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furnace or chimney, without setting it on fire, though it turns into Aame itself on meeting with the exterior air.

A considerable heat, kept up among burniisg combustibles, contributes powerfully to the production of new heat, by occafioning a decompofition of the pure air with the inflammable, instead of its conversion into fixed air. Experience has taught the Chinese, who often have only straw for fuel, to economisc their fire (its beat being at the same time confined, and collected on the body to be heated), by continually blowing it; and that the more vivid the flame, the greater is the total heat produced.

The Author is hence led to a particular examination of Are gand's lamp, which excellently illuftrates and confirms bis principles. Its vivid Aame, without smoke, arises from the total con. version of the oil into inflammable air, and the subsequent deftruction of that air with the pure air of the ambient atmosphere. When the lamp is in good order, the eye, placed on a level with the circular wick, will distinguish, between the wick and the flame, a very sensible space, perfečtly transparent, the inflammable air rising with fufficient rapidity (the draught being increased by the glass chimney) to maintain this interval for itself alone; but as soon as it meets with the pure air, rising both on the inside and on the outside of the wick, the two airs are decomposed together, and form the fine flame that crowns the current of inflammable air. If such a decomposition does really take place, water ought to result from it; and accordingly, an alembic head being placed over one of these lamps, though much of the vapour escaped be{ween it and the Aame, half an ounce of pure water was collecto ed in two hours. Part of this water, indeed, was probably no other than what exifted in the oil; but the quantity appears to have been greater tban could have arisen wholly from that source.

The next section (sth) explains the phenomena of heat relative to liquefaction; and proves, in a clear and satisfactory manner, that the change of a solid body to a Auid state is owing to the chemical union of a quantity of fire with it; and the converse change, to the separation of that fire. Water is the grand example of the phenomena of this class. When ice is at the melting temperature, whatever heat we apply to it, it does not become hotter; a thermometer, in the middle of the mass, continues fteady at the thawing point as long as any of the ice remains about it; so that the same cause, which, in other circum, stances, would produce an augmentation of heat, produces here only liquefaction. The quantity of heat absorbed by the ice in its change into water (for the discovery of which the Author gives due'honour to Dr. Black), is found to be such as would increase the temperature of the water itself about 140 degrees of Fahrenheit's scale. Conversely, water may be cooled far below Rev. April, 1787.

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the freezing point, down to 14 of Fahrenheit, without freezing: congelation cannot take place till the combined fire is disengaged: when any part does congeal, the fire, let loose from it, warms the water, the thermometer rises to the freezing point, and continues steady there till the whole is frozen; after which, as the water in the other case, so the ice in this, obeys the external temperature,

The Author answers an objection that may be made to this theory, from a disagreement in the proportions of heat which appear to be lost in some freezing mixtures; and refutes the hypothesis o: Dr. Crawford, who attributes all these diminutions and augmentations of heat to a mere variation in the capacity of the fubject-matter, or its becoming capable of containing a greater or less quantity. Beside many particular difficulties with which this hypothesis is encumbered, it has the disadvantage of leaving all the grand phenomena unexplained, and accounting only for a single circumstance attending them; for if the diminution of heat in liquefaction be owing to the body being capable of containing more heat in a Auid than in a solid state, what is the cause of that increase of capacity, and of the great transformation itsell?

The next section, which concludes the chapter on fire, considers the phenomena of beat proceeding from the gross atinospheric Auids. As great part of the heat in combustion has been thewn to arise from a decomposition of these Auids, the Author endeavours here to give some idea of the quantity of fire contained in them. He describes an experiment made by Mr. Watt for ascertaining the quantity of it in watery vapour, by conveying the vapour of boiling water into a known quantity of cold water, with the necessary precautions to prevent any decomposition of the vapour in its passage ; and he finds it to be fuch, as would communicate to all the water in the vapour (if water could bear so great a heat) the temperature of 943° of Fahrenheit. Though this appears to be a considerable source of heat, it is far inferior to that of the decomposition of inflammable and pure air : when a mixture of these airs, confined by mercury, is decomposed by the elechic spark, an expansive vapour is produced, which, bea ing merely aqueous, must contain the quantity of fire effential to that state, notwithstanding the dissipation of fire on all sides during the combustion, which is so abundant, that part is decompored, and emits its light.

The fourth and last chapter, which makes above half of this volume, is on ELECTRICITY. The Author enters into a circumstantial detail of all the leading experiments hitherto published on this obscure subject, and adds many new ones of his own; all concurring to establish a very ingenious theory, to which, be acknowledges, the experiments of Mr. Volta first

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pointed the way, and by which all the phenomena are clearly and consistently explained.

