Contributions to Terrestrial Magnetism.--No. IV

IX. Contributions to Terrestrial Magnetism.—No. IV. By Lieut.-Colonel Edward Sabine, R.A., F.R.S. Received May 5,—Read May 18, 1843. § 7. Second Series of Magnetic Determinations, by Captain Sir Edward Belcher, R.N. In the present number of these Contributions, I resume the consideration of Captain Sir Edward Belcher's magnetic observations, of which the first portion, viz. that of the stations on the north-west coast of America and adjacent islands, was discussed in No. II. The return to England of Her Majesty's ship Sulphur by the route of the Pacific Ocean, and her detention for some months in the China Seas, have enabled Sir Edward Belcher to add magnetic determinations at thirty-two stations to those at the twenty-nine stations previously recorded. In the notice of the earlier observations, a provisional coefficient was employed in the formula for the temperature corrections of the results with the intensity needles, as no experiments had then been made for the determination of their individual coefficients. As soon therefore as Sir Edward Belcher had completed the observation of the times of vibration of those needles at Woolwich, as the concluding station of the series made with them, Lieut. Riddell, R.A. undertook the determination of their several coefficients, which was performed in the manner and with the results described in the subjoined memorandum. "The observations were made in the instrument room attached to Lieut.-Colonel Sabine's office in the Royal Military Repository, Woolwich. "The instruments rested on wooden stands detached from the floor. "The deflections were observed with one of Weber's transportable magnetometers; the variations of declination and horizontal force with the larger instruments. "The needles were placed upon open Y supports, in the centre of a wooden trough about nine inches in length, six broad and six deep, and were fixed so that their magnetic axes should be in the line passing through the centre of the suspended magnet perpendicular to the magnetic meridian. "The trough was filled alternately with warm and cold water, and the instruments were registered after a sufficient time had elapsed to allow the needles to take up the temperature of the water; care was taken not to raise the temperature of the water above 110° or 120°, to avoid the permanent loss of magnetism which might have been occasioned thereby." "The 'readings' are the means, each, of three or four separate readings, at intervals of two or three minutes. "Similar series were observed with eight other needles; the approximate results for each needle are as follows: | Date | No. of Needle | Value of q | Means | |----------|---------------|------------|---------| | October 14. | 5 | 0-00041 | 0-00042 | | | | 0-00043 | | | | | 0-00056 | 0-00065 | | November 22. | 6 | 0-00074 | | | | | 0-00090 | 0-00005 | | | | 0-00017 | | | | | 0-00014 | 0-00014 | | | | 0-00012 | 0-00012 | | | | 0-00009 | 0-00009 | | | | 0-00019 | 0-00019 | | | | 0-00014 | 0-00014 | | | | 0-00022 | 0-00022 | These coefficients have accordingly been used in calculating the results in the present Number. A careful examination of the observations at the foreign stations had led me to infer that Nos. 5. and 6. would probably be found to have larger coefficients than the other needles, which has proved to be the case. The variation in the amount of the coefficients in the different needles, considerable as it is, is not unprecedented; it probably depends on the quality and temper of the steel, and may be particularly influenced by the portions of soft iron which a needle may contain. A species of steel has been recently employed for magnets in the Russian observatories, in which the coefficient for temperature has even a negative sign, i.e. the magnetic intensity of the bar increases with heat. In a letter which I have received from M. Adolphe Erman, he describes this particular kind of steel as consisting of alternate very thin layers of soft iron and of steel, so that when heated the soft iron layers would increase their magnetic intensity, and the steel layers diminish theirs; the amount and sign of the coefficient depending on the preponderance of the layers of soft iron or of steel, which is subject to much variation. It is called "Boulat," or "damascened steel," and is considered the pride of the Uralian forges. In a bar of this steel, kindly sent me by General Tcheffkine, at the request of M. Kupffer, the usual effect is thus reversed. Experiments made with it at Woolwich by Lieutenant Riddell gave the results stated in the following memorandum: "The effect of temperature on the bar of Russian steel, sent by M. Kupffer, was tried in the usual manner by means of the magnet of the declination magnetometer, the bar being placed with its axis in the line passing through the centre of the suspended magnet perpendicular to the magnetic meridian. The subjoined observations furnish satisfactory proof that the ordinary effect of temperature on bars of steel which are hardened throughout is reversed in this bar, but the value of the coefficient, or change of force for $1^\circ$ of Fahrenheit, deduced from them, must be taken only as a rough approximation, as in addition to the probable error of the observations themselves, the bar was placed with its centre at a distance of three feet, or only $1\frac{1}{2}$ times its length from the magnetometer, in order to produce a sufficient deflection, the magnetism being weak*." * After the completion of this experiment with the bar in the state in which it was received from General Tcheffkine, a portion was cut off, softened, and made into 3-inch cylinders of the dimensions used with the portable magnetic apparatus. The effect of temperature on one of these cylinders, hardened afresh and remagnetised, was tried in a similar manner, and the value of its coefficient found to be about '0003, the force decreasing with an increase of temperature, which is the ordinary effect. Abstract. November 21st, 1842. | Times | Temperature | Means | Diffs. | Readings. | Diffs. | Corrections. | Readings. | Corrected Readings. | Means. | Diffs. | AX/X | Temp. | Diff. | |-------|-------------|-------|--------|-----------|--------|--------------|-----------|---------------------|--------|--------|------|-------|-------| | d h m | o | Before deflection. | Sc. Div. | Sc. Div. | Sc. Div. | Sc. Div. | Se. Div. | Se. Div. | Se. Div. | Se. Div. | AX/X | Temp. | Diff. | | 20 23 40 | 50-3 | 2° 4 | 0-6 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | | 21 0 32 | 50-3 | 3° 0 | 1-0 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | | 0 50 | 54-3 | 45-7 | 1-0 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | | 1 10 | 58-3 | 47-0 | 1-0 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | | 28 | 57-0 | 59-5 | 1-0 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | 2-3 | | 45 | 55-7 | 3° 0 | 0-6 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | 1-4 | Approximately \( q = \frac{48-7}{1492-5} = 0-00011 \). "The readings in the several columns so entitled are the means each of three or more observations at intervals of 1\(\frac{1}{2}\) or 2 minutes. The 'corrections' are obtained by multiplying the differences of the readings of the spare declination magnetometer by the ratio of the angular value of the two declination scales. The corrections for changes of horizontal intensity are omitted as inappreciable. "The bar was placed in a wooden trough filled alternately with warm and cold water, and its temperature was registered by a thermometer near its centre." We have next to consider the more important question of the steadiness with which the needles may have maintained their magnetic condition during a voyage of so many months, and under such numerous and various trials. When there are many needles, all of generally steady magnetism, their intercomparison affords on the whole a not unsatisfactory mode of discovering the periods when any one amongst the number may have sustained an accidental loss, and of obtaining an approximate correction for it. I have already shown in No. II. of these Contributions*, the steadiness of Nos. 5. 7. 8. 9. 11. 12. and 13. of Sir Edward Belcher's needles, from October 1838 to March 1839, by means of the observations made at Panama at both those dates. I have also noticed in the same paper that the intercomparison between March and November 1839, had shown that No. 8. was apparently more subject than the other needles to small occasional losses, and that I deemed it therefore less fit than the others for carrying on a chain of magnetic determinations. Subsequent experience with this needle has confirmed this early indication, as will be more fully shown in the sequel. For the present investigation we shall therefore employ only Nos. 5. 7. 9. 11. 12. and 13. A similar opportunity to the one above noticed (at Panama), of evidencing the general steadiness of these needles, was afforded by Sir Edward Belcher's return to Singapore in December 1841, having previously visited that station in the October of the preceding year: the agreement in the respective times of vibration at those two periods is shown in the following Table: | Periods | Designation of the Needles | |------------------|----------------------------| | | 5. | 7. | 9. | 11. | 12. | 13. | | October 1840 | s | s | s | s | s | s | | | 466·9 | 532·8 | 433·2 | 469·1 | 397·0 | 390·5 | | December 1841 | s | s | s | s | s | s | | | 465·8 | 532·3 | 434·0 | 467·8 | 397·9 | 390·4 | We are therefore warranted by the observations at Panama and Singapore, in regarding the usual condition of these needles to be that of steady magnetism, subject nevertheless, as all magnets appear to be, to occasional loss of force from accidental causes, the nature and operation of which are not perfectly understood. The ratio of the squares of the times of vibration of two needles, or the difference of the logarithms of the squares, at stations at which they were both used, should be a constant quantity (within the limit of errors of observation), if both needles have continued steady; consequently a loss of magnetism occurring in either will be shown by an alteration in the ratio exceeding in amount the ordinary errors of observation; if the ratio diminishes, the loss has taken place in the needle, which for the purpose of comparison is regarded as unity; if it augments, the loss is in the needle with which it is compared. A simultaneous loss in both needles to an equal amount will not * Philosophical Transactions, 1841, Part I., p. 13. indeed be detected; but when the intercomparison is extended from two to several needles, the improbability of all being affected at the same time and to an equal amount becomes considerable. It is still however possible, because the intercomparison can show nothing beyond the relative condition of the needles. In the present case the incompleteness in this respect of the evidence furnished by the intercomparison, is supplied by Nos. 7. and 9. having been vibrated at Woolwich in August 1839 and in October 1842: the