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the Weft was on the increafing hand at that period. Since that time it has become ftationary and may; foon (conjectures our Hiftorian) affume a retrograde motion. He thinks, moreover, that the obfervations that have been made on this fubject feem to render it probable, that the extent of the variation of the needle is confined within the limits of an ofcillation of about 30 degrees.
Memoir III. Remarks on the Temperature of the Cellars of the Obfervatory. M. GENTIL, who went to India in 1760, carried with him three excellent thermometers, conftructed by Mr. Micheli, which, all three, marked in the cellars of the Obfervatory 10 degrees; he brought back one of them, which in the fame place marked 8 degrees, both in fummer and winter. In thefe obfervations, M. GENTIL compared the thermometer conftructed by M. Sigau de la Fond with that of Micheli, and found, that the former marked 9 degrees while the latter remained without variation at 8 deg. .
Memoir I. Concerning the Organs of the Circulation of the Blood in the Foetus. It is well known, that, at the instant of the paffage of the foetus to a state of existence independent on the mother, the circulation must undergo a remarkable change. In the foetus, the blood, which iffues from the placenta by a vein, is carried back to it by arteries: at the inftant of the birth, this vein and thefe arteries, which communicated with the placenta, are contracted, and grow almoft impervious, and the blood opens a new paffage into the lungs.-The queftion then is, by what difpofition of the organs can a change of this kind be effectuated in a little time, and without occafioning any disorder in the animal economy? The folution of this interefting queftion is here attempted by M. SABBATIER, in confequence of new and interefting obfervations on the Valve of Euftachius, and the Canalis arteriofus.
Memoir II. Concerning the Inequality in the Size or Capacity of the Cavities of the Heart and the Pulmonary Veffels. By M. SABBATIER. This diverfity of fize in the cavities of the heart (of which the right auricle is known to be of a larger capacity than the left) has been differently accounted for by different anatomifts. The various ways in which Helvetius, Michelotti, Senac, and Santorini, followed by Haller, explain this phenomenon, though all ingenious, do not fatisfy M. SABBATIER, who, after examining them with great attention, and fhewing the ftrong cbjections and difficulties to which they are fubject, propofes his own account of the matter. According to him, the cavities, which are found unequal in dead bodies, are entirely equal in living ones: but thofe cavities, which, at the moment of death, contain the greatest quantity of blood, and on which
the blood has exerted its last action, must acquire then, and by thefe means, a larger capacity. M. SABBATIER has illuftrated and confirmed his hypothefis by a multitude of experiments.
Memoir III. Concerning the Analogy between the Ufes and Structure of the Four Extremities in the Human Body and also in Quadrupeds. By M. VICQ D'AZYR.-We have here a new kind of comparative anatomy, in which the analogies and affinities between the different parts of the fame individual animal are confidered. If the obfervation of the structure of the fame parts in different kinds of animals open useful views to the anatomift, the confideration of the refemblance of different parts in the fame animal may have its utility; and our learned Academician has, certainly, an uncommon talent for this line of inveftigation. In this Memoir he compares the fuperior extremities of the human body with the inferior, and the anterior extremities of different kinds of quadrupeds with the pofterior. Under this point of view he examines their bones, muscles, and veffels, and obferves every where ftriking refemblances and diverfities, which feem, in general, to depend upon the different functions which thefe extremities are defigned to perform. Thus the thigh, the leg, and the foot, in the human body, refemble the arm, the fore-arm, and the hand; fo that, with fmall variations of their pofition and fhape, they may be brought to perform fimilar functions, and to execute all the motions neceffary for the defence and nourishment of man, and the labours required in the different arts. The fame thing is obfervable in the animal kinds, where the refemblance is ftill more perfect, because the functions of their members are lefs diverfified. The anatomical details into which our Academician enters, in order to point out these interesting analogies, fuch as his accurate parallels between the bones, mufcles, nerves, and veffels that compofe the extremities in queftion, are certainly inftructive, and render the matter palpable enough. And this business may be rendered intelligible even to the vulgar, by the analogy between a kick and a cuff,-by the Jack-Pudding who walks upon his hands, and by the man whom we have feen writing Italian hand with his foot. The conclufion of our Academician is just with refpect to the economy and fimplicity that reign amidst the diverfified operations of nature. In this new kind of comparative anatomy, as well as in the other, we obferve (fays be) the two characters that NATURE feems to have stamped upon all beings, that of STABILITY in the type (or original form), and VARIETY in the modifications it undergoes. She (i. e. Nature) feems to have formed the different kinds of beings, and their correfpondent parts, upon one and the fame plan, which fhe has developed in an infinite variety of modifications, as he directs all the motions of the celeftial bodies by one, and the
fame force, whofe effect, varying according to their respective distances, produces all the phenomena which they exhibit to our obfervation.' Such is the conclufion of M. Du VICQ: and we take the liberty of concluding farther from from this, that Nature is a very fenfible lady, and, if fhe does the bufinefs of herfelf, deferves at leaft, the honours of a Goddess; and then we hall not difpute with the Atheist about the gender.
Memoir I. Concerning the Calcination of Tin in clofed Veffels, and the Caufe of the Augmentation of the Weight which this Metal acquires during that Operation. The defign of M. LAVOISIER, in this Memoir, is to prove, by direct and fatisfactory experiments, that the weight which metals are known to acquire by calcination is owing to the addition of air. Having calcined tin in retorts, hermetically fealed, after having weighed accurately both the tin and the retort, Mr. L. perceived, that in a certain space of time the calcination ceased; and that, though he continued the fire, he could not carry it on any farther he then suspended the operation, and, weighing his retort before he opened it, he found that the weight of the whole had not changed at length, opening the retort, he weighed the tin, whose weight he found augmented to the amount of fome grains, while the retort, weighed feparately, had the fame weight as before the operation: the real augmentation of the weight of the tin was therefore derived from the addition of the air fhut up in the retort, fince neither the weight of the whole together, nor the weight of the retort had at all changed. The calcination of metals does not therefore confift (concludes M. Lavoifier) only in the feparation of their phlogifton from their earth; this calcination is accompanied with a new combination of their earth with the air; the air is not only a mechanical, but is moreover a chemical agent in this operation, combining itself with the metallic earth, and difengaging from it the phlogiston.
