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this evaporation. The body loses a degree of heat proportional! to the force with which the heat is attracted by these dis! solved and evaporated particles. Thus, substances produced by the agency of fire, as spirit of wine, and ether, which con-' tain such a quantity of heat, that it is scarcely possible to keep them in well-closed veftels, carry off, on this account, the more heat ir tveir evaporation, and cool proportionally the bodies from which they have been separated. The mercury, therefore, must fall in the thermometer when the moisture that is colleded 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 glass. In this case the mercury, by the loss of its heat, is diminished in its volume, occupies a smaller portion of space, and thus marks the degree of cold.

When these subtile particles, carried off by the heat, and surrounded with their atmospheres, meet with a body which has the fame, or a greater degree of heat, the body is repelled by them to some distance. But if a refrigerated body wants more heat than it can derive from the ambient air, the vapours are carried towards it, to supply its defect by their excess, and the air also deprived of heat becomes a conductor. Then there va. pours,' lofing their heat and their atmospheres, adhere to the surface of the body, and appear there in the form of drops; but an excess of heat repels them from it, under the form of vapoari, towards the parts that are the coldet.

The same cause precipitates the vapours that are raised by heat in a rarefied air. This air, becoming more free by its rarefaction, is capable of receiving a greater quantity of absolute beat, than it had before : beside, it attracts heat more strongly than water does. Thus it not only promotes the ascent of vapours from the masses which furnish them, but also deprives the ascending particles of their heat: then these particles approach caca other, and are brought together in larger drops which descend, iv their own weight, in forms of small clouds and drizzling

in; and refra&t the light. But if the matter, which is modis

linto vapours, attracts the heat with as much, or with more · ce, than the air does, then the particles of this matter reta! *78* pellent atmosphere which they have acquired, and for a ind of elaltic air, which mixes with this atmosphere, sublt: 1. and augments its quantity and its pressure. This is evi

'the cale with ether; when a small part of it is mixed i omron air by evaporation, an inflammable air is formed 1. mixture.

mans of this theory of the elasticity of heat, and of the dif{"1:1 at there is between the degrees of force with which is 1. Sabi different bodies, we may, says our Academiciar bir ļ bouing ihend how (according to the expression of Sir ljes,

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of he: Newton) the particles that have emaned from a body met wit sed in a real repulfion when they get beyond the sphere of attraction (. Face that body, as also when one of these particles has escaped from

azeri in the sphere of attraction of another. The same theory explains dat also not only all the phenomena that have now bren exactice, zing but also an infinite number of effe&ts that are produced by her solir and fire ; especially if, with M. Scheele, wę admit, that in sem heat itself, as in electricity, there are several more simple sudsitz Itances whose separation or re-union would furnith probably ef

feéts analogous to those which have been now under consideracomo tion. Our Academician therefore looks upon the preceding exCome periments as a demonstrative proof of the elasticity, and of the

unequal distribution of heat, and these two properties, as tre cause of the ascent, 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 observed in the atmosphere of our earth, and from this application of it he deduces the following propofitions :

Air and fire are, by their elasticity, and their unequal distribution, the true and only cause of the ascent of vapours, and of the meteors which result from thence. The first separation of

the vapours, which are emited from bodies, is produced by " heat, which forms an atmosphere round each particle of these

bodies. Their subsequent ascent is cauled by these elastic a't

mospheres, which, in an air also saturated with heat, dilate = 1334 more freely, and find less refiftance, or are attracted with more pre tree force, by an air more rare in its upper region, less compreited Entity Ord and impregnated with more relative heat. at Does It is by the influence of the same cause that vapours and other e aces* bodies are the more refrigerated in proportion as they rise higher

desires in the atmosphere, where the heat that accompanies them dilates Erricies 23 itself with more facility, and where even the air itself is the most drops to adapted to deprive them of their warmth : so that there reigns clouds always in these higher regions a greater degree of relative cold matter, st than on the earth. as much, G! The diminution of the density and pressure of the air, which Tes of tbs is indicated by the descent of the mercury in the barometer, pro.

acquisitions duces the reunion of the vapours in the form of rain, not oeniy mis 2:00 by their fall, which is the effect of their own gravity, but more

üre elpecially by impelling them downwards by the influence of nial, i part of which, to reunite itself to the air, escapes from the particles ub made it has raised, and thus gives them a tendency to run togeite,

or to conglomerate them selves into falling drops. This, an ob of these na server may perceive clearly when the barometer descents, ai. force when a clear and serene sky is covered with clouds, from whence .8 QUE the vapours fall in rain. Thus the tenour and motions of ine

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barometer have a more intimate connection with the ftate of! heat (which is here the true cause), and with the variations of the atmosphere, than with the aqueous vapours, which are co" more than an accessory effect, and do not act as an efficient and primitive cause. A more exact knowledge of nature, and of the mechanism of heat, will furnith, some 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- IMember of several Academies. 8vo. 4 Vols. London. (Paris.)

1785. W E know not who is the Author of these dialogues, but he

. seems to be one of those speculative writers that conside mankind, not as they really are, but as they would have thes to be : and, as in these Utopian performances, the prince and the subject are equally the creatures of his own imagination, te can mould them as he pleases, and raise a system of government, which, though it may appear very plausible on paper, it would be extremely difficult, if not impoffibie, to reduce to pra&tice.

