buffaloe | 42° 53 | 281° 06 | Locke. | 1°825 | ... | 13°81 | | Lockport | 43° 11 | 281° 14 | Locke. | 1°808 | ... | 13°68 | | Allegheny Summit | 40° 27 | 281° 50 | Locke. | 1°800 | ... | 13°62 | | Rochester | 43° 08 | 282° 09 | Locke. | 1°806 | ... | 13°67 | | Cumberland | 40° 13 | 283° 10 | Locke. | 1°789 | ... | 13°54 | | Brockville | 44° 35 | 284° 15 | Younghusband. | 1°812 | ... | 13°71 | | Utica | 43° 07 | 284° 47 | Locke. | 1°809 | ... | 13°69 | | Bristol | 40° 06 | 285° 13 | Locke. | 1°768 | ... | 13°38 | | Trenton | 40° 13 | 285° 20 | Locke. | 1°790 | ... | 13°55 | | Princeton | 40° 22 | 285° 20 | Locke. | 1°783 | ... | 13°50 | | Princeton | 40° 22 | 285° 20 | Lefroy. | 1°783 | ... | 13°50 | | Princeton* | 40° 22 | 285° 20 | Locke. | 1°781 | ... | 13°48 | | Princeton† | 40° 22 | 285° 20 | Locke. | 1°790 | ... | 13°55 | | New Brunswick | 40° 30 | 285° 25 | Locke. | 1°785 | ... | 13°51 | | Newark | 40° 43 | 285° 50 | Locke. | 1°784 | ... | 13°50 | * Pott's Woods. † Rock Hills (trap). ‡ Apparent local influence; omitted in the map. ### OBSERVATIONS OF THE MAGNETIC FORCE. #### TABLE XLVIII. (Continued.) | Station | Lat. | Long. | Observer | Magnetic force. | |--------------------------|------|-------|----------|-----------------| | | | | | Relative scale. | In absolute measure. | | | | | | Toronto = 1:836. | Horizontal | Total | | Between the latitudes of 40° and 45° (continued). | | | | | | | | New York* | 40° 49' | 285° 57' | Locke. | 1·781 | ... | 13·48 | | New York* | 40° 49' | 285° 57' | Lefroy. | 1·769 | ... | 13·39 | | Yew York* | 40° 49' | 285° 57' | Lefroy. | ... | 4·008 | 13·49 | | New York* | 40° 49' | 285° 57' | Renwick. | ... | 4·091 | 13·85 | | New York† | 40° 48' | 285° 58' | Locke. | 1·784 | ... | 13·50 | | Sandy Hook | 40° 27' | 285° 58' | Renwick. | ... | 4·127 | 13·82 | | New York† | 40° 43' | 285° 59' | Locke. | 1·785 | ... | 13·51 | | New York‡ | 40° 43' | 285° 59' | Renwick. | ... | 4·132 | 13·88 | | West Point | 41° 24' | 285° 59' | Lefroy. | 1·807 | ... | 13·67 | | Opposite Powkeepsie | 41° 41' | 286° 04' | Locke. | 1·811 | ... | 13·71 | | Powkeepsie | 41° 41' | 286° 05' | Locke. | 1·787 | ... | 13·52 | | Albany | 42° 39' | 286° 14' | Locke. | 1·792 | ... | 13·56 | | Albany | 42° 39' | 286° 14' | Lefroy. | 1·797 | ... | 13·60 | | Greenbush | 42° 39' | 286° 16' | Locke. | 1·791 | ... | 13·55 | | Oyster Bay | 40° 52' | ... | Renwick. | ... | 3·953 | 13·51 | | Bridgeport | 41° 11' | 286° 48' | Renwick. | ... | 3·738 | 13·05 | | Newhaven | 41° 18' | 287° 02' | Locke. | 1·774 | ... | 13·42 | | Newhaven | 41° 18' | 287° 02' | Lefroy. | 1·773 | ... | 13·42 | | Newhaven | 41° 18' | 287° 02' | Renwick. | ... | 3·876 | 13·51 | | Greenport | 41° 06' | 287° 38' | Renwick. | ... | 3·850 | 13·14 | | Stamford | 41° 03' | ... | Renwick. | ... | 3·943 | 13·51 | | Saybrook | 41° 17' | 287° 39' | Renwick. | ... | 3·564 | 13·39 | | Stonington | 41° 20' | 288° 05' | Renwick. | ... | 3·749 | 13·13 | | Mount Washington | 44° 17' | 288° 31' | Locke. | 1·780 | ... | 13·47 | | Providence | 41° 50' | 288° 35' | Lefroy. | 1·781 | ... | 13·48 | | Near Mount Washington | 44° 16' | 288° 31' | Locke. | 1·780 | ... | 13·47 | | Gorham | 44° 27' | 288° 47' | Locke. | 1·794 | ... | 13·58 | | Cambridge | 42° 22' | 288° 52' | Locke. | 1·774 | ... | 13·42 | | Cambridge | 42° 22' | 288° 52' | Lefroy. | 1·777 | ... | 13·45 | | Cambridge | 42° 22' | 288° 52' | Lefroy. | ... | 3·665 | 13·55 | | Boston | 42° 22' | 289° 01' | Locke. | 1·767 | ... | 13·37 | | Bethel | 44° 27' | 289° 09' | Locke. | 1·789 | ... | 13·54 | | Locke's Mills | 44° 24' | 289° 16' | Locke. | 1·786 | ... | 13·52 | | Portland | 43° 41' | 289° 40' | Locke. | 1·776 | ... | 13·44 | Between the latitudes of 45° and 50°. | Upper Fort Garry | 49° 53' | 262° 58' | Lefroy. | 1·862 | ... | 14·09 | | Upper Fort Garry | 49° 53' | 262° 58' | Lefroy. | ... | 2·849 | 14·05 | | Lake of the Woods | 49° 19' | 265° 18' | Lefroy. | 1·867 | ... | 14·13 | | Lake of the Woods | 49° 28' | 265° 20' | Lefroy. | 1·856 | ... | 14·05 | | Rat Portage | 49° 46' | 265° 21' | Lefroy. | 1·858 | ... | 14·06 | | Rat Portage | 49° 46' | 265° 21' | Lefroy. | ... | 2·876 | 13·97 | | Rainy River | 48° 48' | 265° 29' | Lefroy. | 1·895§ | ... | 14·34 | | Fort Francis | 48° 37' | 266° 31' | Lefroy. | 1·853 | ... | 14·03 | | Fort Francis | 48° 37' | 266° 31' | Lefroy. | ... | 3·044 | 14·18 | | Lac de la Pluie | 48° 32' | 267° 04' | Lefroy. | 1·859 | ... | 14·07 | | Sturgeon Lake | 48° 27' | 267° 19' | Lefroy. | 1·861 | ... | 14·08 | | 2nd Pe. from L. à la Crosse | 48° 15' | 267° 33' | Lefroy. | 1·855 | ... | 14·04 | | Lac à la Crosse | 48° 24' | 267° 50' | Lefroy. | 1·860 | ... | 14·08 | | Portage des deux Rivières| 48° 35' | 268° 33' | Lefroy. | 1·862 | ... | 14·09 | * Lunatic Asylum, Manhattanville. † New Lunatic Asylum. ‡ Columbia College. § Apparent local disturbance; omitted in the map. | Station | Lat. | Long. | Observer | Magnetic force | |-------------------------|------|-------|--------------|----------------| | | | | | Relative force | In absolute measure | | | | | | Toronto = 1°336 | Horizontal | Total | | Portage des deux Rivières | 48° 35' | 268° 33' | Lefroy. | ... | 2°930 | 13°89 | | French Portage | 48° 35' | 268° 53' | Lefroy. | 1°860 | ... | 14°08 | | La Pointe | 46° 47' | 269° 02' | Locke. | 1°875 | ... | 14°19 | | Savannah Portage | 48° 53' | 269° 57' | Lefroy. | 1°867 | ... | 14°13 | | Prairie Portage | 48° 58' | 269° 59' | Lefroy. | 1°858 | ... | 14°06 | | Prairie Portage | 48° 58' | 269° 59' | Lefroy. | ... | 2°844 | 14°18 | | Portage Écarté | 48° 25' | 270° 15' | Lefroy. | 1°852 | ... | 14°02 | | Portage du Chien | 48° 39' | 270° 26' | Lefroy. | 1°865 | ... | 14°12 | | Portage du Chien | 48° 39' | 270° 26' | Lefroy. | ... | 2°836 | 14°17 | | Ontanogon River | 46° 52' | 270° 29' | Locke. | 1°865 | ... | 14°12 | | Fort William | 48° 24' | 270° 37' | Lefroy. | 1°866 | ... | 14°12 | | Fort William | 48° 24' | 270° 37' | Lefroy. | ... | 2°875 | 13°91 | | Pointe Tonnerre | 48° 19' | 270° 58' | Lefroy. | 1°876 | ... | 14°20 | | Isle Royale | 48° 06' | 271° 13' | Locke. | 1°889* | ... | 14°30 | | Eagle River | 47° 27' | 271° 37' | Locke. | 1°861 | ... | 14°08 | | United States Agency | 47° 28' | 271° 59' | Locke. | 1°950* | ... | 14°76 | | Houghton's River | 47° 28' | 271° 59' | Locke. | 1°842 | ... | 13°94 | | Magnetic Inlet | 47° 29' | 271° 59' | Locke. | 1°910* | ... | 14°46 | | Isthmus | 47° 28' | 272° 00' | Locke. | 1°895* | ... | 14°34 | | Terreplatte | 48° 49' | 272° 15' | Lefroy. | 1°854 | ... | 14°03 | | Encampment | 46° 44' | 272° 17' | Locke. | 1°856 | ... | 14°05 | | Lake Superior | 48° 46' | 272° 20' | Lefroy. | ... | 3°213 | 15°89 | | Pic Fort | 48° 38' | 273° 29' | Lefroy. | ... | 2°725 | 13°84 | | Pic Fort | 48° 38' | 273° 29' | Lefroy. | ... | 1°846 | 13°97 | | White River | 48° 33' | 273° 33' | Lefroy. | ... | 2°803 | 14°12 | | Otter Island | 48° 06' | 273° 43' | Lefroy. | 1°801* | ... | 13°63 | | South Manitou Island | 45° 05' | 274° 22' | Younghusband. | ... | 1°846 | 13°97 | | Gargantua | 47° 37' | 274° 49' | Lefroy. | ... | 3°190 | 15°26 | | Michipicoton | 47° 56' | 274° 55' | Lefroy. | 1°855 | ... | 14°04 | | Michipicoton | 47° 56' | 274° 55' | Lefroy. | ... | 2°870 | 13°93 | | Pointe au Crêpe | 46° 58' | 275° 02' | Lefroy. | 1°877 | ... | 14°21 | | Pointe aux Pins | 46° 29' | 275° 19' | Lefroy. | 1°862 | ... | 14°09 | | Machinac | 45° 52' | 275° 19' | Locke. | 1°864 | ... | 14°10 | | Sault St. Mary | 46° 31' | 275° 26' | Lefroy. | ... | 3°026 | 13°98 | | Sault St. Mary | 46° 31' | 275° 26' | Locke. | 1°861 | ... | 14°08 | | Tessalon Point | 46° 16' | 276° 29' | Lefroy. | 1°852 | ... | 14°02 | | Snake Island | 46° 10' | 277° 10' | Lefroy. | 1°833 | ... | 13°87 | | Fort la Cloche | 46° 07' | 277° 35' | Lefroy. | ... | 3°108 | 13°64 | | Lake Huron | 46° 00' | 278° 10' | Lefroy. | 1°840 | ... | 13°93 | | Pointe au Croix | 45° 55' | 278° 42' | Lefroy. | 1°852 | ... | 14°02 | | Ricolet Falls | 45° 57' | 278° 59' | Lefroy. | 1°870 | ... | 14°15 | | Lake Nipissing | 46° 13' | 280° 01' | Lefroy. | 1°836 | ... | 13°90 | | Lake du Grand Vase | 46° 18' | 280° 34' | Lefroy. | 1°846 | ... | 13°97 | | Little River | 46° 18' | 281° 17' | Lefroy. | 1°838 | ... | 13°91 | | Trou Portage | 46° 15' | 281° 27' | Lefroy. | 1°841 | ... | 13°93 | | Deux Joachim's Point | 46° 12' | 281° 41' | Lefroy. | 1°830 | ... | 13°85 | | Pointe Baptême | 46° 06' | 282° 34' | Lefroy. | 1°822 | ... | 13°79 | | Fort Coulange | 45° 56' | 282° 56' | Lefroy. | 1°844 | ... | 13°95 | | Grand Calumet | 45° 45' | 283° 20' | Lefroy. | 1°836 | ... | 13°82 | | Chat Falls | 45° 26' | 283° 28' | Lefroy. | 1°840 | ... | 13°93 | | Point Aylmer | 45° 29' | 284° 12' | Lefroy. | 1°825 | ... | 13°81 | | Cornwall | 45° 02' | 284° 13' | Younghusband. | ... | 1°822 | 13°79 | | Pointe aux Chênes | 45° 37' | 285° 05' | Lefroy. | 1°805 | ... | 13°66 | | La Combes | 45° 32' | 285° 51' | Lefroy. | 1°825 | ... | 13°81 | * Apparent local disturbance; these are omitted in the map. ## OBSERVATIONS OF THE MAGNETIC FORCE. ### TABLE XLVIII. (Continued.) | Station | Lat. | Long. | Observer | Magnetic force. | |--------------------------|------|-------|------------------|-----------------| | | | | Relative scale. | In absolute measure. | | | | | Toronto = 1:836. | Horizontal. | | | | | | Total. | | **Between the latitudes of 45° and 50° (continued).