on the obfervations, when the weather permitted, for about nine months, during which the thermometer had fallen fo low as 15° of Fahrenheit, in the clock cafe, and rifen as high as 84; and with confiderable variations. Unfortunately I have milaid or loft the particulars of each observation; but I have preferved the greatest difference from the rate of its going. Counting on, according to the rate of its going, during the whole time it never exceeded the fun, half a fecond, nor was ever lefs than half a fecond, whether it was taken from day to day, month to month, or from any one to any other period during the obfervation." P. 17.

1

Thofe Interested in the accuracy of time-keepers, either as philofophers or artists, will doublefs find both pleafure and improvement in the perufal of Dr. Forlyce's paper, and thefe will be more complete, if Mr. Whitehurst's publication be previously examined.

ART. III. Some Facts relative to the late Mr. John Hunter's Preparation for the Croonian Lecture. By Everard Home, Efq. F. R. S. Read November 14, 1793, p. 21. I plate. THIS ftatement of facts, and a letter to Sir Jofeph Banks from Mr. Hunter, which accompanies it, would convince every candid and judicious reader, that the late Mr. -Hunter was great both as a philofopher and an anatomift, even if his eminent abilities and attainments had not been previously af certained and acknowledged. He had announced to the Royal Society that he would make the ftructure of the cryftalline humour of the eye the iubject of the Croonian lecture for the year 1793; having for many years entertained an idea that the cryftalline humour was enabled by its own internal actions to adjust itself, so as to adapt the eye to different diftances. Unfortunately for the caufe of fcience, the ingenious author of this hypothefis died before he had completed his experiments and obfervations on the fubject; but as it has fince been purfued by Mr. Home and Mr. Ramfden, and a very confiderable difcovery has been the refult of their inveftigation, we have lefs to regret, in this particular matter, than on the account of phyfiological science in general.

ART. IV. Obfervations of a Quintuple Belt on the Planet Saturn. By William Herfchel, L. L. D. F. R. S. Read December 19, 1793. p. 28. 1 plate.

BY thefe obfervations Dr. Herfchel eftablishes a strong analogy between the planets Jupiter and Saturn, in the appearance of their belts; and from this refemblance he feems inclined to infer that the latter planet has a quick revolution about its axis.

"That

That belts are immediately connected," he remarks," with the rotation of the planets will hardly be denied, when those of Jupiter. are fo well known always to lie in the direction of its equatorial motion. Since, then, it appears that the belts of Saturn. are very numerous, like thofe of Jupiter, and are alfo placed in the direction of the longeft diameter of the planet, it may not be without fome reason that we infer the period of the rotation of the former to be short, like that of the latter."

"The planet Mars, in all my obfervations, never presented itself with any parallel belts, nor do we obferve fuch phænomena on the disk of Venus. The first is known to have a rotation much flower than Jupiter; and the latter, according to the accounts of Caffini and Bianchini, is certainly not one that moves quickly upon its axis." "However, I do not mean to enter into the ftrength of an argument for a quick rotation of Saturn, that may be drawn from the condition of its belts. The circumftance of a quintuple belt, is adduced here with no other view, than merely to point out an analogy in the condition of the two largeft planets of our fyftem; and from thence to infer, that every conclufion on the atmofphere and rotation of the one, drawn from the appearance of its belts, will equally apply to the other." P. 31.

A beautiful reprefentation of the quintuple belt and ring of Saturn accompanies this paper.

ART. V. Obfervations on the Fundamental Property of the Lever; with a Proof of the Principle affumed by Archimedes, in his Demonftration. By the Rev. S. Vince, A. M. F. R. S. Read December 19, 1793. p. 33.

A Demonftration of the properties of the lever, from clear and indifputable principles, has been confidered as a great defideratum in the theory of mechanics. Of the importance of fuch a proof no doubts can be entertained, as it is upon the fundamental properties of the lever that fome of the most important branches of philofophy ultimately depend, and many machines for great and ufeful purposes are constructed. In the paper before us Mr. Vince gives a fuccinct account of the principal endeavours which have been made to clear the fubject of all doubt and obfcurity, and at the fame time he ftates his objections to the methods propofed by the authors whom he mentions. Of thefe particulars we deem it unnecellary to give a recital. Judging from ourfelves, we are inclined to believe that the utility of fuch a demonstration, as mentioned above, has induced every mathematical reader to take a fuller view of the fubject than we could give without fpecific reference to figures, and by fuch readers only a general account could be understood.

The principle affumed by Archimedes is, that two equal

powers at the extremities, or their fum at the middle of a lever, will have equal effects to move it about any point: and of this Mr. Vince gives a demonftration fhort, fimple, and complete. He fuppofes a ftraight lever, having its fulcrum at one extremity, and its other extremity fupported by a prop, and two equal bodies to be laid upon the lever, at equal distances from the extremities. From thefe conditions it is evident, that the prop and fulcrum must bear equal parts of the whole weight, and therefore the prop will be preffed with a weight equal to that of one of the two equal bodies placed upon the lever. If now the two equal bodies be removed, and one equal in weight, to the fum of theirs be placed in the middle of the lever, the prop and fulcrum muft fuftain equal parts of the whole weight, and therefore the prop will fuftain the fame weight as before. Hence, if the prop be taken away, the moving force to turn the lever about the fulcrum, in both cafes, muft evidently be the fame. And the fame is manifeftly true, if the two bodies be placed without the fulcrum and prop, at equal distances from them. Having established this principle, Mr. Vince briefly, and clearly, proves the general property of the lever, namely, that the weights of bodies fufpended are to one another, in the reciprocal proportion of their diftances from the ful

crum.

