Observations to determine the amount of Atmospherical Refraction at Port Bowen in the Years 1824-25

IX. Observations to determine the amount of Atmospheric Refraction at Port Bowen in the Years 1824-25. By Captain W. E. Parry, R. N. F. R. S. Lieutenant Henry Foster, R. N. F. R. S. and Lieutenant J. C. Ross, R. N. F. L. S. To ascertain correctly by actual observation the amount of atmospherical refraction at low altitudes and at various states of the barometer and thermometer, is a problem which has long occupied the attention of practical astronomers; and many elaborate theories have also been given to explain the anomalies which have hitherto attended the most careful observations. In Mr. Ivory's Paper, printed in the Philosophical Transactions for 1823, he states (page 495), that his table of refractions has been constructed merely with the view of comparing the theory in the paper with observation. He adds, however, "that it would be more satisfactory to determine "the same quantity (f) by the comparison of many observed "refractions at low altitudes between the distances of 85 "and 88 degrees from the zenith; and by this means a "table might be constructed that would be deserving of "greater confidence." With a view, therefore, to supply the desideratum alluded to, three distinct series of observations were made at Port Bowen, by Captain Parry, Lieutenant Foster, and Lieutenant Ross; the details of which are given in the following Paper. Various methods suggested themselves for the determination of this question. The first was to measure the zenith distance of known stars at a given moment, with the repeat- Observations to determine the amount, &c. ing circle, and then to have computed the true altitude; whence the actual refraction might have been deduced. The difficulties, however, attending the use of the repeating circle, during the winter of the polar regions, have already been alluded to on several occasions, in the accounts of the two preceding voyages of discovery. The most material of these consist in the extreme contraction of the spirit in the long level, when filled in the usual way; the instantaneous freezing of the breath or other vapour on the glasses, obliging the observer to hold his breath during each observation; and the pain, amounting to the sensation, and producing the effects of burning consequent on touching intensely cold metal with the naked hand. The first of these was obviated, on the present occasion, by inserting a larger quantity of spirit than usual, so as to keep both ends of the bubble in sight, even during the most intense cold: this latter circumstance, however, afforded the opportunity of remarking an increased sluggishness in the level at very low temperatures, arising possibly from a certain degree of thickening in the spirit, which required the instrument to stand unmoved for at least two minutes after the contact had been made, in order to insure an accurate reading. It is unnecessary to point out, how unfavourable to minute accuracy this circumstance must prove, in observing an object having quick motion, either in altitude or in azimuth. A set of zenith distances, consisting of only eight observations, cannot, indeed, under such circumstances, be satisfactorily obtained in less than thirty-five or forty minutes. If to the difficulties already mentioned be added the annoyance sometimes experienced by the extinction of the lamp for illuminating the wires during an obser- Observations to determine the amount of vation, in consequence of the freezing of the oil; the frequent occurrence of snow drift; and the haze which usually hangs near the horizon during a Polar winter, it must be admitted, that the repeating circle is not calculated, under such circumstances, either for obtaining numerous observations, or for ensuring the degree of accuracy indispensibly requisite in observations for determining the amount of atmospherical refractions. Another method was suggested by Captain Kater, in April, 1824, which is explained in the following words: "Select a star which passes the zenith, and when this star and the Pole star are at the same altitude, take the distance between them by means of the repeating reflecting circle; do the same when the star is in the zenith, and also when upon the meridian under the Pole. From the first observations the true zenith distance of the stars may be readily obtained. By observations made when the star is in the zenith, the absolute refraction of the Pole star will be given, and from the observations made when the star is under the Pole, the refraction at that altitude can be easily deduced. Pursue the same method with other stars, carefully marking at each observation the time and state of the barometer and thermometer. We shall thus be furnished with data, from which the refraction at the various altitudes can be computed with facility and accuracy." On considering, however, the difficulties already detailed in the use of the repeating circle, which rendered it impossible to take advantage of this ingenious suggestion of Captain Kater; it occurred to Lieutenant Foster, that a more simple and accurate method of determining the amount of refraction, would be to observe the setting of stars within certain limits of azimuth, behind the high land which encircles this harbour, and then determining at leisure the zenith distance of that part behind which the star set. As the ruggedness of the land, however, combined with the frequent alteration of the star's azimuth, would materially affect results thus obtained; Captain Parry proposed, as a modification of this idea, to place a board edge-wise, and strictly horizontal, on the spot behind which the star set, thus rendering it unimportant upon what part of the board the occultation of the object took place, as well as affording more ready means of obtaining its apparent altitude. Two boards were accordingly fixed with all possible firmness and accuracy upon a neighbouring hill, to the westward of the observatory, for observing the setting of α Aquilæ and Arcturus respectively, the board for the former being on a N 75°½ W bearing, distant 924 feet, and for the latter N 40°W, 1590 feet. The observations by Captain Parry, given in Tables II. and VI., were made with a small theodolite, having its legs immovably fixed by freezing, across a cask filled with sand; those in Table IV. by a ship telescope, two feet in length, securely attached to the cask itself, and having no motion whatever. Lieutenant Foster's observations contained in Tables VIII. to XI. inclusive, were made with a small repeating circle by Dollond, furnished with two telescopes, which afforded the means of obtaining double observations of each star the same evening. This instrument stood 122 feet above the level of the sea, on a cask filled with sand, firmly frozen to the ground, and was secured from the weather by a suitable covering. MDCCCXXVI. * E e Observations to determine the amount of The observations by Lieutenant Ross, in Tables XIII. to XV. inclusive, were obtained with a small variation transit instrument as an upper telescope, and those in Tables XVI. and XVII. by a pocket telescope below; both being fixed to a cask filled with sand. None of the instruments used by either of the three observers were removed, till after the completion of the whole series of observations. The hour angle by which the true altitude of the setting star was determined, was obtained by taking its right ascension from that of the meridian, at the time of observation, as found by transits of well known stars, which took place within three quarters of an hour of the other star's setting, thus rendering the observations as independent as possible of any want of uniformity in the rates of the pocket chronometers employed by the observers. The transits were taken exclusively by Lieutenant Foster, and comparisons with the chronometer he employed, were taken by the other observers about the time of transit, in order to deduce their horary angles, contained in the respective Tables. The position of the transit instrument was rigidly verified by the transits of high and low stars in their passages across the meridian, as well as by a constant reference to a meridian mark, and by the most minute attention to the level. The heights of the barometer, and of the thermometer, suspended with its bulb on the same level with the observers in the open air, were taken at the time of every observation. The registered height of the barometer, however, in the Tables, has been corrected for instrumental errors, and brought up to a certain temperature, which is specified at the head of each of the columns containing it. The latitude, $73^\circ 13' 39''$, N.