** | | | | | | Foxes Point | 45° 32' | 286° 26' | LEFROY. | 1·832 | 13·86 | | Isle d'Urval | 45° 24' | 286° 14' | LEFROY. | 1·806 | 13·67 | | Montreal* | 45° 30' | 286° 24' | YOUNGHUSBAND. | 1·788 | 13·53 | | St. Helen's | 45° 30' | 286° 24' | LEFROY. | 1·823 | 13·79 | | St. Helen's | 45° 30' | 286° 24' | LEFROY. | 3·064 | 13·78 | | Sorel | 46° 02' | 287° 00' | LEFROY. | 1·815 | 13·74 | | Three Rivers | 46° 19' | 287° 24' | LEFROY. | 1·826 | 13·82 | | Kingssey | 45° 48' | 287° 41' | LEFROY. | 1·808 | 13·69 | | Stanstead | 45° 02' | 287° 50' | LEFROY. | 1·799 | 13·61 | | Quebec | 46° 49' | 288° 44' | LEFROY. | 3·040† | 13·78 | | Quebec | 46° 49' | 288° 44' | LEFROY. | 1·827‡ | 13·83 | | Quebec | 46° 49' | 288° 44' | YOUNGHUSBAND. | 1·801§ | 13·63 | | **Between the latitudes of 50° and 55°.** | | | | | | Fort Edmonton | 53° 31' | 247° 08' | LEFROY. | 1·809 | 13·69 | | Fort Edmonton | 53° 31' | 247° 08' | LEFROY. | 2·942 | 14·04 | | Saskatchewan River | 54° 05' | 248° 16' | LEFROY. | 2·829 | 13·71 | | Saskatchewan River | 53° 50' | 249° 30' | LEFROY. | 2·746 | 13·84 | | Fort Pitt | 53° 34' | 250° 41' | LEFROY. | 2·778 | 14·15 | | Saskatchewan River | 53° 07' | 251° 30' | LEFROY. | 2·847 | 14·24 | | Saskatchewan River | 52° 23' | 252° 56' | LEFROY. | 2·865 | 14·09 | | Carlton House | 52° 51' | 253° 47' | LEFROY. | 2·737 | 13·74 | | Saskatchewan River | 53° 16' | 255° 12' | LEFROY. | 2·615 | 13·94 | | Cumberland House | 53° 57' | 257° 41' | LEFROY. | 1·866 | 14·12 | | Cumberland House | 53° 57' | 257° 41' | LEFROY. | 2·358 | 14·12 | | Beaver Lake | 54° 32' | 257° 50' | LEFROY. | 1·869 | 14·14 | | Near the Pas | 53° 48' | 258° 32' | LEFROY. | 2·386 | 14·32 | | Devil's Drum Island | 53° 19' | 259° 15' | LEFROY. | 2·399 | 13·82 | | Cedar Lake | 53° 12' | 259° 30' | LEFROY. | 1·871 | 14·16 | | Cross Lake | 53° 10' | 260° 28' | LEFROY. | 1·876 | 14·20 | | Cross Lake | 53° 10' | 260° 28' | LEFROY. | 2·352 | 14·21 | | Grand Rapid | 53° 08' | 260° 32' | LEFROY. | 1·875 | 14·19 | | Grand Rapid | 53° 08' | 260° 34' | LEFROY. | 2·343 | 14·11 | | Lake Winnipeg | 53° 31' | 260° 48' | LEFROY. | 1·862 | 14·09 | | Norway House | 53° 59' | 261° 53' | LEFROY. | 1·873 | 14·18 | | Norway House | 53° 59' | 261° 53' | LEFROY. | 2·173 | 14·18 | | Old Norway House | 53° 42' | 261° 59' | LEFROY. | 1·874 | 14·18 | | Lake Winnipeg | 52° 29' | 262° 47' | LEFROY. | 1·866 | 14·12 | | Hairy Lake | 54° 21' | 262° 50' | LEFROY. | 1·859 | 14·07 | | Lake Winnipeg | 52° 23' | 262° 51' | LEFROY. | 1·879 | 14·22 | | Lake Winnipeg | 52° 21' | 262° 51' | LEFROY. | 2·398 | 14·38 | | Lake Winnipeg | 51° 45' | 263° 07' | LEFROY. | 1·904§ | 14·42 | | Lake Winnipeg | 51° 44' | 263° 12' | LEFROY. | 2·763§ | 15·37 | | Lake Winnipeg | 51° 38' | 263° 12' | LEFROY. | 1·912§ | 14·47 | | Lake Winnipeg | 51° 04' | 263° 15' | LEFROY. | 1·863 | 14·10 | | Lake Winnipeg | 51° 34' | 263° 20' | LEFROY. | 2·721 | 14·40 | | Lake Winnipeg | 50° 27' | 263° 22' | LEFROY. | 1·867 | 14·13 | * Garden on the Mountain. † At the Royal Artillery Barracks, apparent local disturbance; omitted in the map. ‡ Near Wolfe's Monument. § Apparent local disturbance; these are omitted in the map. ### Table XLVIII. (Continued.) | Station | Lat. | Long. | Observer | Magnetic force | |--------------------------|------|-------|----------|----------------| | | | | | Relative scale. Toronto = 1:836. | In absolute measure. | | | | | | Horizontal. | Total. | | Between the latitudes of 50° and 55° (continued). | | | | | | | White Fall Portage | 54°24' | 263°34' | Lefroy. | 1·869 | ... | 14·15 | | Fort Alexander | 50°37' | 263°39' | Lefroy. | 1·857 | ... | 14·05 | | Fort Alexander | 50°37' | 263°39' | Lefroy. | ... | 2·698 | 14·08 | | Lake Winnipeg | 51°04' | 263°39' | Lefroy. | ... | 2·640 | 14·52 | | Mouth of the Red River | 50°19' | 263°19' | Lefroy. | 1·864 | ... | 14·11 | | Windy Lake | 54°37' | 263°58' | Lefroy. | 1·870 | ... | 14·15 | | Slave Portage | 50°11' | 264°23' | Lefroy. | 1·867 | ... | 14·13 | | Oxford House | 54°56' | 264°30' | Lefroy. | 1·877 | ... | 14·21 | | Winnipeg River | 50°10' | 264°51' | Lefroy. | 1·877 | ... | 14·21 | | Between the latitudes of 55° and 60°. | | | | | | | Fort Dunvegan | 55°56' | 241°35' | Lefroy. | 1·809 | ... | 13·69 | | Fort Dunvegan | 55°56' | 241°35' | Lefroy. | ... | 2·732 | 14·03 | | Fort Vermilion | 58°25' | 243°55' | Lefroy. | 1·811 | ... | 13·71 | | Fort Vermilion | 58°25' | 243°55' | Lefroy. | ... | 2·250 | 14·07 | | Lesser Slave Lake | 55°33' | 244°07' | Lefroy. | ... | 2·731 | 13·87 | | Pierre au Calumet | 57°24' | 248°25' | Lefroy. | 1·938* | ... | 14·66 | | Pierre au Calumet | 57°24' | 248°25' | Lefroy. | ... | 2·172* | 14·33 | | Pointe Brulée | 58°07' | 248°35' | Lefroy. | 1·852 | ... | 14·02 | | Pointe Brulée | 58°07' | 248°35' | Lefroy. | ... | 2·067 | 14·00 | | Athabasca | 58°43' | 248°42' | Lefroy. | 1·838 | ... | 13·91 | | Athabasca | 58°43' | 248°42' | Lefroy. | ... | 2·030 | 13·94 | | Clearwater River | 56°39' | 249°11' | Lefroy. | 1·850 | ... | 14·00 | | Clearwater River | 56°39' | 249°11' | Lefroy. | ... | 2·262 | 13·85 | | Portage de la Loche | 56°34' | 250°23' | Lefroy. | 1·835 | ... | 13·89 | | Portage de la Loche | 56°34' | 250°23' | Lefroy. | ... | 2·278 | 13·95 | | River de la Loche | 56°15' | 250°37' | Lefroy. | 1·826 | ... | 13·82 | | River de la Loche | 56°15' | 250°37' | Lefroy. | ... | 2·336 | 13·90 | | Buffaloe Lake | 56°05' | 251°19' | Lefroy. | 1·854 | ... | 14·03 | | Buffaloe Lake | 56°05' | 251°19' | Lefroy. | ... | 2·278 | 13·97 | | Isle à la Crosse | 55°27' | 252°06' | Lefroy. | 1·851 | ... | 14·01 | | Isle à la Crosse | 55°27' | 252°06' | Lefroy. | ... | 2·394 | 14·01 | | Portage Sonnante | 55°54' | 252°34' | Lefroy. | 1·858 | ... | 14·06 | | Snake Rapid | 55°46' | 253°30' | Lefroy. | 1·874 | ... | 14·18 | | Pine Portage | 55°43' | 254°10' | Lefroy. | 1·884 | ... | 14·26 | | Great Devil's Portage | 55°40' | 255°11' | Lefroy. | 1·875 | ... | 14·19 | | Little Rock Portage | 55°34' | 255°27' | Lefroy. | 1·995* | ... | 15·10 | | Frog Portage | 55°28' | 256°30' | Lefroy. | 1·857 | ... | 14·06 | | Portage des Epinettes | 55°04' | 257°18' | Lefroy. | 1·871 | ... | 14·16 | | Long Portage | 55°15' | 265°35' | Lefroy. | 1·879 | ... | 14·22 | | Hill River | 55°22' | 266°00' | Lefroy. | 1·871 | ... | 14·16 | | White Earth Portage | 55°32' | 266°10' | Lefroy. | 1·862 | ... | 14·09 | | Shamatawa | 56°21' | 267°04' | Lefroy. | 1·861 | ... | 14·08 | | York Factory | 57°00' | 267°34' | Lefroy. | 1·854 | ... | 14·03 | | York Factory | 57°00' | 267°34' | Lefroy. | ... | 1·523 | 14·07 | | Between the latitudes of 60° and 67°. | | | | | | | Fort Good Hope | 66°16' | 231°30' | Lefroy. | ... | 1·678 | 13·64 | | Fort Norman | 64°31' | 235°16' | Lefroy. | ... | 1·763 | 13·63 | | Fort Resolution | 61°10' | 246°15' | Lefroy. | ... | 1·767 | 13·99 | | Fort Simpson | 61°51' | 238°35' | Lefroy. | ... | 1·957 | 13·84 | * Local disturbance; omitted in the map. § 12. Observations of the Inclination. With Mr. Fox's apparatus.—The Inclinations obtained with needle F. A. of Mr. Fox's apparatus were observed with the face of the circle successively to the east and to the west; the mean of the arcs read in the two positions and at both ends of the needle is the result entered in the Table. The observations were made either direct, i.e. without the employment of deflectors, or with a deflector placed successively at the same angle on either side of the Inclination, and deflecting the needle to the opposite side: half the sum of the arcs read in the two deflected positions is the result in the Table. The poles of the needle F. A. were at no time reversed. When received in England from the maker in the spring of 1842, the mean of the two arcs with the face east and face west were found to give the true Inclination without sensible index error. At Sorel, in September of the same year, the Inclination obtained with needle F. C. of the same apparatus, of which the poles were on that occasion reversed, was found to agree with that shown by needle F. A. within the usual limits of observation error; and at Toronto in October 1842, the Inclination observed with needle F. A. agreed within the same limits with that observed with Gambey's needles of which the poles were reversed. This needle is therefore considered to have had no index error. With Gambey's Inclinometer.