prevent him from falling into fuch errors as it is not beyond the power of human nature to avoid,-be thou ever bleffed, and mayeft thou be worshipped wherever men are not infallible, and wherever millions of men may fuffer from a fingle mistake!" To this we heartily fay, AMEN, and add, "Divine liberty,which permitteth men of all nations and kindreds, and languages to come among us, and to exprefs with freedom their ideas concerning our political regulations; whether these ideas be abfurd or reafonable, may that ever be permitted, feeing their reafonings may be afterwards fed with care, by whoever lifteth, and the corn be thoroughly winnowed from the chaff fo as to render it both wholefome and pleafant for thofe to whom it shall be administered!" Before we clofe our remarks on this performance, we cannot help taking notice of the inconvenience which refults to the caufe of literature, from an affectation of fingularity by authors of diftinguished merit. Montefquieu wrote a book on the Spirit of Laws, which holds a confpicuous rank among the political writings of the prefent age. It poffeffes great merits and defects, and has been praifed by a few who could diftinguifh its merits, but by an infinitely greater number who could not judge either of its defects or merits. That author, perhaps with a view to conceal faults which he knew not how to remove, has affected an oracular obfcurity in uttering his dogmata, an immethodical arrangement, an abrupt transition from fubject to fubject, and a quaintnefs of reafoning which throws a cloud over his work, that gives it a deep air of myfticifm, which has a strong tendency to command the veneration of mankind, where an idea has been preconceived of the Author's talents. In confequence of this, many of his affertions, which if they had been attempted to be fupported by plain reafoning only, muft have fallen into contempt the moment they were uttered, have been retailed by fucceeding authors as indifputable axioms, to doubt of which would feem to indicate a very blameable degree of prefumption indeed. Other authors, fince Montefquieu, obferving the effects of this mode of procedure, have, on too many occafi ns, endeavoured to avail themfeives of the fame device. All fhallows, faid Johnson, with much ingenuity, when put to a fhift, and when he had no other argument at hand, All fhallows are clear. Our philofophers feem to act as if they wished their readers to believe the converfe of this propofition, viz. that all obfcurity indicates profundity of knowledge; hence, like the cuttle fish, when they think they are in danger of being feen at a lofs, they take care to throw fuch an obfcurity around, as to become imperceptible. Perhaps we may attribute to this caufe, no fmall part of that feemingly profound obfcurity, of which fo many readers com Y 4 plain ift plain in the celebrated work of Dr. Adam Smith on the Wealth of Nations. But we have more frequently occafion to complain of that kind of mystical obfcurity in the work now before us; and we give the prefent gentle hint, as a caveat for future authors to avoid running into this very unpardonable fault; and as an inducement for them to guard against it, we beg leave to affure them that although a few may have thus obtained a certain degree of celebrity for a fhort time longer than they otherwise would have done-yet for one that has fucceeded in it, twenty have failed. At the beft, it affords but a temporary fame, which, fooner or later, is blasted, and is the cause of burying in oblivion, works which perhaps poffefs, in other respects, very great merit: for, as foon as men difcover defects of this kind, in a few inftances, they naturally reverse the reasoning of Socrates, and instead of faying that because they find that the few paffages in an obfcure work which they happen to underftand are excellent, therefore they conclude that the other parts of it which they cannot understand are equally fo; they fay that fince they find that the few obfcure paffages which have been analyfed are difcovered to be nonfenfe, they conclude that all the other obfcure paffages deferve the fame degree of condemnation. The tranflation of this work has much more the appearance of an original than tranflations in general can boaft; for, except a few Gallicifms, fuch as capitalist, deficit, ensemble, and one or two more, we difcover no other marks of its French origin. The ftyle poffeffes all the spirit and freedom of an original English production ;-though it can by no means be faid to excel in correctnefs or purity.-In the French of the Marquis de Cafaux, we obferve an uniform degree of elegance. A= n. ART. V. Idées fur la Méteorologie, &c. Thoughts on Meteorology. WE E are glad to learn, that this ingenious philofopher still continues his Inquiries into the modifications of the atmoSphere; and that the publication of the fequel of that work has only been interrupted for a time by what must ultimately be of advantage to it, viz. new objects ftarting up and inviting the Author's purfuit. The prefent treatife is intended as a general view of a fyftem which is to be profecuted more in detail in the continuation of his great undertaking. As we are always happy in being able to promote the diffufion of rational and ufeful knowledge, we fhall endeavour to gratify the English reader with as full an outline of Mr. De Luc's theory of the atmospheric fluids, as our limits will admit; convinced, that clear and fatisfactory explications explications of natural phenomena, especially fuch as are immediately interefting to all, cannot be unacceptable to any defcription of our Readers. It is neceffary to premife, that, inftead of the common appellation of elastic fluids, our Author uses that of expanfible fluids; confidering them as compofed of difcrete particles, capable of diffufing themselves into all free space when they obey no other law than that of their expanfibility and to the idea of mutual repulfion, afigned by fome as the cause of their expanfibility, he fubftitutes motion of the particles, continued or renewed; continued motion, if nothing interrupts it; renewed, when it has been fuppreffed for a time, either by collifion, or by combination with other substances. Expanfible fluids, in this view, comprehend not only air and vapours, but light, fire, and the electric fluid; and fome of the diftinctive characters of thefe fluids are conceived to arife from the different fpecies of the progreffive motion of their particles, He begins with the confideration of watery vapours, which afford an excellent key to the compofition of the other fluids. By watery vapour is meant, not the vifible or opake steam (for that is the vapour in a ftage of decompofition), but the invifible or transparent exhalations, which conftitute a peculiar fluid, diftinct in its nature from all others, expanfible, compreffible, and poffeffing the mechanical properties of the aeriform fluids, independently of any mixture of air with it. Its