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of the muscle will remain after the amputation, than if the operation had been performed when the muscle was contracted. It is, however, to be remarked, that of the muscles which are placed on the two sides of the bone, those, on one fide, are contracted when the member is ftretched out, and dilated or diftended when the member is bent or folded; while those, on the other side, are distended 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 Aretched 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. Vice-D'Azer. 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 structure of birds, laid down the plan, which he continues to execute, fixed the genera or classes that form the basis of his researches, indicated the new nomenclature, which he employs in his descriptions, 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 shoulder-blade. In the second memoir, now before us, he examines the state of eleven regions, viz. the higher region of the shoulder, 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 interesting, and the mechanism, that produces the various motions of the winged tribe, is displayed with great perspicuity. It is more especially worthy of observa. tion, that in comparing the muscles and bones of birds, with those of the human species, the analogies are found to be much greater, and more striking, thán could have been expected conlidering the little resemblance there is between the external forms of thele two clafles. This shews the beautiful uniformity that reigns in the great scheme of nature, and that in orders of Being so different: it is also a remarkable proof of final causes, when we consider, that the diversities in this otherwise uniform plan, are exactly suited to the nature, structure, and motions, that characterise each class.

CHYMISTRY.

CHYMISTRY. Memoir I. New Observations on the Analysis of Crystals of Ver

degrife and Salt of Lead, relative to the Air that is combined in these two Mixts, and considered as one of their conftituent Principles, -as also on a Copper and Saline Sublimate, which the Vere degrise yields in a certain Period of the Analysis. By M. DE LASSONE,

The operation, by which the acetous spirit, called Radical Vinegar, is obtained by distilling verdegrise, or crystals of verdegrise, has been often repeated ; but the phenomena which ac. company this operacion, have not, in the judgment of M. DE LASSONE, attracted sufficiently the attention of chymical observers. He had formed the design of ascertaining the following fact, that during the distillation of crystals of verdegrise, and falt of lead, a Auid escapes, of the nature of those which the ancient chymists called Gas, and to which the moderns give more commonly the appellation of Air ; but as there escaped also, towards the end of the operation, acid vapours under a visible form, it became necessary to examine the result of his distillation, before the moment in which these vapours begin to appear. When M. DE LASSONE compared the weight of the product and refiduum of the distillation, with the weight of the verdegrise that was employed in this experiment, he found that the latter was considerably diminished, and that consequently a proportionable quantity of Gas had escaped, or disengaged itself in the operation.

By interrapting thus the distillation at a certain period, our Academician observed circumstantially and fully a fingular fact, which had been perceived before by some chymifts, but in a cursory manner. The neck of the retort, employed in diftilling the crystals of verdegrise, contained a solid, light, and white substance, which assumed a yellowith colour when it was exposed to the air. This substance, on examination, appears to be a copperish, volatile falt, entirely diffolvable in water ;if the distillation be continued, the acid vapours, highly concentrated, which pass towards the end of the operation, diffolve this salt and carry it along with them; and of consequence, the copperith flowers are only to be obtained, when the distillation is suspended, 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 copperish flowers, carried along by the acid vapours, mix themselves with this vinegar: if it is then rectified by a new distillation, these flowers are no more subJimed, and therefore, a radical vinegar, exempt from copper, may be extracted from verdegrife: however, the radical vinegar, obtained by this process, cannot be looked upon as absolutely pure before it is rectified.---The copperith flowers observed M. De Lassone, are caustic in a very high degree, and inay be considered as a violent poison. Memoir II. Researches concerning the Composition of Flint-Glass,

and the Means of giving it a higher Degree of Perfektion. . By M. MACQUER.

This ingenious Academician perceiving, that the difficulty of making Aint-glass, absolutely disengaged from filaments, proceeded from the difficuliy of blending together the two substances (calx of lead and fund) of which it is composed, recommends the two following methods, as adapted to facilitate the union of these two lubitances. - First, to deprive the calx of lead, as far as is possible, of the phlogiston, which adheres so 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 substances, that are to be united in the composition of the Aint-glass, the greatest poffible degrees of Ruidity and mobility.-M. Macquer thinks, that the first of these may be effectuated by combining the vitriolic acid with minium or red lead, and then exposing this composition to the operation of fire to disengage from it the acid ; and as to the second method, it is to be executed by mixing with the composition a considerable quantity of solvents. For the detail of the experiments that illustrate this subject, we must refer our Readers to the memoir itself. MEMOIR III. Concerning fome New and fingular Phenomena pro

duced by different Saline Mixts. By M. De LASSONE. This memoir contains the observation of a very singular substance, a saline mixt, which is liquid and transparent, when cold-affumes a solid consistence, when speedily exposed to a lively heat-is liquified anew in proportion as it cools—and paffes repeatedly through these alternatives, without being subject to any alteration. This fubftance may be obtained, by mixing a folution of Epsom salt with lime-water, and every combination of calx, fixed alkali, and cream of tartar, has the fame property.