—This instrument is the property of Captain Robert FitzRoy of the Royal Navy, by whom it has been kindly lent for general magnetic service. It is the same instrument which was employed by that officer in his voyage of circumnavigation, and was afterwards used by myself in the magnetic survey of the British Islands. It has since travelled with Lieut. Lefroy over the continent of America to the Arctic Circle and back, having been used at more than 100 stations during that journey; and it should be recorded, to the credit of the excellent artist by whom it was made, that it is still in use apparently quite unimpaired. The observations made with the needles of this instrument in different azimuths, and recorded in the Memoir of the Magnetic Survey of the British Islands*, have shown that the curvature of the axles is without sensible fault, and consequently that there is no index error, whatever may be the Inclination. The Inclination with Gambey's circle and needles entered in the Tables are the mean of the arcs in the sixteen positions of the circle and needle; viz. eight positions with the poles direct, and the same number with the poles reversed. * Report of the British Association, 1838, pages 59 and 60. ### Table XLIX. Inclinations observed with the Needles of Fox's Apparatus in Canada and the United States in 1842. Needle F. A. was always employed except when otherwise noticed. | Station | 1842 | Direct or with deflectors | Inclination | |------------------|------|----------------------------|-------------| | Quebec | Sept. 1 | Direct. | 77° 23' 0" | | Quebec | 1 | Def. N. at 40° | 77° 08' 5" | | Quebec | | Def. S. at 50° | 77° 14' 3" | | Three Rivers | 6 | Direct. | 77° 13' 2" | | Three Rivers | 6 | Def. N. at 40° | 77° 09' 9" | | Three Rivers | | Def. N. at 50° | 77° 09' 9" | | Sorel | 8 | Direct. | 77° 22' 6" | | Sorel | 8 | Def. S. at 40° | 77° 14' 3" | | Sorel | | Def. S. at 50° | 77° 16' 1" | | Sorel | 8 | Direct. | 77° 13' 9" | | Sorel | 8 | Def. S. at 40° | 77° 18' 0" | | Sorel | | Def. S. at 50° | 77° 17' 4" | | Sorel | 8 | Direct. | 77° 21' 6" | | Sorel | 8 | Def. S. at 40° | 77° 23' 3" | | Kingsley | 10 | Direct. | 77° 46' 0" | | Kingsley | 10 | Def. N. at 40° | 77° 39' 3" | | Kingsley | | Def. N. at 50° | 77° 34' 4" | | Stanstead | 12 | Direct. | 76° 27' 9" | | Stanstead | 12 | Def. N. at 40° | 76° 14' 0" | | Stanstead | | Def. N. at 50° | 76° 16' 7" | | St. John's | 14 | Direct. | 77° 09' 1" | | St. John's | 14 | Def. N. at 40° | 76° 56' 0" | | St. John's | | Def. N. at 50° | 76° 55' 1" | | St. Helen's | 16 | Direct. | 77° 20' 4" | | St. Helen's | 16 | Def. N. at 40° | 77° 08' 7" | | St. Helen's | | Def. N. at 50° | 77° 10' 1" | | New York | 26 | Direct. | 72° 35' 5" | | New York | 26 | Def. N. at 40° | 72° 35' 5" | | New York | | Def. N. at 50° | 72° 44' 5" | | Providence | 28 | Direct. | 74° 02' 3" | | Providence | 28 | Def. S. at 40° | 73° 59' 2" | | Providence | | Def. S. at 50° | 73° 59' 2" | | Dorchester | Oct. 1 | Direct. | 74° 18' 6" | | Dorchester | | Def. N. at 40° | 74° 05' 0" | | Dorchester | | Def. N. at 50° | 74° 14' 9" | | Station | 1842 | Direct or with deflectors | Inclination | |------------------|------|----------------------------|-------------| | Cambridge | Oct. 3 | Direct. | 74° 23' 1" | | Cambridge | | Def. S. at 40° | 74° 16' 7" | | Cambridge | | Def. S. at 50° | 74° 18' 7" | | Philadelphia | 6 | Direct. | 72° 09' 0" | | Philadelphia | | Def. N. at 40° | 71° 58' 1" | | Philadelphia | | Def. N. at 50° | 71° 58' 0" | | Baltimore | 8 | Direct. | 71° 34' 0" | | Baltimore | | Def. N. at 40° | 71° 35' 4" | | Baltimore | | Def. N. at 50° | 71° 38' 5" | | Baltimore | 8 | Direct. | 71° 47' 5" | | Baltimore | | Def. S. at 40° | 71° 46' 7" | | Baltimore | | Def. S. at 50° | 71° 49' 2" | | Baltimore | 8 | Direct. | 71° 41' 1" | | Baltimore | | Def. N. at 40° | 71° 40' 7" | | Washington | 10 | Direct. | 71° 13' 7" | | Washington | | Def. N. at 40° | 71° 13' 8" | | Washington | | Def. N. at 50° | 71° 13' 9" | | Princeton | 14 | Direct. | 72° 46' 4" | | Princeton | | Def. N. at 40° | 72° 46' 0" | | Princeton | | Def. N. at 50° | 72° 44' 0" | | Newhaven | 18 | Direct. | 73° 31' 4" | | Newhaven | | Def. N. at 40° | 73° 24' 7" | | Newhaven | | Def. N. at 50° | 73° 26' 2" | | West Point | 19 | Direct. | 73° 33' 3" | | West Point | | Def. N. at 40° | 73° 30' 4" | | West Point | | Def. N. at 50° | 73° 30' 4" | | Albany | 21 | Direct. | 74° 54' 5" | | Albany | | Def. N. at 40° | 74° 38' 7" | | Albany | | Def. N. at 50° | 74° 44' 6" | | Toronto | 26 | Direct. | 75° 19' 2" | | Toronto | | Def. S. at 40° | 75° 14' 9" | | Toronto | | Def. S. at 50° | 75° 14' 8" | Observations made with the same Instrument by Lieut. Younghusband, R.A. | Station | 1842 | Direct or with deflectors | Inclination | |------------------|------|----------------------------|-------------| | Toronto | Oct. 29 | Direct. | 75° 17' 9" | | Toronto | | Def. N. at 40° | 75° 19' 3" | | Toronto | | Def. N. at 50° | 75° 14' 0" | | Cleveland | Nov. 3 | Direct. | 73° 02' 3" | | Detroit | 4 | Direct. | 73° 28' 7" | | South Manitou Island | 7 | Direct. | 75° 55' 8" | | South Manitou Island | 7 | Def. N. at 40° | 75° 56' 5" | | South Manitou Island | 7 | Def. N. at 50° | 75° 57' 8" | | Chicago | Nov. 15 | Direct. | 72° 37' 6" | | Chicago | | Def. N. at 40° | 72° 38' 8" | | Chicago | | Def. N. at 50° | 72° 41' 6" | | Toronto | Dec. 30 | Direct. | 75° 16' 0" | | Toronto | | Def. N. at 40° | 75° 15' 9" | | Toronto | | Def. N. at 50° | 75° 17' 8" | --- * In front of the Artillery Barracks. * Mr. Bell's garden. * East of the Roman Catholic Church. * Needle C., poles direct α. * Needle C., poles reversed β. * Captain Cox's garden. * Hotel garden. * A quarter of a mile above the bridge. * 100 yards S.S.W. of barracks. * Lunatic Asylum, Manhattanville. * At the Steam-boat landing. * Near Grove Hall. * Garden of Observatory. * Magnetic Observatory. * 400 yards N. 42° E. from Washington's Monument. * 600 yards north of Monument. * St. Mary's College. * In the grounds of the Capitol, west front. * 200 yards east of the College. * Near the Cemetery. * Professor Bartlett's garden. * N. 39° W. from north tower of the North Dutch Church. * Magnetic Observatory. Inclination observed on the same day with Gambley's needles, poles direct and reversed, 75° 17' 6". * By the angles of deflection with weights. * Inland from the wharf. * Dr. Eldridge's inclosure. ### Table L.—Observations of the Inclination made with Captain FitzRoy's Gambe in 1842, 1843, 1844 and 1845. A large portion of the observations in the countries north of Canada were made by Bombardier Henry. | Station | Date | Needle | Poles, α Direct, β Reversed | Inclination | |------------------|------------|--------|-----------------------------|-------------| | Kingston | Nov. 11 | 1 | 77° 17' | 77° 18' | | Kingston | 11 | 1 | 77° 20' | | | Kingston | 14 | 2 | 77° 14' | 77° 19' | | Kingston | 14 | 2 | 77° 23' | 77° 18' | | Kingston | April 18 | 1 | 77° 18' | | | Kingston | 18 | 1 | 77° 18' | | | Toronto | Dec. | 1 | 75° 14' | 75° 14' | | Hamilton | 29 | 1 | 74° 54' | 74° 55' | | Hamilton | 29 | 2 | 74° 56' | 74° 56' | | Hamilton | 29 | 2 | 74° 52' | 74° 58' | | Hamilton | 29 | 2 | 75° 03' | | | Williamsburg | April 20 | 1 | 76° 30' | 76° 31' | | Williamsburg | 20 | 1 | 76° 31' | 76° 29' | | Williamsburg | 20 | 1 | 76° 26' | 76° 30' | | Williamsburg | 20 | 1 | 76° 31' | | | St. Helen's | 25 | 1 | 76° 59' | 77° 02' | | St. Helen's | 25 | 1 | 77° 05' | 77° 05' | | St. Helen's | 29 | 2 | 77° 03' | 77° 08' | | St. Helen's | 29 | 2 | 77° 13' | 77° 21' | | Isle d'Urval* | 30 | 1 | 77° 21' | 77° 21' | | La Combes | May | 2 | 76° 50' | 76° 50' | | La Combes | 2 | 1 | 76° 50' | 76° 50' | | Pointe aux Chênes*| 3 | 1 | 76° 55' | 76° 55' | | Pointe aux Chênes*| 3 | 1 | 76° 55' | 76° 55' | | Foxes Point | 4 | 1 | 76° 35' | 76° 35' | | Foxes Point | 4 | 1 | 76° 35' | 76° 35' | | Point Aylmer | 5 | 1 | 76° 37' | 76° 41' | | Point Aylmer | 5 | 1 | 76° 44' | 76° 44' | | Chat Falls | 6 | 1 | 75° 11' | 75° 16' | | Chat Falls | 6 | 1 | 75° 11' | 75° 16' | | Grand Calumet | 7 | 1 | 76° 42' | 76° 44' | | Grand Calumet | 7 | 1 | 76° 42' | 76° 44' | | Fort Coulonge | 8 | 1 | 77° 28' | 77° 29' | | Fort Coulonge | 8 | 1 | 77° 30' | 77° 29' | | Pointe Baptême | 9 | 1 | 77° 18' | 77° 26' | | Pointe Baptême | 9 | 1 | 77° 18' | 77° 26' | | 2 Joachim's Portage.| 10 | 1 | 77° 03' | 77° 03' | | 2 Joachim's Portage.