change in their times of vibration at those dates, compared with the loss of magnetism deduced for each by the intercomparison with the other needles, shows whether any and what unaccounted loss has taken place in the interval in those two needles, and consequently in all those compared with them. In what has been said above, it has been assumed that a change taking place is always occasioned by a loss of magnetism in one or other of the needles; it generally is so; but should the case occur, that one of the needles should gain instead of lose by any accidental disturbance of its magnetism, the intercomparison with others would equally point it out and mark its character. An alteration in the ratio of the squares of the times of vibration may be occasioned at a particular station by an observation error of unusual magnitude, or by some unknown accidental cause of a temporary nature affecting at the one station only the time of vibration of the needle which is compared; an alteration to nearly the same amount will, in such case, equally pervade its comparisons with all the needles; but this case is readily distinguished from that of a permanent loss or gain of magnetism, requiring a correction to be sought out and applied,—by the ratio reverting to its original amount at the succeeding stations. The process which has been followed in assigning the corrections for the losses thus discovered to have taken place may be best shown by an example. On the simple inspection of the observations, it was evident that Nos. 5. and 7. had each sustained a loss of magnetism between the Seychelles Islands and Mojambo Bay in the Island of Madagascar. The logarithms of the squares of the times of vibration of No. 5. at the three stations preceding the period of the loss, and at the three stations following the same, being severally subtracted from the corresponding logarithms of the squares of the times of vibration of Nos. 9. 11. 12. and 13. at the same stations, the differences are arranged in the subjoined Table. The differences for each needle are seen to be nearly a constant quantity (a) at Penang, Point de Galle, and Seychelles; to have undergone a change between Seychelles and Madagascar; and to have become again a nearly constant, though a different, quantity (b) at Madagascar, the Cape of Good Hope, and Ascension. The amount of the change between Seychelles and Madagascar (b — a) is shown by No. 9. to be 9·9856; by No. 11, 9·9859; by No. 12, 9·9856; and by No. 13, 9·9859. The mean, 9·9857, must be added to the logarithm of the square of the time of vibration of No. 5. at Madagascar and all the succeeding stations, to make them strictly comparable with the observations of that needle at the Seychelles and all preceding stations: or if the ratio of the intensity is sought between those stations and one visited subsequently to Madagascar,—(as for example Woolwich, where the observations with No. 5. were made in December 1842),—9·9857 must be subtracted from, or its arith. comp. 0·0143 added to, the squares of the times of vibration at the earlier stations. Differences of the logarithms of the squares of the time of vibration of No. 5. with those of Nos. 9. 11. 12. and 13. | Stations | No. 9. | No. 11. | No. 12. | No. 13. | |-------------------|----------|----------|----------|----------| | Preceding | | | | | | the loss; | | | | | | Penang | 9·9401 | 0·0049 | 9·8674 | 9·8470 | | Point de Galle | 9·9406 | 0·0036 | 9·8678 | 9·8458 | | Seychelles | 9·9408 | 0·0041 | 9·8680 | 9·8481 | | Mean (a) | 9·9405 | 0·0042 | 9·8677 | 9·8476 | | Following | | | | | | the loss; | | | | | | Madagascar | 9·9265 | 9·9901 | 9·8530 | 9·8331 | | Cape of Good Hope.| 9·9261 | 9·9885 | 9·8530 | 9·8315 | | Ascension | 9·9256 | 9·9918 | 9·8538 | 9·8341 | | Mean (b) | 9·9261 | 9·9901 | 9·8533 | 9·8329 | | (b) — (a) = | 9·9856 | 9·9859 | 9·9856 | 9·9859 | By a similar comparison, of which the particulars are also subjoined, No. 7. is shown to require a correction of 9·9885 to be added to the logarithms of the squares of the times of vibration at Madagascar and the subsequent stations, or of 0·0115 to be added to the logarithms at the stations antecedent to Madagascar, to render the series of observations with this needle before and after the loss thus ascertained comparable with each other. Differences of the logarithms of the squares of the times of vibration of No. 7. with those of Nos. 9. 11. 12. and 13. | Stations | No. 9. | No. 11. | No. 12. | No. 13. | |-------------------|----------|----------|----------|----------| | Preceding | | | | | | the loss; | | | | | | Penang | 9·8232 | 9·8880 | 9·7505 | 9·7301 | | Point de Galle | 9·8217 | 9·8847 | 9·7489 | 9·7269 | | Seychelles | 9·8224 | 9·8857 | 9·7496 | 9·7297 | | Mean (a) | 9·8224 | 9·8861 | 9·7497 | 9·7289 | | Following | | | | | | the loss; | | | | | | Madagascar | 9·8100 | 9·8736 | 9·7373 | 9·7166 | | Cape of Good Hope.| 9·8120 | 9·8744 | 9·7389 | 9·7174 | | Ascension | 9·8103 | 9·8765 | 9·7377 | 9·7188 | | Mean (b) | 9·8108 | 9·8748 | 9·7380 | 9·7176 | | (b) — (a) = | 9·9884 | 9·9887 | 9·9883 | 9·9887 | The loss of magnetism thus manifested in Nos. 5. and 7. at the Seychelles is the most considerable change undergone by any of the needles between March 1839 and December 1842. The only change of nearly equal amount (being also a loss for which the correction is 0·0093) was sustained by No. 7. at Mazatlan in November 1839, and has been noticed and the circumstances connected with it stated in No. II. of these Contributions*. The corrections of Nos. 5. 7. 9. 11. 12. and 13, derived from the intercomparison, commencing with the observations at Panama in March 1839, and ending with those at Woolwich in December 1842, are as follows: they are all additive at the stations named and at all antecedent stations, and render the whole series with each needle comparable throughout with each other, and with the observations at Woolwich in December 1842. No. 5. 0·0143 from Seychelles; 0·0027 (additional) from San Blas. No. 7. 0·0115 from Seychelles; 0·0013 (additional) from Amboyna; and 0·0093 (additional) from Mazatlan. No. 9. 0·0018 from Point de Galle; 0·0021 (additional) from Singapore, October 1840; 0·0038 (additional) from Tahiti. No. 11. 0·0035 from Jobie Island. No. 12. 0·0020 from the Cape of Good Hope; 0·0012 (additional) from Point de Galle; 0·0030 (additional) from Macao, September 1841. No. 13. 0·0034 from Amboyna; 0·0017 (additional) from Tahiti. We have next to examine how far the corrections thus derived correspond with the change in the times of vibration of Nos. 7. and 9, shown by direct observation at Woolwich at the two dates of August 1839 and December 1842. | | No. 7. | No. 9. | |----------------|--------|--------| | In August 1839 the times of vibration observed were | 767·0 | 627·6 | | The corrections assigned by intercomparison are equivalent to | + 19·8 | + 5·6 | | Observed times of vibration in August 1839, corrected | 786·8 | 633·2 | | Observed times of vibration in December 1842 | 789·1 | 635·7 | | Differences | 2·3 | 2·5 | The differences are in the same sense in both needles, and are such as would correspond to a small loss of magnetism still undetected by the intercomparison. It is possible that they may be partially or wholly due to this cause, without prejudice to the effectiveness of the method itself, because, in its present application, the intercomparison has not been pursued to the correction of very small differences; it has however been carried out to such extent, that even the very moderate differences indicated by the above figures would not have escaped detection had they occurred at any single station or period. They correspond respectively to 0·006 and 0·007 parts of the whole horizontal force; and were there no liability to observation errors,—and were the horizontal force at Woolwich at all times a constant quantity,—we might be justified in meeting them with a special correction. But they are exceeded in amount by the fluctuations of the force itself, which is subject both to periodical variations, dependent on the hour and season, and to other fluctuations of irregular occurrence, * Philosophical Transactions, 1841, p. 15. which sometimes for several days together raise the intensity above, or depress it below, its average value; and experience shows that either from these natural causes, or from observation errors, or from both combined, the results obtained at the same station on different days with needles of assured steadiness, do occasionally vary to as great and greater amounts than those under consideration; we should scarcely be justified, therefore, in applying any further correction. Employing the corrections obtained by the intercomparison of the needles, and combining the times of vibration of each at Panama in March 1839 with those at Woolwich in December 1842, we obtain the ratio of the horizontal force at Panama to the force at Woolwich, regarded as unity, by the several needles as follows: | No. | 5. | 2·078 | |-----|------|-------| | | 7. | 2·078 | | | 9. | 2·087 | | | 11. | 2·082 | | | 12. | 2·077 | | | 13. | 2·084 | Mean 2·081. The partial results do not differ from each other more than those might be expected to do which should have been obtained by the repetition of observations with one and the same needle. The general table of results in the sequel has been calculated by the aid of the corrections thus derived, and the intensity as given by each of the needles severally is entered in the Table. The time of vibration of No. 11. at Woolwich, in October 1842, appears to have been affected by some accidental cause of error. Its discordance with the general series was perceived a few days after the observations were made, and error suspected, because the time of vibration would have corresponded to a considerable increase in the magnetism of the needle. The suspicion was confirmed by the repetition of the observations at Woolwich on the 27th and 28th December 1842, and at Falmouth on the 9th of February 1843, though no cause has been discovered either then or subsequently for the error in the first observation. Viewing the more than usual importance of accuracy in the observations at a base station, I have selected a different station for that purpose for this particular needle, and have chosen Singapore, both because the ratio of the horizontal force at that station to the force at Woolwich appears to have been extremely well determined by Sir Edward Belcher's observations in 1840 and 1841, and because any error in that determination will be corrected with certainty before long by the absolute determinations at the magnetic observatory there. The horizontal force at Woolwich being unity, its value at Singapore is 2·135 by Sir Edward Belcher's observations in 1840, and 2·140 by those in 1841. The mean is 2·1375. The time of vibration of No. 11. at Singapore was 468s·7 in 1840, and 467s·3 in 1841; mean 468s·0 at 75° Fahr. We have now to notice the two needles Nos. 6. and 8, which have not been included in the intercomparison which the others have undergone. By means of the horizontal intensity derived for each station from the mean of Nos. 5. 