ART. VI. Account of fome Particulars obferved during the late Eclipfe of the Sun. By William Herschel, L. L. D. F. R. S. Read January 9, 1794. p. 39. I plate.

IN the obfervations here inferted, Dr. Herfchel's attention. was not directed to fuch circumftances as are commonly noticed by aftronomers during an eclipfe, the beginning, the end, and the digits eclipfed. Knowing that these would be carefully watched and recorded by other astronomers, he ju diciously availed himself of the power and diftinctness of his telescopes," in order to fee whether any appearances would arife that might deferve to be recorded." Of fuch appearances, however, few seem to have occurred. The first impreffion made was by the entrance of two mountains of the moon on the difk of the fun. The moft elevated of thefe he fuppofed not to exceed a mile and a half. The internal luminous angle made on the fun, by the interfection of the limb of the moon, was perfectly sharp, up to the very point; and not in the leaft disfigured by the refraction of the lunar atmosphere. Its fhape, however, he obferves, was not favourable for showing the effects of that atmosphere.

ART.

ART. VII. The Latitudes and Longitudes of feveral Places in Denmark; calculated from the Trigonometrical Operations. By Thomas Bugge, F. R. S. Regius Profeffor of Aftronomy at Copenhagen. Read January 9, 1794. p. 43. I plate."

A Geographical furvey of Denmark was begun in the year 1762; and it appears, from the paper now before us, to have been executed with great care and accurate inftruments. The angles of the triangles were obferved with a circular inftrument of foot radius, having double divifions, viz. thofe which arife from confidering the quadrant as containing 90 and 96 equal parts or degrees." I beg leave to obferve, says Mr. Bugge, that the Danish aftronomers and geographers. for 31 years, have been before hand in making ufe of circular inftruments, which now begia to be of a more general ufe in aftronomical and geographical obfervations. The royal obfervatory at Copenhagen has, fince the year 1781, been adorned with a circular inftrument of 4 feet radius, which, at least at that time, was the only circular inftrument of that size.”

Mr. Bugge publifhed a full defcription of the inftruments and methods ufed in the abovementioned furvey, in the Danish language, at Copenhagen, in 1779. In the paper now before us, he gives a new method of computing the longitude and latitude of places, laid down by trigonometrical operations. It depends upon fome properties of the eclipfe, combined with calculations founded on actual measurement. In a table of Jatitudes and longitudes of places, which makes a part of the paper, the latitude of the obfervatory of Copenhagen is put down 55° 41′4′′. In the fame table the latitude of Anholt light-houfe is put down 56° 44′ 20", and its longitude o° 55′ 24" W. of the obfervatory of Copenhagen, which is here confidered as in the first meridian.

We trust that the following extract from Mr. Bugge's paper will be acceptable to fome of our readers.

"In all the best maps of the Kattegat, as that by Mr. Lous, publifhed at Copenhagen, 1790; that by M. Verdun de la Crenne, M. Borda, and M. Pingré, Paris, 1778; that by Mr. Akeleie, Copenhagen, 1771; that by Mr. Ankerkrona, Stokholm, 1782; the pofition of Anholt is very erroneous. The light-house of Anholt, and the whole ifle, is from 7 to 9 minutes too much wefterly; and the diftance from the light houfe to the Swedish coaft, in a direction perpendicular to the meridian of the light-houfe, is, in all maps hitherto published, nearly 4 English miles, or th part of the whole too great. Experience has taught the navigators, that they come too foon down upon Anholt; or that they, cruifing between Anholt and Sweden, overrun their reckoning, which was afcribed to the currents; although the true reafon of it was the great error in the geographical

and

and hydrographical position of Anholt in a narrow and dangerous paffage."

ART. VIII. On the Rotation of the Planet Saturn upon its Axis. By William Herfchel, L. L. D. F. R. S. Read January 23, 1794. p. 48. 1 plate.

Dr. Herfchel, in his paper on the quintuple belt of Saturn, of which we have already given an account, was led, from the analogy between its belts and thofe of Jupiter, to furmise that it had a pretty quick rotation upon its axis; and he now announces the reality of that rotation. "The following feries of obfervations," fays Dr. Herfchel in the beginning of the paper now under our eye, "in which Saturn has been traced through one hundred and fifty-four revolutions of its equator, will fufficiently confirm it." During the obfervations here recorded, the belts on Saturn appeared to undergo no very material change, and therefore Dr. Herfchel hopes that the rotation of this planet, as now affigned, may be looked upon as having a confiderable degree of exactnefs. As the obfervations and calculations in this curious paper do not admit of abridgement, we content ourselves with laying before our readers Dr. Herfchel's conclufion.

"I fhall only add one general remark, which is, that if we lengthen the time of the rotation but 2 minutes, it will throw the laft obfervation back above 116 degrees; and if we diminish it by 2 minutes, there will arife an excefs of more than 117; and in either cafe, the calculations and obfervations would be totally at variance: from which we may conclude that our period must be exact to much lefs than 2 minutes, either way. Indeed, what alterations may have taken place in the belts themfelves, it is impoffible to determine. That there have been fome, we may admit, and rather suppose, but we have no particular reafon to fufpect them to have been very confiderable. And, after we have fhewn that a proper motion, in the spots of the belts, of 116 degrees one way, or of 117 the other, would only occafion an error of 2 minutes in time, we need not hesitate to fix the rotation of the planet Saturn upon its axis at 10" 16′0′′. 4′′. P. 66.

(To be continued.)

ART. III. Wakefield's Horace.

(Concluded from Page 156.)

IT is always of importance to obferve how far critics in their fucceffive publications adhere to their former opi