* used in these computations, is the result of 91 sets of observations on Polaris, at different horary distances from the north and south meridians, by Captain Parry and Lieutenant Foster; employing Dr. Young's Table of Atmospherical Refractions, published at the end of the Nautical Almanack for each year. As soon as the sun afforded sufficient light for obtaining the apparent altitudes of the boards from the respective telescopes, observations were commenced for that purpose. The circle used by Lieutenant Foster afforded the direct means of doing this, for the upper telescope, by which the zenith distance of the edge of the board at the spot where the star set, was at once obtained by observation. The angular distance between this telescope and the lower one, as seen from the board, was determined by means of a double wire micrometer, attached to one of Dollond's achromatic telescopes 46 inches focal length, the object-glass of which was let into the board, so as to make its centre exactly coincide with that part behind which the star set. The telescopes employed by Captain Parry and Lieutenant Ross, not being attached to an instrument calculated for measuring zenith distances, required some further contrivance to obtain the altitudes of the boards with respect to them. In order to place the repeating circle precisely at the same altitude with Captain Parry's upper telescope, a levelling staff was fixed into the ground, half way between the place of observation and the board. This being adjusted by sliding up or down till a fine brass point on its upper end exactly * The elements of this result, are given in the Appendix to Capt. Parry's Narrative of the Third Voyage for the Discovery of a North West Passage into the Pacific Ocean. Observations to determine the amount of coincided with the edge of the board, when seen through the upper telescope; the repeating circle was also raised or lowered until the same coincidence obtained, when looking through its telescope. The accuracy of the position thus obtained was finally verified by observing the setting of the star, through each telescope, when it was found to disappear to both observers at the same instant. For the altitude of the board, with respect to the lower telescope used by Captain Parry, a short staff, exactly equal in length to the measured distance between the telescopes, was fixed vertically above the board, and the zenith distance of its well defined top observed by the repeating circle in its former place. And as a confirmation of the results thus obtained, the method described above, as adopted by Lieutenant Foster, by means of the micrometer, was also resorted to; a mean of the two methods (which differed $2''8$), being used in the computation of the refractions. Lieutenant Ross's zenith distances were obtained by a repeating circle, placed on the same cask which held the telescopes he employed, the angular distance between each of these, and that of the circle (when directed to the board), being determined by repeated observations with the micrometer, fixed upon the respective boards in the manner already described. In some instances, Lieutenant Ross observed the re-appearance of $\alpha$ Aquilæ under the board, thus obtaining an observation at another altitude. The corresponding zenith distance of that part of the board was determined by measuring with the micrometer, the angle subtended by the board at the place of observation. The zenith distances of the boards, as obtained by the respective observers, are given in the Tables attached to the corresponding observations for refraction, except those of Lieutenant Ross, the details of which, were unfortunately left on board the Fury at the time of her loss. While making the above mentioned observations for the zenith-distances of the boards, Captain Parry had occasion to notice, on the 28th of February, some anomalies which had never before occurred, and which were at first attributed to some slight and imperceptible change in the position of the repeating circle (see Table III.) On-continuing the observations, however, it soon appeared that the changes coincided nearly with particular times of the day, the greatest zenith distance always occurring when the thermometer stood the highest, and the weather was most calm. To clear the zenith distances of this effect of refraction, the repeating circle was carried up the hill, the object-glass of its telescope being placed in a notch cut in the board, as already described above in using the micrometer; when by several days' observations, continued from morning till night, it was found that the same phenomenon as before occurred, the zenith distance of the station below uniformly increasing from the morning till the afternoon, and again decreasing as the sun fell. Two sets of observations taken at the board after midnight, by means of a lamp viewed through the tube of the telescope, at the lower station, gave nearly a mean of all the other observations. Thus it appeared that whether observed from the top or the bottom of a hill whose altitude was $4^\circ \frac{1}{2}$, an increase of zenith distance (varying from $9''$ to $17''$), took place about the same hours, indicating a comparatively rare medium near the surface of the ground, and giving such a curvature to the visual ray, as to produce a similar effect at both stations. Table I. | Day | Time | No. of Observations | Mean Reading of the four Verniers | Apparent Altitude | Correction for Level | Index | Barom. Corr. to Temp. Fahl. | Temp. Fahl. | Velocity of Winds | Weather | Remarks | |-----------|-----------------------|---------------------|----------------------------------|-------------------|----------------------|------|-----------------------------|------------|------------------|---------|---------| | 1825- | | | | | | | | | | | | | Mar. 23rd | 6h to 6h 40m A.M. | 8 | 299 45' 55'' | 18' 75'' | -16 | 19 75' | -36.5 | Very clear & Fine | Ditto | Ditto | | | | | | | | | | | | | | | | | 7h to 7h 40m A.M. | 8 | 239 31' 43'' | 19' 75'' | -19 | 9' 75'' | -35 | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 9h 10m to 10h A.M. | 8 | 179 17' 22.5'' | 19' 75'' | -21 | 9' 75'' | -31 | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | Noon to ob. 40° P.M. | 8 | 299 47' 18.75'' | 29' 75'' | +1 | 29' 75'' | -25' 16'' | in O | Ditto | Ditto | | | | | | | | | | | | | | | | | 1h 15m to 2h 30m P.M.| 8 | 239 33' 44.5'' | 29' 75'' | +1 | 29' 75'' | -26' 12'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 3h 10m to 4h P.M. | 8 | 299 46' 52.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 4h 40m to 5h 15' 2m P.M.| 8 | 239 34' 10'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 5h 30m to 6h 10P.M. | 8 | 299 46' 55'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | Mar. 24th 6h 20' to 6h 35'A.M.| 8 | 299 45' 57.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 1h 15m to 2h P.M. | 8 | 299 47' 15'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 2h 10m to 2h 40' P.M.| 8 | 239 33' 54'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 4h 30m to 5h 30' P.M.| 8 | 299 47' 27.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | Mar. 25th 6h 10m to 6h 50'A.M.| 8 | 299 46' 37.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 1h to 1h 40' P.M. | 8 | 299 45' 43.75'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 2h to 2h 45' P.M. | 8 | 239 32' 45.75'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 5h 15' to 6h 15' P.M.| 8 | 179 19' 02.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | Apr. 2nd 6h 30' to 7h 30' A.M.| 8 | 299 46' 21.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 1h 30m to 2h 15' P.M.