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o it; a third fignified that fuch a difpofition is poffible; thefe, aken together, form the word intelligible: a fourth fign tranforms the adjective into the fubftantive, and a fifth, expreffing egation, completes the word required. M. LINGUET afterward propofed this question, "What do you understand by meaphyfical ideas?" which, being committed to writing, a young ady immediately anfwered on paper in the following terms,

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I understand the ideas of things which are independent of our enfes, which are beyond the reach of our fenfes, which make no impreffion on our fenfes, which cannot be perceived by our enfes." On reading this, we cannot help exclaiming with the poet: Labor omnia vincit improbus ! a maxim by none more forcibly illuftrated, than by the Abbé DE L'E'PÉE.

EXPERIMENTAL PHILOSOPHY.

Memoir I. Experiments performed with a view to determine whether the degree of heat of boiling water be fixed and invariable, independent of every accidental circumstance, except the pressure of the atmosphere. By M. ACHARD.

It has been generally fuppofed, that water and all other homogeneous fluids, when boiling, have acquired the greateft degree of heat which they can receive, provided the denfity of the atmosphere remains unaltered: for, if this be increased, it is known that boiling water becomes capable of a greater, and, if diminished, a lefs degree of heat. In order to examine how far this opinion is well founded, M. ACHARD tried the experiments here related, which, for the fake of greater accuracy, were all E made with diftilled water. From thefe trials, it appears that, of water boiling in a brass veffel, the heat, as expreffed by the thermometer, is confiderably diminished when a current of external air is permitted to act, either on the fides of the veffel, or on the furface of the water contained in it; and that this degree of heat, fo far from being fixed, undergoes an immediate change from the leaft motion of the air; and is varied in proportion to the force with which the air acts on it. But, of water boiling in a glafs veffel, the heat is fixed, and remains unaltered during the whole time of ebuilition, without being affected by a current of air, even when fuffered to act on the furface of the fluid. Hence M. ACHARD infers, that metals more eafily part with their heat than glass, and transmit it more readily to those bodies, which have lefs: this fact is confirmed by another experiment, in which the end of a small iron bar was immerfed in water boiling in a glass veffel, by which it was fo much deprived of heat, that the ebullition ceafed, but foon recommenced; and the mercury in the thermometer, fufpended in the veffel, rofe again to its former height on blowing against that end of the bar, which was above the surface of the water, the mercury fell 1-20th of a degree

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degree on Reaumur's fcale; but rofe again, as before, when this impulfe of the air was removed. The Academician alfo fous that the degrees of heat were different in water boiling in different veffels at the fame time, and in the fame fand-bath; and that its heat was greater in proportion to the intensity of that which the veffel containing it had received from the fire previous to its ebullition; but when once in this ftate, its diftance from the fire, if not fo great as to interrupt the boiling, produced no alteration in this refpect. It also appeared that, cæteris paribus, water acquired heat more flowly, and was longer in coming to a state of ebullition, in proportion as the mouth of the veffel exposed a greater furface of the fluid contained in it to the external air; and that, when the latter was excluded, the heat of boiling water was the fame, of whatever materials the veffels that contained it might be made.

Mem. II. Experiments made to ascertain whether any regular proportion prevails, between the times required for the cooling of heated bodies, and the denfities of the air in contact with them; ali whether there is any juch proportion between the fucceffive periods of time, in which a heated body, while cooling, parts with equal degrees of heat; and lastly, to determine the influence of the temperature of the air, with respect to the time in which heated bodies, in contact with it, lofe their acquired heat. By the fame. These experiments were very ingeniously contrived, and M. ACHARD has here given, in two tables, the refults of above thirteen hundred trials; but, though these were made with the utmost attention, he acknowleges that no fuch regular proportions as he had expected, are deducible from them.

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Mem. III. Experiments to afcertain the effects produced on et mospheric air, and on the feveral factitious airs, by the operation of flacking quick lime in them. By the fame. Fixed air was entirely! abforbed by this process, which had no effect at all on common, dephlogifticated, inflammable, and nitrous, air.

