Iithly, the fame earth decompounds fal ammoniac, and difengages from it the volatile alkali:-12thly, it also becomes at leaft, in part, by the means of calcination, diffolvable in water:-13thly, fixed air, if it be joined with calcined vegetable earth diffolved in water, will immediately occafion its precipitation. Now as all the properties of the vegetable earth, that we have here enumerated, are precifely the fame with those which characterise calcareous earth, and diftinguish it from all other earths yet known, it is not without reason that M. ACHARD confiders the vegetable and calcareous as one and the same earth.

From this our Academician proceeds to an account of seventeen experiments, which he made on animal earths; we fay earths, for it appears from these experiments that there are two kinds of animal earth, one which has all the properties of calcareous earth, another an alkaline earth, different from all those hitherto known. He examines the opinions of Meffrs. Buffon, Baumé, and Poerner, relative to animal and vegetable earths, refutes them with modefty and evidence, and concludes this memoir by the relation of an interefting experiment, that renders his refutation victorious and unanfwerable.

A Memoir concerning the Force with which folid Bodies adhere to Fluids, determining the Laws, by which that Force is directed, conformably both to the Nature of the Fluid and the Solid. By M. ACHARD. This piece is not fufceptible of any abridgment that would be intelligible without the twelve tables in which the ingenious Academician has placed, in order, the refult of his experiments.

A Supplement to the Memoir concerning the Topaz of Saxony. By M. MARGRAFF. This Academician had promifed to give a fuller account of the gelatinous matter, which he found in his operations on the Topaz of Saxony by the means either of falt of tartar or spirit of vitriol, and he relates here the different experiments he had made with this view. From these experiments it appears, that the gelatinous matter derives its origin from falt of tartar calcined, digefted with the vitriolic acid, and that it perhaps is united with a part of the calcined Topaz.

Concerning the Changeable Stone (otherwife called the Oculus Mundi). By M. GERHARD. The first naturalist, who spoke with precision of this fingular stone, and pointed out its diftinctive property of opacity in the air and tranfparence in water, was the celebrated Boyle. The greatest part of the German writers on Natural History have done little more than copy him; and one of them (Ihie) has given to this ftone the name of Hydrophanus, from the property already mentioned. Thefe authors had only feen detached fragments of the ftone in queftion, without knowing any thing of its natal bed; and this circumftance

circumftance rendered it fo rare, that one, about the fize of a pea, was fold in London for two hundred pounds. It is now known, that the cculus mundi is to be found in the mines i Hartz, and (as our Academician obferves) in fome places in Silefia. Baron Veltheim vice-captain, of the mines of Hartz, fent a fragment of it to M. Gerhard, which occafioned the experiments mentioned in this memoir, of which it will noc be amifs to prefent to the lovers of Natural History the following fummary:

*

The oculus mundi is folid and compact, and yet there are neither filaments, grains, nor any fort of foliation difcernible in it: When broken it refembles potter's earth, ftrongly baked, or fine China ware; when strack against steel, it does not give fire, fo that it is inferior in hardness to quartz, fint, and jafper; it rather approaches in its qualities to the aphi and the jade and its parts may be feparated with the knife. Though foft, it is fufceptible of a fine polish; thofe are so more efpecially whofe colour refembles ivory, and which are diftinguithed by fpots of a milky white: feveral of thefe ftones are of a greenish hue, variegated with white ftreaks, others between green and yellow, with ftraw-coloured fpots, others, again, brown; it is not yet known, with certainty, whether thefe colours are the effect of a metallic principle; our Author thinks it probable, from his having difcovered ferrugineous particles in the brownish Silefian Oculus Mundi. Its specific gravity is to that of water as two to one, or thereabouts, and it does not, when rubbed, become electric; nay, it acquires but a small degree of electricity, even by communication.