7. 9. 11. 12. and 13, and the observed times of vibration of No. 8. at the several stations, the corresponding times of vibration which that needle would have had at the respective periods at Woolwich have been computed, and are as follows: | Location | Time of Vibration | |---------------------------|-------------------| | Mazatlan, November 1839 | 677·7 | | San Blas, December 1839 | 678·5 | | Martin's Island, January 1840 | 678·8 | | Bow Island, March 1840 | 679·6 | | Tahiti, May 1840 | 678·8 | | Nukulau, June 1840 | 679·6 | | New Ireland, July 1840 | 680·7 | | Jobie Island, August 1840 | 680·2 | | Amboyna, September 1840 | 680·7 | | Macassar, September 1840 | 681·8 | | Singapore, October 1840 | 681·6 | | Singapore, December 1841 | 682·9 | | Penang, December 1841 | 683·2 | | Point de Galle, January 1842 | 683·0 | | Seychelles, February 1842 | 683·0 | | Madagascar, March 1842 | 684·6 | | Cape of Good Hope, April 1842 | 684·3 | | Ascension, May 1842 | 685·1 | | Woolwich, October, December | 686·1 | The progressive increase in the times of vibration indicates that No. 8. was continually parting with small portions of its magnetism, a condition, which, when it occurs in one needle amongst many, renders that particular needle of less value in general deductions than those which have the character of general steadiness with only occasional loss. Corrections might be assigned for No. 8., derived either from its comparison with the other needles, or on a supposition of uniform loss in reference to time or to occasions of employment, but the latter could only be regarded as approximate, and the former would add no independent value to the general conclusions. The observations with No. 8. therefore are given in the Tables, but no deductions have been made from them. The derangement in the magnetic state of No. 6., which took place in a journey to the summit of the volcano of Conchagua in December 1838, and its subsequent unsteadiness, have been already noticed in No. II. of these Contributions. The magnetism of this needle continued unsettled for the whole remainder of the voyage, affording an instructive example of the extent of injury which an exposure to unfavourable circumstances may produce in a long-tried and valuable needle; the one in question having been in use during the twenty-one previous months without undergoing apparently the slightest change in its magnetism. It unfortunately happened that No. 6. is one of two needles, No. 5. being the other, which Sir Edward Belcher employed throughout his voyage at stations where time did not permit him to use more than two; and it is desirable therefore to draw from the observations with No. 6. at such stations, all the evidence they are capable of affording. For this purpose I have made the stations at which several needles were used base stations, for the deduction of the force with No. 6. at any intermediate place where Nos. 5. and 6. only were employed: the deductions by No. 6. being in all such cases dependent on the determinations by all the other needles at the base stations visited immediately before and after. When the force at the intermediate place has appeared by No. 6. to be nearly the same, whether derived from the base station preceding, or the one following it, the mean result has been considered to have an independent value, and has been employed accordingly. When otherwise, the observations have been entered in the table, but no deductions have been made from them. The values of the horizontal force which are contained in the final column of the general table are expressed in absolute measure, referring to the units prescribed in the magnetic Instructions which have received the sanction of the Royal Society*. Experiments made by Lieutenants Lefroy and Riddell in the Royal Military Repository at Woolwich in May 1842, with magnets of four inches in length, gave 3·72 as the approximate value of the horizontal force at Woolwich at that period, agreeably to the following memorandum: "The number 3·72, given as the approximate value of the horizontal intensity at Woolwich, expressed in English units of feet, seconds, and grains, was determined from experiments of deflection and vibration made with one of Weber's transportable magnetometers. "The experiments of deflection were made after the method of M. Gauss, with the axis of the deflecting magnet perpendicular to the magnetic meridian, the angles being measured on the scale fixed over the reading telescope. The deflecting and suspended magnets were of the same dimensions, about four inches in length and four-tenths in diameter. "The values of $\frac{m}{X}$ were calculated from the several pairs of observations by the formula $$\frac{m}{X} = \frac{r^{15} \tan u' - r^5 \tan u}{2(r^2 - r'^2)}.$$ "The partial results, distances, and angles of deflection are given in the accompanying abstracts. "The moment of inertia of the vibrating magnet was determined by observing a * "The number obtained for the force of the earth's magnetism expresses the ratio which that force bears to the unit of force, the unit of force being that which, acting on the unit of mass, through the unit of time, generates in it the unit of velocity. These units are entirely arbitrary; but for the sake of convenience in comparison, it is desirable that they should be the same in all the observations which shall be made according to this system. For the unit of mass, then, we may take a grain; for the unit of time a second; and, if a foot be taken as the unit of space, the unit of velocity will be that of one foot per second. "As the magnetic force operates effectively only on the free or uncombined elements of the magnetic fluid, we are to understand by the earth's magnetic force, its action on the elementary unit of free magnetism; and we must take for that unit the quantity of free magnetism, which, acting on another equal quantity at the unit of distance, exerts an effect equal to the unit of force already defined."—Royal Society, Report of the Committee of Physics, &c., approved by the President and Council, 1840, pp. 21, 22. MDCCXLIII. second series of vibrations with two cylinders of equal weight and dimensions suspended across the end of the bar, in the manner described by M. Weber. The times of vibration are uncorrected for the torsion of the suspension thread, or for the changes of horizontal intensity occurring during the intervals of the experiments. "Abstract of Observations of the absolute Horizontal Intensity." | No. of Needle | Distances in feet | Angles of Deflection | Log of m X | Times of vibration | Values of X. | Temp. of Magn. | |---------------|------------------|---------------------|------------|-------------------|-------------|----------------| | May 26 | 10 | 1:4746 | 1:8671 | 7 56-8 | 9:34969 | 6:218 | 11:630 | | | | | | | | | 0:49070 | | | | | | | | | 3:7196 | | | | | | | | | 0:832 | | | | | | | | | 62 | | 28. | 15 | 1:4832 | 1:8668 | 7 20-5 | 9:32349 | 6:433 | 0:46439 | | | | | | | | | 7:192 | | | | | | | | | 783 | | | | | | | | | 63 | | 28. | 13 | 1:4831 | 1:8669 | 7 20-7 | 9:32296 | 6:442 | 0:46410 | | | | | | | | | 7:202 | | | | | | | | | 783 | | | | | | | | | 62 | | 30. | 13 | 1:4831 | 1:5164 | 7 17-4 | 9:31982 | 6:481 | 12:078 | | | | | | | | | 0:45885 | | | | | | | | | 7:112 | | | | | | | | | 775 | | | | | | | | | 67 | | 30. | 15 | 1:4165 | 1:4832 | 8 23-0 | 9:32244 | 6:433 | 12:000 | | | | | | | | | 0:46439 | | | | | | | | | 7:237 | | | | | | | | | 782 | | | | | | | | | 68 | From these experiments we may regard 3·72 as the approximate value of the horizontal force at Woolwich at the period referred to; and 3·72 + e as the corrected value at the same station, corresponding to the period which shall hereafter be taken as the epoch of the magnetic maps of the globe, which these and similar contributions will combine to form,—e being a small quantity depending partly on the epoch, and partly on the possibly increased precision of determinations hereafter to be made with improved apparatus. In the mean time 3·72 has been adopted, and will continue to be used, as the provisional value of the horizontal force at Woolwich; and the intensities at Sir Edward Belcher's stations have been computed and are expressed accordingly. The general table of the determinations of the horizontal force (Table I.) is divided into three portions. Part I. contains a condensed abstract of the observations with Nos. 5, 6, 7 and 8, antecedent to March 1839, at several of the ports of the west coast of America. The column entitled "corrected times," shows the mean times of vibration corrected for the chronometer's rate and for the arc of vibration, and reduced to a mean temperature of 75°; employing for that purpose the coefficients found experimentally for each needle. The corrections for the arc of vibration have been made by multiplying the time of vibration by $1 - \frac{a a'}{16}$, $a$ and $a'$ being the sines of the semiarcs at the commencement and conclusion of the observation. Previous to March 1839, the commencing semiarc was always 40°; subsequent to that period always 20°. The concluding arcs are specified in the Table. Panama is here employed as a base station; and the means of the corrected times in March 1837, October 1838, and March 1839, have been taken, for each needle respectively, as the approximate times throughout the interval; the values of the horizontal force are given in reference to the scale of absolute measure, the force at Panama being taken as = 7·743 (Part II. of Table I. of this memoir). Part II. contains a condensed abstract of the observations with Nos. 5, 6, 7, 8, 9, 11, 12 and 13, between March 1839 and April 1840, more detailed particulars of which have been already given in Table V. of No. II. of these Contributions. Part III. comprises the whole remainder of the observations from May 1840 at Rarotonga Island to December 1842 at Woolwich. The manner in which the values of the horizontal force in the final column of Parts II. and III. have been computed, has been already explained. Table II. contains the observations of the Inclination subsequent to March 1840, made with the same six-inch Inclinometer, by Robinson, employed at the earlier stations: this Table is a continuation of Table IX. in No. II. of these Contributions. The Declinations inserted in the general table were observed with a nine-inch altitude and azimuth instrument by Cary, having a four-inch magnetic needle attached to it. The general table, Table III., comprises in one view, the Declination, Inclination, horizontal and total Intensity, resulting from the whole of the observations, and is the best evidence, especially to those who are familiar with the practical details of such observations, of the amount of obligation which magnetical science owes to Sir Edward Belcher, and to the officers of the Royal Navy employed under his direction. **Table I.—Part I.