fpecific gravity is only about half that of common air, when they are both brought to an equal degree of expanfibility, or refiftance to compreffion. As this fluid can fubfift, and may be produced, without any concurrence of air, the theory which has for fome years prevailed, of its being formed by the union of water with air in the manner of chemical folution, falls at once to the ground. That theory indeed was never countenanced by Mr. De Luc: according to his fyftem, the vapour confifts of particles of fire united to those of the water; a principle which he feems to have fully eftablifhed, and on which he very ingeniously explains the phenomena of evaporation, and all the modifications of vapour. When the vapour is compreffed beyond a certain degree, that is, when the particles are brought within a certain proximity to one another, a decompofition takes place; the watery particles, in virtue of their natural tendency, reuniting together, and difengaging the fire that was affociated with them. There is neceffarily a minimum diftance of the watery particles, beyond which the vapour cannot be compreffed without undergoing decompofition; and this minimum muft be different in different degrees of heat, but conftant in the fame heat. When the heat is about temperate, and the barometer at 30 inches or a little a little more, watery vapours, compreffed to this minimum, are found to have between and of the expanfive force of air, and less than of its weight. When mixed with air, they can fubfift under a much greater preffure than they can by themselves; because the air fupports the preffure, and prevents the aqueous particles from being forced within their minimum distance; and hence vapours fubfift in the atmosphere without being decompofed by its preffure. In the heat of boiling water, they can fupport the weight of the atmosphere without any mixture of air; for ebullition, under any given preffure, cannot take place till the vapour, produced in the liquor, has acquired a degree of expanfive force fufficient to raife the liquor into bubbles under that preffure; and fo long as the vapour retains this heat, it must continue capable of refifting the fame preffure. As the heat abates, a decompofition begins; hence the opake fteam over boiling water; which becoming vapour again by uniting with the fire it meets with in a larger space, is diffufed by its expanfibility. Thus vapours are continually undergoing decompofitions and new vaporifications. Though boiling water, under the fame preffure, has always the fame heat, it may be made to receive a greater heat before it boils, than it can retain when it does boil. In a veffel with a very narrow orifice, quite filled with the water and purged of air, though the water fuftains on its furface no other preffure than that of the atmosphere, yet its particles meet with so much refiftance to their feparation, that the Author has found it to receive, without boiling, a heat 22° of Fahrenheit's fcale above the boiling point: as foon as vapours could form themselves, their expantive force was fo great, that they pushed a large quantity of the water out of the veffel, in the way of explosion, and the remainder was immediately reduced to the degree of boiling heat. The fixity of the heat of boiling water is an immediate confequence of the above principles: vapours cannot be formed in the mafs, without having expanfive force fufficient to difplace or raise it into bubbles: they cannot acquire this force till the heat is arrived at a certain point, and as foon as they have acquired it, they efcape, in virtue of that expanfion: further acceflions of fire muft pafs off in like manner, and can do no more than accelerate the evaporation. Hence alfo the phenomenon obferved by Mr. Cavendish, that the vapour of boiling water, paffing through a veffel in which it cannot be decompofed, is more fixed in its heat than the water itself, and better adapted for afcertaining the boiling point of thermometers: in a thermometer placed in boiling water, there are always fome little ofcillations, arifing from the vapours not being able to carry off all the fire inftantaneously; whereas, in the vapours themselves, themfelves, which efcape as foon as the heat is fufficient to form them, no fuch inequalities are obferved. The vapours of boiling water arife from within the mass; but water may yield alfo, from its furface, vapours of equal expanfive force, if they are confined in a place of the fame temperature with themselves. If water be introduced above the mercury in a barometer, the vapours it produces in a temperate warmth will prefs down the mercury near half an inch in the heat of boiling water, they will deprefs it to the level of the mercury in the bafon, being equivalent to the preffure of the atmosphere; and in a greater heat, they will prefs it below the level, and escape at the bottom of the tube; the water giving no figns of ebullition to the laft. Having thus confidered, in the firft chapter, the laws of the denfity, and the mechanical effects, of watery vapours, the author proceeds, in the fecond, to their chemical properties, which are the immediate objects of hygrology, or the fcience of local humidity. As thefe vapours confift of water and fire, united by affinity into a new compound, the fpecific properties of each of the component parts are fuppreffed, as in other chemical combinations: the water lofes its faculty of moistening, and the fire that of producing heat, both of them becoming ftrictly latent: hence the lofs of heat which is obferved in the evaporation of liquids, and the augmentation of heat in the decomposition of vapour. Vapours are decompofed, either by the mutual approach of their particles as already explained, or in virtue of the affinity of the water to fome other fubftances, viz. to thofe called bygroscopic, of which fire may of course be reckoned one. The only law of this affinity is, that the water diftributes itself to all the fubftances of this clafs that are within its reach, to every one alike, proportionally to its fpecific power of retention, or its capacity. If new fire be introduced into a fpace where there is no fuperabundant water, it will take away fome of the water from all the hygrofcopic fubftances there, and diminish their humidity: if fome of the fire be taken away, the water that was united with it will be divided among all the reft: and if any other hygrofcopic fubftance be introduced, containing a greater or lefs proportion of humidity than thofe already there, the furplus of humidity will be divided among, or its deficiency made up by, the others. It is by fire that this diftribution is effected; the particles of that element, being continually in motion, take up the water from one that has more than its hare, and give it out to another that has lefs. Thus hygrofcopic fubftances have their humidity always proportional to that of the place they are in; and they vary accordingly in weight and dimenfions. In |