cryftals after diffolution and evaporation. This was the opnion of Geoffroy, which is maintained likewife by the intelligent and more modern authors of the Encyclopedie: and Cartheufer denies even the existence of any native ammoniacal falt whatever. Nunquam,' fays he, fal ammoniacum nativum, vulgari fimile, in ullo terrarum angulo repertum fuit, &c.' We shall give fome of the leading characters by which the Author eftablishes its existence at Solfatara; leaving to the philofophical chemifts to discover the particular origin of its volatile alcaline principle. We fhall only ftop to hint, that we have observed fome modern chemifts naming certain foffile fubftances as capable of furnishing it, by the affiftance of fire, without the admixture of any animal or vegetable matter; particularly foffile coal; cretaceous, calcareous, and other earths mixed with pyrites, or the marine acid; and even iron: any or all of which may be fupposed to exift in this place. An inquiry into the manner in which fal ammoniac is produced by nature, is not a matter of mere curiofity, but of importance fufficient to deferve the attention of the practical chemift, as well as of the philofopher : as will readily be acknowledged by those who are acquainted with the many ineffectual attempts, which have been made in this kingdom, to produce the true fal ammoniac, at a lefs expence than that at which it is procured from Egypt.-But to return to the Author's proof of the identity of the native and factitious falt. The falt of Solfatara fublimes into the pots, in the form of needles. It affects the tongue with a brifk, acrid tafte, exactly fimilar to that of the common fal ammoniac. In the act of dif folution in water, it produces a degree of cold even fuperior, as the academicians at Naples affirm, to that caufed by the lastmentioned falt. The folution, after evaporation, shoots into fimilar vegetations. Like it, this falt being laid on a red-hot coal, is entirely diffipated, without any previous fufion; and the vapour strikes the nose with the peculiar pungency of the volatile alcali. Finally, the Author having added fome foffil fixed alcali to a folution of this falt, the fame volatile alcaline vapour arofe; and having evaporated the liquor, he obtained cubical chryftals, as well as others of a different figure; but which were both true fea-falt, formed by the union of the marine acid with the fixed alcali which had taken the place of the volatile alcali. This native falt therefore contains, according to the Author, a volatile alcali combined with the marine acid, and therefore differs not from the true fal ammoniac. He might, however, have placed the truth of this conclufion out of all doubt, had he actually collected the volatile alcaii, by the well known process by which it is procured from the true sal ammoniac; and by other experiments might have difcovered whether L14 any any other fubftances are combined with thefe two principles befides fome which he mentions, and which have poffibly contributed fo long to difguife its true nature. MEMOIR IV. Obfervations on a coal-mine, which has continued burning for a long time paft. By the fame. Our own country furnishes many inftances of this kind. The mine, which is the fubject of this memoir, is fituated at St, Genis, near the city of St. Etienne in France, and has been on fire for the space of 100 years paft. The ground is burnt to a confiderable extent, and in different parts of it are fpiracles, or openings, through which a hot vifible vapour afcends in the day, and a flame is faid to be fometimes perceived rifing in the night; the heat at all times being fufficient to be employed in fome articles of the cookery of the neighbouring peafants. The Author relates fome ineffectual and ridiculous attempts which have been made to extinguish this fire, by cutting trenches round it; and a propofal of extinguifhing it by water. He apprehends danger to the neighbouring cities of Chambon and St, Etienne, from the progrefs of this undermining fire, in a coun try where the vein of coal is very rich and extenfive; and proposes the ftopping up all the communications with the external air, as one of the most probable means to extinguish it. MEMOIR V. Botanical and meteorological obfervations made at Denainvilliers, in the Year 1764. By M. Du Hamel. We find nothing obfervable in this meteorological journal; nor, for the fame reason, shall we make any extract from fome fhort phyfical obfervations, with which this clafs is terminated. ANATOMY. MEMOIR I. and II. On the circulation of the blood in the liver of the foetus. Second and third memoirs. By M. Bertin. In the memoirs for the year 1753, M. Bertin first proposed his new theory on this fubject. He endeavoured to prove, in oppofition to the opinion of the most celebrated anatomists, that the liver of the foetus, in utero, receives the greatest part of its blood from the umbilical vein; that this vein forms two branches, one of which enters into the vena cava, and the other into the vena porta; and that the blood moves in this vein through the liver from the left to the right hand, though, according to the common opinion, it is fuppofed to follow a contrary direction: but that, at the inftant of birth, on the ligature of the umbilical chord, the umbilical vein lofing its former office, the blood in the vena porta turns back, in order to enter into the veffels of the umbilical vein, which it fills by a communication established between them, and in which the blood afterwards flows, till the death of the subject, in a di rection reation abfolutely contrary to that which it followed in the fetus, or from right to left *. In this fecond memoir the Author further profecutes this fubject, and with great anatomical precifion describes the course of the hepatic veins, and particularly certain branches or canals, hitherto unknown to anatomifts, which he has difcovered, and which form an immediate communication between thefe veins and the branches of the vena porta or the umbilicalis. He draws feveral confequences from this ftructure, and indicates the refources which nature has by these means provided, with regard to the disorders of the liver. Of these communicating canals, which are from 2 to 5 lines in length, and about a line in diameter, the Author has conftantly discovered 4, 5, and sometimes 6, in different fubjects but he is confident that their number is much larger. By their means, he obferves, we may easily conceive in what manner the circulation is carried on, for feveral years, in the liver, although its glandular fubftance be obftructed, and become hard, or nearly schirrous, and when the motion of the blood through the capillary anaflomofes is, by these means, entirely fuppreffed, He concludes with this confolatory reflection, that on this dif covery of these larger anaftomofes, or communicating canals, we may hereafter treat the disorders of the liver arifing from these obftructions, with greater and better