Mem. IV. Concerning Aneurifms. By M. WALTER. This ingenious anatomift here gives a minute defcription of the ftructure of the arteries, together with a concife hiftory of the dreadful diforder to which they are liable, accompanied with an account of four extraordinary cafes, illuftrated with plates, in which the difeafed parts are reprefented. M. WALTER obferves that he has never yet feen an inftance of an aneurism of the femoral artery, in which the branches, that form a communication between this and the collateral veffels, could be fufficiently dilated to carry on the circulation; but the reader will find a very curious cafe of this nature in the London Medical Journal, vol. VIII. in which, a true aneurism of the femoral artery, occafioned by a wound received very near it, was cured by compreffion; and, though the cavity of the artery was entirely obli

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ated, and all the symptoms of intercepted circulation enfued, The thefe foon diminished, and the patient was completely reEvered, and able to follow the daily labour of a husbandman ithout any inconvenience, except an obtufe fenfe of torpor in tione leg, and a little cedematous fwelling of it after long ftandg; which, however, always went off after lying a few hours bed.

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er Mem. V. On the Diseases of the Heart. By the fame. Under
pais title, M. WALTER comprehends all thofe diforders, which
cay fo affect the motion of the heart, as to stop or impede the
Operculation of the blood; and confiders thofe accidental cir-
theumftances in the fize and conformation of this vifcus, by which
laney may be produced. He obferves, that, in tall robuft per-
fons, it has fometimes been found remarkably fmall; and, on the
ontrary, very large, in perfons of lefs than the common ftature
trend ftrength. Its fize, however, is of little confequence, pro-
wided the greater blood-veffels, as the aorta, the pulmonary veins
and artery, have a due proportion to each other, but he fays he
has generally found that, in fmall hearts, there is less fat than in
shofe of a greater fize; that the mufcular fibres are relaxed, and
confequently the ventricles rather too large, in proportion to
the fize of the heart. Hence perfons of this defcription have
generally a very rapid pulfe, and are fubject to faintings and
Depalpitations. M. WALTER informs us, that he has feen two in-
ftances, in which the human heart was as large as that of an ox:
the firft was that of a man, of small ftature and of no extraordinary
ftrength, who died of a marafmus at very advanced age: the
greater blood-veffels were well proportioned to each other. The
fecond inftance was the heart of a very tall robuft mah of forty

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gas years of age, who had, during many years, been troubled with anxiety and palpitations, and fuffered extremely from them for fome days before his death; which was occafioned by an apoplexy. On diffection, the abdominal vifcera were found in a healthy ftate; but the lungs were filled with extravafated blood, and adhered to the pleura, though the thorax was remarkably large the cavity of the aorta, in the part whence the left carotid and fubclavian arteries branch off, was remarkably contracted, and that of the pulmonary artery greatly dilated. The anatomist also gives fome inftances, where nature has varied from her ufual forms, with refpect to the rife and courfe of the greater blood-veffels; but for the particulars of thefe, we must refer to the memoir and the plates by which it is illustrated. Sometimes, M. WALTER obferves, diforders are occafioned by offifications in the pericardium, or by too great a vifcidity of the fluid which it contains; fometimes, there are tumours on the heart itself; he gives an inftance of a fteatoma on the apex of that of a girl, who died of an apoplectic fit, and of a meliceris

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on the heart of an ox. Laftly, they may be derived from inflammation, either of the heart, or the pericardium: this is exemplified in the cafe of a middle-aged man, whofe pericardium was highly inflamed and filled with pus, which had not only corroded the iurface of the heart, but penetrated into its mul cular fibres.

Mem. VI. On the degrees of heat, which folutions of differents falts acquire in ebullition. By M. ACHARD. We have here the refults of eighteen experiments, of which the following are the moft important-common falt, when either decrepitated, or regenerated, thrown into boiling water, increafed its heat in proportion to the quantity of falt diffolved; but, when not decre pitated, it had an oppofite effect.-Glauber's falt, fedative falts, vitriolated tartar, prifmatic nitre, also increased the heat acquired by the water, but in a lefs degree than decrepitated common falt, and, fome of them, to no determinate point.-Sal ammoniacum, when only three drachms were added, diminished the heat of the water; but larger quantities ferved to increase it in a greater proportion than the decrepitated common fait-Calcined borax, Epfom falts, and felenite, diminished the hear, but in no regular proportion.-Vitriol of copper, and alium, did not alter it; but white vitriol and fugar of lead produced a diminution of heat, which continued to be the fame, whatever quantity of these falts was added to the water; that produced by the fugar of lead, was the moft confiderable.