** Abstract of Observations with the Intensity Needles between March 1837 and March 1839; in these observations the commencing semi-arc was 40°. | Station | 1837. | Needle. | No. of observations. | Time of vibration. | Thermometer. | Chronometer rate. | Final semi-arc. | Corrected time, 75° F. | Horizontal Intensity. | |------------------|-------|---------|----------------------|--------------------|--------------|-------------------|-----------------|------------------------|---------------------| | Panama | | | | | | | | | | | March 10. | 5 | 2 | 472·7 | 79 | L. 1·1 | 14 | 467·8 | | | | | 10 | 6 | 512·5 | 76 | L. 1·1 | 14 | 507·4 | | | | | 12 | 7 | 522·7 | 71 | L. 1·1 | 4 | 531·3 | | | | | 12 | 8 | 470·4 | 76 | L. 1·1 | 7 | 468·1 | | | | Fort Etches | August 28. | 5 | 736·7 | 50 | L. 8·6 | 5 | 737·9 | 3·13 | | | | 28 | 6 | 792·4 | 50 | L. 8·6 | 8 | 734·2 | 3·16 | | | Acapulco | January 17. | 6 | 508·1 | 88 | L. 5·4 | 13 | 501·4 | 7·94 | | | | 17 | 7 | 530·7 | 91 | L. 5·4 | 3 | 529·2 | 7·87 | | | Callao | June 20 & 21. | 5 | 487·1 | 68 | L. 2·0 | 14 | 483·1 | 7·31 | | | | 25 | 6 | 525·0 | 79 | L. 2·0 | 13 | 519·2 | 7·41 | | | | 27 | 7 | 546·1 | 72 | L. 2·0 | 5 | 544·3 | 7·44 | | | | 27 | 8 | 483·8 | 70 | L. 2·0 | 6·5 | 481·8 | 7·32 | | | Puna Island, Guayaquil | Sept. 3. | 5 | 476·1 | 78 | L. 1·4 | 14 | 471·2 | 7·69 | | | | 17-23.| 6 | 513·2 | 89 | L. 1·4 | 13 | 505·9 | 7·80 | | | Panama | October 28. | 5 | 475·3 | 82 | Not recorded. | 14 | 470·0 | | | | | 28 | 6 | 514·6 | 83 | Not recorded. | 13 | 508·3 | | | | | 28 | 7 | 536·8 | 83 | Not recorded. | 4 | 535·1 | | | | | 28 | 8 | 471·4 | 83 | Not recorded. | 6 | 469·1 | | | | 1839. | March 16. | 5 | 476·2 | 85 | L. 2·1 | 14 | 470·7 | | | | | 16 | 7 | 536·1 | 84 | L. 2·1 | 3·5 | 534·5 | | | | | 16 | 8 | 471·4 | 87 | L. 2·1 | 5 | 469·4 | | | 82 ### Table I.—Part II. Abstract of Observations with the Intensity Needles between March 1839 and April 1840; in these observations the commencing semi-arc was 20°. | Station | 1839. | Needle. | No. of observations. | Time of vibration. | Thermometer. | Chronometer rate. | Final semi-arc | Corrected time, 75° Fahr. | Horizontal Intensity | |---------------|-------|---------|----------------------|--------------------|--------------|-------------------|---------------|--------------------------|---------------------| | | | | | | | | | | | | Panama | | | | | | | | | | | March 16 | | | | | | | | | | | 16. | 5 | 2 | 472-45 | 85 | L. 2-1 | 7-5 | 470-2 | 7-731 | | | 16. | 6 | 3 | 522-80 | 87 | L. 2-1 | 6-2 | 519-7 | | | | 16. | 7 | 3 | 534-53 | 85 | L. 2-1 | 2-0 | 533-6 | 7-727 | | | 16. | 8 | 3 | 469-30 | 87 | L. 2-1 | 2-5 | 468-5 | 7-763 | >7-743 | | 16. | 9 | 3 | 436-85 | 83 | L. 2-1 | 2-7 | 436-2 | 7-745 | | | 16. | 11 | 1 | 473-26 | 87 | L. 2-1 | 2-5 | 472-2 | 7-745 | | | 16. | 12 | 1 | 403-22 | 87 | L. 2-1 | 3-5 | 402-4 | 7-726 | | | 16. | 13 | 1 | 393-24 | 88 | L. 2-1 | 3-5 | 392-2 | 7-768 | | | April 8 | | | | | | | | | | | 8. | 5 | 2 | 466-68 | 82 | L. 2-5 | 5-7 | 465-0 | 7-907 | | | 8. | 6 | 2 | 514-77 | 81 | L. 2-5 | 7-0 | 512-3 | | | | Cocos Island | | | | | | | | | | | 8. | 11 | 2 | 465-68 | 78 | L. 2-5 | 3-0 | 465-0 | 7-988 | >7-924 | | 8. | 12 | 2 | 397-43 | 77 | L. 2-5 | 3-0 | 396-9 | 7-939 | | | 8. | 13 | 2 | 390-00 | 78 | L. 2-5 | 3-7 | 389-3 | 7-864 | | | June 4–9 | | | | | | | | | | | Oahu | | | | | | | | | | | 5–9. | 6 | 4 | 513-89 | 87 | L. 1-3 | 5-7 | 511-4 | 6-536 | | | 5–9. | 6 | 4 | 575-77 | 86 | L. 1-3 | 5-0 | 572-6 | | | | Kodiack | | | | | | | | | | | July 7 | | | | | | | | | | | Woolwich | | | | | | | | | | | Sitka | | | | | | | | | | | Fort Vancouver| | | | | | | | | | | Baker's Bay | | | | | | | | | | | Port Bodega | | | | | | | | | | | San Francisco | | | | | | | | | | | Monterey | | | | | | | | | | | Santa Barbara | | | | | | | | | | | San Pedro | | | | | | | | | | | San Diego | | | | | | | | | | | San Quentin | | | | | | | | | | | San Bartholomew | | | | | | | | | | --- This table provides detailed observations with intensity needles between March 1839 and April 1840, focusing on the commencing semi-arc at 20°. Each entry includes station names, dates, needle numbers, observations, times, thermometers, chronometer rates, final semi-arcs, corrected times, and horizontal intensities. | Station | 1839. | Needle. | No. of observations. | Time of vibration. | Thermometer. | Chronometer rate. | Final semi-arc. | Corrected time, 75° Fahr. | Horizontal Intensity. | |------------------|-------|---------|---------------------|-------------------|--------------|-------------------|----------------|--------------------------|----------------------| | Magdalena Bay | | | | | | | | | | | November 1. | 5 | 1 | 490-08 | 73 | L. 2-7 | 5-5 | 489-3 | 7-141 | 7-160 | | 1. | 6 | 1 | 547-36 | 73 | L. 2-7 | 4-0 | 546-9 | 7-180 | | | Bay of SanLucas | | | | | | | | | | | 21. | 5 | 1 | 487-90 | 83 | L. 2-7 | 6-0 | 486-0 | 7-238 | | | 21. | 6 | 1 | 545-92 | 84 | L. 2-7 | 6-0 | 543-1 | 7-280 | | | 28. | 5 | 1 | 488-08 | 71 | L. 1-9 | 6-5 | 487-3 | 7-200 | | | 28. | 6 | 1 | 546-16 | 71 | L. 1-9 | 6-0 | 545-6 | 7-200 | | | 29. | 7 | 1 | 552-84 | 73 | L. 1-9 | 2-0 | 552-5 | 7-208 | | | Nov. 30 and | | | | | | | | | | | Mazatlan | | | | | | | | | | | Dec. 2. | 7 | 3 | 558-83 | 74 | L. 1-9 | 2-0 | 558-4 | 7-214 | | | Nov. 29 to | | | | | | | | | | | Dec. 2. | 8 | 4 | 487-22 | 74 | L. 1-9 | 3-0 | 486-7 | 7-222 | | | Nov. 28. | 9 | 3 | 452-82 | 74 | L. 1-9 | 3-5 | 452-2 | 7-245 | | | November 28. | 11 | 1 | 488-52 | 72 | L. 1-9 | 2-0 | 488-3 | 7-245 | | | 28. | 12 | 1 | 416-94 | 72 | L. 1-9 | 3-0 | 416-6 | 7-208 | | | 28. | 13 | 1 | 407-28 | 72 | L. 1-9 | 3-5 | 406-9 | 7-200 | | | Dec. 6 and 19. | 5 | 2 | 482-42 | 83 | L. 1-9 | 4-2 | 480-8 | 7-394 | | | 6. and 19. | 6 | 3 | 539-09 | 81 | L. 1-9 | 4-2 | 537-2 | 7-410 | | | 6. and 19. | 7 | 3 | 551-36 | 80 | L. 1-9 | 2-0 | 550-7 | 7-410 | | | 6. and 19. | 8 | 2 | 481-14 | 82 | L. 1-9 | 2-5 | 480-4 | 7-421 | | | San Blas | | | | | | | | | | | 6. and 19. | 9 | 2 | 446-04 | 81 | L. 1-9 | 2-5 | 445-4 | 7-446 | | | 6. and 19. | 11 | 2 | 482-92 | 83 | L. 1-9 | 2-0 | 482-2 | 7-429 | | | 6. and 19. | 12 | 2 | 410-77 | 82 | L. 1-9 | 2-2 | 410-2 | 7-432 | | | 6. and 19. | 13 | 2 | 401-66 | 82 | L. 1-9 | 2-5 | 401-0 | 7-414 | | | Socorro Island | 26. | 5 | 477-92 | 84 | L. 3-5 | 6-5 | 475-9 | 7-477 | | | Clarion Island | 26. | 6 | 553-78 | 85 | L. 3-5 | 4-0 | 551-2 | 7-597 | | | 29. | 5 | 2 | 481-70 | 85 | L. 3-5 | 6-2 | 479-6 | 7-597 | | | 29. | 6 | 2 | 550-47 | 84 | L. 3-5 | 5-0 | 547-9 | 7-597 | | | Martin’s Island | | | | | | | | | | | Jan. 23–29. | 5 | 5 | 478-74 | 87 | L. 3-6 | 6-0 | 476-5 | 7-578 | | | 23–29. | 6 | 6 | 543-03 | 86 | L. 3-6 | 5-0 | 540-1 | 7-578 | | | 25–27. | 7 | 2 | 544-78 | 87 | L. 3-6 | 2-2 | 544-1 | 7-593 | | | 25–27. | 8 | 2 | 475-88 | 85 | L. 3-6 | 2-7 | 475-1 | 7-593 | | | 25–27. | 9 | 2 | 441-17 | 88 | L. 3-6 | 3-2 | 440-3 | 7-594 | | | 25–27. | 11 | 2 | 477-94 | 89 | L. 3-6 | 2-0 | 476-9 | 7-593 | | | 25–27. | 12 | 2 | 406-58 | 87 | L. 3-6 | 3-0 | 405-8 | 7-595 | | | 25–27. | 13 | 2 | 397-54 | 88 | L. 3-6 | 3-7 | 396-4 | 7-585 | | | Bow Island | | | | | | | | | | | Feb. 6–29. | 5 | 14 | 484-2 | 86 | L. 5-3 | 7-0 | 482-1 | 7-402 | | | March 20–21. | 5 | 14 | 484-30 | 83 | G. 5-8 | 6-5 | 545-1 | 7-402 | | | Feb. 6–29. | 6 | 22 | 547-77 | 87 | L. 5-3 | 5-5 | 545-1 | 7-402 | | | March 20–21. | 6 | 14 | 548-53 | 84 | G. 5-8 | 6-5 | 545-1 | 7-402 | | | 22. | 7 | 3 | 551-24 | 76 | G. 5-8 | 3-0 | 550-6 | 7-415 | | | 22. | 8 | 4 | 481-55 | 77 | G. 5-8 | 3-0 | 480-9 | 7-425 | | | 22. | 9 | 3 | 446-47 | 82 | G. 5-8 | 4-0 | 445-6 | 7-440 | | | 22. | 11 | 3 | 482-83 | 85 | G. 5-8 | 2-5 | 481-9 | 7-440 | | | 22. | 12 | 3 | 411-08 | 87 | G. 5-8 | 3-0 | 410-2 | 7-432 | | | 22. | 13 | 3 | 401-97 | 86 | G. 5-8 | 3-4 | 400-8 | 7-419 | | | Ap. 4 to May 6. | 5 | 11 | 482-47 | 84 | L. 4-0 | 6-2 | 480-4 | 7-453 | | | April 11. | 6 | 11 | 546-15 | 83 | L. 4-0 | 5-5 | 543-6 | 7-453 | | | Tahiti, Point Venus | | | | | | | | | | | May 6–7. | 7 | 3 | 548-07 | 88 | L. 3-7 | 2-3 | 547-3 | 7-505 | | | 6–7. | 8 | 4 | 479-03 | 82 | L. 3-7 | 2-7 | 478-3 | 7-505 | | | 6–7. | 9 | 3 | 443-65 | 81 | L. 3-7 | 3-2 | 443-0 | 7-525 | | | 6–8. | 11 | 3 | 480-55 | 80 | L. 3-7 | 2-6 | 479-9 | 7-501 | | | 6–8. | 12 | 3 | 409-01 | 82 | L. 3-7 | 2-7 | 408-4 | 7-498 | | | Tahiti, Papeete | April 17. | 5 | 2 | 480-13 | 77 | L. 5-2 | 6-0 | 479-1 | 7-498 | | | 17. | 6 | 2 | 544-36 | 84 | L. 5-2 | 5-0 | 541-8 | 7-498 | | ### Table I.—Part III. Observations with the Intensity Needles between May 1840 and December 1842; in these observations the commencing semi-arc was 20°. | Stations | 1840 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc | Corrected time, 75° F.A.H.R. | Horizontal Intensity | |---------------------------|------|--------|------------------|-------------|------------------|---------------|-------------------------------|---------------------| | Rarotonga Island, Harvey Group | May 15 | 5 | 486:34 | 77 | L. 5:8 | 5:0 | 484:9 | 7:315 | | | 15 | 5 | 486:46 | 80 | L. 5:8 | 6:5 | | | | | 15 | 6 | 555:48 | 85 | L. 5:8 | 5:5 | | | | | 15 | 6 | 555:40 | 85 | L. 5:8 | 5:0 | | | | | 22 | 5 | 474:16 | 77 | L. 5:6 | 6:5 | | | | | 22 | 5 | 473:68 | 77 | L. 5:6 | 7:5 | 472:4 | 7:706 | | Vavao Island, Hapae Group | 22 | 5 | 473:92 | 78 | L. 5:6 | 7:0 | | | | | 22 | 6 | 530:88 | 78 | L. 5:6 | 6:5 | | | | | 22 | 6 | 529:96 | 77 | L. 5:6 | 6:5 | | | | | 22 | 6 | 530:24 | 76 | L. 5:6 | 7:0 | | | | | 30 | 5 | 474:00 | 80 | L. 5:6 | 6:5 | | | | | 30 | 5 | 473:76 | 80 | L. 5:6 | 6:5 | | | | | 30 | 5 | 474:08 | 85 | L. 5:6 | 6:5 | | | | | 30 | 6 | 532:74 | 85 | L. 5:6 | 6:0 | | | | | 30 | 6 | 533:14 | 83 | L. 5:6 | 5:5 | | | | | 30 | 6 | 532:24 | 82 | L. 5:6 | 6:0 | | | | | 30 | 6 | 532:60 | 79 | L. 5:6 | 7:0 | | | | | 31 | 7 | 540:46 | 80 | L. 5:6 | 2:5 | | | | | 31 | 7 | 540:00 | 80 | L. 5:6 | 2:5 | 540:0 | 7:676 | | June 1 | 1 | 7 | 541:46 | 79 | L. 5:6 | 3:0 | | | | Nukulau Island, Feejee Group | 1 | 8 | 472:68 | 79 | L. 5:6 | 3:5 | | | | | 1 | 8 | 472:70 | 79 | L. 5:6 | 3:5 | | | | | 1 | 8 | 472:88 | 80 | L. 5:6 | 3:5 | | | | | 1 | 9 | 440:12 | 85 | L. 5:6 | 3:5 | | | | | 1 | 9 | 439:52 | 86 | L. 5:6 | 3:5 | | | | | 1 | 9 | 439:34 | 86 | L. 5:6 | 3:5 | | | | May 30 | 11 | 9 | 439:60 | 81 | L. 5:6 | 3:0 | | | | | 11 | 11 | 474:32 | 86 | L. 5:6 | 2:5 | | | | | 11 | 11 | 474:72 | 85 | L. 5:6 | 3:0 | | | | | 12 | 11 | 403:10 | 85 | L. 5:6 | 3:0 | | | | | 12 | 12 | 403:68 | 86 | L. 5:6 | 3:5 | | | | | 12 | 12 | 403:32 | 85 | L. 5:6 | 3:0 | | | | | 13 | 13 | 394:52 | 82 | L. 5:6 | 4:0 | | | | | 13 | 13 | 395:14 | 82 | L. 5:6 | 3:5 | | | | Banga Island, Feejee Group | 13 | 13 | 394:96 | 82 | L. 5:6 | 3:5 | | | | June 15 | 5 | 15 | 474:32 | 89 | L. 6:0 | 5:5 | | | | | 6 | 15 | 533:36 | 91 | L. 6:0 | 4:0 | | | | | 22 | 5 | 470:62 | 75 | L. 6:2 | 6:5 | | | | Tanna Island, Port Resolution, New Hebrides | 22 | 5 | 470:44 | 72 | L. 6:2 | 6:5 | | | | | 22 | 5 | 470:76 | 72 | L. 6:2 | 7:0 | | | | | 22 | 6 | 527:80 | 72 | L. 6:2 | 6:0 | | | | | 22 | 6 | 527:40 | 70 | L. 6:2 | 5:5 | | | | July 7 | 5 | 7 | 464:16 | 77 | L. 6:3 | 7:5 | | | | | 7 | 5 | 463:72 | 77 | L. 6:3 | 8:0 | | | | | 15 | 5 | 463:92 | 78 | L. 6:3 | 7:0 | | | | | 7 | 6 | 520:73 | 79 | L. 6:3 | 7:0 | | | | | 7 | 6 | 520:40 | 79 | L. 