ation was too small for obfervation. M. TOALDO has not been difcouraged by this decifion of his learned friend; and the important feries of barometrical obfervations, and reasonings founded on them, which is contained in this Memoir, fhews that the barometer indicates the alteration in question.

Obfervations on the Bobak of Poland, and a Hiftory of this Quadrupede, fent to the Academy. By M. J. B. DUBOIS, Counsellor to his Polish Majefty. M du BUFFON claffes this animal (whofe kind abounds in the Ukraine) with the Marmottes; our Academician, better informed, thinks that it comes nearer to the clafs of rabbits. His defcription of the animal is circumftantial and curious. We fhall only mention the following particularities it often happens that three or four of the habitations of the Bobaks are comprehended within the space of a fquare fathom: their holes are deep and perpendicular: each is occupied only by a male and female: but it frequently happens that nine or ten couples fix their dwellings near each other, and form a kind of republic. Sometimes this neighbourhood is a model of union and concord ;-this is, however, but rare; for it is much more frequently the centre of disturbances, civil commotions, and bloody wars (juft as it is among us): there are remarkable diversities of character among thefe animals, which deftroy that natural equality that might be expected among uncivilized beings. Some are active,-fome negligent, fome ambitious;-but thofe who difcover laziness in the feafon of labour, are loaded with fevere talks, and diftinguished by public marks of ignominy; they are treated like flaves: they are laid upon their backs; loads of herbs, plants, and provifions are placed on their bellies, which they hold faft with their paws; and thus they are drawn by the tail, to holes, where their burthens are to be unloaded. (Would it were fo among us!) The Bobaks never go out of their holes, either to amufe themselves or to feek for provifions, without placing a fentry on an eminence or hillock, to warn them of the approach of danger. This fentinel, when he fees any one coming, raises himself on his hinder-feet, and whiftles; on which signal all the ftragglers fave themselves in their holes, and remain there. till the danger is paft.

After having given a lift of the Printed Works, Manufcripts, Machines, and Inventions, that were prefented to the Academy during the courfe of the year 1778; M. FORMEY concludes the hiftorical part of this volume by a curious Eulogy on M. JOHN HENRY LAMBERT, a Stay-maker's fon, born at Malhaufen, in the Upper-Alfatia, 1728; who, notwithstanding the defects of a poor education, his being bred to his father's trade, his unpleafing perfon, his rough and ungracious manners, and almost every thing inelegant and difagreeable in his external appearance, rofe to the honourable rank of Academician, and

was,

was, indeed, one of the moft able members of the Berlin Academy, in the mathematical Inie.

EXPERIMENTAL PHILOSOPHY.

I. Memoir. Experiments made on a Kind of Earth, which remains in the laft Lixivium of common Salt, or on the Bafts of bitter Salt, fo far as is relative to the Property it has to render other Earths fufible. By M. MARGRAFF.

II. Memoir. Concerning the Dephlogistication of phlogisticated Air. By M. ACHARD. First Memoir.-It is well known, that the elementary air (by which is meant the air of the atmofphere, difengaged from all the heterogeneous particles that it contains) is capable of uniting itfelf with different fubftances, diffolves, with facility, the phlogifton, with which it has a great affinity, and from its union with which it becomes what we call phlogifticated air. The phlogifton, according to our Academician, having fuch an affinity with the air, is always more or less charged or impregnated with it; and the dephlogistication of the air is an important object of the inquiries of the Naturalift, as dephlogifticated air is of all others the most proper for refpiration, and its mixture with the air that has been corrupted by animal breath, or other caufes, removes the noxious qualities of fuch air, and reftores its falubrity. On the other hand, the production of dephlogifticated air, which is directly drawn from bodies, is fubject to many difficulties, and becomes expenfive by the fmall portions of it that are attainable. Thefe confiderations induced M. ACHARD to make a great number of experiments in order to feparate the phlogifton from the air which is charged with it: many proved unsuccessful; but he obtained his purpose at length, by the detonation of nitre, or, in other words, by the detonation of phlogifticated air tranfmitted through melted nitre, with the nitrous acid. Thefe experiments, which he made fucceffively with phlogifticated, fixed, corrupted, and inflammable air, verified his conjectures; they fhew, that the affinity of the phlogifton with the nitrous acid, warmed to a degree which makes the nitre boil, is greater than its affinity with the air, from which it (the nitrous acid) ditengages the phlogifton: and this circumftance is every way adapted to furnish new ideas with respect to the compofition of different kinds of air.

