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method of separating perfect metals from each other. We refer the chemical reader, and the officers of the Mint, to the Memoir itself for a circumftantial account of M. TILLET's method of proceeding, which is plain, but too long in the manipulation part of it for insertion here. . The utility arising from this process is not its only merit: it presents, moreover, to the natural philosopher, the fingular phenomenon of substances, which, after having been subjected to the action of fire and chemical agents, mixed with other substances and combined with acids, may be restored to their primitive state without any loss. M. Tiller has subjoined to this Memoir a description of the furnaces he employed, and an account of his methods of regulating, or aug. menting, 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 consequence, arising from the experiments made by this Academician are : 1. That the reciprocal action of metallized zinc, its calx, and the concrete acid of tartar, are fully ascertained. 2. That the zinc is entirely soluble by the tartareous acid; but that, in order to obtain this saline 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 chat of the acid. 4. That the combination, in this laline mixt, on account of this double affinity, appears encire and not cafily to be destroyed, as the agents that are the most proper to destroy is fiuch as fixed and volatile alkalies) produce scarcely any effect of that kind. Our Author concludes his Memoir with a kind of advercsement that deserves notice :-“ After the small number of experiments (says he) that I have tried with this faline mixt (i. e. the combination or the concrete acid of tartar with zinc), applied, as an external remedy in certain disorders of the eyes, I have found it superior in eificacy to the cutty, or the simple flowers of zinc, as they are generally used.

Mem. III. Concerning the existence of the Nitrous Acid, and the Methods of decompounding and recompounding that Acid. By M. LAVOISIER. The greateít part of the experiments mentioned in this Memoir (we believe the whole, were formerly made by Dr. Priestley; but the same facts have led theie two eminent philosophers to conclusions not only different, but opposite. Among leveral of the Doctor's conclusions, which this Academic cian thinks inadmissible, there is one that he takes particular notice of, as he imagines it may be of dangerous consequence.

The celebrated English philosopher having observed, that, from
a combination of the nitrous acid with any kind of earth, he al-
ways obtained common air, or air of a superior kind, thought
himself authorised to conclude, from this experiment often re-

peated,

4

peated, that the air of the atmosphere is a compound of earth and the nitrous acid. But M. LAVOISIER concludes from his expe. riments, and a careful analysis of those made by Dr. Priestley, that it is not air which is composed of the nitrous acid, but the nitrous acid which is composed of air ; and he thinks that this observation furnishes the true explication of the experiments related in the 3d, 4th, and sth sections of Dr Priestley's second volume. • Mem. IV. An Account of a series of Experiments which firew the Nature and Properties of several kinds of dir, or Aeriform * Ema. nations, extracted by different Methods from a considerable Number of Bubstances. By M. De LASSONNE. This Memoir contains thirty-one experiments, which ascertain the existence of an in. flammable air, quite distinct from that which is commonly so call. ed. It is obtained by a distillation of Prussian blue, or of the calx of zinc mixed with powder of coal. It is infamed with, out detonation or the least explofion, and it yields a blue Aame 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 interesting detail of facts, whose results will lead to fe. veral new methods of obtaining various aerial, inflammable ema. nations; also fixed air, and dephlogisticated air.

Third Memoir concerning Verdigrise. By M. MONTET. This Memoir was sent by the Royal Society of Montpellier to the Academy, with which it forms one body, as appears by the Royal Edict of 1706. It contains new improvements of the method of making verdigrise, which were suggefted by an accidental circumstance, that happened at Saint Andre, a village about fix leagues from Montpellier. A woman who was employed in making verdigrise, giving to her ass skins of pressed grapes to eai, let some of them fall, through inattention, on plates of copper, which were covered with them, and lay for fome time forgotten. After several days the woman wept to gather up these skins, and found the plates covered with a layer of verdigrise. Thus the leavings of the wine-press became an ingredient in the manufactory of this substance, and M. MonTer Thows 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 astronomer relates here the obfervations of the spots of the fun, made by Galileo and Fabricius; the conclufions they drew from these observations to determine and ascertain the motion of rotation of that

:. We adopt this term, as it expresses happily the resemblance which certain fuids (whuse nature is yet but very imperfectly known) bear to aire

luminous

and the meid certain ble on accopothefis, make this

luminous body, and the methods chey proposed to render' this determination more easy and certain. He afterwards proposes his method, which he thinks preferable on account of its facility and fimplicity. He then gives us a new hypothesis, relative to the production of spots in the sun. He supposes that this great source of light is a kind of folid nucleus, covered with a Auid in fufion : this being the case, the points of the eminences of the nucleus are sometimes covered with this fuid, and sometimes uncovered, and less luminous than the matter in fufion; so that they in this latter cale exhibit the appearance of obscure fpors on the sun. This bypothesis is not entirely new; its principal idea is the same with that of M. De la Hire, who considered the spors in queftion as the eminences of a folid and permanent body, Aoating in the Ruid mass of which the fun is formed. Conjecture for conjecture ; that of Mr. Wilson is the most ingenious of the three; but as it is well known to our astronomical Readers, we need not mention it. M. De l'a LANDE terminates this Memoir by the examination of an effect of the folar rotation, which has not hitherto been con sidered by philosophers, but may one day (though it be not likely that we shall see it) become a remarkable phenomenon in cosmology : this supposed effect is a motion of translation, by which the sun changes more or less his place. But this local change is merely hypothetical ; it may be ascertained in some future period, by observations of the fixed stars. At present, it is only a mathematical opinion, founded on this supposition, that the motion of rotation being communicated to the sun by one single impulsion, must have affected its centre of gravity, and produced in it a progressive motion. All this may have been, and may not have been. If the impulsion 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 sure that this was not the case ?