| 8 | 299 47' 08.75'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 2h 30m to 3h 10' P.M.| 8 | 239 34' 27.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | 6h 30m to 7h P.M. | 8 | 299 47' 38.75'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | | | | | | | | | | | | | | | | Apr. 6th 2h to 2h 40' P.M.| 8 | 299 47' 37.5'' | 29' 75'' | +1 | 29' 75'' | -27' 9'' | Ditto | Ditto | Ditto | | Observations to determine the amount of Mean apparent altitude \( \theta = 31^\circ 38' \) used for the refractions in Table II. \( \cdot \) The index not reset to \( 360^\circ \). ### Observations for the Atmospheric Refraction observed by the setting of Arcturus, 1824-5, by Captain Parry. #### Apparent Altitude 7° 31' 38" 52'. | Day | Time of Arcturus setting by No. 2 | Transit Observed | Rate of lossing | Star | Time reduced | Arcturus's hour angle at setting | Arcturus's observed refraction | Barom. corr. to Temp. + 50° | Temp. Fah. | Winds | Weather | Remarks | |-----|----------------------------------|-----------------|----------------|-----|--------------|---------------------------------|-------------------------------|-----------------------------|-----------|-------|---------|--------| | Nov. 28th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | Dec. 1st | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 2nd | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 3rd | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 4th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 5th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 6th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 7th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 8th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 9th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 10th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 11th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 12th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 13th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 14th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 15th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 16th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 17th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 18th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 19th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 20th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 21st | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 22nd | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 23rd | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 24th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 25th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 26th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | | 27th | 14h 48m 0s | Andromeda | 1 | 9 | 32° 8' 23" | 50° 3' 48" | 3° 32' 8" | 29° 9' 36" | Easterly Fresh | Ditto | Very Clear | Means: 8 23° 35' 29° 79' 23° 58' ### Table III. Observations for determining the apparent altitude of *a* Aquilæ at setting, by Captain Parry's upper telescope. The corresponding observations for refraction are contained in Table IV. | Day | Time | No. of Observations | Mean Reading of the four Verniers | Correction for Index | Level | Apparent Altitude | Barom. Corr. to Temp. + 50° | Temp. in Shade Falt. | Winds True. | Weather. | Remarks. | |-----------|-----------------------|---------------------|-----------------------------------|----------------------|-------|------------------|----------------------------|----------------------|-------------|----------|----------| | Feb. 2d | 10 30 A.M. | 8 | 323 40 12.5 | +10 | -2.25 | 4 32 27.47 | 30.04 | -39.5 | Easterly very light | Very clear | The sun did not rise upon the board till the 14th, nor on the place of observation till the 14th. | | | to 2 P.M. | 8 | 323 41 10 | +10 | -3.45 | 24.31 | -40.5 | -40.5 | NNE Fresh Easterly Light | Hazy | Clear and warm | | 5th | 11 to Noon. | 8 | 323 41 07.5 | +10 | -4.05 | 25.37 | 29.05 | -26 | Easterly Light | Clear & fine | | | 11th | 1 to 2 P.M. | 8 | 323 40 15 | +7.5 | +2.15 | 24.53 | 30.15 | -31.5 | Northerly Light | Hazy | | | 15th | Noon to 1 P.M. | 8 | 323 40 30 | +11.25 | -8 | 25.84 | 29.65 | -31.5 | Easterly very light | Clear and warm | | | | 10 30 to 11 30 A.M. | 8 | 323 37 53.25 | +7.5 | +40.5 | 39.84 | 29.90 | -18 | Easterly very light | | | | 0 to 0 40 P.M. | 8 | 287 18 17.5 | * | -108.25 | 35.53 | 29.90 | -19 | Easterly very light | | | | 45 to 1 30 P.M. | 8 | 250 56 35.75 | * | -8 | 39.62 | 29.90 | -19 | Easterly very light | | | | 1 25 to 2 15 P.M. | 8 | 214 36 37.5 | * | -8 | 30.78 | 29.90 | -18.5 | Easterly very light | | | | about sunset. | 8 | 178 16 32.5 | * | -11.75 | 32.04 | 29.93 | -19 | Easterly very light | | | | Mean of observations at lower station | | | | | | | | | | | All the following observations were made at the upper station. | Mar 7th | 10 30 A.M. | 20 | 90 54 40 | +10 | +10.25 | 4 32 45.01 | 30.19 | -35 | Varia. & Light | Clear | Sun bright and very warm. | | | to 0 40 P.M. | 20 | 90 51 57.5 | 0 | -1'47.75 | 30.49 | 29.98 | -27 | Easterly Light | Cloudy | Breaking through the clouds. | | | 10 A.M. to Noon. | 20 | 181 46 12.5 | * | -1'26.25 | 38.44 | 30.00 | -27 | Easterly Light | | | | 2 to 4 30 P.M. | 20 | 272 36 48.75 | * | -50.75 | 29.27 | 30.00 | -28.5 | Easterly Light | | | | 11 A.M. to 0 30 P.M. | 10 | 225 24 34.25 | +10 | +27.25 | 31.13 | 30.26 | -28 | Easterly Light | | | | 0 46 to 1 50 P.M. | 10 | 90 50 13.75 | * | +1'10 | 41.95 | 30.28 | -29 | Easterly Light | | | | 2 to 2 55 P.M. | 10 | 316 14 29.25 | * | +1'16.25 | 33.17 | 30.28 | -29 | Easterly Light | | | | 3 to 0 45 P.M. | 6 | 181 40 17.5 | * | +29 | 31.02 | 30.30 | -30 | Easterly Light | | | | 4 15 to 5 40 P.M. | 6 | 28 54 32.5 | * | +29 | 27.33 | 30.30 | -30.5 | Easterly Light | | | | 6 30 to 7 40 A.M. | 6 | 225 23 17.5 | +6.2 | +18.25 | 22.19 | 30.37 | -37 | Easterly Light | | | | 7 50 to 8 40 A.M. | 6 | 261 43 03.75 | * | +9 | 29.41 | 30.38 | -35 | Easterly Light | | | | 9 45 to 10 40 A.M. | 10 | 225 23 42.5 | +10 | +31 | 26.35 | 30.38 | -34 | Easterly Light | | | | Noon to 1 P.M. | 10 | 167 39 58.75 | * | +22.25 | 31.35 | 30.39 | -29 | Easterly Light | | | | 1 25 to 2 30 P.M. | 8 | 293 05 15 | * | +26.25 | 34.25 | 30.34 | -28 | Easterly Light | | | | 3 to 0 4 P.M. | 8 | 36 20 58.75 | +12.5 | -30.25 | 35.13 | 30.34 | -29 | Easterly Light | | | | 4 50 to 5 30 P.M. | 8 | 64 26 32.5 | * | -35.25 | 26.22 | 30.35 | -33 | Easterly Light | | | | 6 30 to 7 30 A.M. | 8 | 225 24 38.75 | +7.5 | -25.75 | 26.95 | 30.20 | -35.5 | Easterly Light | | | | 11 45 to 0 35 P.M. | 10 | 225 25 30 | +6.5 | +28.25 | 36.47 | 30.12 | -27 | Easterly Light | | | | 2 50 to 3 30 P.M. | 10 | 167 44 05 | * | +59.5 | 39.20 | 30.05 | -27.5 | Easterly Light | | | | 4 10 to 4 50 P.M. | 8 | 95 51 17.5 | * | -55 | 33.75 | 30.02 | -31 | Easterly Light | | | | 6 15 to 7 15 A.M. | 8 | 36 19 50.5 | +6.2 | -71.5 | 20.59 | 29.79 | -35 | Easterly Light | | | | 1 30 to 2 30 P.M. | 10 | 202 19 05.5 | * | +7 | 37.80 | 75 | -26.5 | Easterly Light | | | | 4 20 to 5 40 P.M. | 12 | 54 21 51.25 | +7.5 | -45.5 | 26.10 | 70 | -30 | Easterly Light | | | | 21st 10 40 to 11 50 P.M. | 8 | 36 21 17.5 | +10 | -58.75 | 33.59 | 29.90 | -33 | Easterly Light | | | | 22d o till 1 A.M. | 8 | 72 42 12.5 | * | -3.25 | 36.47 | 30.05 | -35 | Easterly Light | | Mean of 2 sets taken at night at the upper station 4 32 35.03 * Index not reset to 360° after the last observation. † Index not reset after an observation for another object. Index error 202°15'07",5. ‡ Ditto †† Ditto ‡‡ Ditto ‡‡‡ Ditto ‡‡‡‡ Ditto ** Ditto Altitude. Mean of 80 zenith distances taken at the lower station 4 32 30.35 Mean of 278 at the upper station - 4 32 32.13 Mean of both stations by day - 4 32 31.67 Mean of 16 zenith distances taken at night - 4 32 35.03 Mean of all the above - 4 32 32.34 used in computing the refractions in Table IV. ### Table IV. **Observations for the Atmospheric Refraction observed by the setting of α Aquilae 1824-5, by Captain Parry.