this evaporation. The body lofes a degree of heat proportional to the force with which the heat is attracted by thefe diffolved and evaporated particles. Thus, fubftances produced by the agency of fire, as fpirit of wine, and ether, which contain fuch a quantity of heat, that it is fcarcely poffible to keep them in well-clofed veffels, carry off, on this account, the more heat in their evaporation, and cool proportionally the bodies from which they have been feparated. The mercury, therefore, muft fall in the thermometer when the moisture that is collected around the ball is deprived of its heat by the air, the glass by the moisture, and the mercury (which retains the heat the moft feebly) by the glafs. In this cafe the mercury, by the lofs of its heat, is diminished in its volume, occupies a smaller portion of fpace, and thus marks the degree of cold.

When thefe fubtile particles, carried off by the heat, and furrounded with their atmospheres, meet with a body which has the fame, or a greater degree of heat, the body is repelled by them to fome diftance. But if a refrigerated body wants mer heat than it can derive from the ambient air, the vapours are carried towards it, to fupply its defect by their excefs, and the air alfo deprived of heat becomes a conductor. Then these vapours, lofing their heat and their atmospheres, adhere to the furface of the body, and appear there in the form of drops; but an excess of heat repels them from it, under the form of vapours, towards the parts that are the coldest.

The fame caufe precipitates the vapours that are raised by heat in a rarefied air. This air, becoming more free by its rarefac tion, is capable of receiving a greater quantity of abfolute beat, than it had before: befide, it attracts heat more ftrongly than water does. Thus it not only promotes the afcent of vapours from the maffes which furnish them, but also deprives the afcending particles of their heat: then thefe particles approach eac other, and are brought together in larger drops which defcend, y their own weight, in forms of fmall clouds and drizzling in; and refract the light. But if the matter, which is modi

into vapours, attracts the heat with as much, or with more ce, than the air does, then the particles of this matter retain • repellent atmosphere which they have acquired, and form i rd of elaftic air, which mixes with this atmosphere, fubfif 1. and augments its quantity and its preffure. This is evithe cale with ether; when a fmall part of it is mixed Tom on air by evaporation, an inflammable air is formed mixture.

44

ans of this theory of the elafticity of heat, and of the dif that there is between the degrees of force with which ed by different bodies, we may, fays our Academiciar. Cochend chend how (according to the expreffion of Sir Ias Newton

Newton) the particles that have emaned from a body mest with a real repulfion when they get beyond the fphere of attraction ca that body, as alfo when one of thefe particles has escaped from the fphere of attraction of another. The fame theory explains alfo not only all the phenomena that have now been examined, but also an infinite number of effects that are produced bohat and fire; especially if, with M. Scheele, we admit, that in heat itself, as in electricity, there are feveral more fimple fubftances whofe feparation or re-union would furnish probably efects analogous to thofe which have been now under confideration. Our Academician therefore looks upon the preceding experiments as a demonftrative proof of the elafticity, and of the unequal distribution of heat, and thefe two properties, as the caufe of the afcent, and of all the other modifications of vapours in the air-pump.

M. Wilcke, in the following part of this memoir, applies his theory to the meteors which are obferved in the atmosphere of our earth, and from this application of it he deduces the following propofitions:

Air and fire are, by their elafticity, and their unequal diftribution, the true and only caufe of the afcent of vapours, and of the meteors which refult from thence. The first feparation of the vapours, which are emitted from bodies, is produced by heat, which forms an atmosphere round each particle of thefe bodies. Their fubfequent afcent is caufed by thefe elaftic atmofpheres, which, in an air alio faturated with heat, dilate more freely, and find lefs refiftance, or are attracted with more force, by an air more rare in its upper region, lefs comprcifed and impregnated with more relative heat.

It is by the influence of the fame caufe that vapours and other bodies are the more refrigerated in proportion as they rife higher in the atmosphere, where the heat that accompanies them dilates itself with more facility, and where even the air itself is the most adapted to deprive them of their warmth: fo that there reigns always in thefe higher regions a greater degree of relative cold than on the earth.

The diminution of the denfity and preffure of the air, which is indicated by the defcent of the mercury in the barometer, produces the reunion of the vapours in the form of rain, not merely by their fall, which is the effect of their own gravity, but m especially by impelling them downwards by the influence of near, which, to reunite itfelf to the air, efcapes from the particles wh it has raised, and thus gives them a tendency to run togethe., or to conglomerate them felves into falling drops. This, an obferver may perceive clearly when the barometer defcends, and when a clear and ferene fky is covered with clouds, from whence the vapours fall in rain. Thus the tenour and motions of the

barometer have a more intimate connection with the fate of heat (which is here the true caufe), and with the variations of the atmosphere, than with the aqueous vapours, which are no more than an acceffory effect, and do not act as an efficient and primitive caufe. A more exact knowledge of nature, and of the mechanism of heat, will furnish, fome time or other, a more accurate and complete explication of these phenomena.

ART. XXXIII.

Entretiens d'un jeune Prince avec fon Gouverneur. Dialogues between a young Prince and his Governor. Published by Mr. G- L-, Member of feveral Academies. Svo. 4 Vols. London. (Paris.) 1785.

E know not who is the Author of thefe dialogues, but he feems to be one of thofe fpeculative writers that confider mankind, not as they really are, but as they would have them to be and, as in thefe Utopian performances, the prince and the fubject are equally the creatures of his own imagination, he can mould them as he pleafes, and raife a fyftem of government, which, though it may appear very plaufible on paper, it would be extremely difficult, if not impoffible, to reduce to practice. He has divided his work into three parts, to which he has given the titles of Natural, Social, and Political Inftitution.