6:3 | 7:0 | | | | Cocos Island, Port Carteret, New Ireland | 15 | 6 | 521:44 | 78 | L. 6:3 | 6:5 | | | | | 7 | 7 | 529:20 | 80 | L. 6:3 | 3:5 | | | | | 7 | 7 | 529:44 | 81 | L. 6:3 | 3:5 | | | | | 15 | 7 | 528:98 | 77 | L. 6:3 | 3:5 | | | | Station | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc | Corrected time, 75° Fahr. | Horizontal Intensity | |--------------------------|--------|------------------|-------------|------------------|---------------|---------------------------|----------------------| | Cocos Island, Port Carteret, New Ireland. | July 7 | 8 | 463·64 | 83 | L. 6·3 | 3·5 | 8·039 | | | 7 | 8 | 463·68 | 84 | L. 6·3 | 4·0 | | | | 7 | 8 | 463·68 | 80 | L. 6·3 | 4·0 | | | | 15 | 8 | 464·26 | 77 | L. 6·3 | 4·0 | | | | 7 | 9 | 430·84 | 83 | L. 6·3 | 5·5 | | | | 7 | 9 | 430·88 | 85 | L. 6·3 | 5·0 | | | | 7 | 9 | 431·16 | 82 | L. 6·3 | 4·5 | | | | 15 | 9 | 430·88 | 77 | L. 6·3 | 5·0 | | | | 7 | 11 | 464·54 | 85 | L. 6·3 | 3·5 | | | | 7 | 11 | 464·76 | 85 | L. 6·3 | 3·5 | | | | 7 | 11 | 464·84 | 81 | L. 6·3 | 3·0 | | | | 7 | 12 | 395·42 | 84 | L. 6·3 | 4·0 | | | | 7 | 12 | 395·96 | 84 | L. 6·3 | 4·0 | | | | 7 | 12 | 395·54 | 81 | L. 6·3 | 5·0 | | | | 7 | 13 | 386·60 | 84 | L. 6·3 | 4·0 | | | | 7 | 13 | 387·16 | 83 | L. 6·3 | 4·0 | | | | 7 | 13 | 387·16 | 82 | L. 6·3 | 4·5 | | | | 27 | 5 | 470·12 | 77 | L. 6·2 | 8·0 | | | | 27 | 5 | 469·64 | 77 | L. 6·2 | 7·5 | | | | 27 | 5 | 470·43 | 78 | L. 6·2 | 7·5 | | | | 27 | 6 | 527·54 | 78 | L. 6·2 | 6·5 | | | | 27 | 6 | 527·84 | 78 | L. 6·2 | 7·0 | | | | 27 | 6 | 527·76 | 78 | L. 6·2 | 6·5 | | | | August 8 | 5 | 463·80 | 83 | L. 6·2 | 6·5 | | | | 8 | 5 | 465·62 | 83 | L. 6·2 | 8·0 | | | | 8 | 5 | 464·24 | 82 | L. 6·2 | 7·0 | | | | 8 | 5 | 463·16 | 83 | L. 6·2 | 7·0 | | | | 8 | 5 | 463·88 | 84 | L. 6·2 | 7·0 | | | | 8 | 6 | 520·86 | 82 | L. 6·2 | 6·5 | | | | 8 | 6 | 521·28 | 85 | L. 6·2 | 6·5 | | | | 8 | 6 | 521·16 | 83 | L. 6·2 | 6·0 | | | | 8 | 7 | 529·24 | 84 | L. 6·2 | 3·0 | | | | 8 | 7 | 529·40 | 82 | L. 6·2 | 3·0 | | | | 8 | 8 | 463·08 | 82 | L. 6·2 | 3·5 | | | | 8 | 8 | 462·92 | 82 | L. 6·2 | 3·5 | | | | 8 | 8 | 462·08 | 82 | L. 6·2 | 3·5 | | | | 8 | 9 | 429·64 | 80 | L. 6·2 | 5·5 | | | | 8 | 9 | 430·12 | 80 | L. 6·2 | 5·0 | | | | 8 | 9 | 430·36 | 82 | L. 6·2 | 5·5 | | | | 8 | 11 | 463·24 | 82 | L. 6·2 | 3·0 | | | | 8 | 11 | 463·04 | 82 | L. 6·2 | 3·0 | | | | 8 | 11 | 462·96 | 82 | L. 6·2 | 3·5 | | | | 8 | 12 | 395·14 | 82 | L. 6·2 | 4·0 | | | | 8 | 12 | 395·05 | 81 | L. 6·2 | 4·0 | | | | 8 | 12 | 395·10 | 81 | L. 6·2 | 4·0 | | | | 8 | 13 | 386·96 | 81 | L. 6·2 | 4·5 | | | | 8 | 13 | 386·44 | 81 | L. 6·2 | 4·0 | | | | 8 | 13 | 386·84 | 81 | L. 6·2 | 4·5 | | | | Shell Rock, Jobie Island. | 14 | 5 | 463·88 | 86 | L. 5·8 | 5·5 | | | | 14 | 5 | 463·62 | 92 | L. 5·8 | 6·0 | | | | 14 | 6 | 522·32 | 91 | L. 5·8 | 5·5 | | | | 14 | 6 | 522·38 | 89 | L. 5·8 | 6·0 | | | | 24 | 5 | 464·68 | 86 | L. 5·8 | 7·0 | | | | 24 | 5 | 464·36 | 86 | L. 5·8 | 7·0 | | | | 24 | 5 | 465·44 | 87 | L. 5·8 | 6·5 | | | | 24 | 5 | 464·84 | 82 | L. 5·8 | 7·5 | | | | 24 | 6 | 522·72 | 81 | L. 5·8 | 6·5 | | | | 24 | 6 | 522·60 | 87 | L. 5·8 | 6·5 | | | | 24 | 6 | 523·12 | 88 | L. 5·8 | 6·0 | | | | Amsterdam Island, New Guinea. | 24 | 5 | 463·88 | 86 | L. 5·8 | 5·5 | | | | 24 | 5 | 463·62 | 92 | L. 5·8 | 6·0 | | | | 24 | 6 | 522·32 | 91 | L. 5·8 | 5·5 | | | | 24 | 6 | 522·38 | 89 | L. 5·8 | 6·0 | | | | 24 | 5 | 464·68 | 86 | L. 5·8 | 7·0 | | | | 24 | 5 | 464·36 | 86 | L. 5·8 | 7·0 | | | | 24 | 5 | 465·44 | 87 | L. 5·8 | 6·5 | | | | 24 | 5 | 464·84 | 82 | L. 5·8 | 7·5 | | | | 24 | 6 | 522·72 | 81 | L. 5·8 | 6·5 | | | | 24 | 6 | 522·60 | 87 | L. 5·8 | 6·5 | | | | 24 | 6 | 523·12 | 88 | L. 5·8 | 6·0 | | | Station | 1840 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time, 75° PAIR | Horizontal Intensity | |-------------------------|------|--------|------------------|-------------|-----------------|----------------|--------------------------|---------------------| | Fort Defence, Bouro Island | | | | | | | | | | August 31 | 5 | 463-28 | 89 | L. 6-4 | 6-0 | 461-2 | 8-088 | | | Sept. | 5 | 463-36 | 85 | L. 6-4 | 6-5 | | | 8-093 | | August 31 | 6 | 521-52 | 89 | L. 6-4 | 5-0 | | | | | Sept. | 6 | 520-08 | 89 | L. 6-4 | 6-0 | 517-4 | 8-097 | | | | 4 | 460-65 | 76 | L. 6-1 | 8-0 | | | | | | 5 | 461-08 | 80 | L. 6-1 | 8-0 | 459-1 | 8-161 | | | | 4 | 460-28 | 77 | L. 6-1 | 7-5 | | | | | | 6 | 518-04 | 76 | L. 6-1 | 6-5 | | | | | | 6 | 517-96 | 78 | L. 6-1 | 7-0 | 516-2 | | | | | 6 | 517-78 | 79 | L. 6-1 | 6-0 | | | | | | 7 | 525-30 | 84 | L. 6-1 | 3-0 | | | | | | 7 | 525-80 | 84 | L. 6-1 | 2-5 | 525-0 | 8-157 | | | | 7 | 526-00 | 86 | L. 6-1 | 2-0 | | | | | | 8 | 461-40 | 86 | L. 6-1 | 2-5 | | | | | | 8 | 460-80 | 87 | L. 6-1 | 2-5 | 460-1 | 8-144 | | | | 8 | 460-32 | 87 | L. 6-1 | 2-5 | | | | | | 9 | 427-60 | 84 | L. 6-1 | 3-0 | | | | | | 9 | 428-04 | 77 | L. 6-1 | 3-0 | 427-2 | 8-163 | | | | 9 | 427-93 | 77 | L. 6-1 | 4-5 | | | | | | 11 | 463-32 | 80 | L. 6-1 | 3-0 | | | | | | 11 | 463-42 | 85 | L. 6-1 | 2-5 | 462-6 | 8-136 | | | | 11 | 463-36 | 85 | L. 6-1 | 2-5 | | | | | | 12 | 392-72 | 84 | L. 6-1 | 3-0 | 392-1 | 8-134 | | | | 13 | 385-48 | 81 | L. 6-1 | 4-0 | | | | | | 13 | 384-56 | 82 | L. 6-1 | 4-0 | 384-0 | 8-116 | | | | 13 | 384-50 | 84 | L. 6-1 | 4-0 | | | | | | 26 | 465-00 | 73 | L. 6-2 | 8-0 | | | | | | 27 | 464-34 | 78 | L. 6-2 | 7-0 | 463-1 | 8-021 | | | | 27 | 464-44 | 78 | L. 6-2 | 7-0 | | | | | | 30 | 464-80 | 87 | L. 6-2 | 6-0 | | | | | | 26 | 522-20 | 74 | L. 6-2 | 7-0 | | | | | | 27 | 523-28 | 79 | L. 6-2 | 6-5 | 521-2 | | | | | 27 | 523-04 | 79 | L. 6-2 | 6-5 | | | | | Fort Rotterdam, Macassar Island | | | | | | | | | | October 4 | 5 | 431-21 | 90 | L. 6-2 | 3-5 | | | | | | 9 | 430-76 | 90 | L. 6-2 | 3-0 | 430-1 | 8-054 | | | | 11 | 466-92 | 91 | L. 6-2 | 2-0 | | | | | | 11 | 466-46 | 91 | L. 6-2 | 2-5 | 465-6 | 8-032 | | | | 12 | 395-86 | 90 | L. 6-2 | 3-0 | 395-1 | 8-014 | | | | 12 | 395-84 | 90 | L. 6-2 | 2-5 | | | | | | 13 | 388-32 | 89 | L. 6-2 | 3-5 | 387-6 | 8-031 | | | | 13 | 388-76 | 87 | L. 6-2 | 3-0 | | | | | Solombo Island | 5 | 466-72 | 91 | L. 6-2 | 6-5 | | | | | | 4 | 466-92 | 92 | L. 6-2 | 6-5 | 464-1 | 7-988 | | | | 4 | 466-86 | 94 | L. 6-2 | 6-5 | | | | | | 6 | 525-92 | 92 | L. 6-2 | 5-0 | | | | | | 6 | 525-48 | 92 | L. 6-2 | 5-5 | 521-8 | 8-019 | | | | 6 | 526-00 | 94 | L. 6-2 | 5-5 | | | | | | 7 | 466-16 | 85 | L. 6-6 | 8-0 | | | | | Rendezvous Island, Pulo Kambal (S.W. Pt of Borneo) | | | | | | | | | | | 7 | 466-07 | 84 | L. 6-6 | 7-5 | 462-4 | 8-047 | | | | 7 | 466-17 | 82 | L. 6-6 | 7-0 | | | | | | 6 | 524-56 | 85 | L. 6-6 | 7-0 | 521-5 | 8-029 | | | | 6 | 524-45 | 85 | L. 6-6 | 7-0 | | | | | | 6 | 524-47 | 84 | L. 6-6 | 7-0 | | | | | Station | 1840 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc | Corrected time, 75° Fahr. | Horizontal Intensity | |-------------------------|------|--------|------------------|-------------|------------------|----------------|--------------------------|---------------------| | Singapore | | | | | | | | | | October | | | | | | | | | | 18. | 5 | 466·61 | s | 79 | L. 6·8 | 7·0 | 465·6 | 7·935 | | | 6 | 467·06 | 70 | L. 6·8 | 7·5 | | | | | | 7 | 524·88 | 70 | L. 6·8 | 7·5 | | | | | | 8 | 532·60 | 75 | L. 6·8 | 3·0 | | | | | | 9 | 533·02 | 75 | L. 6·8 | 2·5 | | | | | | 10 | 467·30 | 79 | L. 6·8 | 3·5 | | | | | | 11 | 467·56 | 79 | L. 6·8 | 3·5 | | | | | | 12 | 467·54 | 80 | L. 6·8 | 3·5 | | | | | | 13 | 433·80 | 82 | L. 6·8 | 3·5 | | | | | | 14 | 433·46 | 84 | L. 6·8 | 3·5 | | | | | | 15 | 432·97 | 83 | L. 6·8 | 3·5 | | | | | | 16 | 468·97 | 77 | L. 6·8 | 3·0 | | | | | | 17 | 469·48 | 78 | L. 6·8 | 2·5 | | | | | | 18 | 397·28 | 79 | L. 6·8 | 3·0 | | | | | | 19 | 396·88 | 80 | L. 6·8 | 3·0 | | | | | | 20 | 397·28 | 82 | L. 6·8 | 3·0 | | | | | | 21 | 391·36 | 83 | L. 6·8 | 3·0 | | | | | | 22 | 390·98 | 84 | L. 6·8 | 3·5 | | | | | | 23 | 390·28 | 85 | L. 6·8 | 3·5 | | | | | Dec. 1 | | | | | | | | | | 1. | 5 | 469·64 | 82 | G. 11·5 | 7·0 | | | | | | 6 | 469·52 | 82 | G. 11·5 | 7·0 | | | | | | 7 | 469·54 | 80 | G. 11·5 | 7·0 | | | | | | 8 | 469·44 | 80 | G. 11·5 | 7·0 | | | | | | 9 | 470·92 | 80 | G. 11·5 | 5·0 | | | | | | 10 | 470·40 | 83 | G. 11·5 | 5·0 | | | | | | 11 | 530·72 | 82 | G. 11·5 | 6·5 | | | | | | 12 | 530·70 | 84 | G. 11·5 | 5·5 | | | | | | 13 | 476·04 | 70 | L. 5·9 | 6·0 | | | | | | 14 | 476·32 | 72 | L. 5·9 | 6·0 | | | | | | 15 | 475·94 | 69 | L. 5·9 | 6·0 | | | | | | 16 | 538·60 | 73 | L. 5·9 | 4·0 | | | | | | 17 | 538·14 | 76 | L. 5·9 | 5·0 | | | | | | 18 | 537·81 | 68 | L. 5·9 | 5·5 | | | | | Island of Sampanchow, Boca Tigris | | | | | | | | | | Feb. 12 | | | | | | | | | | 12. | 5 | 475·82 | 70 | L. 5·7 | 6·0 | | | | | | 13. | 475·80 | 71 | L. 5·7 | 6·0 | | | | | | 14. | 475·36 | 74 | L. 5·7 | 6·0 | | | | | | 15. | 541·60 | 72 | L. 5·7 | 5·0 | | | | | | 16. | 541·68 | 73 | L. 5·7 | 5·5 | | | | | | 17. | 540·46 | 73 | L. 5·7 | 6·5 | | | | | | 18. | 476·04 | 64 | L. 6·4 | 6·5 | | | | | | 19. | 476·13 | 74 | L. 6·4 | 5·5 | | | | | | 20. | 476·44 | 76 | L. 6·4 | 6·0 | | | | | | 21. | 537·40 | 67 | L. 6·4 | 5·0 | | | | | | 22. | 538·12 | 76 | L. 6·4 | 5·0 | | | | | | 23. | 538·64 | 76 | L. 6·4 | 5·5 | | | | | April 9 | | | | | | | | | | 9. | 5 | 478·04 | 84 | L. 6·4 | 6·5 | | | | | | 10. | 477·90 | 83 | L. 6·4 | 6·5 | | | | | | 11. | 477·48 | 83 | L. 6·4 | 7·5 | | | | | | 12. | 542·38 | 89 | L. 6·4 | 5·5 | | | | | | 13. | 542·70 | 92 | L. 6·4 | 6·0 | | | | | | 14. | 542·32 | 86 | L. 6·4 | 5·5 | | | | | | 15. | 544·60 | 85 | L. 6·4 | 2·5 | | | | | | 16. | 544·42 | 86 | L. 6·4 | 3·0 | | | | | | 17. | 544·03 | 88 | L. 6·4 | 2·5 | | | | | | 18. | 478·16 | 87 | L. 6·4 | 3·0 | | | | | Macao | | | | | | | | | | 9. | 8 | 477·92 | 84 | L. 6·4 | 3·5 | | | | | | 9. | 478·44 | 85 | L. 6·4 | 3·0 | | | | MDCCXLIII. | Station | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time, 75° Fahr. | Horizontal Intensity | |------------------|--------|-------------------|-------------|------------------|----------------|--------------------------|---------------------| | Macao | April 9 | s | 85 | L. 6'4 | 2'5 | s | 7'596 | | | 9 | 442-94 | | L. 6'4 | 2'5 | 442-3 | 7'653 | | | 9 | 442-96 | | L. 6'4 | 3'0 | | | | | 9 | 442-92 | | L. 6'4 | 3'5 | | | | | 9 | 480-40 | | L. 6'4 | 3'0 | 479-5 | 7'538 | | | 9 | 480-20 | | L. 6'4 | 3'0 | | | | | 9 | 480-36 | | L. 6'4 | 3'0 | | | | | 9 | 405-88 | | L. 6'4 | 3'5 | | | | | 9 | 405-36 | | L. 6'4 | 3'0 | 405-5 | 7'606 | | | 9 | 406-44 | | L. 6'4 | 3'5 | | | | | 9 | 400-48 | | L. 6'4 | 4'0 | | | | | 9 | 400-16 | | L. 6'4 | 3'5 | 399-7 | 7'548 | | | 9 | 400-04 | | L. 6'4 | 3'5 | | | | | 12 | 476-84 | | G. 18'2 | 6'5 | | | | | 12 | 475-84 | | G. 18'2 | 7'5 | 475-2 | 7'618 | | | 12 | 476-10 | | G. 18'2 | 7'5 | | | | | 12 | 539-20 | | G. 18'2 | 6'5 | | | | | 12 | 539-13 | | G. 18'2 | 6'0 | 538-2 | | | | 12 | 538-86 | | G. 18'2 | 6'0 | | | | | 19 | 544-28 | | L. 6'4 | 2'0 | | | | | 20 | 544-38 | | L. 6'4 | 3'0 | 543-8 | 7'625 | | | 20 | 544-40 | | L. 6'4 | 2'0 | | | | | 20 | 478-68 | | L. 6'4 | 3'0 | | | | | 20 | 478-06 | | L. 6'4 | 3'0 | 477-6 | | | | 20 | 478-08 | | L. 6'4 | 2'0 | | | | | 21 | 443-72 | | L. 6'4 | 3'5 | | | | | 