** Apparent Altitude 4° 32' 32" 34'. | Day | Time of Aquila setting by No. 2 | Transit Observed | Star | Rate of Losing | No. 2 Losing | True Altitude | Observed Refraction | Baron. Corr. to +50° | Temp. Fall | Winds True | Weather | Remarks, &c. | |-----|-------------------------------|------------------|------|---------------|-------------|---------------|-------------------|---------------------|-----------|------------|---------|-------------| | Dec. 8th | 2 41 40 48 5 | α Arietis | h. m. s. | 5 | 6 | 5 | 21 35 | 19 44 8 | 29 45 44 | -18 | NNE Fresh | Very Clear | Ditto | | 10th | 3 10 10 48 5 | α Andromedae | 0 36 07 55 | 2 22 22 | 6 | 5 | 28 55 | 20 10 8 | 21 54 54 | 50 4 | Northerly Light | Clear | Ditto | | 11th | 3 10 06 51 | α Arietis | 2 29 48 38 | 2 22 22 | 6 | 5 | 28 55 | 20 05 12 | 26 84 | 70 7 | NNW Fresh | Very Clear | Ditto | | 13th | 2 59 06 55 | Ditto | 2 21 51 43 | 2 22 22 | 6 | 5 | 28 55 | 19 13 13 | 19 34 34 | 90 6 | North Light | ENE Ditto | Calm | | 16th | 2 49 14 5 | Alderbaran | 4 38 06 79 | 2 22 22 | 6 | 5 | 28 55 | 19 03 18 | 28 54 | 90 6 | North Ditto | SW Light | Ditto | | 17th | 2 49 14 5 | α Arietis | 1 54 06 77 | 2 22 22 | 6 | 5 | 28 55 | 19 19 28 | 18 11 54 | 80 0 | Ditto Fresh | Ditto | | 21st | 2 27 20 | Ditto | 1 50 06 77 | 1 57 52 | 6 | 5 | 26 55 | 19 42 22 | 12 50 14 | 98 7 | Ditto | Ditto | | 22d | 2 23 23 | Ditto | 1 46 09 38 | 1 57 52 | 6 | 5 | 26 55 | 19 19 28 | 13 13 14 | 81 0 | Ditto | Ditto | | 23d | 2 19 26 | Ditto | 1 42 13 36 | 1 57 52 | 6 | 5 | 26 55 | 19 22 33 | 13 10 04 | 81 0 | Ditto | Ditto | | 26th | 2 07 39 | Ditto | 1 30 24 96 | 0 73 | 6 | 5 | 21 55 | 19 42 22 | 12 50 14 | 98 7 | Ditto | Ditto | | 29th | 1 55 35 | Ditto | 1 18 34 43 | 0 73 | 6 | 5 | 16 05 | 20 00 12 | 31 64 | 66 6 | Ditto | Ditto | | Jan. 2d | 1 39 42 | Ditto | 1 02 32 13 | 3 25 | 6 | 5 | 22 95 | 19 32 23 | 13 00 04 | 84 7 | Ditto | Ditto | | 3d | 1 35 49 | Ditto | 0 58 33 36 | 3 25 | 6 | 5 | 22 95 | 19 10 33 | 13 21 73 | 83 8 | Ditto | Ditto | | 5th | 1 27 49 3 | Ditto | 0 50 38 36 | 3 25 | 6 | 5 | 23 55 | 19 29 58 | 12 02 54 | 36 6 | Ditto | Ditto | | 6th | 1 23 49 | Ditto | 0 46 49 86 | 3 25 | 6 | 5 | 23 55 | 19 44 44 | 12 47 94 | 36 6 | Ditto | Ditto | | 10th | 1 08 06 2 | Ditto | 0 30 59 28 | 2 11 | 6 | 5 | 28 60 | 19 07 55 | 12 24 84 | 30 9 | Ditto | Ditto | | 11th | 1 04 12 2 | Ditto | 0 26 59 01 | 2 11 | 6 | 5 | 28 60 | 18 45 | 13 47 34 | 39 3 | Ditto | Ditto | | 12th | 1 00 09 | Ditto | 0 22 52 86 | 2 11 | 6 | 5 | 28 60 | 19 06 | 13 26 04 | 39 3 | Ditto | Ditto | | 17th | 0 49 17 | Ditto | 0 02 59 46 | 2 5 | 6 | 5 | 28 99 | 19 00 | 13 32 14 | 63 3 | Ditto | Ditto | | 20th | 12 28 05 5 | Ditto | 11 50 56 17 | 2 3 | 6 | 5 | 27 70 | 19 35 | 13 57 34 | 37 2 | Ditto | Ditto | | 25th | 11 24 49 5 | Ditto | 10 47 33 12 | 2 3 | 6 | 5 | 28 81 | 19 04 | 13 27 84 | 78 7 | Ditto | Ditto | | Feb. 2d | 10 16 45 5 | Ditto | 10 39 35 03 | 6 02 | 6 | 5 | 28 55 | 19 06 | 13 25 64 | 83 3 | Ditto | Ditto | | 7th | 9 59 34 5 | Ditto | 10 13 14 08 | 5 91 | 6 | 5 | 28 94 | 18 46 | 13 46 34 | 24 4 | Ditto | Ditto | | 8th | 9 53 24 5 | Ditto | 9 53 09 44 | 5 77 | 6 | 5 | 28 99 | 18 32 | 13 59 54 | 74 9 | Ditto | Ditto | | 9th | 9 45 00 75 | Ditto | 7 51 21 35 | 5 77 | 6 | 5 | 28 77 | 19 02 | 13 29 84 | 90 0 | Ditto | Ditto | | 11th | 9 14 16 7 | Ditto | 7 39 19 13 | 5 77 | 6 | 5 | 28 77 | 18 54 | 13 38 04 | 39 1 | Ditto | Ditto | Means: 13 12 51 | 29 76 01 | -29 94 MDCCCXXVI. Observations to determine the amount of Table V. Observations for determining the Apparent Altitude of α Aquilæ at setting, by Captain Parry's lower telescope. The corresponding observations for Refractions are contained in Table VI. | Day | Time | No. of Observations | Mean Reading of the 4 Verniers | Correction for Index | Apparent Altitude | Barom. Corr. to Temp. + 50° | Tem. Fah. | Winds True | Weather | Remarks | |-----------|----------|---------------------|--------------------------------|----------------------|-------------------|----------------------------|----------|------------|---------|---------| | Feb. 16th | 1 to 2 P.M. | 8 | 322 48 33.75 | +10 | 10.25 | 38 55.81 | 29.831 | Easterly | Fine | had been on the board just before the observation. | | | 2 to 3 P.M. | 8 | 285 37 12.5 | * | 16.25 | 57.19 | 29.831 | Easterly | | not up. | | | 8 to 9 A.M.| 8 | 322 48 00 | +2.5 | +29.25 | 56.03 | 29.608 | Easterly | Clear | had set. | | | 2½ to 4 P.M.| 8 | 285 35 12.5 | * | +1'24.25 | 55.41 | 29.645 | Easterly | ESE | Ditto | | | 8 to 9 A.M.| 8 | 322 48 12.5 | +10 | -12.25 | 58.72 | 29.791 | Ditto | | not on the board. | Mean altitude by repeating circle... 4 38 56.63 Ditto for upper telescope... 4 32 32.34 See Tab. III. Difference of the two telescopes by zenith distances 6' 24",29 Observations by the micrometer, to obtain the angular distance between the two telescopes used for observing the setting of α Aquilæ. The telescope placed on the board as before described. March 12th, 1825. From 10h 30m to 11h 30m A.M. | Upper wire fixed. | Lower wire moved. | |-------------------|-------------------| | 61.2 | 45.8 | | 58.8 | 50.6 | | 59.2 | 53 | | 60.2 | 46.3 | | 60.9 | 48.8 | | 62.3 | 51 | | 60 | 49 | | 62 | 49.4 | | 61 | 49.3 | | 63 | 49.3 | | 60.86 | 49.25 | | 49.25 | | 11.61 + 8 turns of the screw = 811,61 divisions. 811,02 = + 8 turns 11.02 Mean 811,31 × 47" (the value of each division) = 6' 27"09. Difference of altitude between the two telescopes by the repeating circle........6' 24",29 by the micrometer..............6 27",09 Altitude observed for the upper telescope (Table III.).........................4 32 32.34 Altitude for lower telescope, used for the refractions, in Table VI...........4 38 58.03 ## Observations for the Atmospheric Refraction, observed by the setting of α Aquilae, 1824-5, by Captain Parry. | Day | Time of a. Aquile setting (by No. 2) | Transit observed. | Rate No. 2 losing. | Apparent Altitude 4° 38' 58".03 | z. Aquilae. | Hor. ∠ at setting. | True altitude. | Oberved Refraction. | Baron's corr. to Temp. Fall; +50¢ | Temp. Falls. | Winds True. | Weather. | Remarks. | |---------------------------|-------------------------------------|------------------|--------------------|-------------------------------|-------------|-------------------|-----------------|-----------------|---------------------------------|---------------|-------------|----------|----------| | Dec. 20th | l.m-s. | | | | | | | | | | | | | | Dec. 21st | 1.54 - 93° 36' s. | | | | | | | | | | | | | | Dec. 22d | Ditto | | | | | | | | | | | | | | Dec. 23d | 1.42 - 99° 18' s. | | | | | | | | | | | | | | Dec. 26h | Ditto | | | | | | | | | | | | | | Dec. 29th | Ditto | | | | | | | | | | | | | | Jan. 2d | Ditto | | | | | | | | | | | | | | Jan. 3d | Ditto | | | | | | | | | | | | | | Jan. 4th | Ditto | | | | | | | | | | | | | | Jan. 5th | Ditto | | | | | | | | | | | | | | Jan. 6th | Ditto | | | | | | | | | | | | | | Jan. 7th | Ditto | | | | | | | | | | | | | | Jan. 8th | Ditto | | | | | | | | | | | | | | Jan. 9th | Ditto | | | | | | | | | | | | | | Jan. 10th | Ditto | | | | | | | | | | | | | | Jan. 11th | Ditto | | | | | | | | | | | | | | Jan. 12th | Ditto | | | | | | | | | | | | | | Jan. 13th | Ditto | | | | | | | | | | | | | | Jan. 14th | Ditto | | | | | | | | | | | | | | Jan. 15th | Ditto | | | | | | | | | | | | | | Jan. 16th | Ditto | | | | | | | | | | | | | | Jan. 17th | Ditto | | | | | | | | | | | | | | Jan. 18th | Ditto | | | | | | | | | | | | | | Jan. 19th | Ditto | | | | | | | | | | | | | | Jan. 20th | Ditto | | | | | | | | | | | | | | Jan. 21th | Ditto | | | | | | | | | | | | | | Jan. 22th | Ditto | | | | | | | | | | | | | | Jan. 23rd | Ditto | | | | | | | | | | | | | | Jan. 24th | Ditto | | | | | | | | | | | | | | Jan. 25th | Ditto | | | | | | | | | | | | | | Jan. 26th | Ditto | | | | | | | | | | | | | | Jan. 27th | Ditto | | | | | | | | | | | | | | Jan. 28th | Ditto | | | | | | | | | | | | | | Jan. 29th | Ditto | | | | | | | | | | | | | | Jan. 30th | Ditto | | | | | | | | | | | | | | Feb. 2d | Ditto | | | | | | | | | | | | | | Feb. 3d | Ditto | | | | | | | | | | | | | | Feb. 4th | Ditto | | | | | | | | | | | | | | Feb. 5th | Ditto | | | | | | | | | | | | | | Feb. 6th | Ditto | | | | | | | | | | | | | | Feb. 7th | Ditto | | | | | | | | | | | | | | Feb. 8th | Ditto | | | | | | | | | | | | | | Feb. 9th | Ditto | | | | | | | | | | | | | | Feb. 10th | Ditto | | | | | | | | | | | | | | Feb. 11th | Ditto | | | | | | | | | | | | | Meaning of symbols: - l.m-s.: Local Mean Sidereal Time - h.m-s.: Hour, Minute, Second - s.s.: Seconds - °': Degrees, Minutes - [ ]: Indicates uncertainty or error Legend: - **Very clear**, **Clear**, **Moorlight**, **Moonlight**: Conditions of visibility and lighting. - **Do.