founded hopes of fuccefs. In the third memoir M. Bertin returns to the confideration of the manner in which the circulation is carried on, in the live of the fœtus, before and after its birth: but a relation of the Author's minute enquiries into the structure and difpofition of the veffels concerned; their different capacities; the refpective velocities of the blood flowing through them, and many other objects by which he endeavours to establish his theory, would lead us too far into a subject, interefting only to a few; to whom, befides, we could not render our account intelligible, within the compafs which we can allot to an article of this pature. MEMOIR III. Obfervations on an aneurism attended with fome pery fingular circumflances. By M. Petit. J The relation of rare cafes or events in medicine and furgery is undoubtedly of ufe; efpecially when the fymptoms, or the appearances on diffection, lead to a knowledge of the nature of the difeafe, and indicate the proper method of treating it, or put us on our guard against its bad effects. Although the fingularity of fuch cafes affords a prefumption that, as they have feldom been obferved, they will probably feldom occur; yet the very infrequency, which renders them fingular, renders the * Hiftoire de l'Acad. 1753, Page 487, Edit. in 12mo, know knowledge of them more ufeful to the practitioner, who may happen to meet with an inftance of a fimilar nature, and may happily avail himself of the lights held out to him, by a preceding obferver, on a cafe totally new to him. For thefe reafons we fhall endeavour to give the fubftance of the present article; not only as containing a phyfiological curiofity, but as it prefents us with a view of a fituation attended with the moft imminent danger, without carrying the leaft appearance of it. M. Veillard perceived a fmall tumor under his right jaw, which in three months had acquired the fize of a pigeon's egg, and which, from its pulfation and other evident fymptoms, was pronounced, by M. Petit and others confulted, to be a true aneurifm, formed in the trunk of the right carotid artery, where it feparates into its two principal branches. Frequent bleedings and a most exact regimen were prefcribed, and the utmost tranquillity both of mind and body earnestly recommended to the patient. In this courfe he perfifted three months; when the tumor was reduced to half its fize. He now therefore gave up all attention to regimen: nevertheless the tumor continued to diminish, and finally disappeared; leaving no other inconveniencies than a difficulty or ftammering in his fpeech, an habitual flux of faliva, and an inability to put his tongue out of his mouth. In this ftate the patient lived feven years, and was carried off, after appearing for three or four days like a perfon who was drunk, by a fit of an apoplexy, immediately caused by a rupture of fome of the blood-veffels of the brain; but whose remote caufe appears, from the Author's account, to have had its origin above feven years before: the aneurism having only been the first visible effect of it. On diffection, the cavity of the right carotid artery was found to be intirely obliterated, and its large trunk converted into a ligament of 2 lines diameter, from the place of its origin out of the fubclavian, to the feat of the tumor; which was become likewise a very small, hard knot, without any cavity. But another aneurismal tumor, full of hardened blood and a fatty matter, (the existence of which the Author could not before even fufpect) was discovered at the lowest part of the carotid, where it fprings from the subclavian; by the enlarged capacity of which, and the confequent diminution of the motion of the blood, he accounts for the gradual obliteration of the whole cavity of the artery above it. After this accident, all the blood which was fent into the head was obliged to pafs only through the left carotid and its branches; except a fmall part of it which would enter the correfpondent branches of the right carotid, by the well known anastomoses between them; where it would move in a kind of retrograde courfe down towards the main trunk; finding the paffage of which abfolutely clofed, it would naturally diftend diftend all the branches above it, at the place of their conflux, and form the aneurifmal tumor firft obferved under the jaw; which may be confidered as a cul-de-fac, the blood contained in which must foon ftagnate, gradually part with its ferum in the adjacent cellular membrane, diminish in bulk, and finally in great measure be expelled by the natural elasticity of the coats of the arteries; which would afterwards grow together, and form the little knot which was found, on diffection, in the place where the aneurism had formerly been obferved. Thus the first aneurismal tumor was only a confequence of the concealed aneurifm below it, and did not appear till the trunk of the right carotid had been actually clofed up, by the caufes affigned. The Author more eafily accounts for the other fymptoms. The blood flowing flowly and with difficulty through the abovementioned numerous and fmall anaflomofes, parted with a greater proportion of its ferocity in the neighbourhood of the falival glands, and thereby increased the quantity of their dif charge. To the fame retarded motion of the blood he attributes the difficulty of fpeech, and the patients inability to put his tongue out of his mouth as it is neceffary to the proper action of a mufcle, that the blood fhould have a free course through it. The cause of the laft and fatal fymptom is ftill more evident. On the obliteration of the trunk of the right carotid, the left now carried nearly all the blood which had formerly flowed through both thefe arteries. Its trunk and branches were accordingly found confiderably diftended; and as the coats of thefe branches, as foon as they enter the skull, become as thin and weak as even those of the veins in other parts of the body, it is not wonderful that, being ftill further dilated and weakened by the increafed quantity of the blood, they fhould at laft yield to its diftending force, and burft, and overflow the brain. Under thefe circumstances, the life of M. Vieillard, during fix or feven years, may be faid to have hung by a fingle thread; and it is rather wonderful that that thread did not fnap much fooner. The principal practical inference which we would draw from this cafe (on which we have been thus particular, that we might make ourfelves understood) is that, fhould a fimilar cafe occur, the furgeon fhould not be lulled into a state of fecurity, dangerous and perhaps fatal to the patient, by the deceitful difappearance or diminution of a fimilar aneurism of the carotid artery: as it appears from hence at least highly probable that, in fuch a cafe, the artery is become actually impervious, and the patient's life in the utmost danger from that circumftance, at the very time when all apprehenfions of danger are vanished, in confe quence |