As to the natal bed and the manner of finding this ftone, Baron de Veltheim obferved to our Author, that it envelopes, in an opaque covering, the opal and the calcedonius of Iceland and the Ifles of Ferroe, and alfo the opals of Bavaria and Saxony, especially that kind which is diftinguished by the denomination of lapis piceus. In this form, its external afpect is grofs and porous, but its inner parts, which are contiguous to the opal or calcedonius which it covers, are more compact and of a finer grain. Sometimes alfo it is found in beds, among beds of the calcedonius, fo that the former appear milkwhite, and the latter greenifh or black. Befides the places already mentioned, the oculus mundi is found at Kosemutz, in the duchy of Nimpfch, and, in a ftill greater abundance, at Grache in the duchy of Munsterburg; it is in this latter district

Our Academician, we apprehend, is mistaken, when he fuppofes a refemblance between this stone and the jade, for the jade is much harder than the jafper.

that

that it appears in the form of an envelope to the green, yellow, and white chryfophrafus.

M. GERHARD made fixteen phyfical experiments on this fingular stone, and fome chymical ones. The results of the former are as follows: The oculus mundi or hydrophanus imbibes fluids like a fpunge, as appears from the increase of its weight, when it has been fometime, in water, and other experiments.-2. The fluids that diffolve fat or unctuous fubftances accelerate the transparence of this ftone; which fhews that it contains particles of this kind.-3. The inconfiderable fpecific gravity of the oculus mundi fhews that it is very fpungy and porous.-4. The pores, however, of this ftone must be very fmall, fince they admit no particle of the folid fubftances that have been diffolved in fluids.-5. The oculus mundi becomes tranfparent by the affiftance of fluids, exactly as paper and other fimilar bodies, when they have abforbed a fluid.-The rays of light are attracted by the fluid, which has entered in a large quantity; and the pores of the ftone, being thus widened, give the rays a paffage in right lines, and thus produce transparence.

The chymical experiments made on this ftone by M. GERHARD fhew, that it is compofed of earth of alum, of vitrificable earth and an unctuous matter, in fuch proportions, that the first of thefe, conftituent parts makes two-thirds of the whole:-from hence it appears, that the oculus mundi cannot belong either to the genus of quartz, or to thofe of flint, agate, onyx, jafper, or any other vitrificable ftone, but that it muft be placed in the claís of unctuous, aluminous ftones, formerly called argillaceous and apyri. These confiderations have led our Academician to confider the oculus mundi as a kind of fmectite, in which cafe its defcription would be smettis porofus, in aere opacus, in aqua pellucidus. There are many acute obfervations in this piece, which we must pafs over in filence, but which render it peculiarly worthy of the attention of Naturalifts.

An Extract of the Meteorological Obfervations made at Berlin in 1776. By M. BEGUELIN.

MATHEMATICS.

Concerning the Alteration of the mean Motions of the Planets. By M. de la Grange.

Solutions of fome Problems in Spherical Aftronomy, by the Means of Seriefes. By the fame.

Concerning the Ufe of continued Fractions in the integral Calculus. By the fame.

12

Concerning a Problem in plane Geometry, which is looked upon as difficult. By M. de CASTILLON. Nine plates, with figures, are given to illuftrate the folution of this problem.

Concerning

Concerning a new Property of Conic Sections. By the fame. A Memoir, containing, 1. Obfervations of the Occultations and Re-appearances of the Anfe of Saturn's Ring, in the Years 1773 and 1774.-2. Obfervations of feveral luminous Points frequently feen on the Anfe of the Ring, which justify a Conjecture that the Ring is an Earth, which has Inequalities.-3. Obfervations of the three Oppofitions of Saturn in 1773, 1774, and 1775, in order to afcertain the Place of that Planet.-4. A Chart of the apparent Courfe of Saturn, which represents the four Obfervations of the Occultations and Apparitions of the Anfæ. By M. MESSIER.

Extract of a Letter from M. Euler to M. Beguelin, dated in May 1778. This letter relates to firft numbers.

Extract of a Letter, written from Petersburg, by M. Fufs to M. Beguelin. June 1778. Relates to M. Euler's method of examining great numbers, in order to find whether or not they are firft numbers.

SPECULATIVE PHILOSOPHY.