He has divided bis work into three parts, to which he has given the titles of Naturai, Social, and Political Institution.

The first part, to use the words of the Author, considers the exigencies of man, and the means of fupplying them. I treats of the manner of conducting the education of his pupil, of exciting his curiosity, or inítruciin; him in physical and 010ral truth, and in the first principles of the social union.

The second part treats of man as a member of society, ard explains the various species of property. These take up the fora and second volumes, and are by far the best part of the work; they contain many judicious, though not new observations. The Author affe&is to be profound, but is ro racher in his ftyle that in his reasoning; and he affuines an appearance of originality, from the peculiar turn of his expresion, rather than from the novelty of his ideas. As an instance of this, he inculcates the neceflity of benevolent inftitutions under the strange title of burement of the patrimony of beneficence.

The third pari, whico fills the two remaining volumes, Treats of inftitution. There volumes are calculated merely to 1 an absolute monarchy: for thosgh the Author profesles to have wristen, and the Editor to have published, a book for the in ftruction, not only of France, but of princes and subjeds ci? Every nation, we apprehend it will send but litrle to the edifi: cation of those who live under governments that are founded a a regard to the righes of c.ankind, and the liberty of the subject.

Such!

Such will be apt to consider the Author's foundation as falses and his superstructure as vifionary and romantic.

He afferts that an absolute monarchy is the only government which is agreeable to the order of nature. To the republicar form he is an inveterate enemy; and of the English constitucion his opinion may be collected from the following expressions : • There are nations where assemblies of the nobility and people deliberate and vote upon public affairs. To such 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 confistent with nature; it is not calculated for duration. With respect to the two first points, it is not worth our while to dispute them with the Author; and with regard to the last, we trust the event will prove him an ignoramus.

Yet, with all his aversion to free conftitutions, he cannot be totally blind to the advantages of liberty : he displays, in the most forcible terms, the misery and ill consequences arising from the servitude of the peasants; and afferts, that the freedom and security of the husbandman is the bafis of national power. He observes, that if France, notwithstanding its oppressive system and wretched adminiftration of finance, together with all its other political vices, be able to undertake and carry on great designs; it is because, in some of its larger provinces, the fertility of the soil, and the nature of the markets, enable the inhabitants to carry on and improve the culcivation of their lands to a very high degree; by which immense revenues accrue to government. The powerful exertions that Great Britain is enabled to make ainidit all its disadvantages, which he paints in very strong, and, we bope, in exaggerating colours, he ascribes to the protection and encouragement afforded to agriculture, and to the security of the farmer in the poíTeNion of his property, and the produce of bis labours.

In justice 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 cause of cultivated humanity. He endeavours to inspire his pupil with an inviolable regard to the obligations of morality, and the sentiments of benevolence, wiih an urcer aversion to every species of oppression, and a constant attention to promo:e the happiness of his subjects, especially of those in the lower clafes. Though it may be improbable inat the plans he has suggested should be carried into execution, their benevolent tendency admits of no dispuce. A prince of the amiable character here delineated would doubtless exert bis power to render his people happy; but how few such does hirtory commemorate; and, if we are to judge of the future by the experience of the past, how few such monarchs are to be expeacd! Belde, when we refiect that the intelligence of the

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wiseft is confined within very narrow limits, and the influence even of the most powerful circumscribed within a small sphere ; how many inttances of oppreffion, committed by those who act under th. uncii a of reral authority, may escape the knowledge, or el le ene justice of the best and most absolute monarchs ! This, in eff&t, our Author acknowledges, when he observes, that a king has power en ugh to do good, but not fufficient to prevent wiongl bein: done in his name. This concession evidinily shews that the liberty of the subject 2quires some security more esfretual and permanent, than the benevolent disposition of the prince.

A RT. XXXIV. Perhardelingen van de Natuur en Gereekundige Correspondentie Societeit

in de Vereenigde Nederlanden, opgericht in 's Hage. • Transactions of a physical and medical Society of Correspondents in the United Provinces, established at the Hague. Vol. II. & III. 8vo. Hague.

1785 & 1786. FACH volume of this work is divided into two parts, the

former containing meteorological, and the other medical observations, made in various parts of the United Provinces. The first part contains also some curious remarks concerning the influence of the moon with respe&t to the weather, and a comparison of it in the several months of the years 1780 and 178 , with the corresponding lunations of two Chaldean pes riods, viz. in 1744 and 1745, and in 1762 and 1763, and also with those of two meronic cycles in 1742 and 1743, and in 1761 and 1762. The coincidence of the weather with that in the corresponding lunations of the faros was much greater than in those of the metonic cycle, and though attended with several deviations, was, upon the whole, very remarkable. The society have allo brought Mr. Sennebier's and Professor Toaldo's prognostics to the left, and have found them generally confirmed by the event.

The second part of each volume contains what may be termed medical annals, consisting of accounts, drawn up by physicians or surgeons of the different places, of the diseases which occurred during the years 1780 and 1781 in the several cities and dis. tricts of the United Provinces, and of such local circumstances and customs of each as may be either advantageous or prejudicial to the health of the inhabitants. This plan might be rendered mure elegant as well as useful, if the materials were properly digested by an able band. For though some of the accounts are drawn up with judgment and precifion, many of them are exçessively prolix, and swelled with trifting and unimportant defails. The cases are generally such as are common in low marchy fituations, and the treatment of many of them such as

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