| 10 | 1 | 77° 03' | 77° 03' | | Teon Portage | 11 | 1 | 77° 24' | 77° 24' | | Teon Portage | 11 | 1 | 77° 24' | 77° 24' | | Little River | 12 | 1 | 77° 26' | 77° 28' | | Little River | 12 | 1 | 77° 26' | 77° 28' | | Lac du Grand Vase| 13 | 1 | 77° 21' | 77° 21' | | Lac du Grand Vase| 13 | 1 | 77° 22' | 77° 22' | | Lake Nipissing | 14 | 1 | 77° 06' | 77° 09' | | Lake Nipissing | 14 | 1 | 77° 12' | 77° 12' | | Ricollet Falls | 15 | 1 | 76° 43' | 76° 45' | | Ricollet Falls | 15 | 1 | 76° 43' | 76° 45' | | Pointe au Croix | 16 | 1 | 76° 30' | 76° 31' | | Pointe au Croix | 16 | 1 | 76° 32' | 77° 05' | | Lake Huron | 17 | 1 | 77° 05' | 77° 05' | | Snake Island | 18 | 1 | 77° 05' | 77° 05' | | Snake Island | 18 | 1 | 77° 05' | 77° 05' | | Tessalon Point | 19 | 1 | 76° 59' | 76° 59' | | Tessalon Point | 19 | 1 | 76° 59' | 76° 59' | | Pointe au Pins | 20 | 1 | 77° 12' | 77° 13' | | Pointe au Pins | 20 | 1 | 77° 12' | 77° 13' | | Pointe au Crêpe | 21 | 1 | 77° 10' | 77° 11' | | Pointe au Crêpe | 21 | 1 | 77° 12' | 77° 12' | | Fort Michipicoton| 23 | 1 | 78° 04' | 78° 06' | | Fort Michipicoton| 23 | 1 | 78° 04' | 78° 06' | | Otter Island | 24 | 1 | 79° 43' | 79° 43' | | Otter Island | 24 | 1 | 79° 43' | 79° 43' | | Pic Fort | 25 | 1 | 78° 45' | 78° 45' | | Pic Fort | 25 | 1 | 78° 45' | 78° 45' | * The poles were not reversed at these four stations. | Station | Date | Needle | Poles. Direct. | Inclination. | Station | Date | Needle | Poles. Reverse. | Inclination. | |-------------------------|------------|--------|----------------|--------------|--------------------------|------------|--------|-----------------|--------------| | Shamatawa | Aug. 22 | 1 | α 83° 35'6" | 83° 36'2" | Athabasca | Feb. | | β | 81° 37'0" | | Shamatawa | | | β 83° 36'7" | | Athabasca | | | | | | York Factory | | | α 83° 50'1" | 83° 50'5" | Near Big Island | Mar. 18 | 1 | α 82° 02'5" | 82° 08'7" | | York Factory | | | β 83° 50'9" | | Near Big Island | | | β 82° 14'9" | | | York Factory | | | α 83° 40'3" | 83° 44'0" | Fort Simpson | | | α 81° 52'9" | 81° 54'0" | | York Factory | | | β 83° 47'6" | | Fort Simpson | | | β 81° 55'2" | | | Hill River | | 1 | α 82° 54'5" | 82° 55'0" | Fort Simpson | | 2 | α 81° 47'7" | 81° 50'7" | | Hill River | | | β 82° 55'4" | | Fort Simpson | | | β 81° 53'8" | | | Oxford House | | 3 | α 82° 37'7" | 82° 38'8" | Fort Norman | | 5 | α 82° 32'2" | 82° 34'3" | | Oxford House | | | β 82° 39'8" | | Fort Norman | | | β 82° 30'5" | | | Windy Lake | | 4 | α 81° 56'8" | 81° 57'0" | Fort Good Hope | | 9 | α 82° 54'7" | 82° 55'8" | | Windy Lake | | | β 81° 57'2" | | Fort Good Hope | | | β 82° 57'0" | | | White Fall Portage | | 5 | α 81° 46'6" | 81° 47'9" | Fort Good Hope | | 2 | α 82° 52'3" | 82° 56'1" | | White Fall Portage | | | β 81° 49'7" | | Fort Good Hope | | | β 82° 59'7" | | | Hairy Lake | | 6 | α 81° 81'4" | 81° 20'9" | Fort Resolution | June 22 | 1 | α 82° 48'8" | 82° 43'5" | | Hairy Lake | | | β 81° 21'3" | | Fort Resolution | | 2 | α 82° 45'2" | 82° 44'4" | | Old Norway House | | 12 | α 80° 43'8" | 80° 45'4" | Fort Resolution | | 22 | α 82° 39'4" | 82° 45'4" | | Old Norway House | | | β 80° 16'7" | | Portage Gr. Detour | | 25 | α 82° 31'6" | 82° 33'6" | | Lake Winnipeg | | 14 | α 80° 16'9" | 80° 16'8" | Portage Gr. Detour | | | β 82° 35'6" | | | Lake Winnipeg | | | β 80° 31'1" | | Pelican Portage | | 27 | α 82° 24'4" | 82° 26'8" | | Grand Rapid | | 15 | α 80° 19'5" | 80° 21'5" | Pelican Portage | | | β 82° 29'2" | | | Grand Rapid | | | β 80° 24'5" | | Point Providence | July 5 | 1 | α 81° 42'9" | 81° 46'1" | | Cross Lake | | 16 | α 80° 27'1" | 80° 28'2" | Point Providence | | | β 81° 49'3" | | | Cross Lake | | | β 80° 29'4" | | Peace River | | 7 | α 81° 34'2" | 81° 36'9" | | Cedar Lake | | 18 | α 80° 06'5" | 80° 07'1" | Peace River | | | β 81° 39'6" | | | Cedar Lake | | | β 80° 07'7" | | Poplar Island | | 9 | α 81° 04'5" | 81° 04'8" | | Cumberland House | | 24 | α 80° 28'4" | 80° 28'7" | Poplar Island | | | β 81° 05'2" | | | Cumberland House | | | β 80° 29'1" | | Falls of Peace River | | 10 | α 80° 50'5" | 80° 50'8" | | Cumberland House | | 24 | α 80° 31'1" | 80° 30'2" | Falls of Peace River | | | β 80° 51'2" | | | Cumberland House | | | β 80° 32'4" | | Fort Vermilion | | 11 | α 80° 46'9" | 80° 48'4" | | Beaver Lake | | 26 | α 80° 33'3" | 80° 34'2" | Fort Vermilion | | | β 80° 48'0" | | | Beaver Lake | | | β 80° 35'2" | | Fort Vermilion | | 11 | α 80° 44'7" | 80° 47'6" | | Carp Portage | | 27 | α 80° 39'0" | 80° 39'6" | Fort Vermilion | | | β 80° 50'6" | | | Carp Portage | | | β 80° 40'1" | | Peace River | | 17 | α 79° 26'4" | 79° 27'0" | | Portage des Epinettes | | 28 | α 80° 52'1" | 80° 52'6" | Peace River | | | β 79° 27'7" | | | Portage des Epinettes | | | β 80° 53'2" | | Peace River | | 15 | α 79° 59'2" | 80° 00'7" | | Frog Portage | | 29 | α 80° 57'0" | 80° 59'3" | Peace River | | | β 80° 02'3" | | | Frog Portage | | | β 81° 01'6" | | Peace River, opp. | | 19 | α 79° 20'1" | 79° 20'7" | | Little Rock Portage | | 31 | α 80° 15'0" | 80° 16'5" | Peace River, opp. | | | β 79° 21'4" | | | Great Devil's Portage | | 31 | α 80° 17'9" | 80° 30'9" | Peace River, opp. | | | β 79° 21'4" | | | Great Devil's Portage | | | β 80° 29'8" | | River Cadotte | | | β 78° 43'8" | 78° 45'7" | | Pine Portage | | 31 | α 80° 40'6" | 80° 40'3" | River Cadotte | | | β 78° 47'6" | 78° 46'2" | | Pine Portage | | | β 80° 40'6" | | Fort Dunvegan | | 22 | α 78° 47'8" | 78° 46'8" | | Snake Rapid | | 4 | α 80° 38'4" | 80° 38'7" | Fort Dunvegan | | | β 78° 47'8" | | | Snake Rapid | | | β 80° 39'1" | | Fort Dunvegan | | 22 | α 78° 47'8" | | | Portage Sonnante | | 7 | α 80° 80'7" | 80° 11'2" | Lesser Slave Lake F. | Aug. 3 | 1 | α 78° 34'5" | 78° 36'2" | | Portage Sonnante | | | β 80° 12'7" | | Lesser Slave Lake F. | | | β 78° 37'9" | | | Isle à la Crosse | | 9 | α 80° 08'1" | 80° 09'1" | Lesser Slave Lake F. | | 3 | α 78° 39'3" | 78° 39'0" | | Isle à la Crosse | | | β 80° 10'1" | | Lesser Slave Lake F. | | | β 78° 44'5" | | | Isle à la Crosse | | 9 | α 80° 08'5" | 80° 10'5" | Point Dejala | | 6 | α 78° 28'7" | 78° 29'9" | | Isle à la Crosse | | | β 80° 36'7" | | Lesser Slave L. | | | β 78° 31'1" | | | Buffalo Lake | | 13 | α 80° 36'7" | 80° 37'0" | Point Dejala | | | β 78° 53'3" | 78° 55'2" | | Buffalo Lake | | | β 80° 37'2" | | Forks of Athabasca and Slave River | | | β 78° 57'1" | | | River de la Loche | | 14 | α 80° 18'7" | 80° 19'7" | Forks of Athabasca and Slave River | | | β 78° 57'1" | | | River de la Loche | | | β 80° 20'6" | | Athabasca River | | 9 | α 78° 33'7" | 78° 34'1" | | Portage de la Loche, S. end | 16 | α 80° 35'9" | 80° 36'4" | Athabasca River | | | β 78° 34'6" | 78° 34'1" | | Portage de la Loche, N. end | 16 | β 80° 36'8" | | Athabasca River | | | β 78° 15'6" | 78° 16'9" | | Portage de la Loche, N. end | 17 | α 80° 36'7" | 80° 38'0" | Athabasca River | | | β 78° 18'3" | 78° 13'5" | | Portage de la Loche, N. end | 17 | β 80° 40'0" | | Athabasca River | | | β 78° 13'8" | 78° 13'5" | | Clearwater River | | 19 | α 80° 31'8" | 80° 36'2" | Pembina River | | 14 | α 77° 53'8" | 77° 54'0" | | Clearwater River | | | β 80° 30'6" | | Pembina River | | | β 77° 54'3" | | | Pierre au Calumet | | 20 | α 81° 16'1" | 81° 16'8" | Pembina River | | 14 | α 77° 54'3" | 77° 54'2" | | Pierre au Calumet | | | β 81° 17'3" | | Fort Edmonton | | 17 | α 77° 52'2" | 77° 53'4" | | Pointe Brûlée | | 21 | α 81° 30'6" | 81° 30'6" | Fort Edmonton | | | β 77° 54'3" | | | Athabasca | | 30 | α 81° 31'1" | 81° 30'6" | Fort Edmonton | | | β 77° 55'1" | 77° 54'2" | | Athabasca | | | β 81° 36'9" | | Saskatchewan River | | 20 | α 78° 05'2" | 78° 05'2" | | Athabasca | | 30 | α 81° 37'7" | 81° 37'6" | Saskatchewan River | | | β 78° 33'7" | | | Athabasca | | | β 81° 37'9" | | Saskatchewan River | | 21 | α 78° 33'7" | 78° 33'5" | ### Table L. (Continued.) | Station | Date | Needle | Poles | Direct. | Reversed. | Inclination | |--------------------------|----------|--------|-------|---------|-----------|-------------| | Fort Pitt | Aug. 22. | 1 | 78 | 42°2' | | 78 43°0' | | Fort Pitt | | 2 | 78 | 48°9' | | 78 39°1' | | Fort Pitt | | 2 | 78 | 40°4' | | 78 39°1' | | Saskatchewan River | | 1 | 78 | 28°3' | | 78 28°1' | | Saskatchewan River | | 2 | 78 | 16°1' | | 78 16°6' | | Saskatchewan River | | 2 | 78 | 17°1' | | 78 17°1' | | Carlton House | | 2 | 78 | 30°3' | | 78 30°2' | | Carlton House | | 2 | 78 | 30°3' | | 78 30°2' | | Carlton House | | 2 | 78 | 31°1' | | 78 31°2' | | Saskatchewan River | | 2 | 79 | 11°2' | | 79 11°2' | | Cumberland House | | 2 | 80 | 19°6' | | 80 20°5' | | Cumberland House | | 2 | 80 | 21°5' | | 80 19°7' | | Cumberland House | | 2 | 80 | 18°1' | | 80 19°0' | | Cumberland House | | 2 | 80 | 19°9' | | 80 19°9' | | Above the Pas | | 1 | 80 | 24°4' | | 80 24°4' | | Above the Pas | | 1 | 80 | 