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ation was too small for observation. M. TOALDO has not been discouraged by this decision of his learned friend ; and the important series of barometrical observations, and reasonings founded on them, which is contained in this Memoir, shews that the barometer indicates the alteration in question.

Observations on the Bobak of Poland, and a History of this Quadrupede, sent to the Academy. By M. J. B. Dubois, Counsellor to his Polith Majesty. M du BUFFON claffes this animal (whose kind abounds in the Ukraine) with the Marmottes; our Academician, better informed, thinks that it comes nearer to the class of rabbits. His description of the animal is circumftantial and curious. We shall 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 square 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 (just as it is among us): there are remarkable diversities of character among these animals, which destroy that natural equality that might be expected among uncivilized beings. Some are active,- some negligent,--some ambitious;—but those who discover laziness in the season of labour, are loaded with severe tasks, and distinguished by public marks of ignominy; they are treated like flaves : they are laid upon their backs; loads of herbs, plants, and provisions are placed on their bellies, which they hold fast with their paws; and thus they are drawn by the tail, to holes, where their burthens are to be unloaded. (Would it were so among us!) The Bobaks never go out of their holes, either to amuie themselves or to seek for provisions, without placing a fentry on an eminence or hillock, to warn them of the approach of danger. This sentinel, when he fees any one coming, raises himself on his hinder-feet, and whistles; on which signal all the stragglers fave themselves in their holes, and remain there till the danger is past.

After having given a list of the Printed Works, Manuscripts, Machines, and Inventions, that were presented to the Academy during the course of the year 1778; M. FOR MEY concludes the historical part of this volume by a curious Eulogy on M. JOHN HENRY LAMBERT, a Stay-maker's son, born at Malhausen, in the Upper-Alsatia, 1728; who, notwithstanding the defects of a poor education, his being bred to his father's trade, his unpleasing person, his rough and ungracious manners, and almost every thing inelegant and disagreeable in his external appearance, rose to the honourable rank of Academician, and

was,

was, indeed, one of the most able members of the Berlin Aca. demy, in the mathematical lnie.

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

II. Memoir. Concerning the Dephlogistication of phlogisticated Air. By M. ACHARD. First Memoir.-It is well known, that the clementary air (by which is meant the air of the atmosphere, disengaged from all the heterogeneous particles that it contains) is capable of uniting itself with different substances, diffolves, with facility, the phlogiston, with which it has a great affinity, and from its union with which it becomes what we call phlogisticated air. The phlogiston, according to our Aca. demician, having such 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 Naturalist, as dephlogisticated air is of all others the most proper for respiration, and its mixture with the air that has been corrupted by animal breath, or other causes, removes the noxious qualities of such air, and restores its falubrity. On the other hand, the production of dephlogisticated air, which is directly drawn from bodies, is subject to many difficulties, and becomes expensive by the small portions of it that are attainable. These considerations induced M. ACHARD to make a great number of experiments in order to separate 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 phlogisticated air transmitted through melted nitre, with the nitrous acid. These experiments, which he made fucceflively with phlogisticated, fixed, corrupted, and inflammable air, verified his conjectures; they ihew, that the affinity of the phlegifton with the nitrous acid, warmed to a degrce which makes the nitre boil, is greater than its affinity with the air, from which it (the nitrous acid, diiengages the phlogiston : and this circumftance is every way adapted to furnith new ideas with respect to the composition of different kin./s of air.

Among several other principles and facts, that result from the experiments and oblervations contained in this Memoir, we shall enumerate the following :-all bodies, susceptible of evaporation, by degrees of heat, natural or artiticial, combine wich and diffolve in air. When the heat, necessary to unite air with certain bodies, ceases, the air separates itself only from a part of the fubftance, wnich it has diffolved, and always retains a certain questa tity of it, which is small in proportion to the degree of the din minution of the heat. lnfummable arr is not decompounded,

Like nitrous air, by the addition of a kind of air, which, not being faturated with the phlogiston, may still admit a farther portion of it, because the afinity of the phlogision with inflammable air, and its acid, surpasses that of the phlogiston with elementary air. --Therefore dephlogisticated air, which receives the phlogiston with the utmost facility, does not diminish the volume of inflammable air, and augments its infiammability, inItead of lefiening ir.

