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of the muscle will remain after the amputation, than if the operation had been performed when the mufcle was contracted. It is, however, to be remarked, that of the mufcles which are placed on the two fides of the bone, thofe, on one fide, are contracted when the member is ftretched out, and dilated or diftended when the member is bent or folded; while thofe, on the other fide, are diftended when the member is stretched out, and contracted when it is folded or bent inward :-the confequence deducible from this, is, that the member must be ftretched out during the amputation of the former, and folded, contracted, or bent inward, during that of the latter. IV. A SECOND MEMOIR Relative to the Anatomy of Birds. By M. VICQ-D'AZYR.

In the first memoir, this ingenious Academician, who has formed a high idea of the importance of the anatomical obfervations that may be yet made upon the ftructure of birds, laid down the plan, which he continues to execute, fixed the genera or claffes that form the bafis of his refearches, indicated the new nomenclature, which he employs in his defcriptions, and divided into twenty-four regions, the different parts of the body of a bird. In the first memoir, he described the anterior thoracic region, the region of the clavicle or collar-bone, and that of the fhoulder-blade. In the second memoir, now before us, he examines the ftate of eleven regions, viz. the higher region of the fhoulder, the internal and external regions of the humerus, the internal and external regions of the cubitus, or that part which supplies the places of a fore-arm and hand, the fuperior region of the back and neck, the inferior region of the neck, the fuperior and lateral regions of the cranium or skull, the inferior region of the head, and that of the surface of the skin. Ten regions more are to be exhibited and described in a following memoir. The details contained in this memoit are certainly curious and interefting; and the mechanifm, that produces the various motions of the winged tribe, is displayed with great perfpicuity. It is more efpecially worthy of obfervation, that in comparing the mufcles and bones of birds, with thofe of the human fpecies, the analogies are found to be much greater, and more ftriking, than could have been expected confidering the little refemblance there is between the external forms of thefe two claffes. This fhews the beautiful uniformity that reigns in the great fcheme of nature, and that in orders of Being fo different: it is alfo a remarkable proof of final causes, when we confider, that the diverfities in this otherwife uniform plan, are exactly fuited to the nature, ftructure, and motions, that characterise each class.

CHYMISTRY.

CHYMISTRY.

MEMOIR I. New Obfervations on the Analysis of Crystals of Verdegrife and Salt of Lead, relative to the Air that is combined in thefe two Mixts, and confidered as one of their conflituent Principles,- -as alfo on a Copper and Saline Sublimate, which the Verdegrife yields in a certain Period of the Analyfis. By M. DE LASSONE.

The operation, by which the acetous fpirit, called Radical Vinegar, is obtained by diftilling verdegrife, or crystals of verdegrife, has been often repeated; but the phenomena which accompany this operation, have not, in the judgment of M. DE LASSONE, attracted fufficiently the attention of chymical obfervers. He had formed the defign of afcertaining the following fact, that during the diftillation of cryftals of verdegrife, and falt of lead, a fluid escapes, of the nature of those which the ancient chymifts called Gas, and to which the moderns give more commonly the appellation of Air; but as there escaped alfo, towards the end of the operation, acid vapours under a vifible form, it became neceffary to examine the refult of his diftillation, before the moment in which thefe vapours begin to appear. When M. DE LASSONE compared the weight of the product and refiduum of the diftillation, with the weight of the verdegrife that was employed in this experiment, he found that the latter was confiderably diminished, and that confequently a proportionable quantity of Gas had escaped, or difengaged itself in the operation.