Mem. VII. Experiments made to invefligate the proportion of the increase of a given volume of water, to the quantity of falts diffolved in it. By the lame. It has been afferted by many, that, when a faline fubftance is diffolved in water, the volume of the folu tion is lefs than the volume of the water, added to that of the falt before its being melted. Hence they maintain that a part of the falt, thus diffolved, is lodged in the interftices between the particles of the water, which will not increase in volume, till thefe are filled up. This opinion appearing doubtful, the indefatigable Academician was induced to examine it; and, by means of an apparatus ingeniously contrived, but not eafily defcribed without a plate,. he performed a confiderable number of experi ments, for this purpofe; by which it appears that, of Sal ammsniacum and of falt of tartar, fome part does infinuate itfelf into the pores of the water, without enlarging its bulk: yet that, in the folution of all other falts, the volume is increafed in proportion to the quantity diffolved. This increase was always more confiderable after, than before, the faturation of the water; except when the experiment was made with fedative falt, in which cafe, this circumftance made no difference refpecting the proportion in which the volume is increased.

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Mem. VIII. Meteorological Obfervations made at Berlin, in the year 1785. By M. DE BEGUELIN. For thefe, we must refer the curious reader to the volume.

MATHEMATICS.

Mem. I. Aftronomical and critical inquiries concerning the longitude of feveral places in India. Part I. By M. JEAN BERNOULLI. In preparing for the prefs an hiftorical and geographical defcription of India, this ingenious writer met with feveral circumftances that well deferve to be inveftigated; fome of which fall within his peculiar province as an aftronomer. Those which he propofes to confider in thefe memoirs, relate to Mr. Rennel's new map of Hindoftan, who has made the distance between the mouths of the Indus and the Ganges, two degrees and a quarter greater, and the breadth of the fouthern part of the peninfula, three quarters of a degree lefs, than former geographers. To ascertain whether Mr. Rennel be right in the latter of these alterations, M. BERNOULLI propofes, in this part of his memoir, to investigate the longitude of Goa, on the western coaft, in about fifteen degrees of latitude; for, he obferves, the longitude of that part of the eastern coaft, under the fame parallel, is pretty well known from the obfervations taken at Madras and Pondichery. For this purpose, he gives the obfervations on an eclipse of the moon, Dec. 21, 1684, taken, at Goa, by Father NOEL, a Jefuit; from which, compared with his own, at Paris, M. CASINI calculated the longitude of Goa to be 71° 25' weft from Paris this refult was adopted by the Academy of Sciences, and by M. D'ANVILLE, in his map. But, according to Father NOEL'S account, the beginning of the eclipfe was not diftinctly observed; for this reafon, M. BERNOULLI, by comparing this with other obfervations, has endeavoured to rectify any error, which might arife from that circumftance; but cannot make the longitude of Goa amount to more than 71° 26' from Paris, and therefore 75° 46′ from Greenwich; and, by the mean refult of his calculations, Goa is only 78° 8' from the former, and 73° 28′ from the latter meridian. Confequently, according to M. BERNOULLI, our English geographer, who makes it 74° 15' eaft from Greenwich, has committed an error of halt, or, more probably, of three quarters of a degree, and is wrong in thus diminishing the breadth of the peninfula. But, before the Academician prefumes to decide this point, he propofes to examine, in the second part of this memoir, the results of obfervations made at Goa, Rome, and Leipfic, on a lunar eclipfe in the year 1707.

Mem. II. Concerning an univerfal manner of integrating equations with partial differences of the first degree, when these are linear. By M. LE GRANGE. The method is very fhort and easy, and

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