BOTANY. Memoir I. Concerning the natural Classifications, 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 some other Trees in Senegal, which yield the reddish Gum, commonly called Gum Arabic. By M. ADAMSON,

ASTRONOMY. Memoir I. New Analytical Methods for calculating Eclipses of

the Sun, the Occultations of the fixed Stars and Planets by the Moon, 86. XI. Memoir, in which the Equations demonstrated in the preceding Ones, are applied to the Solution of several Aftronomical Problems. By M. DIONIS DU SEJOUR.

This laborious Academician goes on, indefatigably, in the execution of his immense plan, which is designed to change the whole face of astronomical science, and to render it more methodical, accurate, and easy, by substituting analytical in the place of graphical methods. Memoir' II. Concerning the Diminution of the Length of the

Year. By M. BAILL!. This truly learned and ingenious man is often expatiating in the regions of conjecture:-which may be, and undoubtedly is, one of the respectable inconveniencies of extensive genius, We could, however, wish to see such 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 diminish-so that, at last, the earth must be united (reunited would Mr. Buffon say) with the sun ? Or is not the year rather subject to alternative augmentation and diminution, so that, at the term of a long period, the eartli begins anew the same motions ? Or, finally, in case the year diminishes, what is the law, which this diminution follows ? These are questions, the solution of which requires á longer series of observations, and a more improved theory than we can yet pretend to, and which is, therefore, reserved for future generations. It is impossible to come to any determination upon the subject of this memoir, that is not merely conjectural: M. Bailli does not, indeed, undertake to give us any thing but conjectures, attended with Come degree of probability. His conjectures, however, produce nothing but uncertainty and doubts, not only with respect to the quantity of the diminution of the year, but even with respect to che very existence of that diminution. He would be glad to send the carth back to the sun, in order to make us believe the more easily, that it was dashed originally from thence, according to the romantic hypothesis of Buffon. The Historian of the academy, in the account he gives of M. Bailli's memoir, exposes its emptiness and nullity, with learning, judgment, and modesty.

III. and IV. Two MEMOIRS of Meftrs. CASSINI and Le Monnier, designed to determine the Variations in the Obliquity of the Ecliptic, contain astronomical observations, tending to prove, that these variations, if they exist, do not amount to near a minute in a hundred years : such, at least, is the result of the observations made by M. Le Monnier, with the gnomon of Saint-Sulpice. MEMOIR V. Goncerning Horizontal Refractions at Sun-setting.

By M. LE MONNIER. APP. Rev. Vol. Ixi.

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MEMOIR

MEMOIR VI. Containing a direct Method of determining Reo

fractions, so 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 Eilipfes -- One on a Horizontal Eclipse

of the Sun. By M. MESSIER. — One on the Occultation of a · Star in Cancer 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 Hallo on occasion of the lasi Opposition of Saturn. By M.

LE MONNIER. Observation of the Dif appearances of Saturn's Ring, made ai

Ife Adam. By M. CASSINI DE Thury. Observation of Saturn's Ring, and its Dif- appearances.

By M. LE MONNIER.- Memoir. concerning the Appearances of Satura's Ring in the Years 1773 and 1774. By M. DE LA LANDE.

These three memoirs, more especially the two first, treat of an object of great importance in astronomy, as it may tend to improve the theory of that famous ring, which is yet so imperfect; and more especially, to inform us, whether its situation is changed by the attraction of the Sun, that of Jupiter, or even by the attraction of Saturn's satellites.

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 sometimes come near the earth's orbit. Memoir XV. Containing the Observations of two Comets, that

appeared in the Year 1766. By M. MessieR. MEMOIR. XVI. Containing the Operations and Observations made

on board the King's Frigate, the Flora, and in several Perts in Europe, Africa, and America, to ascertain the accuracy of the Instruments and Methods employed to determine the Longitudes at Sea, and to illustrate other Points relative to Navigation. By Messrs. De BordA, PINGRE, and De VERDUN.

This important and curious memoir, which is not fufceptible of abridgement, deserves, in a very singular manner, the attention of all those who have at heart the improvement of navigation and aftronomy. We fee, in this interesting piece, how far the art of navigation has been perfected, and how greatly the progress of astronomy and natural philosophy has contributed to its improvement: but we see here, at the same time, its imperfections and defects, and the necessity of a farther progress in these sciences in order to their removal.

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

and

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