24°4' | | 80 24°4' | | Devil's Drum Island | Sept. | 1 | 79 | 59°2' | | 80 00°0' | | Devil's Drum Island | | 1 | 80 | 30°6' | | 80 31°6' | | Grand Rapid | | 2 | 80 | 32°7' | | 81 11°1' | | Norway House | | 7 | 81 | 10°5' | | 81 11°1' | | Norway House | | 7 | 81 | 11°7' | | 81 11°1' | | Norway House | | 7 | 81 | 10°8' | | 81 11°1' | | Norway House | | 7 | 81 | 12°0' | | 81 11°1' | | Lake Winnipeg | | 14 | 80 | 24°4' | | 80 24°4' | | Lake Winnipeg | | 14 | 80 | 24°4' | | 80 24°4' | | Lake Winnipeg | | 16 | 79 | 38°9' | | 79 39°0' | | Lake Winnipeg | | 16 | 79 | 39°1' | | 79 06°1' | | Lake Winnipeg | | 17 | 79 | 05°9' | | 79 06°1' | | Lake Winnipeg | | 17 | 79 | 06°4' | | 79 31°5' | | Lake Winnipeg | | 18 | 79 | 31°8' | | 79 03°4' | | Fort Alexander | | 19 | 79 | 03°2' | | 79 02°5' | | Fort Alexander | | 19 | 79 | 03°7' | | 79 02°5' | | Fort Alexander | | 19 | 79 | 02°5' | | 79 02°5' | | Fort Francis | | 30 | 77 | 44°7' | | 77 44°4' | | Fort Francis | | 30 | 77 | 44°7' | | 77 44°4' | | Fort Francis | | 30 | 77 | 45°1' | | 77 44°4' | | Fort William | | 1 | 78 | 07°2' | | 78 07°5' | | Fort William | | 2 | 77 | 55°2' | | 77 55°5' | | Fort William | | 2 | 77 | 55°8' | | 77 55°5' | | Fort William | | 1 | 77 | 54°9' | | 77 55°5' | | Fort William | | 1 | 77 | 56°1' | | 78 24°0' | | S.shore Lake Superior | | 14 | 78 | 23°2' | | 78 24°0' | | S.shore Lake Superior | | 14 | 78 | 24°8' | | 78 24°0' | | Pic Fort | | 17 | 78 | 32°0' | | 78 32°8' | | Pic Fort | | 17 | 78 | 33°6' | | 78 31°4' | | Pic Fort | | 17 | 78 | 29°9' | | 78 30°1' | | Pic Fort | | 17 | 78 | 30°4' | | 78 33°7' | | White River | | 21 | 78 | 33°4' | | 78 33°7' | | White River | | 21 | 78 | 34°1' | | 78 33°7' | | White River | | 21 | 78 | 31°2' | | 78 32°5' | | White River | | 21 | 78 | 33°3' | | 78 33°7' | * Below the forks of the north and south branches. * The observation with Needle No. 1 was repeated in consequence of the difference between the results with Nos. 1 and 2. * Observed by Lieut. Younghusband, R.A. b Royal Artillery Barracks. c Garden at Rockfort. d Orchard behind Chesleys. e Garden on the Mountain. f Near Wolfe's Monument. g Near the Clifton Hotel. h Behind the High School. i Garden of the Hon. J. Gordon. k North-west corner of Lafayette and Orleans Straits. l Garden near the Ferry. m Garden at the foot of the hill. ### Table LI. General Table of the Observations of the Magnetic Inclination. | Station | Lat. | Long. | Year | Observer | Inclination | |------------------|------|-------|------|----------|-------------| | Princeton | 38°23' | 272°30' | 1840. | Locke | 69°22'8" | | Mount Vernon | 37°59' | 272°13' | 1840. | Locke | 68°56'3" | | New Harmony | 38°11' | 272°12' | 1840. | Locke | 69°03'6" | | St. Louis | 38°38' | 269°56' | 1839. | Locke | 69°31'4" | | St. Louis | 38°38' | 269°56' | 1841. | Loomis | 69°25'5" | | St. Louis | 38°38' | 269°56' | 1841. | Nicollet | 69°27'9" | Between 68°30' and 69°30'. | Station | Lat. | Long. | Year | Observer | Inclination | |------------------|------|-------|------|----------|-------------| | Lexington | 38°06' | 275°42' | 1840. | Locke | 69°54'5" | | Clay's Ferry | 37°54' | 275°42' | 1840. | Locke | 69°49'0" | | Cincinnati | 39°06' | 275°38' | 1838-1844 | Locke | 70°26'5" | | Cincinnati | 39°06' | 275°38' | 1841. | Loomis | 70°27'7" | | Williamstown | 38°36' | 275°38' | 1840. | Locke | 70°04'1" | | Frankfort | 38°14' | 275°20' | 1840. | Locke | 69°54'9" | | Louisville | 38°03' | 274°30' | 1840. | Locke | 69°54'4" | | Paoli | 38°05' | 273°35' | 1840. | Locke | 69°33'8" | | Vincennes | 38°43' | 272°35' | 1840. | Locke | 69°51'0" | | Vincennes | 38°43' | 272°31' | 1841. | Loomis | 69°52'8" | | Edwardsville | 38°50' | 270°07' | 1841. | Loomis | 69°57'7" | | Bunker's Hill | 39°04' | 270°07' | 1841. | Loomis | 69°49'1" | | Upper Alton | 38°55' | 269°57' | 1841. | Loomis | 69°45'7" | | Alton | 38°54' | 269°56' | 1841. | Loomis | 69°34'8" | | Monticello | 38°57' | 269°55' | 1841. | Loomis | 69°38'9" | Between 69°30' and 70°30'. | Station | Lat. | Long. | Year | Observer | Inclination | |------------------|------|-------|------|----------|-------------| | Washingtona | 38°53' | 282°59' | 1839. | Loomis | 71°21'4" | | Washingtona | 38°53' | 282°59' | 1841. | Graham | 71°15'9" | | Washingtona | 38°53' | 282°59' | 1844. | Graham | 71°10'5" | | Washingtona | 38°53' | 282°59' | 1841. | Nicollet | 71°15'0" | | Washingtona | 38°53' | 282°59' | 1842. | Lefroy | 71°13'8" | | Washingtona | 38°53' | 282°59' | 1844. | Locke | 71°13'4" | | Washingtonb | 38°53' | 282°59' | 1844. | Locke | 71°39'3" | | Washingtonc | 38°53' | 282°59' | 1844. | Locke | 71°34'8" | | Washingtond | 38°53' | 282°59' | 1844. | Locke | 71°14'9" | | Washingtone | 38°53' | 282°59' | 1844. | Locke | 71°20'5" | | Georgetown | 38°53' | 282°57' | 1844. | Locke | 71°19'0" | | Mount Vernon | 38°41' | 282°53' | 1844. | Locke | 70°55'5" | | Marietta Island | 39°25' | 278°32' | 1845. | Locke | 71°22'3" | | Hebron | 39°59' | 277°31' | 1841. | Loomis | 71°10'1" | | Columbus | 39°57' | 276°57' | 1840. | Locke | 71°04'9" | | Columbus | 39°57' | 276°57' | 1841. | Loomis | 71°04'3" | | Columbus | 39°57' | 276°57' | 1845. | Locke | 71°04'3" | | Springfield | 39°54' | 276°09' | 1840. | Locke | 71°27'4" | | Lebanon | 39°26' | 275°54' | 1840. | Locke | 71°02'7" | | Carrolton | 39°38' | 275°51' | 1845. | Locke | 71°10'0" | | Mason | 39°22' | 275°47' | 1840. | Locke | 70°54'2" | | Dayton | 39°44' | 275°43' | 1838. | Locke | 71°22'7" | | Dayton | 39°44' | 275°43' | 1840. | Locke | 71°22'0" | | Hamilton | 39°23' | 275°28' | 1840. | Locke | 70°58'0" | | Oxford | 39°30' | 275°22' | 1845. | Locke | 71°10'0" | | Richmond | 39°49' | 275°13' | 1845. | Locke | 71°20'3" | | Pekin | 40°35' | 270°24' | 1841. | Loomis | 71°13'2" | --- *a* Grounds East or West or in front of the Capitol. *b* Magnetic Observatory. *c* Old Depot near Georgetown. *d* Near the Patent Office. *e* Near the War Office. ## Table LI. (Continued.) | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | New York (New Asylum) | 40° 48' | 285° 58' | 1841. | Locke | 72° 21' | | Trenton | 40° 13' | 285° 20' | 1841. | Locke | 71° 59' | | Bristol | 40° 06' | 285° 13' | 1842. | Locke | 72° 25' | | Philadelphia^a | 39° 58' | 284° 50' | 1844. | Graham | 72° 09' | | Philadelphia^b | 39° 58' | 284° 50' | 1839. | Loomis | 72° 07' | | Philadelphia^c | 39° 58' | 284° 50' | 1841. | {Graham, Bache} | 71° 54' | | Philadelphia | 39° 58' | 284° 50' | 1841. | Bache | 71° 58' | | Philadelphia | 39° 58' | 284° 50' | 1841. | Locke | 72° 00' | | Philadelphia | 39° 58' | 284° 50' | 1842. | Lefroy | 71° 59' | | Philadelphia | 39° 58' | 284° 50' | 1842. | Locke | 72° 01' | | Philadelphia | 39° 58' | 284° 50' | 1844. | Locke | 71° 59' | | Cumberland | 40° 13' | 283° 10' | 1844. | Locke | 71° 36' | | Baltimore^d | 39° 17' | 283° 23' | 1839. | Loomis | 71° 50' | | Baltimore^d | 39° 17' | 283° 23' | 1841. | Graham | 71° 47' | | Baltimore^d | 39° 17' | 283° 23' | 1841. | Nicollet | 71° 50' | | Baltimore^e | 39° 17' | 283° 23' | 1842. | Lefroy | 71° 47' | | Baltimore^e | 39° 17' | 283° 23' | 1840. | Bache | 71° 34' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Nicollet | 71° 35' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Graham | 71° 32' | | Baltimore^e | 39° 17' | 283° 23' | 1842. | Lefroy | 71° 36' | | Baltimore^e | 39° 17' | 283° 23' | 1844. | Graham | 71° 32' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Locke | 71° 34' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Graham | 71° 48' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Graham | 71° 49' | | Baltimore^e | 39° 17' | 283° 23' | 1841. | Nicollet | 71° 39' | | Baltimore^e | 39° 17' | 283° 22' | 1841. | Locke | 71° 39' | | Baltimore^e | 39° 17' | 283° 22' | 1841. | Graham | 71° 39' | | Baltimore^e | 39° 17' | 283° 22' | 1842. | Lefroy | 71° 40' | | Baltimore^e | 39° 17' | 283° 22' | 1844. | Graham | 71° 39' | | Mount St. Mary's | 39° 41' | 282° 42' | 1842. | Locke | 71° 46' | | Chambersburg | 39° 55' | 282° 20' | 1842. | Locke | 71° 57' | | Allegheny Summit | 40° 27' | 281° 50' | 1845. | Locke | 72° 27' | | Wheeling | 40° 08' | 279° 13' | 1844. | Locke | 72° 19' | | Wheeling | 40° 08' | 279° 13' | 1845. | Locke | 72° 13' | | Dover | 40° 33' | 278° 30' | 1841. | Loomis | 72° 19' | | Frazerburg | 40° 09' | 277° 52' | 1841. | Loomis | 71° 48' | | Urbana | 40° 05' | 276° 12' | 1840. | Locke | 71° 39' | | Piqua | 40° 06' | 275° 47' | 1840. | Locke | 71° 35' | | St. Mary's | 40° 32' | 275° 41' | 1845. | Locke | 72° 00' | | Ottawa | 41° 15' | 271° 10' | 1841. | Nicollet | 72° 20' | | Juliet | 41° 30' | 271° 09' | 1841. | Nicollet | 72° 16' | | Peru | 41° 23' | 270° 55' | 1841. | Loomis | 71° 51' | | Peru | 41° 23' | 270° 55' | 1841. | Nicollet | 71° 