Among feveral other principles and facts, that refult from the experiments and obfervations contained in this Memoir, we fhall enumerate the following:-all bodies, fufceptible of evaporation, by degrees of heat, natural or artificial, combine with and diffolve in air. When the heat, neceffary to unite air with certain bodies, ceafes, the air feparates itself only from a part of the fubftance, which it has diffolved, and always retains a certain qua tity of it, which is fmall in proportion to the degree of the diminution of the heat. Inflammable air is not decompounded,

like nitrous air, by the addition of a kind of air, which, not being faturated with the phlogifton, may ftill admit a farther portion of it, because the affinity of the phlogifion with inflammable air, and its acid, furpaffes that of the phlogifton with elementary air. Therefore dephlogifticated air, which receives the phlogiston with the utmoft facility, does not diminish the volume of inflammable air, and augments its inflammability, inftead of leffening it.

In a following Memoir M. ACHARD intends to communicate feveral remarks on dephlogisticated air, with various experiments tending to indicate more clearly its nature, and to render its application ufeful. He propofes alfo to answer fome objections that may be made to his experiments, and more particularly, one, that at first fight appears plaufible; he means the objection of those who may attribute the change of the air, which he tranfmitted through melted nitre, not to the decompofition of that air, but to its mixture with the dephlogifticated air, which escapes from the nitre, while it is in fufion.

III. Memoir. Concerning the Manner of calming the Agitation of a Part of the Surface of a Fluid, either by the Affufion of a Fluid fpecifically lighter, and of fuch a Nature as not to mix with the agitated Fluid, or by applying to the Surface of this latter Fluid a folid Body of lefs Specific gravity. By the fame. The first object that employs M. Achard in this Memoir, is to afcertain the fact, that oil has the property of calming or diminishing the agitation of the fea. The experiments he made for this purpofe afcertain the fact, fo far as to prove that the force, which produces the undulatory motion, continuing the fame, that motion will be lefs when oil is poured upon the water, than when it is not. But our Academician thinks, that the obfervations and accounts of the mariners, relative to this fact, are chargeable with exaggeration. It appears incredible to him, that fuch fmall quantities of oil, as they fometimes mention, fhould produce any palpable effect on a furface fo confiderable, as that part of the fea which furrounds a fhip: and even fuppofing (adds he) that this was poffible, for a moment, yet it must be confidered, that, as the motion of the fhip is not exactly fimilar and correspondent to that of the water, the oil must be quickly carried to a confiderable diftance, and confequently become incapable of producing any continued effect on the water, which is contiguous to the fhip.- So much for the fact. The caufe, that operates in its production, is the next object of the experiments and obfervations of our ingenious Academician. Two experiments, circumftantially related here, have convinced him, that oil does not produce the effect under confideration by its fluidity, but by its quality, as a body fpecifically lighter than water. From hence he concludes, that bodies lighter than water, and of a larger furface or extent than that which is formed by the drops

of oil that are poured into the fea, muft produce the fame effect in a much higher degree. In applying therefore the refult of his obfervations and experiments to the benefit of navigation, both in the ocean, and on the great rivers, our Author propofes to fubftitute, in place of oil, barrels full of air, into which the water cannot enter, or rather fquare tin boxes of eight foot in furface, and one or two in height, filled with air, and impenetrable by water. Ships may be provided, without any great difficulty with fome dozens of fuch boxes faftened to cords, fo that they may be let down into the water, when its agitation is fuch as to excite apprehenfion. M. ACHARD has tried this method by experiments in miniature (if we may ufe that expreffion) and with fuch fuccefs, that he ventures to recommend it as adapted to diminish the dangers of navigation,—and it may not perhaps be unworthy of the maritime powers to try the experiment in full length.