** Do.: Indicates that observation matches previous ones. - **Do. bright**, **Do., faint**: Additional notes on visibility. - **Easterly Light**: Indicates light from the east. - **North Light**, **SW Light**: Direction of light observed. - **Do., a thin haze near horizon**: Additional details about observation conditions. --- (debug data removed for clarity) Observations to determine the amount of Table VII. Observations for determining the apparent Altitude of Arcturus at the time of setting, by Lieutenant Foster's upper telescope. The corresponding Observations for Refraction are contained in Tables VIII. and IX. | 1825. Day. | Time, Obs. | No. of Mean Reading of the four Verniers. | Correction for Index. | Level. | Apparent Altitude. | Barom. at Temp. + 48°. | Tem. Fah. | Winds. True. | Weather. | Remarks. | |------------|-----------|------------------------------------------|----------------------|--------|--------------------|-----------------------|---------|-------------|---------|----------| | Feb. 18th | At 10 A.M. | 16 238 34 17.5 | +10.0 +17.75 | 7 35 19.67 | 29.540 | —26 ESE Lt. | Fine & clear | | —*19th | 11 A.M. | 12 147 31 2.5 | — + 6.75 | 7 35 15.69 | 29.610 | —29 Easterly | Hazy, with slight snow | | — 20th | 10 A.M. | 12 56 28 2.5 | + 4.5 | 7 35 14.63 | 29.626 | —35 Calm | Clear & fine | | — 21st | 9 A.M. | 6 190 55 57.5 | + 5.0 | 7 35 20.00 | 29.460 | —40 Calm | Thin haze near the horizon | | | to | 6 325 23 57.5 | + 1.0 | 7 35 18.83 | 29.460 | —……… | Fine weather | | | 1½ P.M. | 6 99 52 6.25 | + 0.25 | 7 35 18.50 | 29.460 | —36 Calm | ………… | | Mar. 4th | 10 A.M. | 16 238 34 10.25 | 0.0 +14.50 | 7 35 20.95 | 29.600 | —31 Calm | Clear & fine | Mean 7° 35' 18.32 being the altitude used in Table VIII. † Micrometrical measure of ∠ between tel. +1 49.82 Apparent altitude of Arcturus at setting by the lower tel. 7 37 8.14 being the altitude used in Table IX. • N.B. The Index was never reset to zero after the observations of the 18th; but the instrument was carefully secured from the weather, without disturbing the verniers, and the succeeding days observations commenced at that part of the arc where the preceding ones left off. The reading, however, of all the verniers was always taken before the commencement of a fresh series of zenith distances; and as no difference in the results of the two days' readings was found, this notice will suffice for all the following observations on the altitude of this board, except that on March 4th, when the principal vernier was set to zero. † N.B. This measurement between the upper and lower telescopes was obtained after the manner already described, by means of a double wire micrometer attached to one of Dollond's achromatic telescopes of 46 inches focal length, and 3½ inches aperture. The number and parts of a revolution being in this case 2° 30′ 8″. The value of a revolution, as determined from a series of observations on stars, is 47″.7, from which we deduce 1° 50″.09 for the angle subtended at the board between the upper and the lower telescopes. But the focal length of the telescope in this measurement being 46.11 in consequence of the distance, instead of 46 inches; the angle thus measured must be reduced in the ratio of these two focal lengths in order to obtain 1° 49″.82, the correct angular distance between the telescopes. ### Observations for the Atmospheric Refraction observed by the setting of Arcturus, 1824 and 1825. Apparent Altitude 7° 35' 18'43'. By Lieutenant Foster. #### Table VII. | Day | Transit observed | Star | Rate of 423s. | Arcturus, Observed Refraction. | Temp. Fall. | Winds (true) | Weather. | Remarks. | |-----|------------------|------|--------------|-------------------------------|-------------|--------------|---------|----------| | Nov. 1824 | h. m. s. | h. m. s. | s | | | | | | | Dec. 1st | 12 43 38 | 9 9 9 | + 2.8 | 0° 09' 6.8" | 8.8 | Easternly Fresh | Fine & clear | | | Ditto | 12 43 38 | 9 9 9 | + 1.72 | 20° 93' 7.7" | 9.9 | North | Hazy near the horizon; clear over head. | | Ditto | 12 39 7.5 | 9 9 9 | + 2.83 | 24° 34' 8.9" | 10.9 | North | Very clear | | Ditto | 12 31 20 | 9 9 9 | + 4.0 | 19° 50' 7.2" | 11.9 | NE | Sky clear; star twinkled much some time before setting. | | Ditto | 12 27 41 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 12.9 | NE | Sky clear and fine. | | Ditto | 12 23 44 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 13.9 | NE | Calm still | | Ditto | 12 19 45 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 14.9 | NE | Calm still | | Ditto | 12 15 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 15.9 | NE | Calm still | | Ditto | 12 11 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 16.9 | NE | Calm still | | Ditto | 12 7 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 17.9 | NE | Calm still | | Ditto | 12 3 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 18.9 | NE | Calm still | | Ditto | 12 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 19.9 | NE | Calm still | | Ditto | 11 24 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 20.9 | NE | Calm still | | Ditto | 11 10 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 21.9 | NE | Calm still | | Ditto | 11 5 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 22.9 | NE | Calm still | | Ditto | 11 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 23.9 | NE | Calm still | | Ditto | 10 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 24.9 | NE | Calm still | | Ditto | 10 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 25.9 | NE | Calm still | | Ditto | 9 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 26.9 | NE | Calm still | | Ditto | 9 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 27.9 | NE | Calm still | | Ditto | 8 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 28.9 | NE | Calm still | | Ditto | 8 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 29.9 | NE | Calm still | | Ditto | 7 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 30.9 | NE | Calm still | | Ditto | 7 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 31.9 | NE | Calm still | | Ditto | 6 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 32.9 | NE | Calm still | | Ditto | 6 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 33.9 | NE | Calm still | | Ditto | 5 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 34.9 | NE | Calm still | | Ditto | 5 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 35.9 | NE | Calm still | | Ditto | 4 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 36.9 | NE | Calm still | | Ditto | 4 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 37.9 | NE | Calm still | | Ditto | 3 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 38.9 | NE | Calm still | | Ditto | 3 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 39.9 | NE | Calm still | | Ditto | 2 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 40.9 | NE | Calm still | | Ditto | 2 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 41.9 | NE | Calm still | | Ditto | 1 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 42.9 | NE | Calm still | | Ditto | 1 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 43.9 | NE | Calm still | | Ditto | 0 30 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 44.9 | NE | Calm still | | Ditto | 0 0 55 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 45.9 | NE | Calm still | | Ditto | 24th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 46.9 | NE | Calm still | | Ditto | 23rd | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 47.9 | NE | Calm still | | Ditto | 22nd | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 48.9 | NE | Calm still | | Ditto | 21st | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 49.9 | NE | Calm still | | Ditto | 20th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 50.9 | NE | Calm still | | Ditto | 19th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 51.9 | NE | Calm still | | Ditto | 18th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 52.9 | NE | Calm still | | Ditto | 17th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 53.9 | NE | Calm still | | Ditto | 16th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 54.9 | NE | Calm still | | Ditto | 15th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 55.9 | NE | Calm still | | Ditto | 14th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 56.9 | NE | Calm still | | Ditto | 13th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 57.9 | NE | Calm still | | Ditto | 12th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 58.9 | NE | Calm still | | Ditto | 11th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 59.9 | NE | Calm still | | Ditto | 10th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 60.9 | NE | Calm still | | Ditto | 9th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 61.9 | NE | Calm still | | Ditto | 8th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 62.9 | NE | Calm still | | Ditto | 7th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 63.9 | NE | Calm still | | Ditto | 6th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 64.9 | NE | Calm still | | Ditto | 5th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 65.9 | NE | Calm still | | Ditto | 4th | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 66.9 | NE | Calm still | | Ditto | 3rd | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 67.9 | NE | Calm still | | Ditto | 2nd | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 68.9 | NE | Calm still | | Ditto | 1st | 12 00 | 9 9 9 | + 3.94 | 19° 50' 7.2" | 69.9 | NE | Calm still | Means: 8 36' 36" 29° 80' 27° 3 Table IX. Observations for the Atmospheric Refraction observed by the setting of Arcturus, 1824 and 1825. Apparent Altitude 7° 37' 8",14. By Lieutenant Foster. | Days | Time of Arcturus setting by No. 649. | Transit observed. | Rate of 649. | Arcturus. | Observed Refraction. | Baromt. at Temp. + 48° | Temp. Fahrt. | Winds (true). | Weather. | Remarks. | |------|-------------------------------------|-------------------|-------------|-----------|---------------------|------------------------|--------------|-------------|----------|---------| | | | Star. | Time by No. 649. | Hor. ∠ at setting. | True altitude. | Inches. | North Light | Sky clear | Star bright at setting; Aurora faint in the SW. | | Dec. 21st | h. m. s. | α Andromeda | 12 22 08.75 | +6.2 | 9 8 44.91 | 7 28 43.83 | 8 24.31 | 29.806 | -28.2 | East ...... | Fine & clear Aurora faint in the SW. | | 22d | 11 35 35.5 | Ditto | 12 18 16.96 | +4.4 | 9 8 53.1 | 7 28 20.76 | 8 47.38 | 29.877 | -29 | NE ...... | Sky clear Aurora faint in the SW; star bright. | | 23d | 11 31 42.5 | Ditto | 12 14 25.46 | +4.2 | 9 8 51.07 | 7 28 24.94 | 8 43.20 | 29.802 | -31 | Calm | Aurora faint in the SE bS. | | 25th | 11 23 56 | Ditto | 12 06 40.75 | 0.0 | 9 8 49.53 | 7 28 29.92 | 8 38.22 | 29.886 | -25.2 | ENE moderate | Sky clear Aurora faint in the SSW; star twinkled a little before setting. | | 26th | 11 20 01 | Ditto | 12 02 50.33 | +5.2 | 9 8 45.07 | 7 28 42.10 | 8 26.04 | 29.989 | -27.8 | | | Jan. 2d | 10 53 03.2 | Ditto | 11 35 51.95 | +5.0 | 9 8 45.29 | 7 28 38.98 | 8 29.16 | 29.881 | -29.4 | East Light | Clear to the westw4, hazy in the eastern quarter. | | 3d | 10 49 11.5 | α Arietis | 13 29 41 | 0.0 | 9 8 43.57 | 7 28 43.75 | 8 24.39 | 29.835 | -31.5 | Still clear even8 | Clear over head and to the westward, thin slight haze to the eastward | | 5th | 10 41 34.5 | α Andromeda | 11 24 17.63 | +4.3 | 9 8 50.77 | 7 28 23.04 | 8 45.10 | 29.336 | -36.5 | Easterly Light | Sky clear | | 7th | 10 33 49.2 | Ditto | 11 16 34.10 | +4.0 | 9 8 48.90 | 7 28 28.56 | 8 39.58 | 29.509 | -35.5 | Calm | Aurora faint to the SSW. | | 10th | 10 22 19 | Ditto | 11 05 02.93 | +5.6 | 9 8 49.78 | 7 28 24.88 | 8 43.26 | 29.961 | -35.5 | Aurora faint to the southward. | | 11th | 10 18 34 | Ditto | 11 1 11.25 | +4.0 | 9 8 56.40 | 7 28 05.68 | 8 52.40 | 30.140 | -38.3 | | | 12th | 10 14 38.5 | Ditto | 10 57 20.23 | +4.9 | 9 8 52.17 | 7 28 17.61 | 8 50.51 | 29.953 | -38.5 | | | 15th | 10 03 00 | Ditto | 10 45 45.85 | +4.5 | 9 8 47.97 | 7 28 29.82 | 8 38.32 | 29.711 | -27.5 | | | 16th | 9 59 09 | Ditto | 10 41 55.78 | +6.2 | 9 8 46.67 | 7 28 32.18 | 8 35.96 | 29.730 | -31.5 | | | 17th | 9 55 17 | Ditto | 10 38 04.91 | +5.07 | 9 8 45.47 | 7 28 35.35 | 8 32.79 | 29.638 | -28 | | | 20th | 9 43 40.8 | α Pegasi | 9 23 24.07 | +5.4 | 9 8 41.24 | 7 28 46.57 | 8 21.57 | 29.409 | -26.2 | | | 22d | 9 35 57 | α Pegasi | 9 15 43.05 | +5.84 | 9 8 38.67 | 7 28 53.44 | 8 14.70 | 29.341 | -25.5 | | | 24th | 9 28 32 | α Andromeda | 10 18 51.2 | +5.2 | 9 8 54.91 | 7 28 07.88 | 9 00.26 | 29.820 | -37.2 | | | 25th | 9 24 37.8 | α Pegasi | 9 08 02.18 | +3.87 | 9 8 50.68 | 7 28 19.51 | 8 48.63 | 29.795 | -42.2 | | | 27th | 9 16 49.5 | Ditto | 9 56 30 | +6.2 | 9 8 43.75 | 7 28 38.49 | 8 29.05 | 29.847 | -27 | | | Feb. 2d | 8 53 48 | α Andromeda | 9 36 29.55 | +3.84 | 9 8 51.14 | 7 28 17.09 | 8 51.05 | 30.139 | -40.9 | | Means | 8 35.07 | 29.786 | -32.0 | Table X. Observations for determining the Apparent Altitude of α Aquilæ at the time of setting, by Lieutenant Foster's upper telescope. The corresponding Observations for Refraction are contained in Tables XI. and XII. | Day | Time | No. of Observations | Mean reading of four Verniers | Correction for Index Level | Apparent zenith distance | Apparent altitude deduced from the apparent zenith distance by the ratio of the No. of observations | Barom. at Temp. + 48° | Temp. Fah. | Winds True. | Remarks | |-----------|----------|---------------------|-------------------------------|---------------------------|-------------------------|-------------------------------------------------------------------------------------------------|----------------------|------------|-------------|-----------------------| | Jan. 28th | At 11 A.M. | 8 | 323° 7' 57.5" | 0° +1" | 85° 23' 29.81" | | | | | Occasionally squally | | | 30 P.M. | 14 | *78 38 30.0 | -8.25 | 85° 23' 37.20" | | | | | | | Feb. 7th | 11 A.M. | 8 | 323° 8' 20.0 | 0.0 -0.5 | 85° 23' 32.44" | | | | | North mod. | | | 2 P.M. | 8 | *286 18 5.0 | +0.75 | 85° 23' 43.22" | | | | | | | 9th | 10 A.M. | 8 | 323° 8' 1.25 | 0.0 +3.0 | 85° 23' 30.53" | | | | | | | | 1 P.M. | 14 | *115 32 16.25 | +2.25 | 85° 23' 44.18" | | | | | Calm Fine & clear | | 10th | 10 30 A.M.| 6 | *152 21 51.25 | +3.25 | 85° 23' 39.08" | | | | | Calm | | | 30 P.M. | 6 | *304 43 41.25 | -2.0 | 85° 23' 38.00" | | | | | | | 15th | 11 A.M. | 12 | *304 43 8.75 | +2.50 | 85° 23' 35.94" | | | | | Cloudy, overcast weather. | | 28th | 11 A.M. | 6 | *152 22 1.25 | -3.50 | 85° 23' 39.62" | | | | | NE Light Clear & fine | | | 30 P.M. | 6 | *304 43 25.00 | +1.00 | 85° 23' 34.12" | | | | | | Mean = the apparent altitude, upper telescope 4° 36' 13.08", being the altitude used in Table XI. † Micrometrical measure of ∠ subtended at the board between the telescopes = + 3° 8.42" Apparent altitude for the lower telescope 4° 39' 31.50", being the altitude used in Table XII. * The principal vernier not reset to zero, and the observations are continued from the preceding reading. † The number and parts of a revolution in this case being 3° 96' 9", we obtain 3° 9" 22" for the angular distance between the telescopes used in the observations on refractions. The focal length, however, of the telescope to which the micrometer was attached being in the present case 46.19, instead of 46 as before stated, and the above angular distance being reduced in the ratio of 46.19 to 46, we have 3° 8" 42" for the correct angle subtended by the distance between the upper and lower telescopes. Observations for the Atmospheric Refraction, observed by the setting of α Aquilae, 1894 and 1895. Apparent Altitude 4° 36' 32",08. By Lieutenant Foster. Table XI. | Day | Time of Transit Observed | Star | Rate of α Aquilae | True Altitude | Barom. Temp. | Winds (true.) | Weather | Remarks | |-----|--------------------------|------|------------------|---------------|-------------|--------------|---------|---------| | Dec 