The first part, to ufe the words of the Author, confiders the exigencies of man, and the means of fupplying them.' It treats of the manner of conducting the education of his pupil, of exciting his curiofity, of inftructing him in phyfical and moral truth, and in the first principles of the focial union.

The fecond part treats of man as a member of society, and explains the various fpecies of property. Thefe take up the firft and fecond volumes, and are by far the best part of the work; they contain many judicious, though not new obfervations. The Author affects to be profound, but is fo rather in his ftyle than in his reafening; and he affumes an appearance of originality, from the peculiar turn of his expreffion, rather than from the novelty of his ideas. As an inftance of this, he inculcates the neceffity of benevolent inftitutions under the ftrange title of dif bursement of the patrimony of beneficence.

The third part, which fills the two remaining volumes, treats of inftitution. Thefe volumes are calculated merely for an abfolute monarchy: for though the Author profeffes to have written, and the Editor to have published, a book for the inftruction, not only of France, but of princes and fubjects ci Every nation, we apprehend it will tend but little to the edification of those who live under governments that are founded en a regard to the rights of mankind, and the liberty of the subject.;

Such will be apt to confider the Author's foundation as false, and his fuperftructure as vifionary and romantic.

He afferts that an abfolute monarchy is the only government which is agreeable to the order of nature. To the republican form he is an inveterate enemy; and of the English conftitution his opinion may be collected from the following expreffions: There are nations where affemblies of the nobility and people deliberate and vote upon public affairs. To fuch we may give the name of mixt government, or any other appellation we please but it is not a monarchy; it is not a government confiftent with nature; it is not calculated for duration.' With respect to the two firft points, it is not worth our while to dif pute them with the Author; and with regard to the laft, we truft the event will prove him an ignoramus.

Yet, with all his averfion to free conftitutions, he cannot be totally blind to the advantages of liberty: he difplays, in the moft forcible terms, the mifery and ill confequences arifing from the fervitude of the peasants; and afferts, that the freedom and fecurity of the husbandman is the bafis of national power. He obferves, that if France, notwithstanding its oppreffive fyftem and wretched administration of finance, together with all its other political vices, be able to undertake and carry on great defigns; it is becaufe, in fome of its larger provinces, the fertility of the foil, and the nature of the markets, enable the inhabitants to carry on and improve the cultivation of their lands to a very high degree; by which immenfe revenues accrue to government. The powerful exertions that Great Britain is enabled to make amidst all its difadvantages, which he paints in very ftrong, and, we hope, in exaggerating colours, he afcribes to the protection and encouragement afforded to agriculture, and to the fecurity of the farmer in the poffeffion of his property, and the produce of bis labours.

In juftice to our Author, we must acknowledge that, though his principles are inimical to the natural rights of mankind, he is a zealous advocate in the caufe of cultivated humanity. He endeavours to infpire his pupil with an inviolable regard to the obligations of morality, and the fentiments of benevolence, with an utter averfion to every fpecies of oppreffion, and a conftant attention to promote the happiness of his fubjects, especially of thofe in the lower claffes. Though it may be improbable that the plans he has fuggefted fhould be carried into execution, their benevolent tendency admits of no difpute. A prince of the amiable character here delineated would doubtless exert his power to render his people happy; but how few fuch does hiftory commemorate; and, if we are to judge of the future by the experience of the pait, how few fuch monarchs are to be expeated! Befide, when we reflect that the intelligence of the

wifeft is confined within very narrow limits, and the influence even of the most powerful circumscribed within a small sphere; how many inftances of oppreffion, committed by those who act under the fanétion of regal authority, may efcape the knowledge, or elude the juftice of the best and most abfolute monarchs! This, in effect, our Author acknowledges, when he obferves, that a king has power en ugh to do good, but not fufficient to prevent wrong being done in his name. This conceffion evidently fhews that the liberty of the fubject requires fome fecurity more effectual and permanent, than the benevolent difpofition of the prince.

ART. XXXIV.

Verhandelingen van de Natuur en Geneeskundige Correspondentie Societeit in de Vereenigde Nederlanden, opgericht in 's Hage. Tranfactions of a phyfical and medical Society of Correfpondents in the United Provinces, eftablished at the Hague. Vol. II. & III. 8vo. Hague. 1785 & 1786.

EACH volume of this work is divided into two parts, the former containing meteorological, and the other medical obfervations, made in various parts of the United Provinces. The first part contains alfo fome curious remarks concerning the influence of the moon with refpect to the weather, and a comparison of it in the feveral months of the years 1780 and 178, with the correfponding lunations of two Chaldean periods, viz. in 1744 and 1745, and in 1762 and 1763, and also with thofe of two metonic cycles in 1742 and 1743, and in 1761 and 1762. The coincidence of the weather with that in the correfponding lunations of the faros was much greater than in thofe of the metonic cycle, and though attended with several deviations, was, upon the whole, very remarkable. The Society have also brought Mr. Sennebier's and Profeffor Toaldo's prognoftics to the teft, and have found them generally confirmed by the event.

The fecond part of each volume contains what may be termed medical annals, confifting of accounts, drawn up by phyficians or furgeons of the different places, of the difeafes which occurred during the years 1780 and 1781 in the several cities and diftricts of the United Provinces, and of fuch local circumftances and cuftoms of each as may be either advantageous or prejudicial to the health of the inhabitants. This plan might be rendered more elegant as well as ufeful, if the materials were properly digefted by an able hand. For though fome of the accounts are drawn up with judgment and precifion, many of them are exceffively prolix, and fwelled with trifling and unimportant details. The cafes are generally fuch as are common in low marthy fituations, and the treatment of many of them fuch as