49' | | Lostgrove | 41° 39' | 269° 51' | 1839. | Locke | 72° 02' | | Wabisepinecon River | 41° 44' | 269° 37' | 1839. | Locke | 72° 15' | | Davenport | 41° 30' | 269° 34' | 1839. | Locke | 71° 55' | | Brown's Settlement | 42° 02' | 268° 54' | 1839. | Locke | 72° 21' | ### 72° 30' to 73° 30' | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | Stonington | 41° 20' | 288° 05' | 1845. | Renwick | 73° 25' | | Greenport | 41° 06' | 287° 38' | 1845. | Renwick | 72° 57' | | Newhaven | 41° 18' | 287° 02' | 1839. | Loomis | 73° 26' | | Newhaven | 41° 18' | 287° 02' | 1842. | Lefroy | 73° 27' | | Newhaven | 41° 18' | 287° 02' | 1842. | Locke | 73° 29' | | Newhaven | 41° 18' | 287° 02' | 1844. | Renwick | 73° 20' | ^a Rittenhouse Square. ^b In front of Dr. Bache's House. ^c Girard College. ^{d e f} are three stations in the grove which extends N. and E. of the Washington Monument. ^g St. Mary's College | Station | Lat. | Long. | Year | Observer | Inclination | |-------------------------|------|-------|------|------------|-------------| | Bridgeport | 41° 11' | 286° 48' | 1845. | Renwick | 73° 21'3" | | West Point | 41° 24' | 285° 59' | 1839. | Loomis | 73° 27'4" | | West Point | 41° 24' | 285° 59' | 1840. | Graham | 73° 20'1" | | West Point | 41° 24' | 285° 59' | 1841. | Bache | 73° 37'2" | | West Point | 41° 24' | 285° 59' | 1842. | Lefroy | 73° 30'4" | | New York, Columbia College | 40° 43' | 285° 59' | 1834. | Bache | 72° 51'7" | | New York, Columbia College | 40° 43' | 285° 59' | 1844. | Renwick | 72° 38'0" | | New York, Columbia College | 40° 43' | 285° 59' | 1839. | Loomis | 72° 52'2" | | New York, Columbia College | 40° 43' | 285° 59' | 1841. | Locke | 72° 41'0" | | New York, Columbia College | 40° 43' | 285° 59' | 1844. | Locke | 72° 42'6" | | New York, Columbia College | 40° 43' | 285° 59' | 1845. | Renwick | 72° 40'6" | | Sandy Hook | 40° 27' | 285° 58' | 1844. | Renwick | 72° 37'9" | | Lunatic Asylum, Manhattanville | 40° 49' | 285° 57' | 1841. | Locke | 72° 39'6" | | Lunatic Asylum, Manhattanville | 40° 49' | 285° 57' | 1844. | Locke | 72° 42'5" | | Lunatic Asylum, Manhattanville | 40° 49' | 285° 57' | 1842. | Lefroy | 72° 39'5" | | Newark | 40° 43' | 285° 50' | 1841. | Locke | 72° 49'0" | | Newark | 40° 43' | 285° 50' | 1844. | Locke | 72° 48'3" | | New Brunswick | 40° 30' | 285° 25' | 1844. | Locke | 72° 43'2" | | Princeton | 40° 30' | 285° 25' | 1844. | Locke | 72° 41'4" | | Princeton | 40° 30' | 285° 25' | 1839. | Loomis | 72° 35'9" | | Princeton | 40° 22' | 285° 20' | 1842. | Lefroy | 72° 47'1" | | Princeton | 40° 22' | 285° 20' | 1844. | Loomis | 72° 39'5" | | Princeton | 40° 22' | 285° 20' | 1844. | Locke | 72° 40'4" | | Pittsburg | 40° 32' | 279° 58' | 1839. | Loomis | 72° 38'9" | | Pittsburg | 40° 32' | 279° 58' | 1841. | Locke | 72° 43'5" | | Pittsburg | 40° 32' | 279° 58' | 1842. | Locke | 72° 43'2" | | Pittsburg | 40° 32' | 279° 58' | 1845. | Locke | 72° 46'7" | | Beaver | 40° 44' | 279° 33' | 1839. | Loomis | 72° 40'3" | | Hartford | 41° 19' | 279° 26' | 1840. | Loomis | 72° 59'8" | | Kinsman | 41° 30' | 279° 26' | 1840. | Loomis | 73° 08'1" | | Wellsville | 40° 38' | 279° 16' | 1844. | Locke | 72° 35'3" | | Bazetta | 41° 20' | 279° 15' | 1840. | Loomis | 72° 59'7" | | Warren | 41° 16' | 279° 11' | 1840. | Loomis | 72° 00'7" | | Warren | 41° 16' | 279° 11' | 1844. | Locke | 72° 55'9" | | Ashtabula | 41° 52' | 279° 08' | 1844. | Locke | 73° 25'0" | | Windham | 41° 15' | 278° 57' | 1840. | Loomis | 73° 03'4" | | Shakersville | 41° 15' | 278° 47' | 1840. | Loomis | 72° 56'6" | | Streetsboro | 41° 15' | 278° 40' | 1840. | Loomis | 72° 53'0" | | Aurora | 41° 20' | 278° 40' | 1840. | Loomis | 72° 55'5" | | Twinsburgh | 41° 20' | 278° 34' | 1840. | Loomis | 72° 51'3" | | Hudson | 41° 15' | 278° 34' | 1838-1842 | Loomis | 72° 48'4" | | Tallmadge | 41° 06' | 278° 33' | 1840. | Loomis | 72° 50'7" | | Bedford | 41° 24' | 278° 28' | 1840. | Loomis | 72° 58'1" | | Fulton | 40° 55' | 278° 22' | 1841. | Loomis | 72° 38'9" | | Clinton | 40° 58' | 278° 20' | 1841. | Loomis | 72° 44'0" | | Cleveland | 41° 30' | 278° 18' | 1839. | Loomis | 73° 26'0" | | Cleveland | 41° 30' | 278° 18' | 1840. | Loomis | 73° 14'1" | | Cleveland | 41° 30' | 278° 18' | 1841. | Loomis | 73° 04'3" | | Cleveland | 41° 30' | 278° 18' | 1842. | Younghusband | 73° 03'8" | | Cleveland | 41° 30' | 278° 18' | 1843. | Locke | 73° 08'0" | | Brooklyn | 41° 30' | 278° 17' | 1841. | Loomis | 73° 16'3" | | Huron | 41° 26' | 277° 33' | 1843. | Locke | 73° 00'0" | | Sandusky | 41° 29' | 277° 13' | 1839. | Loomis | 72° 57'8" | | Amherstburg | 42° 06' | 276° 47' | 1845. | Lefroy | 73° 29'9" | *a* Pott's Wood. *b* Rock Hills (trap). ### Table LI. (Continued.) | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|--------------|-------------| | Munroe | 41°55' | 276°32' | 1839. | LOOMIS. | 73°32'3" | | Munroe | 41°55' | 276°32' | 1841. | LOOMIS. | 73°19'0" | | Toledo | 41°41' | 276°28' | 1839. | LOOMIS. | 73°06'1" | | Maumee | 41°34' | 276°23' | 1839. | LOOMIS. | 72°49'1" | | Ypsilanti | 42°14' | 276°22' | 1839. | LOOMIS. | 73°18'0" | | Ypsilanti | 42°14' | 276°22' | 1841. | LOOMIS. | 73°18'8" | | Ann Arbor | 42°18' | 276°15' | 1839. | LOOMIS. | 73°13'9" | | Ann Arbor | 42°18' | 276°15' | 1841. | LOOMIS. | 73°16'5" | | Ann Arbor | 42°18' | 276°15' | 1843. | LOCKE. | 73°13'6" | | Chicago | 41°53' | 272°16' | 1841. | LOOMIS. | 72°47'8" | | Chicago | 41°53' | 272°16' | 1841. | NICOLLET. | 72°45'8" | | Chicago | 41°53' | 272°16' | 1842. | YOUNGHUSBAND.| 72°39'3" | | Campbells | 43°01' | 270°34' | 1841. | LOOMIS. | 73°28'1" | | Mineral Point | 42°50' | 270°02' | 1839. | LOCKE. | 73°20'6" | | Mineral Point | 42°50' | 270°02' | 1841. | LOOMIS. | 73°23'0" | | Galena | 42°28' | 269°47' | 1841. | LOOMIS. | 73°03'0" | | Platteville | 42°43' | 269°46' | 1841. | LOOMIS. | 73°17'2" | | Farmer's Creek | 42°13' | 269°37' | 1839. | LOCKE. | 72°36'0" | | Dubuques Town | 42°29' | 269°37' | 1839. | LOCKE. | 73°05'0" | | Little Mahoqueta | 42°31' | 269°29' | 1839. | LOCKE. | 73°08'0" | | White Water River | 42°18' | 269°22' | 1839. | LOCKE. | 72°55'0" | | Iron Ore Bed | 41°55' | 269°20' | 1839. | LOCKE. | 72°50'5" | | Turkey River | 42°42' | 269°12' | 1839. | LOCKE. | 73°11'0" | | Mahoqueta, North Branch | 42°23' | 269°08' | 1839. | LOCKE. | 72°51'0" | | Mahoqueta River | 42°14' | 269°05' | 1839. | LOCKE. | 72°43'6" | | Prairie du Chien | 43°01' | 268°51' | 1839. | LOCKE. | 73°16'6" | #### 73°30' to 74°30'. | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|--------------|-------------| | Boston | 42°22' | 289°01' | 1842. | LOCKE. | 74°05'7" | | Boston | 42°21' | 288°56' | 1841. | GRAHAM. | 74°09'4" | | Dorchester | 42°19' | 288°55' | 1842. | LEFROY. | 74°12'8" | | Cambridge | 42°22' | 288°52' | 1839. | LOOMIS. | 74°20'1" | | Cambridge | 42°22' | 288°52' | 1841. | GRAHAM and BOND.* | 74°17'3" | | Cambridge | 42°22' | 288°52' | 1842. | LOCKE. | 74°14'8" | | Cambridge | 42°22' | 288°52' | 1842. | LEFROY. | 74°19'5" | | Cambridge | 42°22' | 288°52' | 1845. | LOCKE. | 74°19'4" | | Cambridge, New Observatory| 42°23' | 288°52' | 1844. | GRAHAM. | 74°18'2" | | Providence | 41°50' | 288°35' | 1839. | LOOMIS. | 73°59'6" | | Providence | 41°50' | 288°35' | 1841. | BACHE. | 74°02'8" | | Providence | 41°49' | 288°35' | 1842. | LEFROY. | 74°00'0" | | Worcester | 42°16' | 288°12' | 1839. | LOOMIS. | 74°20'6" | | Springfield | 42°06' | 287°24' | 1839. | LOOMIS. | 74°06'9" | | Springfield | 42°06' | 287°24' | 1841. | BACHE. | 74°10'7" | | Longmeadow | 42°02' | 287°24' | 1839. | LOOMIS. | 74°05'3" | | Harford | 41°46' | 287°19' | 1839. | LOOMIS. | 73°58'1" | | Powkeepsie | 41°41' | 286°05' | 1844. | LOCKE. | 73°57'7" | | Opposite Powkeepsie | 41°41' | 286°04' | 1844. | LOCKE. | 74°12'3" | | Port Sarnia | 42°58' | 277°26' | 1845. | LEFROY. | 74°15'7" | | Detroit | 42°24' | 277°00' | 1845. | LEFROY. | 73°38'8" | | Detroit | 42°25' | 277°00' | 1839. | LOOMIS. | 73°42'6" | | Detroit | 42°25' | 277°00' | 1841. | LOOMIS. | 73°35'2" | | Detroit | 42°25' | 277°00' | 1841. | NICOLLET. | 73°32'7" | | Detroit | 42°25' | 277°00' | 1842. | YOUNGHUSBAND.| 73°28'7" | | Detroit | 42°25' | 277°00' | 1843. | LOCKE. | 73°32'2" | * Mr. William Cranch Bond, Director of the Cambridge Observatory. This result is the mean of 288 observations with two needles. ### Table LI. (Continued.) | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|-------------|-------------| | **73° 30' to 74° 30' (continued).** | | | | | | | Madison | 43° 04' | 27° 54' | 1839. | Locke | 74° 03'0" | | Madison | 43° 03' | 27° 54' | 1841. | Loomis | 74° 06'5" | | Blue Mound | 43° 01' | 27° 22' | 1839. | Locke | 73° 41'0" | | Blue Mound | 43° 00' | 27° 22' | 1841. | Loomis | 73° 34'9" | | Hickoks | 42° 58' | 27° 13' | 1841. | Loomis | 73° 39'5" | | **74° 30' to 75° 30'.