21 | 443-56 | | L. 6'4 | 4'0 | 443-0 | 7'630 | | | 21 | 443-88 | | L. 6'4 | 3'5 | | | | | 13 | 479-58 | | G. 18'2 | 2'0 | | | | | 13 | 478-82 | | G. 18'2 | 2'0 | 479-0 | 7'553 | | | 13 | 479-28 | | G. 18'2 | 2'0 | | | | | 13 | 405-40 | | G. 18'2 | 2'5 | | | | | 13 | 405-36 | | G. 18'2 | 2'5 | 405-3 | 7'615 | | | 13 | 406-26 | | G. 18'2 | 3'0 | | | | | 19 | 400-80 | | L. 6'4 | 3'5 | | | | | 19 | 400-68 | | L. 6'4 | 3'0 | 400-0 | 7'540 | | | 19 | 400-42 | | L. 6'4 | 4'0 | | | | Island of Sampan-chow. | May 8 | 476-74 | | L. 5'4 | 7'5 | 476-4 | 7'581 | | | 8 | 476-60 | | L. 5'4 | 7'5 | | | | | 8 | 539-26 | | L. 5'4 | 6'5 | | | | | 8 | 538-88 | | L. 5'4 | 7'0 | 539-1 | 7'606 | | August 19 | 5 | 477-56 | | L. 8'1 | 7'0 | | | | | 5 | 477-48 | | L. 8'1 | 7'5 | 474-9 | 7'630 | | | 5 | 476-86 | | L. 8'1 | 7'5 | | | | | 6 | 543-0 | | L. 8'1 | 6'5 | | | | | 6 | 543-38 | | L. 8'1 | 6'5 | 538-8 | | | | 6 | 543-28 | | L. 8'1 | 7'0 | | | | Sept. 24 | 5 | 477-02 | | L. 8'1 | 7'0 | | | | | 5 | 476-52 | | L. 8'1 | 7'0 | 474-7 | 7'634 | | | 6 | 545-62 | | L. 8'1 | 6'5 | | | | | 6 | 545-60 | | L. 8'1 | 6'5 | 542-6 | | | | 6 | 544-24 | | L. 8'1 | 6'5 | | | | | 7 | 543-36 | | L. 8'1 | 2'5 | 542-8 | 7'651 | | | 7 | 543-38 | | L. 8'1 | 2'5 | | | | | 8 | 477-66 | | L. 8'1 | 3'5 | 476-6 | | | | 8 | 477-16 | | L. 8'1 | 3'5 | | | | | 9 | 443-40 | | L. 8'1 | 3'5 | 442-5 | 7'644 | | | 9 | 443-20 | | L. 8'1 | 3'5 | 7'634* | | ### Table (Continued) | Station | 1841 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time 75° Fahr. | Horizontal Intensity | |---------|------|--------|------------------|-------------|-----------------|----------------|--------------------------|---------------------| | Macao | | | | | | | | | | Sept. 25| 11 | 476·84 | 85 | L. 8·1 | 3·0 | 475·5 | 7·665 | >7·634* | | | 12 | 405·96 | 85 | L. 8·1 | 3·0 | 405·2 | 7·616 | | | | 13 | 399·52 | 84 | L. 8·1 | 4·0 | 398·4 | 7·597 | | | Nov. 16 | 5 | 475·90 | 66 | G. 20·2 | 8·0 | | | | | | 6 | 476·14 | 67 | G. 20·2 | 8·0 | 475·3 | 7·616 | | | | 6 | 475·92 | 67 | G. 20·2 | 7·5 | | | | | | 6 | 537·20 | 67 | G. 20·2 | 7·0 | 536·8 | | | | | 6 | 536·74 | 67 | G. 20·2 | 7·0 | | | | | | 7 | 547·58 | 62 | G. 19·0 | 2·5 | | | | | | 7 | 547·96 | 62 | G. 19·0 | 2·5 | 547·0 | 7·537 | | | | 7 | 548·12 | 63 | G. 19·0 | 2·5 | | | | | | 7 | 545·40 | 70 | L. 6·7 | 2·5 | | | | | | 8 | 479·32 | 63 | G. 19·0 | 3·0 | | | | | | 8 | 479·52 | 64 | G. 19·0 | 3·0 | 478·6 | | | | | 8 | 477·92 | 70 | L. 6·7 | 3·0 | | | | | | 9 | 445·05 | 64 | G. 19·0 | 3·5 | | | | | | 9 | 444·92 | 64 | G. 19·0 | 3·5 | 444·1 | 7·575 | | | | 9 | 443·64 | 70 | L. 6·7 | 3·0 | | | | | | 11 | 476·92 | 64 | G. 19·0 | 3·5 | | | | | | 11 | 477·28 | 64 | G. 19·0 | 3·0 | 476·5 | 7·634 | | | | 11 | 476·02 | 70 | L. 6·7 | 2·0 | | | | | | 12 | 407·36 | 64 | G. 19·0 | 3·5 | | | | | | 12 | 407·40 | 64 | G. 19·0 | 3·0 | 406·9 | 7·611 | | | | 12 | 406·80 | 70 | L. 6·7 | 2·5 | | | | | | 13 | 400·80 | 64 | G. 19·0 | 4·0 | | | | | | 13 | 400·76 | 64 | G. 19·0 | 5·0 | 400·0 | 7·536 | | | | 13 | 399·40 | 70 | L. 6·7 | 3·0 | | | | | Dec. 8 | 5 | 465·52 | 84 | L. 8·2 | 6·5 | | | | | | 5 | 466·00 | 83 | L. 8·2 | 7·0 | | | | | | 5 | 467·65 | 86 | L. 8·2 | 7·0 | | | | | | 5 | 467·62 | 86 | L. 8·2 | 6·0 | | | | | | 5 | 467·92 | 86 | L. 8·2 | 5·5 | 465·1 | 7·951 | | | | 5 | 467·48 | 87 | L. 8·2 | 6·0 | | | | | | 5 | 467·32 | 86 | L. 8·2 | 6·5 | | | | | | 5 | 467·80 | 85 | L. 8·2 | 6·5 | | | | | Singapore | | | | | | | | | * The 24th and 25th of September were days of great and general magnetic disturbance. If we collect in one view the determinations of the horizontal force at Macao, we find them as follows: 1841. April 9 ............ six needles — 7·596 April 12–19 .......... six needles — 7·595 September 24 and 25 six needles — 7·634 November 16–20 ....... six needles — 7·585. The comparison of these results leaves little reason to doubt that the discrepancy on the 24th and 25th of September was occasioned by an irregularity in the horizontal force itself; and we may infer that the derangement, which was felt at all stations at which magnetic observations were made on that day, was characterized at Macao by an increase of the horizontal force at the hours when Sir Edward Belcher's observations were made. These hours appear to have been, late in the afternoon of the 24th, and from 11 a.m. to 3 p.m. on the 25th. | Station | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time, 75° Fahr. | Horizontal Intensity | |------------------|--------|-------------------|-------------|------------------|----------------|--------------------------|----------------------| | Singapore | Dec. 8 | 6 | 527:94 | 83 | L. 8:2 | 6:5 | >7:961 | | | | | | | | | | | | | 6 | 527:10 | 84 | L. 8:2 | 6:5 | | | | | | | | | | | | | | 6 | 528:72 | 88 | L. 8:2 | 7:0 | | | | | | | | | | | | | | 6 | 529:08 | 88 | L. 8:2 | 6:0 | | | | | | | | | | | | | | 6 | 532:45 | 89 | L. 8:2 | 4:5 | | | | | | | | | | | | | | 6 | 533:03 | 90 | L. 8:2 | 7:0 | | | | | | | | | | | | | | 6 | 533:12 | 88 | L. 8:2 | 5:0 | | | | | | | | | | | | | | 6 | 533:22 | 88 | L. 8:2 | 3:0 | | | | | | | | | | | | | | 6 | 529:34 | 85 | L. 8:2 | 5:0 | | | | | | | | | | | | | | 6 | 529:72 | 85 | L. 8:2 | 6:0 | | | | | | | | | | | | | | 7 | 531:72 | 88 | L. 8:2 | 2:0 | | | | | | | | | | | | | | 7 | 533:03 | 87 | L. 8:2 | 2:0 | | | | | | | | | | | | | | 7 | 533:08 | 88 | L. 8:2 | 2:0 | | | | | | | | | | | | | | 8 | 466:82 | 87 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 8 | 467:44 | 86 | L. 8:2 | 3:5 | | | | | | | | | | | | | | 8 | 467:48 | 85 | L. 8:2 | 3:5 | | | | | | | | | | | | | | 9 | 434:08 | 84 | L. 8:2 | 3:5 | | | | | | | | | | | | | | 9 | 434:20 | 83 | L. 8:2 | 3:5 | | | | | | | | | | | | | | 11 | 468:08 | 81 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 11 | 468:14 | 82 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 11 | 467:90 | 82 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 12 | 398:36 | 87 | L. 8:2 | 3:0 | | | | | | | | | | | | | | 12 | 398:22 | 88 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 12 | 398:04 | 88 | L. 8:2 | 2:5 | | | | | | | | | | | | | | 13 | 390:84 | 88 | L. 8:2 | 3:0 | | | | | | | | | | | | | | 13 | 390:82 | 88 | L. 8:2 | 3:0 | | | | | | | | | | | | | | 13 | 391:20 | 88 | L. 8:2 | 3:0 | | | | | | | | | | | | | | 5 | 467:44 | 82 | L. 8:2 | 7:5 | | | | | | | | | | | | | | 5 | 467:30 | 82 | L. 8:2 | 7:5 | | | | | | | | | | | | | | 5 | 467:58 | 82 | L. 8:2 | 7:5 | | | | | | | | | | | | | | 6 | 529:76 | 81 | L. 8:2 | 7:0 | | | | | | | | | | | | | | 6 | 529:92 | 80 | L. 8:2 | 7:0 | | | | | | | | | | | | | | 6 | 529:88 | 80 | L. 8:2 | 6:5 | | | | | | | | | | | | | | 5 | 466:24 | 81 | L. 8:0 | 8:0 | | | | | | | | | | | | | | 5 | 466:12 | 81 | L. 8:0 | 8:0 | | | | | | | | | | | | | | 5 | 466:52 | 82 | L. 8:0 | 7:5 | | | | | | | | | | | | | | 6 | 528:76 | 83 | L. 8:0 | 6:0 | | | | | | | | | | | | | | 6 | 528:92 | 85 | L. 8:0 | 6:0 | | | | | | | | | | | | | | 6 | 529:04 | 87 | L. 8:0 | 6:5 | | | | | | | | | | | | | | 7 | 532:05 | 89 | L. 8:0 | 2:5 | | | | | | | | | | | | | | 7 | 532:08 | 90 | L. 8:0 | 2:0 | | | | | | | | | | | | | | 8 | 467:04 | 90 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 8 | 467:52 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 9 | 433:16 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 9 | 433:58 | 89 | L. 8:0 | 3:5 | | | | | | | | | | | | | | 11 | 468:24 | 90 | L. 8:0 | 2:5 | | | | | | | | | | | | | | 11 | 467:84 | 90 | L. 8:0 | 2:0 | | | | | | | | | | | | | | 12 | 398:32 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 12 | 397:60 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 12 | 398:14 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 13 | 390:24 | 89 | L. 8:0 | 3:0 | | | | | | | | | | | | | | 13 | 390:54 | 90 | L. 8:0 | 2:5 | | | | | | | | | | | | | | 13 | 390:32 | 90 | L. 8:0 | 3:0 | | | | | | | | | | | | | | Jan. 10 | 470:04 | 89 | L. 8:0 | 5:0 | | | | | | | | | | | | | | 10 | 469:28 | 85 | L. 8:0 | 6:5 | | | | | | | | | | | | | | 13 | 470:00 | 83 | L. 8:0 | 7:5 | | ## Table. (Continued.) | Station | 1842 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time, 75° Fahr. | Horizontal Intensity | |--------------------------|------|--------|------------------|-------------|-----------------|----------------|---------------------------|---------------------| | Island of Malora, N.W. coast of Sumatra. | | | | | | | | | | January 13 | 6 | 532·56 | 86 | L. 8·0 | 5·5 | 529·7 | 7·871 | 7·863 | | | 6 | 532·76 | 85 | L. 8·0 | 6·0 | | | | | | 6 | 532·82 | 83 | L. 8·0 | 6·5 | | | | | | 6 | 531·68 | 81 | L. 8·0 | 6·0 | | | | | | 11 | 469·96 | 81 | L. 8·0 | 2·0 | | | | | | 11 | 469·60 | 80 | L. 8·0 | 2·0 | | | | | | 12 | 400·20 | 82 | L. 8·0 | 2·0 | | | | | | 12 | 401·20 | 85 | L. 8·0 | 3·0 | | | | | | 13 | 393·25 | 87 | L. 8·0 | 3·0 | | | | | | 13 | 393·32 | 86 | L. 8·0 | 3·5 | | | | | | 5 | 470·72 | 83 | L. 8·0 | 7·0 | | | | | | 5 | 470·44 | 83 | L. 8·0 | 7·0 | | | | | Acheen Island, North coast of Sumatra. | | | | | | | | | | | 5 | 470·32 | 84 | L. 8·0 | 7·5 | | | | | | 6 | 532·98 | 76 | L. 8·0 | 6·0 | | | | | | 6 | 532·96 | 76 | L. 8·0 | 6·0 | | | | | | 6 | 533·00 | 76 | L. 8·0 | 6·5 | | | | | | 6 | 532·88 | 79 | L. 8·0 | 6·5 | | | | | | 5 | 472·80 | 79 | L. 8·0 | 7·5 | | | | | | 5 | 472·60 | 80 | L. 8·0 | 7·5 | | | | | | 5 | 472·94 | 81 | L. 8·0 | 7·5 | | | | | | 6 | 536·04 | 83 | L. 8·0 | 7·0 | | | | | | 6 | 535·92 | 84 | L. 8·0 | 6·5 | | | | | | 6 | 536·00 | 83 | L. 8·0 | 7·0 | | | | | | 6 | 535·44 | 82 | L. 8·0 | 7·0 | | | | | | 7 | 540·96 | 82 | L. 8·0 | 2·5 | | | | | | 7 | 540·56 | 82 | L. 8·0 | 2·0 | | | | | | 7 | 540·80 | 82 | L. 8·0 | 2·0 | | | | | | 8 | 473·52 | 82 | L. 8·0 | 3·0 | | | | | | 8 | 473·96 | 82 | L. 8·0 | 3·5 | | | | | | 9 | 439·80 | 79 | L. 7·8 | 4·0 | | | | | | 9 | 439·60 | 83 | L. 7·8 | 3·5 | | | | | | 9 | 439·91 | 83 | L. 7·8 | 3·5 | | | | | | 11 | 474·20 | 90 | L. 7·8 | 2·0 | | | | | | 11 | 474·12 | 91 | L. 7·8 | 2·0 | | | | | | 11 | 473·90 | 91 | L. 7·8 | 2·0 | | | | | | 12 | 404·04 | 93 | L. 7·8 | 2·5 | | | | | | 12 | 403·98 | 93 | L. 7·8 | 2·5 | | | | | | 12 | 403·92 | 90 | L. 7·8 | 3·0 | | | | | | 13 | 395·52 | 88 | L. 7·8 | 3·5 | | | | | | 13 | 395·30 | 88 | L. 7·8 | 3·0 | | | | | Feb. 21 | 5 | 511·04 | 79 | L. 7·3 | 7·0 | | | | | | 5 | 511·00 | 80 | L. 7·3 | 7·0 | | | | | | 5 | 511·16 | 80 | L. 7·3 | 7·0 | | | | | | 6 | 579·44 | 83 | L. 7·3 | 6·0 | | | | | | 6 | 579·36 | 83 | L. 7·3 | 6·0 | | | | | | 6 | 579·60 | 83 | L. 7·3 | 6·0 | | | | | | 7 | 584·12 | 84 | L. 7·3 | 1·5 | | | | | | 7 | 584·12 | 84 | L. 7·3 | 2·0 | | | | | | 7 | 583·98 | 83 | L. 7·3 | 2·0 | | | | | | 8 | 512·44 | 84 | L. 7·3 | 2·0 | | | | | | 8 | 512·12 | 84 | L. 7·3 | 2·5 | | | | | | 8 | 512·20 | 84 | L. 7·3 | 3·0 | | | | | | 9 | 476·08 | 80 | L. 7·3 | 3·0 | | | | | | 9 | 476·32 | 81 | L. 7·3 | 3·0 | | | | | | 9 | 476·24 | 81 | L. 7·3 | 3·0 | | | | | St. Anne's Island, Seychelles. | | | | | | | | | | | 11 | 511·88 | 83 | L. 7·3 | 2·0 | | | | | | 11 | 512·26 | 83 | L. 7·3 | 2·0 | | | | | | 11 | 512·64 | 82 | L. 7·3 | 2·0 | | | | | Station | 1842 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc | Corrected time, 