Mem. II. Concerning the amplitude of the Sun at Setting, 6b. ferved at St. Sulpice. By M. Le MONNIER.-Observations of 'the total Eclipse of the Moon, the 30th of July, 1776.- Thele Obfervations are contained in several Memoirs, and were made fee parately at Paris, by Meffrs. De Fouchy, Le Monnier, Callini de Thury, Pingié, Bailli, Jeaurat, Mellier,—and Perinaldo, in the couniy of Nice, by M. Maraldi.

Observations on Écripjes of the Satellites of Jupiter, made in the Year 1776, at Perinaldo, in the County of Nice, with an Acromatic Telescope of three Fect. By M. MARALDI.- Obfervation on a dark Band, which appears on the Globe of Saturn. By M. MessieR.- Memoir, relative to the eleventh Comet, observed at Paris, from the Observatory of the Marine, from the 14th of : June, co the 3d of October, 1770. By the lame.

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· Memoir concerning a n: w Constellation. By M. LE MONNIER. This Astronomer observed, under the scales of libra, 2 void, which nobody hitherto thought of filling up. This void nevertheless contains stars often eclipsed by the moon, and which may confequently be of use, both in determining the Jongitudes, and in verifying the theory of the moon. Our Academician has determined the position of twenty-two of these stars, and has joined them in a constellation, which he calis the folitary, after a bird of the Indian seas, mencioned 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 Eclipses of the Sun, the Occultations of the fixed Stars and Planets by the Moon, &c. We have here only the 7th, 8th, and oth Articles of this Memoir, which fill 103 pages. The rest are reserved for the succeeding volume.

GEOGRAPHY New Considerations designed to prove, that Cape Circumcision really exists 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 ift of January, 1739, M. Bouvet, an eminent French navigator, discovered land, the situation of which he fixed at 54 deg. of Southeru latitude, and 28 deg.

of longitude, and which he called the Cape of the Circumcifioni Our immortal navigator Captain Cook, among his various researches, endeavoured to meet with this Cape, but could not find it. This, no doubt, was enough to form a presumption against its existence; M. LE MONNIER, therefore, endeavours to remove this presumption. He imagines, that M. Bouvet was mistaken in the longitude of the place in question, as the methods of finding the longitudes in his time were not exact. This being premised, he examines the declination of the needle observed at Cape Circumcision, by M. Bouvet, and comparing several observations of this kind, he inquires into the change of declination that has taken place since his time in those parts of the world. The result of his inquiry is, that at the time of Captain Cook's voyage, the declination of the needle at Cape Circumcision must have been 10 degrees towards the West; that the place where Captain Cook sought this Cape had a declipation of 13 deg. 1, and that this difference of 3 deg. į answers to 7 deg. of longitude. It is not therefore surprifing, according to M. Le Monnier's account, that the British navigator did not find this Cape, fince it is at 21 deg. { of longitude to the East of the Isle of Ferro, and not at 28 degrees, that it must be sought.

But with all due submission to the opinion of so learned a man as M. Le Monnier, we cannot help observing, that he seems to have laid inore stress on this argument than it can possibly bear :

for,

Sefll with in the Bracket) { was written by mu Wales

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for, to say nothing concerning the uncertainty of M. Bouvet's' inítruments and observations, neither of which, we apprehend, could be better depended on, than those of Captain Cook, and bis associates; we find that those of the latter were not capable of determining the variation to so small a quantity, as that which is so ftrenuoufly insisted on by 'M. Le Monnier, and consequently all arguments which are founded on a contrary sup, position must fall to the ground. For on consulting those ob. servations, we shall find, that barely putting the ship round, would make a difference of near 6 degrees in the variation by the same compass*; and, sometimes near jo degrees f. That the same compars, in the same fituation in every respect, but at two different times of the fame day, would give variations dife: fering from one another 4 and 5 degrees I. That the fame compass, on the same day, and in the hands of the same observer, will give 5 degrees difference in the variation on board the fame Thip when under fail, and when at anchor in a road stead . Again, compasses made by the same artift, on board different fhips ; but at the fame time of the day, differed 39, 40, and upwards in the variation. But, as a case more directly in point to the argument before us, we may observe that on February joth, 1774, in the latitude of 53° S. and longitude 263°É. when Captain Cook was returning northwards from the latitude of 71° S. Mr. Walcs found the variation to be 1597", and Mr. Clerke found it to be 15° 32' East q. But in crossing che Pacific Ocean from New Zealand to Cape Horn, on the uth of December afterwards, Mr. Wales, by the same two compasses, on board the same ship, and within a few miles of the fame place, had 9° 55' and 11° 31'**. These differences, feveral of which happened very near the place in question, are all of them at least equal to, most of them greater, and some of them almost double the difference of variation on which M. Le Monnier founds his argumente; and therefore, in our opi. nion, render it totally invalid. To allege that the instruments which were used for this purpose, in Captain Cook's voyage,

* See “ The original observations, made in the course of a voy, age towards the South Pole, and round the world" by W. Wales, F. R. S, and W. Bayley, p. 372, March aith, 1773.

of Ibid. p. 375. January 24th, 1774.

1 Ibid. p. 371. February 2d, 1773. and p. 382. January 19th, 1775.

Ibid. p. 385. July 14:h, 1775. Il Ibid p. 181, and 369. Aug. 30, gih, and Sept. 4th, 1772. , Also p. 182, and 371. January ina, and 14th, and February 7th, 1773.

See the same Obsesvasivas, p. 375 ** Ibid. p. , 81,

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