By interrupting thus the diftillation at a certain period, our Academician obferved circumftantially and fully a fingular fact, which had been perceived before by fome chymifts, but in a curfory manner. The neck of the retort, employed in diftilling the cryftals of verdegrife, contained a folid, light, and white fubftance, which affumed a yellowish colour when it was expofed to the air. This fubftance, on examination, appears to be a copperish, volatile falt, entirely diffolvable in water;if the diftillation be continued, the acid vapours, highly concentrated, which pass towards the end of the operation, diffolve this falt and carry it along with them; and of confequence, the copperifh flowers are only to be obtained, when the diftillation is fufpended, the moment before the acid concentrated vapours appear under a white form.-Before this period of the operation, the radical vinegar contains no copper; it only begins to contain fome, when the copperifh flowers, carried along by the acid vapours, mix themfelves with this vinegar: if it is then rectified by a new diftillation, these flowers are no more fublimed, and therefore, a radical vinegar, exempt from copper, may be extracted from verdegrife: however, the radical vinegar, obtained by this procefs, cannot be looked upon as abfolutely

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pure before it is rectified.The copperifh flowers obferved by M. DE LASSONE, are cauftic in a very high degree, and may be confidered as a violent poifon.

MEMOIR II. Refearches concerning the Compofition of Flint-Glass, and the Means of giving it a higher Degree of Perfection. By M. MACQUER.

This ingenious Academician perceiving, that the difficulty of making flint-glafs, abfolutely difengaged from filaments, proceeded from the difficulty of blending together the two fubftances (calx of lead and fund) of which it is compofed, recommends the two following methods, as adapted to facilitate the union of thefe two fubitances. - Firft, to deprive the calx of lead, as far as is poffible, of the phlogifton, which adheres fo tenaciously to it for this inflammable principle, according to our Author, is the chief obstacle to the perfect union of this calx with fand; the second is, to give to the two fubftances, that are to be united in the compofition of the flint-glafs, the greateft poffible degrees of fluidity and mobility.-M. MACQUER thinks, that the first of thefe may be effectuated by combining the vitriolic acid with minium or red lead, and then expofing this compofition to the operation of fire to difengage from it the acid; and as to the fecond method, it is to be executed by mixing with the compofition a confiderable quantity of folvents. For the detail of the experiments that illuftrate this fubject, we must refer our Readers to the memoir itfelf.

MEMOIR III. Concerning fome New and fingular Phenomena produced by different Saline Mixts. By M. DE LASSONE.

This memoir contains the observation of a very fingular fubftance, a faline mixt, which is liquid and transparent, when cold-affumes a folid confiftence, when fpeedily exposed to a lively heat-is liquified anew in proportion as it cools-and paffes repeatedly through thefe alternatives, without being fubject to any alteration. This fubftance may be obtained, by mixing a folution of Epfom falt with lime-water, and every combination of calx, fixed alkali, and cream of tartar, has the fame property.

BOTANY.

MEMOIR I. Concerning the natural Claffifications, or Families of Plants, and more especially that of the Ranunculus. By M. A. L. DE JUSSIEU.

MEMOIR II, Concerning the Acacia of the Ancients, and fome other Trees in Senegal, which yield the reddish Gum, commonly called Gum Arabic. By M. ADAMSON.

ASTRONOMY.

MEMOIR I. New Analytical Methods for calculating Eclipfes of the Sun, the Occultations of the fixed Stars and Planets by the Moon, &c. XI. Memoir, in which the Equations demonstrated

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in the preceding Ones, are applied to the Solution of feveral Astronomical Problems. By M. DIONIS DU SEJOUR.

This laborious Academician goes on, indefatigably, in the execution of his immenfe plan, which is defigned to change the whole face of aftronomical science, and to render it more methodical, accurate, and easy, by fubftituting analytical in the place of graphical methods.

MEMOIR II. Concerning the Diminution of the Length of the Year. By M. BAILLI.

