method of feparating perfect metals from each other. We refer the chemical reader, and the officers of the Mint, to the Memoir itfelf for a circumftantial account of M. TILLET's method of proceeding, which is plain, but too long in the manipulation part of it for infertion here. The utility arifing from this procefs is not its only merit: it prefents, moreover, to the natural philofopher, the fingular phenomenon of fubftances, which, after having been fubjected to the action of fire and chemical agents, mixed with other fubftances and combined with acids, may be reftored to their primitive ftate without any lofs. M. TILLET has fubjoined to this Memoir a defcription of the furnaces he employed, and an account of his methods of regulating, or augmenting, the activity of the fire. Mem. II. An Inquiry into the Combination of concrete Acid of Tartar with Zinc. By M. DE LASSONE. The principal confequence arifing from the experiments made by this Academician are: . That the reciprocal action of metallized zinc, its calx, and the concrete acid of tartar, are fully afcertained. 2. That the zinc is entirely foluble by the tartareous acid; but that, in order to obtain this faline combination complete, there must be at least seven or eight parts of tartar to one of zinc. 3. That the tartar, diffolved in boiling water, diffolves the zinc as much by its oily latus as by that of the acid. 4. That the combination, in this faline mixt, on account of this double affinity, appears entire and not cafily to be deftroyed, as the agents that are the moft proper to deftroy it (fuch as fixed and volatile alkalies) produce fcarcely any effect of that kind. Our Author concludes his Memoir with a kind of advertisement that deferves notice :-"After the fmall number of experiments (fays he) that I have tried with this faline mixt (i. e. the combination of the concrete acid of tartar with zinc), applied, as an external remedy in certain diforders of the eyes, I have found it fuperior in efficacy to the tutty, or the fimple flowers of zinc, as they are generally used. Mem. III. Concerning the exiflence of the Nitrous Acid, and the Methods of decompounding and recompounding that Acid. By M. LAVOISIER. The greateft part of the experiments mentioned in this Memoir (we believe the whole, were formerly made by Dr. Priestley; but the fame facts have led there two eminent philofophers to conclufions not only different, but oppofite. Among feveral of the Doctor's conclufions, which this Academician thinks inadmiffible, there is one that he takes particular notice of, as he imagines it may be of dangerous confequence. The celebrated English philofopher having obterved, that, from a combination of the nitrous acid with any kind of earth, he always obtained common air, or air of a fuperior kind, thought himself authorised to conclude, from this experiment often re peated, 이 n peated, that the air of the atmosphere is a compound of earth and the nitrous acid. But M. LAVOISIER Concludes from his experiments, and a careful analyfis of thofe made by Dr. Priestley, that it is not air which is compofed of the nitrous acid, but the nitrous acid which is compofed of air; and he thinks that this obfervation furnishes the true explication of the experiments related in the 3d, 4th, and 5th sections of Dr Priestley's fecond volume. Mem. IV. An Account of a series of Experiments which fhew the Nature and Properties of feveral kinds of dir, or Aeriform * Ema→ nations, extracted by different Methods from a confiderable Number of Subftances. By M. DE LASSONNE. This Memoir contains thirty-one experiments, which afcertain the existence of an inflammable air, quite diftinct from that which is commonly so called. It is obtained by a diftillation of Pruffian blue, or of the calx of zinc mixed with powder of coal. It is inflamed without detonation or the leaft explofion, and it yields a blue flame of the greatest beauty. It is not yet time to attempt the expli cation of this phenomenon; but the Reader will find in this Me moir an interefting detail of facts, whofe refults will lead to fe veral new methods of obtaining various aerial, inflammable emanations; alfo fixed air, and dephlogifticated air. Third Memoir concerning Verdigrise. By M. MONTET. This Memoir was fent by the Royal Society of Montpellier to the Academy, with which it forms one body, as appears by the Royal Edict of 17c6. It contains new improvements of the method of making verdigrife, which were fuggefted by an accidental circumftance, that happened at Saint Andre, a village about fix leagues from Montpellier. A woman who was employed in making