8th | 3:31:58 | α Aquilae | 2:55:46:28 | 3:36 | 6 | 51 | 24:69 | 4:22 | 58:87 | 13 | 4:24:21 | 29:54:44 | NNE Squally | Sky Clear | | 11th | 3:34:26 | Ditto | 2:58:16:49 | + 4:49 | 6 | 51 | 32:55 | 4:23 | 07:45 | 13 | 15:03 | 29:07:08 | Clear and Fine | | 13th | 3:26:59:50 | Ditto | 2:50:34:00 | + 4:40 | 6 | 51 | 30:45 | 4:22 | 42:51 | 13 | 14:57 | 30:05:57 | Star indistinctly seen at setting. | | 16th | 3:15:24 | Aldebaran | 2:46:45:13 | + 6:44 | 6 | 51 | 30:47 | 4:22 | 42:51 | 13 | 14:57 | 30:05:57 | North Light | | 19th | 3:15:24 | Ditto | 2:46:45:13 | + 6:44 | 6 | 51 | 30:47 | 4:22 | 42:51 | 13 | 14:57 | 30:05:57 | ENE Ditto | | 21st | 2:59:58 | Ditto | 2:19:44:27 | + 6:20 | 6 | 51 | 26:79 | 4:23 | 32:61 | 12 | 50:47 | 30:57:44 | SW Fresh | | 22d | 2:52:15 | Ditto | 2:15:59:88 | + 4:44 | 6 | 51 | 26:66 | 4:23 | 32:48 | 12 | 50:47 | 30:57:44 | SW Light | | 25th | 2:48:25 | Ditto | 2:12:47:76 | + 4:22 | 6 | 51 | 26:66 | 4:23 | 32:48 | 12 | 50:47 | 30:57:44 | Calm | | 26th | 2:43:00 | Ditto | 2:04:59:36 | + 5:24 | 6 | 51 | 26:66 | 4:23 | 32:48 | 12 | 50:47 | 30:57:44 | NNE Light | | 29th | 2:25:01 | Ditto | 1:48:55:13 | + 4:11 | 6 | 51 | 18:67 | 4:24 | 03:14 | 12 | 19:04 | 29:06:66 | ENE Moderate | | Jan 1st | 2:13:36:50 | α Ceti | 2:33:03:82 | + 5:2 | 6 | 51 | 23:34 | 4:23 | 33:73 | 12 | 49:35 | 29:83:36 | Eastward Light | | 2d | 2:09:48:40 | α Arietis | 1:33:33:33 | + 4:6 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Fine and Clear | | 3d | 2:05:26:50 | Ditto | 1:29:44:00 | + 4:29 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Thin haze near the horizon, but through which the star was distinctly seen. | | 6th | 1:57:17:50 | Ditto | 1:18:53:66 | + 4:43 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Sky Clear | | 10th | 1:39:16:00 | Ditto | 1:18:53:66 | + 4:43 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Star bright at setting. | | 12th | 1:31:21:00 | Ditto | 1:18:53:66 | + 4:43 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Thin white clouds to the SSW. | | 15th | 1:19:43:80 | Ditto | 0:43:25:66 | + 4:49 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Star bright at setting. | | 17th | 1:15:53:30 | Ditto | 0:39:36:56 | + 4:49 | 6 | 51 | 22:78 | 4:23 | 19:03 | 13 | 02:04 | 29:84:28 | Star bright at setting. | | 18th | 0:06:80 | Ditto | 0:31:53:48 | + 4:41 | 6 | 51 | 25:71 | 4:23 | 39:38 | 12 | 53:70 | 29:56:61 | Star bright at setting. | | 20th | 0:00:24:50 | Ditto | 0:24:12:47 | + 5:4 | 6 | 51 | 23:34 | 4:23 | 22:51 | 13 | 00:57 | 29:37:72 | North Light | | 25th | 0:01:41:50 | Ditto | 0:05:24:20 | + 5:4 | 6 | 51 | 34:37 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | Eastern Ditto | | Feb 2d | 0:12:35:00 | Ditto | 0:11:57:19:53 | + 5:4 | 6 | 51 | 37:12 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | NW Fresh | | 4th | 0:12:35:00 | Ditto | 0:11:57:19:53 | + 5:4 | 6 | 51 | 37:12 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | East Light | | 7th | 0:59:59:50 | α Arietis | 0:11:57:19:53 | + 5:4 | 6 | 51 | 37:12 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | Ditto | | 8th | 0:47:21:80 | α Ceti | 0:11:57:19:53 | + 5:4 | 6 | 51 | 37:12 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | Ditto | | 9th | 0:43:25:20 | α Arietis | 0:11:57:19:53 | + 5:4 | 6 | 51 | 37:12 | 4:22 | 49:56 | 13 | 42:52 | 30:38:36 | Ditto | Means | 13 | 09:37 | 29:80:8 | —29:0 | Eastward Light | Sky perfectly clear. | Table XII. Observations for the Atmospheric Refraction, observed by the setting of α Aquilæ, 1824 and 1825. Apparent Altitude 4° 39' 31",50. By Lieutenant Foster. | Days | Time of α Aquilæ setting by No. 649. | Transit observed. | Rate of 649. | α Aquilæ. | Barom. at Temp. + 48°. | Winds (true). | Weather. | Remarks, &c. | |------|-------------------------------------|-------------------|-------------|-----------|------------------------|--------------|---------|-------------| | | | Star. | Time by 649. | Hor. ∠ at setting. | True altitude. | Observed Refraction. | Temp. Fah. | | | | Dec. 20th | h. m. s. | α Arietis | h. m. s. | h. m. s. | h. m. s. | Inches. | Clear still evening | Aurora faint to the SW. | | 21st | 2 59 11 | Ditto | 2 39 38,26 | 6 50 45,52 | 26 23,13 | 29,666 | North Fresh | Aurora bright to the SW. | | 23rd | 2 55 15 | Ditto | 2 19 48,27 | 6 50 39,49 | 26 48,2 | 29,794 | NNE Light | Aurora faint to the westward. | | 29th | 2 39 49,5 | Ditto | 2 4 20,26 | 6 50 42,09 | 26 36,69 | 29,929 | Eastward | Thin haze near the horizon, through which the stars were distinctly seen. | | 29th | 2 24 16 | Ditto | 1 48 55,13 | 6 50 33,51 | 27 12,28 | 29,666 | Fine & clear | Star bright at setting. | | Jan. 1st | 2 12 51,5 | α Ceti | 2 33 03,82 | 6 50 40,22 | 26 42,82 | 29,836 | Sky clear | Thin white clouds to the SW; star set very bright. | | 2d | 2 09 00 | α Arietis | 3 33 32,33 | 6 50 40,25 | 26 42,7 | 29,847 | Moderate | Sky clear; star bright at setting. | | 3d | 2 05 09 | Ditto | 1 29 41,00 | 6 50 40,64 | 26 40,55 | 29,828 | Light | Thin haze to the eastward, perfectly clear in other parts. | | 5th | 1 57 26 | Ditto | 1 21 56,76 | 6 50 41,78 | 26 35,74 | 29,356 | Easterly | Star distinctly seen at setting. | | 6th | 1 53 33,5 | Ditto | 1 18 05,36 | 6 50 40,69 | 26 39,91 | 29,322 | Clear | Aurora faint to the SSW. | | 10th | 1 38 19 | Ditto | 1 02 42,78 | 6 50 49,65 | 26 01,8 | 29,790 | Clear & fine | Star bright. | | 11th | 1 34 29,7 | Ditto | 0 58 50,31 | 6 50 51,84 | 25 52,11 | 30,125 | Clear | Aurora faint to the southward, star somewhat obscured at setting. | | 12th | 1 30 35 | Ditto | 0 54 59,36 | 6 50 48,03 | 26 8,35 | 29,984 | Moderate | Stars bright; Aurora faint in the SW near horizon. | | 15th | 1 18 58,5 | Ditto | 0 43 25,66 | 6 50 44,18 | 26 23,96 | 29,732 | Fresh | Aurora faint near horizon to the WSW. | | 16th | 1 15 07,5 | Ditto | 0 39 36,36 | 6 50 42,39 | 26 31,35 | 29,754 | Somewhat hazy | Aurora faint near horizon to the southward. | | 17th | 1 11 16,8 | Ditto | 0 35 45,56 | 6 50 43,50 | 26 30,25 | 29,622 | Northw. light | A few thin clouds to the southwest about the moon. | | 20th | 0 59 39,5 | Ditto | 0 24 12,47 | 6 50 42,22 | 26 31,6 | 29,990 | Sky clear | Star bright at setting. | | 25th | 0 40 38,4 | Ditto | 0 05 00,32 | 6 50 50,15 | 25 57,55 | 29,372 | Easterly | ENE strong and squally. Sky clear over head, considerable drift; star bright at setting. | | Feb. 2d | 0 32 54,2 | Ditto | 1 57 19,53 | 6 50 46,68 | 26 11,70 | 29,836 | NW Fresh | Calm, clear and very fine; faint twilight to the westward. | | 4th | 1 01 53,5 | α Arietis | 1 34 10,08 | 6 50 49,59 | 25 58,75 | 30,229 | Easterly Light | Calm, clear still evening. | | 7th | 1 50 10,9 | α Ceti | 1 22 32,6 | 6 50 41,79 | 26 31,22 | 30,056 | ENE strong and squally. Sky clear over head, considerable drift; star bright at setting. | | 8th | 1 46 32,8 | α Andromeda | 1 14 47,94 | 6 50 34,49 | 27 01,45 | 29,583 | Calm, clear and very fine; faint twilight to the westward. | | 9th | 1 42 40,2 | α Arietis | 1 10 28,17 | 6 50 47,92 | 26 05,03 | 29,745 | Calm, clear still evening. | | | | α Ceti | 1 07 04,25 | 6 50 46,99 | 26 8,81 | 29,959 | Eastward Light | Sky perfectly clear. | Means 13. 473 29,742 -31,1 Observations for the Atmospheric Refraction observed by the setting of Arcturus, 1824-25. Apparent Altitude 7° 38' 0" 52'. By Lieutenant Ross. | Date | Time of Arc-turns setting reduced to 649. | Transit Observed. | Rate of Gainings. | Arcturus's Hourly ∠ at True Altitude. | Observed Refraction. | Barom. and Temp. + 50°. | Winds True. | Temp.