75° Fahr. | Horizontal Intensity | |--------------------------|------|--------|------------------|-------------|------------------|----------------|--------------------------|---------------------| | St. Anne's Island, Seychelles | Feb. 21 | 12 | 436-72 | 82 | L. 7-3 | 2-0 | s | >6-632 | | | | | 437-00 | 83 | L. 7-3 | 3-0 | 436-3 | 6-633 | | | | | 437-04 | 82 | L. 7-3 | 3-0 | | | | | | | 428-40 | 83 | L. 7-3 | 3-0 | | | | | | | 428-36 | 82 | L. 7-3 | 3-0 | 427-5 | 6-601 | | | | | 428-12 | 83 | L. 7-3 | 3-5 | | | | March 14 | | | 571-52 | 87 | L. 8-4 | 5-5 | | | | | | | 571-28 | 89 | L. 8-4 | 5-0 | 568-6 | 5-500 | | | | | 571-66 | 90 | L. 8-4 | 5-0 | | | | | | | 570-60 | 90 | G. 8-4 | 4-5 | | | | | | | 641-16 | 82 | L. 8-4 | 4-0 | | | | | | | 640-39 | 82 | L. 8-4 | 5-0 | | | | | | | 643-29 | 93 | L. 8-4 | 4-5 | | | | | | | 640-96 | 91 | G. 8-4 | 4-5 | | | | | | | 650-36 | 92 | L. 8-4 | 1-0 | | | | | | | 650-56 | 90 | L. 8-4 | 1-0 | 650-1 | 5-480 | | | | | 651-64 | 91 | L. 8-4 | 1-0 | | | | Sandy Point, Majambo Bay, Madagascar | April 18 | 5 | 627-20 | 88 | G. 11-6 | 5-5 | | | | | | | 627-36 | 88 | G. 11-6 | 5-5 | 624-3 | 4-561 | | | | | 627-26 | 84 | G. 11-6 | 5-5 | | | | | | | 704-08 | 82 | G. 11-6 | 5-0 | | | | | | | 703-66 | 81 | G. 11-6 | 5-0 | 700-9 | | | | | | 702-68 | 76 | G. 11-6 | 5-5 | | | | | | | 712-90 | 85 | G. 11-6 | 1-5 | | | | | | | 712-78 | 84 | G. 11-6 | 1-5 | 712-0 | 4-569 | | | | | 713-20 | 83 | G. 11-6 | 2-0 | | | | | | | 618-78 | 84 | G. 11-6 | 2-0 | | | | | | | 617-50 | 79 | G. 11-6 | 2-0 | 617-4 | 4-569 | | | | | 618-42 | 76 | G. 11-6 | 2-5 | | | | | | | 573-80 | 74 | G. 11-6 | 2-0 | | | | | | | 574-00 | 65 | G. 11-6 | 2-5 | 573-4 | 4-572 | | | | | 573-64 | 67 | G. 11-6 | 3-0 | | | | | | | 616-94 | 84 | G. 11-6 | 1-5 | | | | | | | 617-36 | 85 | G. 11-6 | 2-0 | | | | | | | 526-60 | 87 | G. 11-6 | 2-5 | | | | | | | 527-12 | 86 | G. 11-6 | 2-0 | 525-9 | 4-566 | | | | | 515-80 | 86 | G. 11-6 | 2-5 | | | | | | | 514-98 | 86 | G. 11-6 | 2-0 | 514-3 | 4-561 | | | | | 624-20 | 71 | G. 11-6 | 4-5 | | | | | | | 623-88 | 67 | G. 11-6 | 5-0 | 623-6 | 4-571 | | | | | 700-75 | 72 | G. 11-6 | 4-0 | | | | | | | 699-14 | 72 | G. 11-6 | 5-0 | 699-4 | 4-571 | | Station | 1842 | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc. | Corrected time, 75° Fahr. | Horizontal Intensity | |-------------------------------|------|--------|------------------|-------------|-----------------|----------------|--------------------------|---------------------| | Sisters' Walk (Station of Captain Ross), Saint Helena. | May 9 | 5 | 553·50 | s | G. 11·4 | 6·0 | 552·2 | 5·831 | | | | | | | | | | | | | 9 | 5 | 554·16 | 78 | G. 11·4 | 7·0 | 552·2 | 5·831 | | | | | | | | | | | | | 9 | 6 | 621·32 | 79 | G. 11·4 | 5·0 | 619·6 | 5·824 | | | | | | | | | | | | | 9 | 6 | 622·16 | 79 | G. 11·4 | 5·5 | 619·6 | 5·824 | | | | | | | | | | | | | 17 | 5 | 527·48 | 87 | G. 10·4 | 5·5 | 524·8 | 6·456 | | | | | | | | | | | | | 17 | 5 | 527·60 | 90 | G. 10·4 | 5·5 | 524·8 | 6·456 | | | | | | | | | | | | | 17 | 5 | 527·68 | 92 | G. 10·4 | 5·5 | 524·8 | 6·456 | | | | | | | | | | | | | 17 | 6 | 592·44 | 95 | G. 10·4 | 5·0 | 587·2 | 6·456 | | | | | | | | | | | | | 17 | 6 | 591·32 | 90 | G. 10·4 | 5·5 | 587·2 | 6·456 | | | | | | | | | | | | | 17 | 6 | 591·08 | 91 | G. 10·4 | 5·0 | 587·2 | 6·456 | | | | | | | | | | | | | 17 | 7 | 599·44 | 88 | G. 10·4 | 1·5 | 599·3 | 6·480 | | | | | | | | | | | | | 17 | 7 | 600·50 | 89 | G. 10·4 | 1·0 | 599·3 | 6·480 | | | | | | | | | | | | | 17 | 7 | 600·04 | 76 | G. 10·4 | 2·0 | 599·3 | 6·480 | | | | | | | | | | | | Sandy Beach, Ascension. | 17 | 8 | 520·80 | 77 | G. 10·4 | 2·5 | 520·0 | 6·457 | | | | | | | | | | | | | 17 | 8 | 520·56 | 77 | G. 10·4 | 3·0 | 520·0 | 6·457 | | | | | | | | | | | | | 17 | 8 | 520·76 | 77 | G. 10·4 | 3·0 | 520·0 | 6·457 | | | | | | | | | | | | | 17 | 9 | 482·28 | 78 | G. 10·4 | 3·0 | 481·7 | 6·480 | | | | | | | | | | | | | 17 | 9 | 482·56 | 78 | G. 10·4 | 3·0 | 481·7 | 6·480 | | | | | | | | | | | | | 17 | 9 | 482·36 | 78 | G. 10·4 | 3·5 | 481·7 | 6·480 | | | | | | | | | | | | | 18 | 11 | 521·04 | 84 | G. 10·4 | 2·0 | 519·8 | 6·444 | | | | | | | | | | | | | 18 | 11 | 520·64 | 85 | G. 10·4 | 2·0 | 519·8 | 6·444 | | | | | | | | | | | | | 18 | 11 | 520·68 | 87 | G. 10·4 | 1·5 | 519·8 | 6·444 | | | | | | | | | | | | | 18 | 12 | 444·20 | 89 | G. 10·4 | 2·5 | 443·0 | 6·463 | | | | | | | | | | | | | 18 | 12 | 443·72 | 92 | G. 10·4 | 2·5 | 443·0 | 6·463 | | | | | | | | | | | | | 18 | 12 | 444·12 | 95 | G. 10·4 | 2·0 | 443·0 | 6·463 | | | | | | | | | | | | | 18 | 13 | 435·04 | 96 | G. 10·4 | 2·5 | 433·5 | 6·417 | | | | | | | | | | | | | 18 | 13 | 435·04 | 96 | G. 10·4 | 2·5 | 433·5 | 6·417 | | | | | | | | | | | | October 12. | 18 | 13 | 434·78 | 96 | G. 10·4 | 2·5 | 433·5 | 6·417 | | | | | | | | | | | | | 12 | 5 | 689·48 | 57 | G. 0·3 | 3·0 | 691·3 | 6·417 | | | | | | | | | | | | | 12 | 5 | 688·77 | 56 | G. 0·3 | 3·0 | 691·3 | 6·417 | | | | | | | | | | | | | 12 | 5 | 688·60 | 57 | G. 0·3 | 3·5 | 691·3 | 6·417 | | | | | | | | | | | | Dec. 27. | 12 | 5 | 689·88 | 59 | G. 5·6 | 4·5 | 691·3 | 6·417 | | | | | | | | | | | | | 12 | 5 | 688·84 | 59 | G. 5·6 | 5·0 | 691·3 | 6·417 | | | | | | | | | | | | | 12 | 5 | 690·20 | 60 | G. 5·6 | 5·0 | 691·3 | 6·417 | | | | | | | | | | | | | 12 | 5 | 688·52 | 28 | G. 5·6 | 3·5 | 691·3 | 6·417 | | October 12. | 12 | 6 | 774·36 | 58 | G. 0·3 | 2·5 | 778·1 | 6·417 | | | | | | | | | | | | | 12 | 6 | 773·48 | 55 | G. 0·3 | 2·5 | 778·1 | 6·417 | | | | | | | | | | | | | 12 | 6 | 773·94 | 55 | G. 0·3 | 3·0 | 778·1 | 6·417 | | | | | | | | | | | | Dec. 27. | 12 | 6 | 775·40 | 60 | G. 5·6 | 3·0 | 778·1 | 6·417 | | | | | | | | | | | | | 12 | 6 | 775·84 | 61 | G. 5·6 | 3·5 | 778·1 | 6·417 | | | | | | | | | | | | | 12 | 6 | 775·68 | 61 | G. 5·6 | 4·0 | 778·1 | 6·417 | | | | | | | | | | | | | 12 | 6 | 768·00 | 30 | G. 5·6 | 3·0 | 778·1 | 6·417 | | October 13. | 12 | 7 | 789·68 | 61 | G. 0·3 | 1·0 | 789·1 | 6·417 | | | | | | | | | | | | | 13 | 7 | 790·12 | 61 | G. 0·3 | 0·5 | 789·1 | 6·417 | | | | | | | | | | | | | 13 | 7 | 790·00 | 61 | G. 0·3 | 1·0 | 789·1 | 6·417 | | Dec. 28. | 13 | 7 | 786·98 | 59 | G. 5·6 | 1·0 | 789·1 | 6·417 | | | | | | | | | | | | | 13 | 7 | 787·52 | 60 | G. 5·6 | 1·0 | 789·1 | 6·417 | | Oct. 13. | 13 | 8 | 684·32 | 61 | G. 0·3 | 0·5 | 686·1 | 6·417 | | | | | | | | | | | | | 13 | 8 | 684·60 | 60 | G. 0·3 | 0·5 | 686·1 | 6·417 | | | | | | | | | | | | | 13 | 8 | 684·02 | 61 | G. 0·3 | 0·5 | 686·1 | 6·417 | | Dec. 28. | 13 | 8 | 684·50 | 32 | G. 5·6 | 1·0 | 686·1 | 6·417 | | | | | | | | | | | | | 13 | 8 | 687·24 | 59 | G. 5·6 | 1·0 | 686·1 | 6·417 | | | | | | | | | | | | | 13 | 8 | 687·78 | 59 | G. 5·6 | 1·5 | 686·1 | 6·417 | | Oct. 13. | 13 | 9 | 634·28 | 59 | G. 0·3 | 1·0 | 635·7 | 6·417 | | | | | | | | | | | | | 13 | 9 | 634·12 | 58 | G. 0·3 | 1·0 | 635·7 | 6·417 | | | | | | | | | | | | | 13 | 9 | 634·24 | 58 | G. 0·3 | 1·0 | 635·7 | 6·417 | | Royal Military Repository, Woolwich. | 13 | 9 | 634·08 | 33 | G. 5·6 | 1·0 | 635·7 | 6·417 | | | | | | | | | | | | | 13 | 9 | 637·28 | 55 | G. 5·6 | 1·5 | 635·7 | 6·417 | | | | | | | | | | | | | 13 | 9 | 637·02 | 58 | G. 5·6 | 2·0 | 635·7 | 6·417 | ### Table (Continued) | Station | Needle | Time of vibration | Thermometer | Chronometer rate | Final semi-arc | Corrected time, 75° Fahr. | Horizontal Intensity | |--------------------------|--------|------------------|-------------|------------------|---------------|---------------------------|---------------------| | Royal Military Repository, Woolwich | Oct. 12. | 11 | 674·20 | 53 | G. 0·3 | 1·0 | 3·720 | | | 13 | 11 | 673·52 | 58 | G. 0·3 | 0·5 | 674·9 | | | 13 | 11 | 673·50 | 57 | G. 0·3 | 0·5 | | | Dec. 27. | 11 | 686·64 | 59 | G. 5·6 | 1·5 | | 686·4 | | | 27 | 11 | 686·00 | 59 | G. 5·6 | 1·5 | | | | 28 | 11 | 682·08 | 28 | G. 5·6 | 0·5 | | | Oct. 13. | 12 | 583·32 | 58 | G. 0·3 | 0·5 | | | | | 13 | 12 | 584·04 | 59 | G. 0·3 | 0·5 | | | | 13 | 12 | 583·68 | 61 | G. 0·3 | 0·5 | | | Dec. 27. | 12 | 582·36 | 59 | G. 5·6 | 1·5 | | 584·0 | | | 27 | 12 | 582·84 | 60 | G. 5·6 | 2·0 | | | | 28 | 12 | 584·14 | 28 | G. 5·6 | 1·0 | | | Oct. 13. | 13 | 568·80 | 61 | G. 0·3 | 0·5 | | | | | 13 | 13 | 569·00 | 61 | G. 0·3 | 0·5 | | | | 13 | 13 | 569·52 | 61 | G. 0·3 | 1·0 | | | Dec. 28. | 13 | 566·32 | 41 | G. 5·6 | 2·5 | | 569·4 | | | 28 | 13 | 566·98 | 42 | G. 5·6 | 2·0 | | | | 28 | 13 | 568·20 | 30 | G. 5·6 | 1·0 | | | Falmouth | Feb. | 11 | 682·74 | 39 | G. 3·3 | 1·5 | 684·8 | | | 11 | 682·54 | 39 | G. 3·3 | 1·5 | | | ### Table II Observations of the Inclination. | Station | Date | Poles | Inclination | Remarks | |--------------------------|---------|----------------|-------------|---------| | | | Direct. | Reversed. | | | Rarotonga Island | 1840. | May 14. | -35 30·0 | -36 47·0 | -36 08·5 | | | | | -35 30·5 | -35 46·9 | -35 08·7 | | Vavao Island | | | -34 27·5 | -35 42·7 | -35 05·1 | | Nukulau Island | | | -35 27·8 | -36 49·0 | -36 08·8 | | | | | -35 31·7 | -36 46·1 | -36 08·9 | | Banga Island | | | -35 30·9 | -36 47·8 | -36 09·8 | | Tanna Island | | | -35 51·5 | -37 08·2 | -36 29·9 | | Port Carteret, New Ireland | | | -39 22·9 | -40 23·3 | -39 53·1 | | Britannia Island | | | -20 13·5 | -21 19·5 | -20 46·5 | | | | | -20 08·5 | -21 35·4 | -20 51·9 | | | | | -21 26·5 | -22 37·1 | -22 01·8 | | Jobie Island | | | -17 30·0 | -17 32·0 | -17 31·0 | | | | | -17 25·5 | -17 35·7 | -17 30·6 | | Shell Rock, Jobie Island | | | -17 19·8 | -17 36·7 | -17 28·2 | | | | | -17 06·5 | -17 40·9 | -17 23·7 | | | | | -18 04·0 | -18 27·7 | -18 15·8 | | | | | -14 51·7 | -15 26·6 | -15 09·1 | | Bouro Island | | | -20 07·1 | -20 39·8 | -20 23·4 | | | | | -18 36·4 | -21 58·8 | -20 17·6 | | | | | -20 03·0 | -20 55·1 | -20 29·1 | | | | | -20 32·6 | -21 22·1 | -20 57·4 | | | | | -20 45·7 | -22 29·1 | -21 37·4 | | | | | -19 24·4 | -22 39·4 | -21 01·9 | | | | | -19 09·1 | -22 56·5 | -21 02·6 | | Amboyna Island | | | | | | | Station | Date | Poles | Inclination | Remarks | |-------------------------|------------|----------------|-------------|---------| | | | Direct. | Reversed. | | | Macassar Island | Sept. 26 | -23°18'4" | -23°36'9" | | | | | -23°45'4" | -23°54'7" | | | | | -23°36'9" | -23°03'2" | | | | | -23°29'4" | -23°51'9" | | | Solombo Island | Oct. 4 | -21°21'8" | -27°08'7" | | | | | -21°25'2" | -27°08'7" | | | | | -16°21'9" | -23°00'6" | | | | | -16°11'9" | -22°58'2" | | | | | -17°17'5" | -22°40'7" | | | | | -17°21'0" | -22°39'0" | | | Pulo Kumpal, Borneo | | | | | | Singapore* | Dec. 1 | -8°47'5" | -15°49'3" | -12°18'4"| | Manila | | | | | | Sampanchow Island | | | | | | Hong Kong Island | Feb. 12 | -34°50'4" | 25°15'0" | | | Macao | April 9 | -34°44'0" | 25°17'6" | | | | Dec. 7 | -11°42'8" | -12°40'6" | -12°11'7"| | | | -11°44'1" | -12°10'5" | -11°57'3"| | | | -11°38'0" | -12°17'2" | -11°57'6"| | | | -11°01'1" | -12°43'5" | -11°52'3"| | | | -9°22'2" | -14°54'0" | -12°08'1"| | | | -7°49'5" | -14°14'2" | | | Penang | | | | | | Malacca | | | | | | Seychelles | | | | | | Majambo Bay | | | | | | Cape of Good Hope | | | | | | Simon's Bay | | | | | | St. Helena | May 9 | -11°55'7" | -22°06'4" | -17°01'0"| * "At Singapore, in October 1840, a cat