verdigrife, giving to her afs fkins of preffed grapes to eat, let fome of them fall, through inattention, on plates of copper, which were covered with them, and lay for fome time forgotten. After feveral days the woman went to gather up thefe fkins, and found the plates covered with a layer of verdigrife. Thus the leavings of the wine-prefs became an ingredient in the manufactory of this fubftance, and M. MONTET fhows how they must be employed for this purpose. ASTRONOMY. Mem. I. Concerning the Spots of the Sun, and the rotation of that Body. By M. DE LA LANDE.. This able aftronomer relates here the obfervations of the fpots of the fun, made by Galileo and Fabricius; the conclufions they drew from thefe obfervations to determine and afcertain the motion of rotation of that We adopt this term, as it expreffes happily the refemblance which certain fluids (whofe nature is yet but very imperfectly known) bear to air. luminous luminous body, and the methods they propofed to render this determination more eafy and certain. He afterwards propofes his method, which he thinks preferable on account of its facility and fimplicity.-He then gives us a new hypothefis, relative to the production of fpots in the fun. He fuppofes that this great fource of light is a kind of folid nucleus, covered with a Auid in fufion: this being the cafe, the points of the eminences of the nucleus are fometimes covered with this fluid, and fometimes uncovered, and lefs luminous than the matter in fufion; fo that they in this latter cafe exhibit the appearance of obfcure fpots on the fun. This hypothefis is not entirely new; its principal idea is the fame with that of M. De la Hire, who confidered the (pots in queftion as the eminences of a folid and permanent body, floating in the fluid mass of which the fun is formed. Conjecture for conjecture; that of Mr. Wilfon is the most ingenious of the three; but as it is well known to our aftronomical Readers, we need not mention it. M. DE LA LANDE terminates this Memoir by the examination of an effect of the folar rotation, which has not hitherto been confidered by philofophers, but may one day (though it be not likely that we fhall fee it) become a remarkable phenomenon in cofmology: this fuppofed effect is a motion of tranflation, by which the fun changes more or lefs his place. But this local change is merely hypothetical; it may be ascertained in fome future period, by obfervations of the fixed ftars. At prefent, it is only a mathematical opinion, founded on this fuppofition, that the motion of rotation being communicated to the fun by one fingle impulfion, must have affected its centre of gravity, and produced in it a progreffive motion. All this may have been, and may not have been. If the impulfion was directed to more than one point, the centre of gravity might have remained unaffected, while the motion of rotation was produced. And who can be fure that this was not the cafe? Mem. II. Concerning the Amplitude of the Sun at Setting, obferved at St. Sulpice. By M. LE MONNIER.-Obfervations of the total Eclipfe of the Moon, the 30th of July, 1776.-Thefe Obfervations are contained in feveral Memoirs, and were made feparately at Paris, by Meffrs. De Fouchy, Le Monnier, Caffini de Thury, Pingré, Bailli, Jeaurat, Meffier,-and Perinaldo, in the county of Nice, by M. Maraldi. - Obfervations on Eclipfes of the Satellites of Jupiter, made in the Year 1776, at Perinaldo, in the County of Nice, with an Acromatic Telescope of three Feet. By M. MARALDI. Obfervation on a dark Band, which appears on the Globe of Saturn. By M. MESSIER.- Memoir, relative to the eleventh Comet, obferved at Paris, from the Obfervatory of the Marine, from the 14th of June, to the 3d of October, 1770. By the fame. NIER. Memoir concerning a new Conftellation. By M. LE MONThis Aftronomer obferved, under the fcales of libra, a void, which nobody hitherto thought of filling up. This void nevertheless contains ftars often eclipfed by the moon, and which may confequently be of use, both in determining the longitudes, and in verifying the theory of the moon, Our Academician has determined the pofition of twenty-two of these ftars, and has joined them in a conftellation, which he calls the folitary, after a bird of the Indian feas, mentioned by M. Pingré, in the account of his voyage to the Isle of Rodrigues. [ Continuation of the Twelfth Memoir of M. DIONIS DU SEJOUR, entitled, New Analytical Methods of calculating the Eclipfes of the Sun, the Occultations of the fixed Stars and Planets by the Moon, &c. We have here only the 7th, 8th, and 9th Articles of this Memoir, which