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 useful. He proposes also to answer fome objections that may be made to his experiments, and more particularly, one, that at first sight appears plausible; he means the objection of those who may attribute the change of the air, which he transmitted through melted nitre, not to the decomposition of that air, but to its mixture with the dephlogisticated 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 Affusion of a Fluid specifically lighter, and of such a Nature as not to mix with ibe agitated Fluidl, or by applying to the Surface of this latter Fluid a folid Body of less specific gravity. By the same. The first object that emplovs M. Achard in this Memoir, is to ascertain the fact, that oil has the property of calming or diminishing the agitation of the lea. The experiments he made for this purpose ascertain the fact, so far as to prove that the force, which produces the undulatory motion, continuing the same, that mosion will be less when oil is poured upon the water, than when it is not. But our Academician thinks, that the observations and accounts of the mariners, relative to this fact, are chargeable with exaggeration. It appears incredible to him, that such small

quantities of oil, as they sometimes mention, should produce any palpable effect on a surface lo considerable, as that part of the sea which surrounds a mip: and even suppofing (adds he) that this was poffible, for a moment, yet it must be considered, that, as the motion of the ship is not exactly similar and correspondent to that of the water, the oil must be quickly carried to a considerable diftance, and consequently become incapable of producing any continued effect on the water, which is contiguous to the ship. -So much for the fact. The cause, that operates in its production, is the next object of the experiments and observations of our ingenious Academician. Two experiments, circumstantially related here, have convinced him, that oil does not produce the effect under consideration by it: fluidity, but by its quality, as a body specifically lighter than water. From hence he concludes, that bodies lighter than water, and of a larger luriace or extent than that which is formed by the drops

of oil that are poured into the sea, must produce the same effect in a much higher degree. In applying therefore the result of his observations and experiments to the benefit of navigation, both in the ocean, and on the great rivers, our Author proposes to substitute, in place of oil, barrels full of air, into which the water cannot enter, or rather square tin boxes of eight foot in surface, and one or two in height, filled with air, and impenetrable by water. Ships may be provided, without any great difficulty with some dozens of such boxes faftened to cords, so that they may be let down into the water, when its agitation is such as to excite apprehenfion. M. ACHARD has tried this method by experiments in miniature (if we may use that expression) and with such success, 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 Compressibility of different sorts of Air, as also concerning the different Degrees of Facility with which Plants germinate respectively in them. By the same.

By the same. After celebrating the important discoveries of Dr. Priestley, which have enabled chymists and natural philosophers to explain a great number of phenomena unaccounted for before him, M. ACHARD avails himself of these discoveries to make some steps farther in the investigation of nature. The fixed, the inflammable, the nitrous, the phlogisticated, and dephilogillicated, are the five different kinds of air, whose weight, elasticity, and compreflibility, are estimated in this Memoir. Our Academician proposes to himself bowever the following previous question, whose solution he considers as of no small importance; viz. Whether the air is in bodies such as we find it when extracted from them, or whether its properties do not proceed from the union it contracts with other substances to which it is united by the very operation which disengages it from the bodies in which it refided ? From the experiments that M. ACHARD made, in order to resolve this question, it appears to him evident, that fixed air, alone, exists in the bodies from whence it is disergaged, such as it is when we extract it from them, and that its acidity does not proceed from the union it contracts wtth an acid at the moment it escapes and resumes its elasticity, but from its previous combination with an acid in the very substance from which it was drawn. But this is not the case with air in general, as we shall see presently.

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

* These Experiments are not described in this Memoir,

different bodies, it appears, ift, That fixed air is, in general, heavier than common air ; but that its weight is very different according to the process employed in disengaging 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, disengaged 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 same metal by the phosphoric acid. 4thly, That the weight of common air is to the weight of dephlogisticated air, drawn from nitre by heat, as I to 108c. 5thly, That nitrous air is lighter than common air *. 6thly, That air charged with phlogiitori, either by the bodies that have been burnt in it, or by the respiration of animals, weighs less 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 separation is combined either with the volatile parts of these bodies, or with the substances which are employed in extracting it from them. As to the experiments of our Academician on the compressibility of different kinds of air, and their dilatability by heat, they yield the following results : sít, That, after the compression has ceased, the air, of whatever kind it may be, occupies the same volume which it occupied before it was compressed. 2dly, That the lighter the air is, the less is it compresible (the compressing power remaining the fame), and the less also is it susceptible of dilatation by the same 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 similar to those of a heat of 32 degrees, M. ACHARD betook himself to an expedient, worthy of his fagacity and genius, and which fully answered his purpose. By a curious experiment, circumstantially described in this Memoir, he found out the degree of electrical force, which, being applied to a Auid, augments its evaporation in the same proportion and measure as a heat of 32 degrees. Judging that this degree of electrical power might be sufficient to develope the cicatricula of an egg,

• M. Achard, indeed, acknowledges, that it was not pofible 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 re. mained in the globe (which received the different forts of air) acled immediately upon the nitrous air, and decompounded it more or less,

he

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