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a reference to his own words has disproved, still we think the amount of the correction, as given by that author, should have been adopted with caution in an inquiry like the present, both because the method of arriving at it is somewhat too conjectural, and also because, admitting its general accuracy, we can hardly allow it to be the precise equation for Captain Kater's case. 'It is obvious,' says Dr Young, that if we were raised on a sphere of earth a mile in diameter, its attraction would be about go of that of the whole globe, and instead of a reduction of in the force of gravity, we should obtain only, or three-fourths as much; nor is it at all probable, that the attraction of any hill a mile in height would be so little as this, even supposing its density to be only two-thirds of the medium density of the Earth; that of a hemispherical hill would be more than half as much more, and in the proportion of 1.586 to 1; and it may easily be shown, that the attraction of a large tract of table land, considered as an extensive flat surface a mile in thickness, would be three times as great as that of a sphere a mile in diameter, or about twice as great as that of such a sphere of the mean density of the Earth; so that, for a plane so situated, the allowance for elevation would be reduced to one-half; and in almost any country chosen for the experiment, it must remain less than three-fourths of the whole correction, deduced immediately from the duplicate proportion of the distance from the Earth's centre. Supposing the mean density of the Earth 5.5, and that of the surface 2.5 only, the correction for a tract of table land of a mile in thick3 2.5 66 ness, will of course be reduced to 1

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(Phil. Trans. 1819, p. 93.) If then be the correction for an elevation of one mile, on the supposition of its being filled by a solid ring of earth, we cannot perceive the grounds on which Captain Kater takes, only a little less than 1%, for the correction applicable to an elevation of 28 feet in the actual state of the superficial inequalities. We may have overlooked some step in his reasoning, or in Dr Young's, but we feel bound to state our difficulty as it occurs.

One other equation of error remains, and that is for the buoyancy of the Atmosphere. The specific gravity of the pendulum was taken at 8.610; and it was found to be, at the time of making the experiments, to the specific gravity of the Air, as 7.099 to 1. This ratio expresses the diminution of the force of gravity arising from the buoyancy of the atmosphere; but the force of gravity varies directly as the length of the pendulum, or inversely as the as the square of the number of vibrations. Hence, if the square of the number of vibrations in 24 hours be increased in the ratio of 7.099 to 1, that is, if 6.07 be added to the number of vibrations, the number in vacuo in the same time will

be obtained. We have already stated the mean number of vibrations to be 86090.77, as determined by observations of the coincidences of the clock and pendulum: We have, therefore, 86096.84 for the number made by the pendulum in a mean solar day in vacuo; to which must be added the correction for elevation above the level of the sea, or 0.12. Captain Kater deducts from this 0.06, to allow for attraction. We have given our reasons for holding this to be too large an allowance, and we should think 0.12 sufficiently near the truth, without any allowance, for so small a height as 28 feet. According to Captain Kater, however, the corrected number of vibrations in vacuo, and at the level of the sea, is 86096.90.

On the 29th July, having finished his experiments at Unst, Captain K. proceeded to Portsoy, the next station of the Survey, where he arrived on the 1st of August. By a process of precisely the same kind with the former, he ascertained the number of vibrations there to be 86086.01 in vacuo and at the level of the sea. The following Table exhibits the results of his observations at all the stations, the experiments being the same at each. They were concluded at the Isle of Wight on the 16th of May 1819.

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The instrument used in determining the latitudes of these stations, was the repeating circle of one foot diameter, made by Troughton; and we cannot omit recording the close agreement which appears between those observations and the latitudes as determined by Colonel Mudge with the zenith sector in the Trigonometrical Survey. This is, in justice, due to the accuracy of that skilful observer; because in a paper of Don Joseph Rodriguez, in Phil. Trans. for 1812, some doubts were expressed upon the subject. In the measurement of an arc of the meridian extending nearly three degrees, from Clifton in

Yorkshire to Dunnose in the Isle of Wight, a remarkable anomaly appeared, for which it was very difficult to account ;-the degrees, instead of increasing with the latitude, seemed, if the measurement could be trusted, to decrease. Thus, for latitude 51° 2′ 54′′, a degree in fathoms, as given by Colonel Mudge (Phil. Trans. 1803), was 60884; for lat. 52° 2′ 20′′ it was 60820; and for lat. 52° 50′ 30′′ it was 60766. Hence we should be led to suppose that the Earth, instead of being flattened at the Poles, is more elevated there than at the Equator, contrary to the received notions of its figure. The apparent variance between these results and the results obtained by the National Institute, led Don J. Rodriguez to examine the matter, in order to reconcile the difference and to detect the error which he concluded must exist in the English observations; and, without adverting more particularly to his measurements and calculations, we may state that he ascribes the appearance of progressive augmentation in the degrees, to error in Colonel Mudge's observed latitudes. (Phil. Trans. for 1812, p. 336.) Bearing this in mind, Captain Kater prepared to ascertain the latitudes at the stations in question with all the exactness possible. The corrections for precession, &c. were those used at Greenwich Observatory; and the mean polar distance of the Pole Star, was taken from the latest observations of the Astronomer Royal. The mean of five series of observations, made between the 3d and 12th of October, gave the latitude of Clifton Beacon 53° 27' 29".89. The observed arc between Greenwich and Clifton Beacon, as given by Colonel Mudge, was 1° 58′ 51′′.59. Add this to the latitude of Greenwich, 51° 28′ 38′′.01, and we have for the latitude of Clifton Beacon, 53° 27' 29".6, differing only by O".29 in defect from that obtained by the repeating circle. Again, at Arbury Hill, the mean of three series of observations, made on the 18th, 22d, and 26th of October, gave the latitude equal to 52° 13' 25''.72. The observed arc between Greenwich and Arbury Hill was 0° 44' 48".19, which therefore gives 52 13' 26".20 for the latitude by the Trigonometrical Survey; differing only 0.48 in excess from the latitude obtained by the repeating circle. Lastly, the latitude of Dunnose was found by the repeating circle to be 50° 37' 5".27, and by the zenith sector, 50° 37' 6".61; the difference being I".34 in excess. It is very probable that this difference, small as it is, arose from Captain Kater being compelled, by the nature of the ground, to take a station at some distance from that used in the Survey. He chose Shanklin Farm instead of Dunnose; and the ground was so unfavourable for measuring a base, that there was great difficulty in connecting the two points. We are the better en