got into the room where the dip instrument was placed and threw it down, breaking the axle of the needle and the levelling screws of the dip circle. A new axle was fitted by a watchmaker, with which the observations were made at Manila and in the Canton River; and on my return to Singapore, in December 1841, I had the satisfaction to find that the results obtained with the needle were in accordance with those of the magnetic observatory at this island." — Extract from Sir Edward Belcher's Memoranda. MDCCCLIII. ### Table III. General Table of Captain Sir Edward Belcher's Magnetic Determinations. The longitudes in this Table are east of Greenwich; the declinations west when positive, east when negative; the values of the horizontal intensity are expressed in the scale of absolute measure, in which the horizontal intensity at Woolwich is $3^\circ 72'$; and the total intensities in the usual arbitrary scale, in which the total intensity at Woolwich (as in London) is $1^\circ 372'$. | Station | Date | Latitude | Longitude | Declination | Inclination | Intensity | |--------------------|--------|----------|-----------|-------------|-------------|-----------| | | | | | | | Horiz. | | | | | | | | Total | | Port Etches | 1837 | +60° 21' | 213° 19' | -31° 38' | +76° 02'9" | 3°15 | | Kodiack | 1839 | +57° 20' | 207° 09' | -26° 43' | +72° 42'9" | 3°635 | | Sitka | 1837 | +57° 03' | 224° 34' | -27° 42' | +75° 51'5" | 1°617 | | Sitka | 1839 | +57° 03' | 224° 38' | -29° 32' | +75° 49'1" | 3°297 | | Baker's Bay | 1839 | +46° 17' | 235° 58' | -19° 11' | +69° 26'9" | 4°394 | | Fort Vancouver | 1839 | +45° 37' | 237° 24' | -19° 22' | +69° 22'2" | 4°475 | | Port Bodega | 1839 | +38° 18' | 236° 58' | -15° 20' | +62° 53'4" | 5°440 | | San Francisco | 1837 | +37° 48' | 237° 37' | -15° 20' | +61° 53'8" | 1°577 | | San Francisco | 1839 | +37° 48' | 237° 37' | -15° 20' | +62° 05'8" | 5°524 | | Monterey | 1839 | +36° 36' | 238° 07' | -14° 13' | +61° 03'6" | 5°666 | | Sta Barbara | 1839 | +34° 24' | 240° 19' | -13° 28' | +58° 54'1" | 5°925 | | San Pedro | 1839 | +33° 43' | 241° 45' | -13° 08' | +58° 21'4" | 5°913 | | San Diego | 1839 | +32° 41' | 242° 47' | -12° 21' | +57° 06'1" | 6°142 | | San Quentin | 1839 | +30° 22' | 244° 02' | -12° 06' | +54° 29'9" | 6°468 | | San Bartholomew | 1839 | +27° 40' | 245° 07' | -10° 46' | +51° 41'0" | 6°780 | | Magdalena Bay | 1839 | +24° 38' | 247° 53' | -9° 15' | +46° 34'0" | 7°160 | | Mazatlan | 1839 | +23° 11' | 253° 36' | -9° 24' | +46° 38'5" | 7°214 | | San Lucas Bay | 1839 | +22° 52' | 250° 07' | -8° 38' | +45° 39'3" | 7°259 | | San Blas | 1837 | +21° 32' | 254° 44' | -8° 34' | +45° 24'3" | 1°372 | | San Blas | 1839 | +21° 32' | 254° 44' | -9° 00' | +44° 32'5" | 7°421 | | Oahu Island | 1837 | +21° 17' | 202° 00' | -10° 39' | +41° 35'1" | 1°376 | | Oahu Island | 1839 | +21° 17' | 202° 00' | -10° 39' | +41° 16'8" | 6°506 | | Socorro Island | 1839 | +18° 43' | 249° 06' | -6° 56' | +40° 43'7" | 7°477 | | Clarion Island | 1839 | +18° 21' | 245° 19' | -8° 05' | +37° 03'0" | 7°597 | | Acapulco | 1838 | +16° 50' | 260° 05' | -8° 13' | +37° 57'4" | 7°91 | | Realejo | 1838 | +12° 28' | 272° 52' | -7° 53' | +34° 36'9" | 1°326 | | Panama | 1837 | +8° 57' | 280° 31' | -7° 02' | +31° 51'9" | 7°743 | | Magnetic Island | 1837 | +8° 04' | 278° 15' | -7° 37' | +31° 11'9" | 1°205 | | Sampanchow Island | 1841 | +22° 43' | 113° 40' | -0° 22' | +30° 25'8" | 7°605 | | Hong Kong | 1841 | +22° 16' | 114° 08' | -0° 37' | +30° 02'7" | 7°574 | | Macao | 1841 | +22° 11' | 113° 30' | -0° 35' | +30° 00'8" | 7°592 | | Cocos Island | 1838 | +5° 34' | 272° 58' | -8° 24' | +23° 33'2" | 1°159 | | Manila | 1840 | +14° 36' | 120° 58' | -0° 18' | +16° 27'5" | 7°869 | | Puna Island | 1838 | -2° 47' | 280° 05' | -8° 55' | +9° 0'8" | 1°036 | | Ascension | 1842 | -7° 56' | 345° 36' | +19° 16' | ........... | 6°457 | | Penang | 1841 | +5° 25' | 100° 19' | -1° 30' | -4° 40'4" | 1°058 | | Malora Island | 1842 | +5° 41' | 95° 24' | -2° 22' | -5° 29'3" | 1°041 | | Acheen Island | 1842 | +5° 36' | 95° 20' | -2° 22' | -5° 58'5" | 1°040 | | Callao | 1838 | -12° 04' | 282° 52' | -10° 44' | -6° 14'3" | 0°980 | | Pt de Galle | 1842 | +6° 02' | 80° 15' | -0° 41' | -8° 07'0" | 1°035 | | Malacca | 1841 | +2° 10' | 102° 15' | -1° 36' | -11° 01'9" | 1°069 | | Singapore | 1841 | +1° 17' | 103° 51' | -1° 39' | -12° 01'4" | 1°074 | | Martins Island | 1840 | -8° 56' | 220° 20' | -6° 16' | -14° 06'0" | 1°024 | | Amsterdam Island | 1840 | -0° 20' | 132° 08' | -1° 24' | -15° 09'1" | 1°097 | | St. Helena | 1842 | -15° 55' | 354° 17' | +22° 11' | -17° 01'0" | 0°805 | Palm Island Beach. ### Table. (Continued.) | Station | Date | Latitude | Longitude | Declination | Inclination | Intensity | Remarks | |------------------|--------|----------|-----------|-------------|-------------|-----------|---------| | Jobie Island | 1840. | -1° 50' | 136° 41' | -4° 09' | -17° 28'4" | 8°056 | 1°116 | | Shell Rock | 1840. | -1° 57' | 136° 21' | -3° 00' | -18° 15'8" | 8°066 | 1°123 | | Pulo Kumpal | 1840. | -2° 44' | 110° 07' | -0° 39' | -19° 48'8" | 8°038 | 1°128 | | Bouro Island | 1840. | -3° 23' | 127° 06' | -1° 06' | -20° 23'4" | 8°093 | 1°141 | | New Ireland | 1840. | -4° 41' | 152° 44' | -7° 13' | -20° 49'2" | 8°039 | 1°136 | | Amboyne Island | 1840. | -3° 42' | 128° 10' | -1° 14' | -21° 09'8" | 8°144 | 1°154 | | Britannia Island | 1840. | -3° 19' | 143° 29' | -4° 55' | -22° 01'8" | 7°832 | 1°116 | | Macassar Island | 1840. | -5° 08' | 119° 23' | -0° 29' | -23° 42'2" | 8°029 | 1°159 | | Solombo Island | 1840. | -5° 35' | 114° 23' | -1° 24' | -24° 16'1" | 8°003 | 1°160 | | Bow Island | 1840. | -18° 05' | 219° 07' | -6° 34' | -30° 16'0" | 7°425 | 1°123 | | Tahiti | 1840. | -17° 29' | 210° 30' | -6° 30' | -30° 17'7" | 7°491 | 1°146 | | Seychelles | 1842. | -4° 36' | 55° 31' | +2° 01' | -32° 02'9" | 6°632 | 1°034 | | Vavao Island | 1840. | -18° 39' | 186° 00' | -9° 34' | -35° 06'9" | 7°706 | 1°245 | | Rarotonga Island | 1840. | -21° 12' | 200° 14' | -8° 34' | -36° 08'5" | 7°315 | 1°197 | | Nakulau Island | 1840. | -18° 10' | 178° 31' | -10° 25' | -36° 09'2" | 7°708 | 1°262 | | Banga Island | 1840. | -18° 20' | 178° 10' | -10° 21' | -36° 29'9" | 7°718 | 1°269 | | Tanna Island | 1840. | -19° 38' | 169° 29' | -11° 37' | -39° 53'1" | 7°790 | 1°342 | | Majambo Bay | 1842. | -15° 14' | 47° 00' | +12° 10' | -48° 18'9" | 5°496 | 1°092 | | Simon's Bay | 1842. | -34° 12' | 18° 26' | +29° 08' | -53° 04'3" | 4°571 | 1°005 | | Cape of Good Hope| 1842. | -33° 56' | 18° 29' | +29° 13' | -53° 20' | 4°569 | 1°011 | Memorandum of the particular spot of observation at Sir Edward Belcher's Magnetic Stations. Port Etches. On the slate beach abreast of the anchorage. Kodiack. On the slate beach, in sight of Cape Greville. Sitka. In 1837, in the Governor's house on the hill. In 1839, in the summer-house of the Governor's private dwelling. Baker's Bay. At the landing-place. Fort Vancouver. One set in a room in the fort, no iron being visible: one set in the garden of the fort. Port Bodega. On a fine slaty beach, near the stream. San Francisco. At Yerba Buena. Monterey. At the back of the house at the landing-place, being the spot where Mr. David Douglas made his observations. Santa Barbara. On the sand at the landing-place. San Pedro. On a small island. San Diego. On the tongue on the eastern side; a sandy flat. San Quentin. On the sandy beach. San Bartholomew. On observation bluff. Magdalena Bay. At the observatory station. Mazatlan. In a house belonging to Messrs. Hayn, Keyser, and Co. Cape San Lucas. In the sandy bay: the surrounding rocks of large-grained granite. San Blas. In 1837, on Palm Island; objectionable, the rocks being volcanic. 1839, on the beach at the arsenal, in a line between the Custom-house and the outer rocky point: the sand is about twenty feet deep. Oahu. In 1837, in a room used as an office by Mr. J. Coffin Jones. In 1838, in a house belonging to Mrs. Holmes; both well-known places. Socorro Island. On the cliff. Clarion Island. On the sandy bank above the beach. Acapulco. Near Fort San Carlos, outside the gate. Realejo. On the N.W. high cliff of Cardon Island; rocks basaltic. Panama. Near the ruins of the convent of San Francisco. Magnetic Island. A small islet. Sampanchow Island. Near Chuenpee, on a beach composed of coarse quartz sand. Hong Kong. Near the harbour, on granite rocks. Macao. In the garden of the house belonging to Messrs. Leslie and Dent. Cocos Island. At the landing-place. The observations in 1838 were made under unfavourable circumstances. Manila. Two positions; one at the house of Mr. Strachan, which did not afford very satisfactory results: the second on the mole head; an entire failure, owing probably to iron clamps used to bind the masonry. Puna Island. On various points of the island. Ascension Island. On the N.W. sandy beach. Penang. In the garden of the Admiralty-house. Malora Island. Called Bouro Island by the natives: it is volcanic. Acheen Island. On the sandy point about 100 yards north of the flag-staff. Callao. On the Plaza de los Muertos. Point de Galle. On Utrecht bastion, behind the magazine. Malacca. Near the small saluting battery. Singapore. In 1840, under a covered landing in front of the Recorder's house, being the position of the French expedition, the Astrolabe and Zélée. In 1841, at the Magnetic Observatory. Martin's Island. In the sandy bay S.E. of Pilot's Hill. Amsterdam Island. A coral islet; on the sand, at the landing-place. Saint Helena. Position of the Erebus and Terror at Sisters' Walk. Jobie Island. On a limestone islet, one mile from the main island. Shell Rock. Volcanic rock; on a sandy tongue projecting from it. Pulo Kumpal. At the landing-place on Rendezvous Island, clay-slate. Bouro Island. Beach in front of the battery. Port Carteret. The sandy landing-place on Cocoa-nut Island. Amboyina. On the S.W. outer curtain; position changed three times. Britannia Island. On coral sand at the landing-place, Victoria Bay. Macassar Island. Position pointed out as that of the French expedition, the Astrolabe and Zélée. Solombo Island. At the landing-place. Bow Island. At five positions on the island. Tahiti. The observations at Papeete were made in the yard of the house belonging to the queen's aunt. The partial results were exceedingly discordant. The house is on the beach. Those at Point Venus were made at the spot usually selected, viz. just clear of the extreme trees; spot marked by a stone sunk for the purpose. The United States' expedition observed about 100 yards more towards the trees near the canoe sheds. Seychelles. Island of St. Mary, on a bluff head on the western side facing the town. Rocks granite. Vavao Island. In the king's garden. Rarotonga Island. At the landing-place, a coarse gravel flat composed of basaltic pebbles. Nukulau Island. On the Coral Island. Banga Island. On a coral islet at the extremity of the eastern reef. Tanna Island. In front of the Missionary-house, at the west landing-place. Majambo Bay. Sandy bay three miles south of Captain Owen's "north point." Simon's Bay. Position of the Erebus and Terror. Cape of Good Hope. Magnetic Observatory.