IV. Memoir. Containing Experiments on the Weight, Elasticity, and Compreffibility of different Sorts of Air, as also concerning the different Degrees of Facility with which Plants germinate respectively in them. By the fame. After celebrating the important discoveries of Dr. Priestley, which have enabled chymifts and natural philofophers to explain a great number of phenomena unaccounted for before him, M. ACHARD avails himself of thefe difcoveries to make fome steps farther in the inveftigation of nature. The fixed, the inflammable, the nitrous, the phlogifticated, and dephlogiflicated, are the five different kinds of air, whose weight, elasticity, and compreffibility, are estimated in this Memoir. Our Academician propofes to himself however the following previous queftion, whofe folution he confiders as of no small importance; viz. Whether the air is in bodies fuch as we find it when extracted from them, or whether its properties do not proceed from the union it contracts with other fubftances to which it is united by the very operation which difengages it from the bodies in which it refided? From the experiments that M. ACHARD made, in order to refolve this question, it appears to him evident, that fixed air, alone, exifts in the bodies from whence it is difengaged, fuch as it is when we extract it from them, and that its acidity does not proceed from the union it contracts with an acid at the moment it efcapes and refumes its elafticity, but from its previous combination with an acid in the very fubftance from which it was drawn. But this is not the cafe with air in general, as we shall fee prefently.

From the experiments (here defcribed) which M. ACHARD made, in order to determine the weight of the air, drawn from

* These Experiments are not defcribed in this Memoir.

different

835

Too

different bodies, it appears, 1ft, That fixed air is, in general, heavier than common air; but that its weight is very different according to the procefs employed in difengaging it, and the bodies from whence it is drawn. 2dly, That inflammable air is lighter than common air, if we except that which is drawn from vegetables by fire. 3dly, That inflammable air, difengaged from the fame metal by different acids, varies in weight; that which is drawn from zinc by the marine acid having only one half of the weight of that which is drawn from the fame metal by the phosphoric acid. 4thly, That the weight of common air is to the weight of dephlog fticated air, drawn from nitre by heat, as I to 5thly, That nitrous air is lighter than common air *. 6thly, That air charged with phlogifton, either by the bodies that have been burnt in it, or by the respiration of animals, weighs lefs than common air. 7thly, That, in general, the air in bodies is not of the fame quality, as it is when extracted from them, but, in the act of feparation is combined either with the volatile parts of thefe bodies, or with the fubftances which are employed in extracting it from them. As to the experiments of our Academician on the compreffibility of different kinds of air, and their dilatability by heat, they yield the following refults: ft, That, after the compreffion has ceafed, the air, of whatever kind it may be, occupies the fame volume which it occupied before it was compreffed. 2dly, That the lighter the air is, the lefs is it compreffible (the compreffing power remaining the fame), and the lefs alfo is it fufceptible of dilatation by the fame degree of heat.

Memoir. Concerning a new Manner of hatching Eggs by means of Electricity. By M. ACHARD. Thirty-two degrees of heat form, according to M. Reaumur, the temperature neceffary to the artificial hatching of hen-eggs. After many unfuccesful attempts to find out the point of electricity which produces effects fimilar to thofe of a heat of 32 degrees, M. ACHARD betook himself to an expedient, worthy of his fagacity and genius, and which fully anfwered his purpofe. By a curious experiment, circumftantially defcribed in this Memoir, he found out the degree of electrical force, which, being applied to a fluid, augments its evaporation in the fame proportion and measure as a heat of 32 degrees. Judging that this degree of electrical power might be fufficient to develope the cicatricula of an egg,

M. Achard, indeed, acknowledges, that it was not poffible for him to determine fo exactly the weight of nitrous air, as that of the other kinds, because the common air, of which a part always remained in the globe (which received the different forts of air) atled immediately upon the nitrous air, and decompounded it more or

lefs.

he