-Fah. | Inches. | Weather. | Remarks. | |------|------------------------------------------|------------------|------------------|-------------------------------------|---------------------|-------------------------|-------------|-----------|---------|---------|----------| | Dec. 15th | 12 02 10.8 | α Andromedae | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 21st | 13 38 58 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 26th | 11 19 34 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | Jan. 4th | 10 44 59 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 5th | 10 41 05.5 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 6th | 10 37 14.7 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 7th | 10 33 23.7 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 10th | 10 21 53 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 11th | 10 18 11 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 12th | 10 14 13 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 15th | 10 2 34.5 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 16th | 9 58 43.5 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 17th | 9 54 52.7 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 20th | 9 43 16 | α Pegasi | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 24th | 9 28 03 | α Andromedae | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 25th | 9 24 10 | α Pegasi | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | | 27th | 9 16 26 | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Ditto | Mean | 8 23 18 | 29.749 | 32.6 | ### Table XIV. Observations for the Atmospheric Refraction observed by the setting of α Aquilae, 1825. Apparent Altitude 4° 37' 41,"08. By Lieutenant Ross. | Date | Time of α Aquilae's setting reduced to 649. | Transit Observed. | Rate of No. 649 gaining | α Aquilae's | Observed Refraction. | Barom. at Temp. +50° | Temp. Fah. | Winds True. | Weather. | Remarks. | |------------|---------------------------------------------|-------------------|-------------------------|-------------|---------------------|----------------------|-----------|-------------|----------|----------| | | | Star. | Time by No. 649. | Horary ∠ at setting. | True Altitude. | | | | | | | 1825. | | h. m. s. | h. m. s. | h. m. s. | | | | | | | | Jan. | | | | | | | | | | | | 5th | | | | | | | | | | | | 6th | | | | | | | | | | | | 7th | | | | | | | | | | | | 10th | | | | | | | | | | | | 11th | | | | | | | | | | | | 12th | | | | | | | | | | | | 15th | | | | | | | | | | | | 16th | | | | | | | | | | | | 17th | | | | | | | | | | | | 20th | | | | | | | | | | | Mean 13 00,42 29,689 -33,37 ### Table XV. Observations for the Atmospheric Refraction observed by the setting of α Aquilae, 1824-25. Apparent Altitude 4° 36'3,"88. By Lieutenant Ross. | Date | Time of α Aquilae's setting reduced to 649. | Transit Observed. | Rate of No. 649 gaining | α Aquilae's | Observed Refraction. | Barom. at Temp. +50° | Temp. Fah. | Winds True. | Weather. | Remark. | |------------|---------------------------------------------|-------------------|-------------------------|-------------|---------------------|----------------------|-----------|-------------|----------|---------| | | | Star. | Time by No. 649. | Horary ∠ at setting. | True Altitude. | | | | | | | 1824. | | h. m. s. | h. m. s. | h. m. s. | | | | | | | | Dec. | | | | | | | | | | | | 26th | | | | | | | | | | | | 29th | | | | | | | | | | | | 1825. | | | | | | | | | | | | Jan. | | | | | | | | | | | | 5th | | | | | | | | | | | | 6th | | | | | | | | | | | | 7th | | | | | | | | | | | | 10th | | | | | | | | | | | | 11th | | | | | | | | | | | | 12th | | | | | | | | | | | | 15th | | | | | | | | | | | | 16th | | | | | | | | | | | | 17th | | | | | | | | | | | | 20th | | | | | | | | | | | Mean 12 58,85 29,712 31,35 ## Table XVI. **Observations for the Atmospheric Refraction observed by the setting of α Aquilæ, 1825. Apparent Altitude 4° 40' 38''.** By Lieutenant Ross. | Date | Time of α Aquilæ's setting reduced to 649. | Transit observed. | Rate of 649. Gaining. | α Aquilæ's | Observed Refraction. | |------|---------------------------------------------|-------------------|-----------------------|------------|---------------------| | | | Star. | Time by 649. | Horary ∠ at setting. | True altitude. | | | | | | ∠ | | | Barometer at Temp. ± 50o. | Temp. Fahren. | Winds True. | Weather. | Remarks. | |---------------------------|---------------|-------------|----------|----------| ### Observations - **Jan. 5th** - 13h 57m 06s.3 - Arietis - Ditto - **Jan. 6th** - 13h 53m 15s.8 - Ditto - **Jan. 7th** - 13h 49m 25s.5 - Ditto - **Jan. 10th** - 13h 37m 57s.5 - Ditto - **Jan. 11th** - 13h 34m 11s. - Ditto - **Jan. 12th** - 13h 30m 13s.8 - Ditto - **Jan. 15th** - 13h 18m 39s.5 - Ditto - **Jan. 16th** - 13h 14m 45s.7 - Ditto - **Jan. 17th** - 13h 10m 56s.3 - Ditto - **Jan. 20th** - 12h 59m 21s.3 - Ditto ### Means 12h 48m 17s. 29.785 −33.37 ## Table XVII. **Observations for the Atmospheric Refraction observed by the setting of α Aquilæ, 1824-25. Apparent Altitude 4° 39' 01'',8.** By Lieutenant Ross. | Date | Time of α Aquilæ's setting reduced to 649. | Transit observed. | Rate of 649. Gaining. | α Aquilæ's | Observed Refraction. | |------|---------------------------------------------|-------------------|-----------------------|------------|---------------------| | | | Star. | Time by 649. | ∠ | | | Barometer at Temp. ± 50o. | Temp. Fahren. | Winds True. | Weather. | Remarks. | |---------------------------|---------------|-------------|----------|----------| ### Observations - **Dec. 14th** - 15h 22m 21s.2 - Arietis - **Dec. 20th** - 14h 59m 13s.6 - Ditto - **Dec. 23d** - 14h 47m 39s.5 - Ditto - **Dec. 26th** - 14h 35m 59s.5 - Ditto - **Jan. 1825** - 14h 24m 20s.6 - Ditto ### Means 12h 51m 14s. 29.748 −30.85 On looking over each individual's observations, it will be seen, that great changes in the amount of atmospherical refraction took place, without any correspondent change in the state of either the barometer or thermometer; and, although the mode of observation adopted by us, is not wholly free from objection, inasmuch, as the ray of light from a bright star may suffer some degree of inflection, by passing over a sharp edge (such as the boards placed edge-wise would present, whereby their apparent altitudes would not be exactly those of the stars at the time of observation); yet we do not consider this circumstance the cause of the anomaly alluded to, for we never entertained the slightest doubt as to the moment of either of the stars' disappearance, both being always instantaneous: and, moreover, when it is recollected, that the use of instruments, proper for measuring altitudes on these occasions, in such a climate, is attended with the difficulties already described in this Paper, it will, in all probability be admitted, that this mode of observation, is at least, calculated to diminish the errors necessarily arising from the use of instruments, under such circumstances. It is, however, with diffidence that we submit the following tabulated results of the preceding observations, for comparison with the various theories, which have from time to time been advanced by many eminent astronomers and mathematicians, to account for all the irregularities which have been noticed in the most careful observations on this important subject. Observations to determine the amount, &c. Recapitulation of the mean results, of the preceding Observations. | Stars Observed | Apparent Altitude | Barometer Corrected | Temperature Fahrenheit | Observed Refraction | No. of Observer | Observer | |----------------|-------------------|---------------------|------------------------|--------------------|-----------------|----------| | Arcturus | | | | | | | | 7 38 0°52 | 29.749 | -32.6 | 8 23.18 | 17 | Lieut. Ross. | | 7 37 8°14 | 29.786 | -32.0 | 8 35.07 | 21 | Lieut. Foster. | | 7 35 18°43 | 29.805 | -27.3 | 8 36.36 | 37 | Capt. Parry. | | 7 31 38°62 | 29.791 | -23.58 | 8 23.95 | 34 | Lieut. Ross. | | 4 40 38°0 | 29.785 | -33.37 | 12 48.17 | 10 | Lieut. Foster. | | 4 39 31°5 | 29.742 | -31.1 | 13 4.73 | 23 | Lieut. Ross. | | 4 39 1°8 | 29.748 | -30.85 | 12 51.4 | 15 | Lieut. Foster. | | 4 38 58°03 | 29.795 | -31.8 | 13 4.72 | 24 | Capt. Parry. | | 4 37 41°08 | 29.689 | -33.37 | 13 0.42 | 10 | Lieut. Ross. | | 4 36 32°08 | 29.808 | -29.0 | 13 9.37 | 32 | Lieut. Foster. | | 4 36 3°88 | 29.712 | -31.35 | 12 58.85 | 12 | Lieut. Ross. | | 4 32 32°34 | 29.701 | -29.94 | 13 12.51 | 27 | Capt. Parry. | The original register of the height of the mercury in the barometer, after being corrected for instrumental errors, has been brought up to the temperature of +50° of Fahrenheit, in the observations by Captain Parry and Lieutenant Ross, but to +48° only, in the observations by Lieutenant Foster. Port Bowen, July 10th, 1825. From the Press of W. Nicol, Cleveland-row, St. James's.