titled to ascribe the discrepancy in this case to the circumstance now mentioned, because the difference was so very minute in the other stations where the points of observation coincided. That these latitudes, then, are as correct as observed latitudes can be, we may safely assume; but it is possible that they may differ from the true latitudes of the several stations. If this difference can be accounted for, the anomaly above alluded to will be satisfactorily explained.

The diminution of the force of gravitation from the Poles to the Equator, may be found by the difference of the lengths of pendulums oscillating in equal times at the Poles and at the Equator; or by the ratio of the squares of the number of vibrations in 24 hours, observed in different latitudes, with the same pendulum. The diminution indicated by the decrease observed to take place in the number of vibrations between any two given latitudes, must be the same, from whatever portions of the me ridian it is computed, unless it be affected by some irregular attraction. But it is found from observations at Unst, and each of the other stations in succession, that the diminution deduced from the arc between Unst and Portsoy, is less than that obtained from the arc between Unst and Leith; the number expressing the diminution being .0053639 in the former case, and .005480 in the latter. When Unst and Clifton are the two latitudes, the diminution is .0056340; Unst and Arbury Hill give .0054282, denoting an increase of gravitation; Unst and London give .0055510; and a still further decrease appears from comparing the observations at Unst and Dunnose, the diminution thus obtained being .0055262. Again, Portsoy and Dunnose give .0055920, being a greater diminution than the last mentioned. Clifton and Dunnose make it only .0052616, which is smaller; while Arbury Hill and Dunnose give .0060212, which is greater than any of the preceding.

From these statements we gather, that in advancing towards the Equator, the decrease of gravity is greater than it ought to be by the theory; and also, that at some of the stations, the action of a disturbing force, proceeding probably from the greater density of the materials in the neighbourhood, has produced an irregularity in the diminution of gravity. The sudden increase perceptible at Arbury Hill deserves particular attention. It should also be observed, that the action of this disturbing force does not extend far; for, by the experiments at London and Dunnose, the number expressing diminution is reduced to .0052837. We may thence infer, that there exists very near Arbury Hill a mass of matter of considerable density. Captain Kater conjectures that this mass is Mount Sorrel, which consists of gra

nite; and other rocks of primitive formation are situated in its vicinity. Be this as it may, the disturbance must arise from some such masses; and they must be situated to the north of Arbury Hill, because we have seen that, at a very small distance in a southerly direction, the force ceases to act. Another effect of these disturbing forces will be to attract the plumb-line northward in which case the observed latitude will be less than the true; consequently the length of the degree computed from the arc between Arbury Hill and Dunnose will exceed, and that deduced from the arc between Clifton and Arbury Hill, will fall short of the true latitudes. This difference between the real and apparent latitudes, sufficiently accounts for the variance which seemed to exist between the lengths of the degrees and the latitudes, in the statements of the Trigonometrical Survey.

We have extended this account of Captain Kater's paper so far, that we have left no room for any additional remarks. The Appendix to his Report contains all the observations from which the results were derived which we have now analyzed. These observations are arranged in distinct Tables, according to the different places of observation. To persons who may be engaged in similar inquiries, they cannot fail to be of the greatest use; while they are the best vouchers of that extreme accuracy which gives to the author's own conclusions the whole value that belongs to such investigations. This is not to be attained, indeed, without the greatest labour and perseverance: But we should be infinitely mistaken in supposing that very great ingenuity is not also required, both in planning the operations, and conducting their details.

ART. IV. Poems. By BERNARD BARTON. 8vo. pp. 280. London, 1820.

THO THOUGH there is much that is pleasing in this little volume, the thing that has pleased us most about it, is to learn that it is the work of a Quaker;—and that, not merely because a Quaker poet is a natural curiosity, but because it is gratifying to find that the most tolerant and philanthropic and blameless of all our sectaries, are beginning to recommend themselves by the graces of elegant literature, and to think it lawful to be distinguished for their successful cultivation of letters as well as of Science. The interdiction of all light and frivolous amusements, and of all those pastimes which merely dissipate the mind, and distract the affections, ought never to have been con

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