Memoir II. Concerning a fixed Alkali, drawn from the Lixivium of the Kali. By M. CADET.
Memoir III. Concerning a new Method of compofing Vitriolic Ether in greater Abundance, with more Facility, and lefs Expence, than by the Method that has been hitherto obferved. By the fame. The like quantity of spirit of wine in this new method produces a much greater quantity of the ether, than in the method hitherto practifed. The new method confifts in re-diftilling new fpirit of wine a great number of times on the fame acid. This operation may be repeated without any damage to the veffels: there must only be a glafs ftopple in the upper part of the retort, which must be carefully luted during the operation, and be taken out in order to pour in new fpirit of wine. For a circumftantial defcription of this method, we must refer the Reader to
the work itself; one of the principal advantages of the operation of M. CADET is, that its refidue, which the chemifts ufually throw away, is the matter that is capable of yielding the moft ether. It is certainly a valuable difcovery to have hit upon a method of producing, without any augmentation of expence, from fix to nine times the quantity of Ether that the ordinary method yields.
NATURAL HISTORY OF ANIMALS.
III. Memoir. Concerning the Anatomy of Birds, by M. Vico D'AZYR. We have here the conclufion of this Academician's labours on the bones and muscles of birds. In the two preceding Memoirs he had gone through 14 of the 24 regions into which (as we formerly obferved) he divides the ftructure of that clafs of animals. The ten remaining regions, through which the ingenious Academician travels in this Memoir, arethe abdomen-the external and internal regions of the ilium, the anus, the tail, and the thigh,-the anterior and pofterior regions of the leg, the fuperior and inferior regions of the foot, and the region of the intercoftal fpaces. He follows his plan here, as in the preceding Memoirs, pointing out the analogy between the ftructure of the parts in a bird and a human body; fhewing how the fame parts are differently modified in different kinds of birds; and, above all, obferving with what admirable wisdom the form and pofition of each part are adapted to their refpective functions and deftination. He fhews, among other examples every way proper to illuftrate the doctrine of final caufes, that the extreme length of that part in the ftructure of a bird which answers to the metatarfus in the human body, is abfolutely neceffary to prevent the fernum from trailing on the ground that the arrangement of its pofterior parts is precisely fuch as is requifite in order to the expansion of its wings; and that the mechanifm by which the bird can augment or diminish, at pleasure, the volume of its body, diftribute through its various parts the air which it breathes, and thus change its specific weight, and diverfify its center of gravity, is admirably contrived for thefe purposes. Our Academician unfolds the nature and powers of this mechanism in an ample and circumftantial detail; and confirms, by new elucidations, the exiftence and ufes of the air that fills the bones of the animals in queftion. This latter fact was first conjectured by Aquapendente, and has been fince proved by Profeffor Camper, whofe laborious and fuccefsful researches entitle him to an eminent rank among the anatomifts of our time.
* See the Appendix to the 61ft volume of the Monthly Review, P. 494.
Memoir. Concerning Gritt-ftones in general, and thofe of Foritainbleau in particular. By M. de LASSONE. This is to be followed by a series of Memoirs on the fame fubject. We fhall lay before our Readers a general view and refult of the whole when they are all published. The difcovery of crystallized gritts, first made by this Academician at Fontainbleau, opens a new field for researches. But when fhall we know any thing of the principles and mechanism of cryftallization? Ignoramus. ASTRONOM Y.
Memoir I. A CONTINUATION of the Application of New Analytical Methods of calculating Eclipfes of the Sun, the Occultations of Fixed Stars and Planets by the Moon, &c. By M. DIONIS DU SEJOUR.
Memoir II. Researches concerning the fecular Equations of the Motions of the Nodes and of the Inclinations of the Orbits of the Planets. By M. DE LA GRANGE. This Memoir contains a new theory of the motions of the nodes and of the variations in the inclinations of the orbits of the planets; as alfo, the application of this theory to each of the fix principal planets. The aftronomical Reader will here find general canons, by which the abfolute pofition of these orbits, in any given time, may be determined, and, consequently, the true laws and principles of the changes to which the planes of thefe orbits are fubject, be diftinctly known. Our Academician feems very defirous that aftronomers should make use of these canons, as he thinks they may be of great use in accounting for the little agreement there is between ancient and modern obfervations. The canons that have been already given by other authors, for this purpose, are insufficient, as they only reprefent the differential variations of the places of the nodes and inclinations, and therefore, after a certain number of years, ceafe to be accurate; whereas the canons of M. DE LA GRANGE may extend to any number of years whatever. This Memoir contains alfo Tables of the fecular variations of the obliquity of the ecliptic, and of the length of the tropical year, with the neceffary canons for calculating the fecular variations of the fixed ftars in longitude and latitude: thefe Tables take in the extent of twenty centuries before and after 1760.-There are allo 14 other Memoirs on aftronomical subjects, by Meffrs. MONNIER, MARALDI, BORDA, DU SEJOUR, MESSIER, CASSINI the younger, and LE GENTIL.
The Memoir of the Academy of Montpellier (which is annually fubjoined to the volume of the Academy of Sciences of Paris) contains alfo Aftronomical Obfervations made by Meffrs. DE RATTE and POITEVIN.