** | | | | | | | Portland | 43° 41' | 289° 40' | 1845. | Locke | 75° 13'7" | | Portsmouth | 43° 05' | 289° 16' | 1844. | Graham | 74° 47'7" | | Portsmouth | 43° 03' | 289° 16' | 1844. | and Whipple* | 74° 53'7" | | Portsmouth | 43° 04' | 289° 15' | 1844. | Whipple* | 74° 58'2" | | Portsmouth | 43° 05' | 289° 15' | 1844. | | 74° 57'4" | | Greenbush | 42° 39' | 286° 16' | 1844. | Locke | 74° 40'6" | | Albany | 42° 39' | 286° 15' | 1839. | Loomis | 74° 51'3" | | Albany | 42° 39' | 286° 15' | 1841. | Bache | 74° 40'1" | | Albany | 42° 39' | 286° 15' | 1841. | Nicollet | 74° 39'9" | | Albany | 42° 39' | 286° 15' | 1842. | Lefroy | 74° 44'6" | | Albany | 42° 39' | 286° 15' | 1844. | Locke | 74° 40'2" | | Schenectady | 42° 48' | 286° 05' | 1839. | Loomis | 74° 36'1" | | Utica | 43° 07' | 284° 47' | 1839. | Loomis | 74° 57'2" | | Utica | 43° 07' | 284° 47' | 1844. | Locke | 74° 48'8" | | Syracuse | 43° 00' | 283° 46' | 1839. | Loomis | 74° 50'9" | | Chat Falls | 45° 26' | 283° 28' | 1843. | Lefroy | 75° 16'1" | | Oswego | 45° 26' | 283° 24' | 1839. | Loomis | 75° 11'3" | | Oswego | 43° 26' | 283° 24' | 1841. | Nicollet | 75° 08'1" | | Rochester | 43° 08' | 282° 09' | 1844. | Locke | 74° 38'8" | | Lockport | 43° 11' | 281° 14' | 1844. | Locke | 74° 44'2" | | Buffaloe | 42° 53' | 281° 06' | 1839. | Loomis | 74° 40'8" | | Buffaloe | 42° 53' | 281° 06' | 1844. | Locke | 74° 36'5" | | Buffaloe | 42° 52' | 281° 06' | 1845. | Lefroy | 74° 37'0" | | Niagara | 43° 05' | 280° 51' | 1841. | Nicollet | 74° 52'4" | | Niagara | 43° 05' | 280° 51' | 1845. | Lefroy | 74° 49'6" | | Toronto Observatory | 43° 39' | 280° 39' | 1841. | Lefroy and Younghusband | 75° 15'5" | | Toronto Observatory | 43° 39' | 280° 39' | 1845. | Locke | 75° 15'0" | | Near Toronto | 43° 39' | 280° 41' | 1844. | Locke | 75° 12'5" | | Hamilton | 43° 16' | 280° 04' | 1842. | Lefroy | 74° 56'7" | | Hamilton | 43° 16' | 280° 04' | 1845. | Lefroy | 74° 55'4" | | Goderich | 43° 45' | 278° 08' | 1845. | Lefroy | 75° 04'8" | | **75° 30' to 76° 30'.** | | | | | | | Bangor | 44° 48' | 291° 13' | 1841. | Graham | 76° 11'6" | | Forks of the Kennebec | 45° 20' | 290° 02' | 1844. | Graham | 76° 23'7" | | Locke's Mills | 44° 24' | 289° 16' | 1845. | Locke | 75° 50'7" | | Bethel | 44° 27' | 289° 09' | 1845. | Locke | 75° 51'0" | | Gorham | 44° 27' | 288° 47' | 1845. | Locke | 75° 33'4" | | Hall's Stream | 45° 01' | 288° 30' | 1845. | Graham | 76° 23'5" | | Mount Washington | 44° 17' | 288° 41' | 1845. | Locke | 75° 45'0" | | Near Mount Washington | 44° 16' | 288° 31' | 1845. | Locke | 75° 40'0" | | Stanstead | 45° 02' | 287° 50' | 1842. | Lefroy | 76° 19'5" | | L. Memphremagog, East shore. | 45° 01' | 287° 41' | 1845. | Whipple* | 76° 08'6" | | Cornwall | 45° 02' | 285° 13' | 1845. | Younghusband | 76° 16'4" | | Brockville | 44° 35' | 284° 15' | 1845. | Younghusband | 76° 18'9" | | Penetanguishene | 44° 49' | 279° 59' | 1844. | Lefroy | 76° 20'1" | | South Manitou Island | 45° 05' | 274° 22' | 1841. | Loomis | 75° 59'3" | | South Manitou Island | 45° 05' | 274° 22' | 1842. | Younghusband | 75° 56'6" | * Lieut. A. W. Whipple, of the United States Corps of Topographical Engineers. The observations at Portsmouth were made at five different stations, which are named in order of succession corresponding with the entries in the Table; Jamaica Island; near the north extremity of the base line of the Trigonometrical Survey of the harbour; Mr. Shellby's field; Shapley's Point; One Tree Island. † Local disturbance; omitted in the map. | Station | Lat. | Long. | Year | Observer | Inclination | |-------------------------------|--------|-------|------|----------------|-------------| | Grand Falls of the St. John | 47° 03' | 292° 15' | 1843 | GRAHAM | 77° 29'5" | | Aroostook Hill | 46° 47' | 292° 13' | 1841 | GRAHAM | 77° 24'1" | | Blue Hill | 46° 38' | 292° 13' | 1841 | GRAHAM | 77° 18'1" | | Park's Hill | 46° 07' | 292° 13' | 1840 | GRAHAM | 77° 02'5" | | Park's Hill | 46° 07' | 292° 13' | 1841 | GRAHAM | 77° 00'7" | | N.E. Boundary Station, No. 1. | 45° 57' | 292° 13' | 1840 | GRAHAM | 76° 57'4" | | Near the Grand Forks of the St. John | 46° 35' | 290° 07' | 1844 | GRAHAM | 77° 25'9" | | S.W. branch of the River St. John | 46° 25' | 289° 56' | 1844 | GRAHAM | 77° 24'7" | | Moose River | 45° 39' | 289° 44' | 1844 | GRAHAM | 76° 48'5" | | Taschereau's | 45° 49' | 289° 36' | 1844 | GRAHAM | 76° 50'4" | | Quebec | 46° 49' | 288° 44' | 1842 | LEFROY | 77° 15'3" | | Quebec | 46° 49' | 288° 44' | 1845 | YOUNGHUSBAND | 77° 08'8" | | Three Rivers | 46° 19' | 287° 24' | 1842 | LEFROY | 77° 10'7" | | St. John's | 45° 20' | 287° 00' | 1842 | LEFROY | 77° 00'1" | | Sorel | 46° 02' | 287° 00' | 1842 | LEFROY | 77° 17'0" | | Rouse's Point | 45° 00' | 286° 37' | 1845 | GRAHAM and WHIPPLE | 76° 39'8" | | St. Helen's | 45° 31' | 286° 25' | 1842 | LEFROY | 77° 13'1" | | St. Helen's | 45° 31' | 286° 25' | 1843 | LEFROY | 77° 05'3" | | Montreal | 45° 30' | 286° 24' | 1845 | YOUNGHUSBAND | 77° 08'6" | | Isle d'Urval | 45° 24' | 286° 14' | 1843 | LEFROY | 77° 21'1" | | La Combes | 45° 32' | 285° 51' | 1843 | LEFROY | 76° 50'6" | | Pointe aux Chênes | 45° 37' | 285° 05' | 1843 | LEFROY | 76° 55'4" | | Williamsburg | 44° 55' | 284° 53' | 1843 | LEFROY | 76° 30'1" | | Fox's Point | 45° 32' | 284° 26' | 1843 | LEFROY | 76° 35'3" | | Point Aylmer | 45° 29' | 284° 12' | 1843 | LEFROY | 76° 41'0" | | Kingston | 44° 13' | 283° 25' | 1842 | LEFROY | 77° 18'7" | | Kingston | 44° 13' | 283° 25' | 1843 | YOUNGHUSBAND | 77° 14'4" | | Grand Calumet | 45° 45' | 283° 20' | 1843 | LEFROY | 76° 44'4" | | Fort Coulange | 45° 56' | 283° 13' | 1843 | LEFROY | 77° 29'7" | | Pointe Baptême | 46° 06' | 282° 34' | 1843 | LEFROY | 77° 26'6" | | Deux Joachim's Portage | 46° 12' | 281° 41' | 1843 | LEFROY | 77° 03'8" | | Trou Portage | 46° 15' | 281° 27' | 1843 | LEFROY | 77° 24'4" | | Little River | 46° 18' | 281° 17' | 1843 | LEFROY | 77° 28'5" | | Lac du Grand Vase | 46° 18' | 280° 34' | 1843 | LEFROY | 77° 21'7" | | Lake Nipissing | 46° 13' | 280° 01' | 1843 | LEFROY | 77° 09'5" | | Ricolet Falls | 45° 57' | 278° 59' | 1843 | LEFROY | 76° 45'4" | | Pointe au Croix | 45° 55' | 278° 42' | 1843 | LEFROY | 76° 31'3" | | Lake Huron | 46° 00' | 278° 10' | 1843 | LEFROY | 77° 05'6" | | Fort la Cloche | 46° 07' | 277° 35' | 1844 | LEFROY | 76° 50'2" | | Snake Island | 46° 07' | 277° 00' | 1843 | LEFROY | 77° 05'5" | | Tessalon Point | 46° 16' | 276° 29' | 1843 | LEFROY | 76° 59'3" | | Port Brady | 46° 30' | 275° 36' | 1841 | LOOMIS | 77° 29'7" | | Sault St. Mary | 46° 30' | 275° 26' | 1843 | LOCKE | 77° 30'3" | | Sault St. Mary | 46° 30' | 275° 26' | 1845 | RAE | 77° 19'5" | | Mackinac | 45° 51' | 275° 19' | 1841 | NICOLLET | 76° 34'5" | | Mackinac | 45° 51' | 275° 19' | 1841 | LOOMIS | 76° 37'5" | | Mackinac | 45° 51' | 275° 19' | 1843 | LOCKE | 76° 38'9" | | Gross Cap | 46° 32' | 275° 17' | 1841 | LOOMIS | 77° 05'3" | | Point aux Pins | 46° 29' | 275° 19' | 1843 | LEFROY | 77° 13'4" | | Point aux Pins | 46° 29' | 275° 19' | 1845 | RAE | 77° 16'0" | | Point au Crêpe | 46° 58' | 275° 02' | 1843 | LEFROY | 77° 11'5" | | Encampment | 46° 44' | 272° 17' | 1843 | LOCKE | 76° 58'3" | | Houghton's River | 47° 28' | 271° 59' | 1843 | LOCKE | 77° 20'7" | | United States' Agency | 47° 28' | 271° 59' | 1843 | LOCKE | 77° 13'5" | | Ontanogon River | 46° 52' | 270° 29' | 1843 | LOCKE | 77° 13'2" | | Portage Ecarté | 48° 25' | 270° 15' | 1843 | LEFROY | 77° 13'5" | | Lapointe | 46° 47' | 269° 02' | 1843 | LOCKE | 76° 56'0" | * Local disturbance; omitted in the map. MDCCXLVI. | Station | Lat. | Long. | Year | Observer | Inclination | |-------------------------------|------|-------|------|----------|-------------| | North bank of the St. John River | 47° 04' | 292° 13' | 1843. | GRAHAM. | 77° 31' | | Peconk Hill | 46° 59' | 292° 13' | 1841. | GRAHAM. | 77° 32' | | Mouth of the Grand River | 47° 11' | 292° 03' | 1844. | GRAHAM. | 77° 38' | | Mouth of the Madawaska | 47° 22' | 291° 41' | 1843. | GRAHAM. | 77° 47' | | Albert's Inn | 47° 17' | 291° 32' | 1843. | GRAHAM. | 77° 44' | | Fort Kent | 47° 15' | 291° 25' | 1843. | GRAHAM. | 77° 43' | | St. Francis River | 47° 11' | 291° 06' | 1843. | GRAHAM and ROBINSON* | 77° 43' | | Head of Beau Lac | 47° 23' | 290° 57' | 1843. | GRAHAM. | 77° 47' | | Mouth of the Passa-ooe-tuc | 47° 07' | 290° 55' | 1844. | GRAHAM. | 77° 40' | | Outlet of Lake Pohenagamook | 47° 28' | 290° 47' | 1843. | GRAHAM. | 77° 49' | | M. of the Chimpassaoeoetuc | 46° 57' | 290° 33' | 1843. | GRAHAM. | 77° 37' | | Kingsey | 45° 48' | 287° 41' | 1842. | LEFROY. | 77° 40'† | | Fort Michipicoton | 47° 56' | 274° 55' | 1843. | LEFROY. | 78° 06' | | Fort Michipicoton | 47° 56' | 274° 