fill 103 pages. The reft are reserved for the fucceeding volume. GEOGRAPHY.. New Confiderations defigned to prove, that Cape Circumcifion really exifts in 54 Degrees of Southern Latitude, and that its geographical Longitude has been hitherto fixed at about 7 Degrees more than it is. By M. LE MONNIER. On the 1ft of January, 1739, M. Boupet, an eminent French navigator, difcovered land, the fituation of which he fixed at 54 deg. of Southern latitude, and 28 deg. of longitude, and which he called the Cape of the Circumcifion. Our immortal navigator Captain Cook, among his various refearches, endeavoured to meet with this Cape, but could not find it. This, no doubt, was enough to form a prefumption against its exiftence; M. LE MONNIER, therefore, endeavours to remove this prefumption. He imagines, that M. Bouvet was miftaken in the longitude of the place in queftion, as the methods of finding the longitudes in his time were not exact. This being premifed, he examines the declination of the needle obferved at Cape Circumcifion, by M. Bouvet, and comparing feveral obfervations of this kind, he inquires into the change of declination that has taken place fince his time in those parts of the world. The refult of his inquiry is, that at the time of Captain Cook's voyage, the declination of the needle at Cape Circumcifion must have been 10 degrees towards the Weft; that the place where Captain Cook fought this Cape had a declination of 13 deg. 1, and that this difference of 3 deg. anfwers to 7 deg. of longitude. It is not therefore furprising, according to M. Le Monnier's account, that the British navigator did not find this Cape, fince it is at 21 deg. of longi tude to the Eaft of the Ifle of Ferro, and not at 28 degrees, that it must be fought. But with all due fubmiffion to the opinion of fo learned a man as M. Le Monnier, we cannot help obferving, that he seems to have laid more stress on this argument than it can poffibly bear: for, WeAll with in the Brackett) was written by Mr Wales for, to fay nothing concerning the uncertainty of M. Bouvet's' inftruments and obfervations, neither of which, we apprehend, could be better depended on, than those of Captain Cook, and his affociates; we find that thofe of the latter were not capable of determining the variation to fo fmall a quantity, as that which is so ftrenuously infifted on by M. Le Monnier, and confequently all arguments which are founded on a contrary fuppofition muft fall to the ground. For on confulting thofe obfervations, we fhall find, that barely putting the fhip round, would make a difference of near 6 degrees in the variation by the fame compafs*; and, fometimes near 10 degrees +. That the fame compafs, in the fame fituation in every refpect, but at two different times of the fame day, would give variations dif fering from one another 4 and 5 degrees . That the fame compafs, on the fame day, and in the hands of the fame obferver, will give 5 degrees difference in the variation on board the fame fhip when under fail, and when at anchor in a roadstead §. Again, compaffes made by the fame artist, on board different fhips; but at the fame time of the day, differed 3°, 4, and upwards in the variation. But, as a cafe more directly in point to the argument before us, we may obferve that on February 10th, 1774, in the latitude of 53° S. and longitude 263° E. when Captain Cook was returning northwards from the latitude of 71° S. Mr. Wales found the variation to be 1597, and Mr. Clerke found it to be 15° 32′ Eaft ¶. But in croffing the Pacific Ocean from New Zealand to Cape Horn, on the 11th of December afterwards, Mr. Wales, by the fame two compaffes, on board the fame fhip, and within a few miles of the fame place, had 9° 55′ and 11° 31'**. Thefe differences, feveral of which happened very near the place in question, are all of them at least equal to, most of them greater, and fome of them almost double the difference of variation on which M. Le Monnier founds his argument; and therefore, in our opi nion, render it totally invalid. To allege that the inftruments which were used for this purpofe, in Captain Cook's voyage, * See "The original obfervations, made in the course of a voyage towards the South Pole, and round the world" by W. Wales, F. R. S. and W. Bayley, p. 372, March 11th, 1773. + ibid. p. 375. January 24th, 1774. Ibid. p. 371. February 2d, 1773. and p. 382. January 19th, 1775 Ibid. p. 385. July 14th, 1775. ibid p. 181, and 369. Aug. 30, 9th, and Sept. 4th, 1772., Alfo p. 182, and 371. January 11th, and 14th, and February 7th, 1773See the lame Obfervations, p. 375. ** Ibid. p. 8. were |