This truly learned and ingenious man is often expatiating in the regions of conjecture:-which may be, and undoubtedly is, one of the refpectable inconveniencies of extenfive genius, We could, however, wish to see fuch genius keeping more frequently in company with evidence. The diminution of the duration of the year is a knotty point, in physical astronomy. -Does the year really diminifh-fo that, at laft, the earth muft be united (reunited would Mr. Buffon fay) with the fun? Or is not the year rather fubject to alternative augmentation and diminution, fo that, at the term of a long period, the earth begins anew the fame motions? Or, finally, in cafe the year diminishes, what is the law, which this diminution follows? Thefe are questions, the folution of which requires á longer feries of obfervations, and a more improved theory than we can yet pretend to, and which is, therefore, referved for future generations. It is impoffible to come to any determination upon the fubject of this memoir, that is not merely conjectural: M. BAILLI does not, indeed, undertake to give us any thing but conjectures, attended with fome degree of probability. His conjectures, however, produce nothing but uncertainty and doubts, not only with refpect to the quantity of the diminution of the year, but even with refpect to the very exiflence of that diminution. He would be glad to fend the earth back to the fun, in order to make us believe the more cafily, that it was dafhed originally from thence, according to the romantic hypothefis of Buffon. The Hiftorian of the academy, in the account he gives of M. Bailli's memoir, expofes its emptinefs and nullity, with learning, judgment, and modefty.

III. and IV. Two MEMOIRS of Meffrs. CASSINI and Le MONNIER, defigned to determine the Variations in the Obliquity of the Ecliptic, contain aftronomical obfervations, tending to prove, that these variations, if they exist, do not amount to near a minute in a hundred years: fuch, at least, is the result of the obfervations made by M. Le Monnier, with the gnomon of Saint-Sulpice.

MEMOIR V. Concerning Horizontal Refractions at Sun-fetting. By M. LE MONNIER.

APP. Rev. Vol. Ixi.

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MEMOIR

MEMOIR VI. Containing a direct Method of determining Refractions, fo as to know, whether they are of equal Quantity in the Northern and Southern Parts of our Hemisphere at the jame Height, and whether the Variations, which they undergo, are uniform. By M. CASSINI DE THURY.

Five Memoirs, on Lunar Eclipfes-One on a Horizontal Eclipfe of the Sun. By M. MESSIER.- One on the Occultation of a Star in Gancer by the Moon, the 10th of February, 1773, by the fame.. One on the Conjunction of Jupiter with the Moon. By M. CASSINI DE THURY.- Remarks on the Tables of Halle on occafion of the laft Oppofition of Saturn. By M. LE MONNIER.

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Obfervation of the Dif appearances of Saturn's Ring, made at Ife Adam. By M. CASSINI DE THURY.Obfervation of Saturn's Ring, and its Dif appearances. By M. LE MONNIER. -Memoir concerning the Appearances of Saturn's Ring in the Years 1773 and 1774. By M. DE LA LANDE. Thefe three memoirs, more efpecially the two first, treat of an object of great importance in aftronomy, as it may tend to improve the theory of that famous ring, which is yet fo imperfect; and more efpecially, to inform us, whether its fituation is changed by the attraction of the Sun, that of Jupiter, or even by the attraction of Saturn's fatellites.

MEMOIR XIV. Concerning Comets. By M. DE LA LANDE: who threw the beaux and belles of Paris into a panic, by observing, that these bodies may fometimes come near the earth's orbit.

MEMOIR XV. Containing the Obfervations of two Comets, that appeared in the Year 1766. By M. MESSIER. MEMOIR XVI. Containing the Operations and Obfervations made on board the King's Frigate, the Flora, and in feveral Perts in Europe, Africa, and America, to afcertain the Accuracy of the Inftruments and Methods employed to determine the Longitudes at Sea, and to illuftrate other Points relative to Navigation. By Meffrs. DE BORDA, PINGRE, and DE VERDUN.

This important and curious memoir, which is not fufceptible of abridgement, deferves, in a very fingular manner, the attention of all those who have at heart the improvement of navigation and aftronomy. We fee, in this interefting piece, how far the art of navigation has been perfected, and how greatly the progrefs of aftronomy and natural philofophy has contributed to its improvement: but we fee here, at the fame time, its imperfections and defects, and the neceffity of a farther progress in thefe fciences in order to their removal.

MINERALOGY.

MEMOIR I. Concerning the Bafaltes, Part III. in which the Author (M. DESMAREST) treats of the Bafaltes of the Ancients,

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