55' | 1844. | LEFROY. | 78° 08' | | Fort Michipicoton | 47° 56' | 274° 55' | 1845. | RAE. | 78° 05' | | Gargantua | 47° 37' | 274° 49' | 1844. | LEFROY. | 77° 56' | | Lake Superior | 48° 46' | 272° 20' | 1844. | LEFROY. | 78° 24' | | Isthmus | 47° 28' | 272° 00' | 1843. | LOCKE. | 78° 28' | | Eagle River | 47° 27' | 271° 37' | 1843. | LOCKE. | 77° 54' | | Isle Royale | 48° 06' | 271° 13' | 1843. | LOCKE. | 78° 07' | | Pointe Tonnerre | 48° 19' | 270° 58' | 1843. | LEFROY. | 78° 23' | | Fort William | 48° 24' | 270° 37' | 1843. | LEFROY. | 78° 10' | | Fort William | 48° 24' | 270° 37' | 1844. | LEFROY. | 77° 59' | | Fort William | 48° 24' | 270° 37' | 1845. | RAE. | 78° 11' | | Chien Portage | 48° 39' | 270° 26' | 1843. | LEFROY. | 78° 26' | | Prairie Portage | 48° 58' | 269° 59' | 1843. | LEFROY. | 78° 26' | | Savannah Portage | 48° 53' | 269° 52' | 1843. | LEFROY. | 78° 21' | | French Portage | 48° 35' | 268° 53' | 1843. | LEFROY. | 78° 20' | | Deux Rivières Portage | 48° 35' | 268° 33' | 1843. | LEFROY. | 77° 49' | | Lac à la Crosse | 48° 24' | 267° 50' | 1843. | LEFROY. | 77° 51' | | Second Portage from Lac à la Crosse | 48° 15' | 267° 33' | 1843. | LEFROY. | 77° 40' | | Sturgeon Lake | 48° 27' | 267° 19' | 1843. | LEFROY. | 77° 44' | | Lac la Pluie | 48° 32' | 267° 04' | 1843. | LEFROY. | 77° 47' | | Fort Francis | 48° 37' | 266° 31' | 1843. | LEFROY. | 77° 27' | | Fort Francis | 48° 37' | 266° 31' | 1844. | LEFROY. | 77° 43' | | Fort Francis | 48° 37' | 266° 31' | 1845. | RAE. | 77° 32' | | Rainy River | 48° 48' | 265° 29' | 1843. | LEFROY. | 77° 57' | | Rat Portage | 49° 46' | 265° 21' | 1843. | LEFROY. | 78° 07' | | Lake of the Woods | 49° 28' | 265° 20' | 1843. | LEFROY. | 78° 16' | | Lake of the Woods | 49° 19' | 265° 18' | 1843. | LEFROY. | 78° 03' | | Upper Fort Garry | 49° 53' | 262° 58' | 1843. | LEFROY. | 78° 17' | | Saskatchewan River | 52° 23' | 252° 56' | 1844. | LEFROY. | 78° 16' | | Saskatchewan River | 53° 07' | 251° 30' | 1844. | LEFROY. | 78° 28' | | Saskatchewan River | 54° 05' | 248° 16' | 1844. | LEFROY. | 78° 05' | | Fort Edmonton | 53° 31' | 247° 03' | 1844. | LEFROY. | 77° 54' | | Pembina River | 54° 08' | 246° 06' | 1844. | LEFROY. | 77° 54' | | Fort Assiniboine | 54° 20' | 245° 32' | 1844. | LEFROY. | 78° 15' | | Point Dejala | 55° 26' | 244° 59' | 1844. | LEFROY. | 78° 29' | * Captain WILLIAM ROBINSON, Royal British Engineers, attached to the Survey and Boundary Commission. † Local disturbance; omitted in the map. ### OBSERVATIONS OF THE MAGNETIC INCLINATION. #### Table LI. (Continued.) | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | | | | | | | | **78° 30' to 79° 30'** | | | | | | | Terreplatte | 48° 46' | 27° 15' | 1843. | Lefroy. | 78° 53'6" | | Magnetic Inlet | 47° 28' | 27° 59' | 1843. | Locke. | 78° 44'5" | | 500 feet East of Ditto | 47° 28' | 27° 59' | 1843. | Locke. | 78° 37'5" | | Slave Portage | 50° 11' | 26° 23' | 1843. | Lefroy. | 78° 57'1" | | Fort Alexander | 50° 37' | 26° 39' | 1843. | Lefroy. | 78° 51'8" | | Fort Alexander | 50° 37' | 26° 39' | 1844. | Lefroy. | 79° 03'0" | | Lake Winnipeg | 50° 27' | 26° 22' | 1843. | Lefroy. | 79° 05'2" | | Lake Winnipeg | 51° 34' | 26° 20' | 1844. | Lefroy. | 79° 06'6" | | Mouth of Red River | 50° 19' | 26° 15' | 1843. | Lefroy. | 78° 32'6" | | Lake Winnipeg | 51° 04' | 26° 15' | 1843. | Lefroy. | 79° 11'8" | | Lake Winnipeg | 51° 45' | 26° 07' | 1843. | Lefroy. | 79° 28'3" | | Saskatchewan River | 53° 16' | 25° 12' | 1844. | Lefroy. | 79° 11'2" | | Carlton House | 52° 51' | 25° 47' | 1844. | Lefroy. | 78° 30'7" | | Fort Pitt | 53° 34' | 25° 41' | 1844. | Lefroy. | 78° 41'0" | | Saskatchewan River | 53° 50' | 24° 30' | 1844. | Lefroy. | 78° 33'5" | | Forks of Athabasca River | 55° 13' | 24° 10' | 1844. | Lefroy. | 78° 55'2" | | Athabasca River | 54° 43' | 24° 00' | 1844. | Lefroy. | 78° 34'1" | | Lesser Slave Lake | 55° 33' | 24° 07' | 1844. | Lefroy. | 78° 39'0" | | Peace River | 57° 19' | 24° 32' | 1844. | Lefroy. | 79° 27'0" | | Opposite River Cadotte | 56° 47' | 24° 58' | 1844. | Lefroy. | 79° 20'7" | | Fort Dunvegan | 55° 56' | 24° 26' | 1844. | Lefroy. | 78° 46'2" | | | | | | | | | **79° 30' to 80° 30'** | | | | | | | Otter Island | 48° 06' | 27° 43' | 1843. | Lefroy. | 79° 43'6" | | Lake Winnipeg | 51° 04' | 26° 39' | 1844. | Lefroy. | 79° 31'5" | | Lake Winnipeg | 51° 44' | 26° 12' | 1844. | Lefroy. | 79° 39'0" | | Lake Winnipeg | 51° 38' | 26° 11' | 1843. | Lefroy. | 79° 38'0" | | Lake Winnipeg | 52° 21' | 26° 51' | 1844. | Lefroy. | 80° 24'4" | | Lake Winnipeg | 52° 29' | 26° 47' | 1843. | Lefroy. | 80° 05'4" | | Lake Winnipeg | 53° 31' | 26° 48' | 1843. | Lefroy. | 80° 16'8" | | Grand Rapid | 53° 08' | 26° 32' | 1843. | Lefroy. | 80° 21'5" | | Grand Rapid | 53° 08' | 26° 32' | 1844. | Lefroy. | 80° 31'6" | | Cross Lake | 53° 10' | 26° 28' | 1843. | Lefroy. | 80° 28'2" | | Cedar Lake | 53° 12' | 25° 30' | 1843. | Lefroy. | 80° 07'1" | | Devil's Drum Island | 53° 19' | 25° 20' | 1844. | Lefroy. | 80° 00'0" | | Above the Pas | 53° 48' | 25° 32' | 1844. | Lefroy. | 80° 24'4" | | Cumberland House | 53° 57' | 25° 41' | 1843. | Lefroy. | 80° 30'2" | | Cumberland House | 53° 57' | 25° 41' | 1844. | Lefroy. | 80° 19'7" | | Little Rock Portage | 55° 34' | 25° 27' | 1843. | Lefroy. | 80° 16'5" | | Portage Sonnante | 55° 54' | 25° 13' | 1843. | Lefroy. | 80° 11'2" | | Isle à la Crosse | 55° 27' | 25° 06' | 1843. | Lefroy. | 80° 09'8" | | Buffaloe Lake | 56° 05' | 25° 09' | 1843. | Lefroy. | 80° 37'0" | | River de la Loche | 56° 15' | 25° 37' | 1843. | Lefroy. | 80° 19'7" | | Peace River | 57° 57' | 24° 30' | 1844. | Lefroy. | 80° 00'7" | | | | | | | | | **80° 30' to 81° 30'** | | | | | | | Lake Winnipeg | 52° 23' | 26° 07' | 1843. | Lefroy. | 80° 39'2" | | Hairy Lake | 54° 21' | 26° 49' | 1843. | Lefroy. | 81° 20'9" | | Old Norway House | 53° 42' | 26° 59' | 1843. | Lefroy. | 80° 45'4" | | Norway House | 53° 59' | 26° 53' | 1843. | Lefroy. | 81° 08'9" | | Norway House | 53° 59' | 26° 53' | 1844. | Lefroy. | 81° 11'2" | | Beaver Lake | 54° 32' | 25° 50' | 1843. | Lefroy. | 80° 34'2" | | Carp Portage | 54° 47' | 25° 21' | 1843. | Lefroy. | 80° 39'6" | | Portage des Epinettes | 55° 06' | 25° 18' | 1843. | Lefroy. | 80° 52'6" | | Frog Portage | 55° 28' | 25° 30' | 1843. | Lefroy. | 80° 59'3" | | Great Devil's Portage | 55° 40' | 25° 11' | 1843. | Lefroy. | 80° 30'9" | * Local disturbance; omitted in the map. | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | Pine Portage | 55° 43′ | 254° 10′ | 1843. | Lefroy. | 80° 40′-3″ | | Snake Rapid | 55° 46′ | 253° 30′ | 1843. | Lefroy. | 80° 38′-7″ | | Portage de la Loche, South end | 56° 34′ | 250° 16′ | 1843. | Lefroy. | 80° 36′-4″ | | Portage de la Loche, North end | 56° 43′ | 250° 08′ | 1843. | Lefroy. | 80° 38′-0″ | | Clearwater River | 56° 39′ | 249° 11′ | 1843. | Lefroy. | 80° 36′-2″ | | Pierre au Calumet | 57° 24′ | 248° 25′ | 1843. | Lefroy. | 81° 16′-8″* | | Poplar Island | 58° 38′ | 246° 03′ | 1844. | Lefroy. | 81° 04′-8″ | | Falls of Peace River | 58° 24′ | 245° 06′ | 1844. | Lefroy. | 80° 50′-8″ | | Fort Vermilion | 58° 25′ | 243° 45′ | 1844. | Lefroy. | 80° 48′-0″ | | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | Long Portage | 55° 15′ | 265° 35′ | 1843. | Lefroy. | 82° 13′-9″ | | Windy Lake | 54° 37′ | 263° 58′ | 1843. | Lefroy. | 81° 57′-0″ | | Whitefall Portage | 54° 24′ | 263° 34′ | 1843. | Lefroy. | 81° 47′-9″ | | Athabasca | 58° 43′ | 248° 42′ | 1843. | Lefroy. | 81° 37′-0″ | | Pointe Brulée | 58° 07′ | 248° 35′ | 1843. | Lefroy. | 81° 30′-6″ | | Pelican Portage | 59° 58′ | 248° 09′ | 1844. | Lefroy. | 82° 26′-8″ | | Point Providence | 58° 58′ | 247° 50′ | 1844. | Lefroy. | 81° 46′-1″ | | Peace River | 58° 58′ | 247° 01′ | 1844. | Lefroy. | 81° 36′-9″ | | Big Island | 61° 12′ | 243° 22′ | 1844. | Lefroy. | 82° 08′-7″ | | Fort Simpson | 61° 51′ | 238° 35′ | 1844. | Lefroy. | 81° 52′-3″ | | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | White Earth Portage | 55° 32′ | 266° 10′ | 1843. | Lefroy. | 83° 02′-9″ | | Hill River | 55° 25′ | 266° 00′ | 1843. | Lefroy. | 82° 55′-0″ | | Oxford House | 54° 56′ | 264° 30′ | 1843. | Lefroy. | 82° 38′-8″ | | Portage Grand Detour | 60° 22′ | 247° 00′ | 1844. | Lefroy. | 82° 33′-6″ | | Fort Resolution | 61° 10′ | 246° 15′ | 1844. | Lefroy. | 82° 44′-5″ | | Fort Norman | 64° 31′ | 235° 16′ | 1844. | Lefroy. | 82° 34′-3″ | | Fort Good Hope | 66° 16′ | 231° 30′ | 1844. | Lefroy. | 82° 56′-0″ | | Station | Lat. | Long. | Year | Observer | Inclination | |--------------------------|------|-------|------|----------|-------------| | York Factory | 57° 00′ | 267° 34′ | 1843. | Lefroy. | 83° 47′-2″ | | Shamatawa | 56° 21′ | 267° 04′ | 1843. | Lefroy. | 83° 36′-2″ | * Local disturbance; omitted in the map.