Concerning the Immortality of the Soul, on the Principles of Natural Philofophy. By M. SULZER. Memoir III. Peace to the foul, and veneration to the memory of this excellent Philofopher, who being now got out of the region of doubt and conjecture, is gone to verify his fpeculations on immortality, and -videt quanta fub nocte jaceret noftra dies.-As for us, who regret his removal, and are yet to remain fome moments behind him, let us attend to the views that opened upon him, while he was paffing through this twilight of humanity. We gave an account * of his two former memoirs on this momentous fubject: this third memoir, is indeed, a production that comes from the dusky region of conjectures. In the two former, the Author produced inconteftible facts to prove that the foul is a substance, different from the animal body, and that it continues to exift entire, after the destruction of the body to which it had been united for fome time; but when he pushes his inquiries farther, he finds himself in the clouds. I am obliged, fays he, to descend into the night of the tomb, and to grope in the darkness. To comfort, however, both himself and his Readers, he defcants for a while on the innocence, pleasure, and utility of conjectures, and fhews, that the true philofopher ought not to reject these flender tapers in the unknown regions of truth, provided, in his dubious walk, he follows a route in which he cannot go totally aftray. I commend, fays he, the fage and modeft timidity of Locke, who never ventured to quit the thread of experience, to ascertain the folidity of the first principles of human knowledge: but I do not, on the other hand, blame the bolder fpirit of Leibnitz, who dared to foar higher. The

6

• See Vol. lviii. of the Monthly Review, p. 521.

English.

English philofopher refembles thofe ancient navigators, who, fearing to lofe fight of the land, fteered a fafe courfe along the coaft, but made no confiderable voyages. Leibnitz, like the adventurous Columbus, boldly left the coaft, and launched out into an immenfe ocean, with only analogy and logic for his compafs.'

Encouraged by this example, M. SULZER penetrates into the dark and unknown regions of the dead, to enquire what becomes, there, of that indeftructible fubftance, which we call the foul, after it has been obliged to quit the body to which it had united during life. This leads him to the third propofition that enters into the conftruction of his fyftem *, even that at death, which feparates the animated molecule from the animal body, all the fenfations and clear perceptions of the foul ceafe, and a lethargy enfues, during which, the foul feems to have loft all its activity, and to be reduced to the fate of an atom of dead matter. This our Author endeavours to prove firft by experience and obfervation, alleging the cafes of perfons drowned or fuffocated, who have been reftored to life; for if, in their cafe, even before the total feparation above mentioned, when the vital motions have ceased, all fenfation, and clear perceptions have been annihilated, how much more muft this effect take place, when the organs of fenfe are entirely deftroyed? This fact may be denied, and our Author himself, fome paragraphs after this, obferves, that it is not impoffible that the foul fhould think and act even after the deftruction of the animal body, though without consciousness: he acknowledges, alfo, that he has neither facts

The Reader will be pleafed to recollect that the firft of our Author's propofitions was, that the vifible animal body is only the cafe, cover or envelope of a more fubtile organized body, which is the feat of the foul, or, according to the Materialift, the foul itself.-This latter our Author calls the animated molécule-and that the fecond propofition was, that the fubtile body or animated molecule is indeftructible, and that the diffolution of the animal body only diffolves the union of the two bodies, without introducing any change in the organization of the animated molecule.See Monthly Review, Vol. lviii. page 522.

† It does not only feem a paradox, that the foul fhould be capable of thinking and acting, without a consciousness of its exerting these operations, or even of its existence, but M. SULZER himself calls it fuch, though he promifes to prove it on another occafion. The few hints he throws out here on this intricate fubject are, without doubt, ingenious. He thinks that confcioufnefs depends on the fenfations, or, in other words, is excited by fome modification of the mind produced by external objects, and that (what he calls) pure thought may exift without confcioufnefs. The cafes of mary, who often think juftly in long fits of abfence, favour this hypothefis, and our Author alleges feveral facts that render it plaufible.

M m

APP. Rev. Vol. Ix.

nor