As fire is ranked among vapours on account of the weak union of its deferent fluid with the other matter, the electric fluid belongs à fortiori to the same class. In fire, the phenomena de. pending on that weak union are so obscure, that they could not easily have been developed, if electricity had not afforded a clue; the corresponding modifications of the ele&ric Auid being marked by distinct and striking phenomena.

The electric Auid agrees with watery vapour, in consisting of a deferent fluid, called the eletric deferent, and a gravitating subftance, called the electric matter ;-in being decomposed when brought to a certain degree of density ;-in its deferent Auid quirting the gravitating matter, to pass to a body that has proportionably less, according to certain laws ;-in the deferent Auid permeating all bodies, to re-establish the equilibrium respecting itself, and depositing the gravitating matter on the body it passes through, but differently, according to the nature of the bodies ;--in the ingredients, though united, retaining their proper tendencies and affinities (as the fire and water in vapour do), and from this fource most of the electrical phenomena result; in the gravitating matter exerting its affinities to different bodies without choice, as the water in vapour does to hygroscopic bodies; -and lastly, in the laws of equilibrium, that when an equilibrium of the deferent fluid is established between neighbouring bodies, those which have most of the electric matter will have most of the deferent also, the excess being in a latent state; and that two quantities may be in equilibrio in respect to expansive force, though one has less of the electric matter than the other, provided it bas more of the deferent.

The differences of the electric fluid from watery vapour are: That when the deferent quits the other matter to re-establish an equilibrium, it does not (like fire quitting its watery affociate) remain free, and diffuse iiseif every way, till the equilibrium is produced, but is determined in its course by its tendency to other bodies, and particularly to some body in the neighbourhood pofleffing less than that which it quitted ;-that the gravitating matter of watery vapour has an affinity, without choice, to hygroscopic substances only, but the electric to all sensible bodies, the groffer atmospheric Auids as well as others; -and that this affinity is not confined to contact, as in watery vapour, but operates at distances, different according to the nature of the body.

The bodies to which the electric or gravitating matter tends at considerable distances, are those called conduElors : its tendency increases, with its approach, in a very low ratio ; and when arrived in contact, it does not adhere, but circulates about them, being carried round by its deferent Auid, analogously to the re

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volution of the planets round the fun: the fhorter the curve, in proportion to the velocity, the more it is disposed to Ay off in a tangent; and the outer parts, most remote from the centre of their tendency, Ay off where the turning is sharpeft. To the bodies called non-conductors it tends only at small distances, but arrived in contact it adheres ; so that on these it may be accumu. lated more copioufly, and retained longer; and by means of an armalure, or conducting medium, to convey it from the whole surface at once, it may be discharged in a much den fer stream.

The general laws of the deferent Auid are: That it tends to all bodies, at greater distances than the electric matter tends to any;-that its tendency, like that of the electric matter, is al. ways from the body which has more, to that which has less ;that, cæteris paribus, the body which has most of the electric fluid, has moft of the deferent also ;-that the tendency of the deferent to other bodies diminishes, like that of the electric matter, in proportion to the distance ;—that it has a particular affinity with the electric matter, but that their union is very weak, insomuch that the electric Auid is in a perpetual state of decompofition and recompofition, even more so than watery vapours.

Such are the general laws which Mr. De Luc, with great sagacity, has developed and applied to the solution of the several phenomena. We shall give, for an example, the hitherto inexplicable phenomenon of the Leyden jar, or (which is the same thing in a fimpler form) the magic picture, that an accumulation of electricity on one fide produces a deficiency on the other.

The electric Auid being analogous to watery vapour, let us suppose a plate of glass, of the fame temperature with the neighbouring bodies, to be bedewed with decomposed vapour on both sides, and to receive on one of its fides, A, a stream of vapour warmer than the plate itself. These vapours, on touching the plate, will be in part decomposed; their water will be deposited on the fide A, and the fire, now liberated, pafling through the glass, will unite with the water on the other side, B, and promote evaporation from that side. This greater evaporation from the fide B consumes the fire that came from A ; and the fide A, by this loss of its heat, becomes able to condense more vapour. Thus the water continues diminishing on the one surface, and increasing on the other, till the whole plate bas acquired the temperature of the vapours: the condensation must then cease, and the inequality of distribution is at iis maximum ; in which state, as the fide B is a little more diftant than A from the source of hear, its vapours will have somewhat less expansive force than those which fall upon A. The Author thews, that the case is precisely the same with the electric Auid ; and describes an apparatus, by which all the phenomena of the electric jar of plate, even the discharge, may be imitated with watery vapour,

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except only in those particulars which depend upon the extreme rapidity, or other characteristic and incommunicable properties of the electric Auid or its deferent,

The chapter concludes with some conjectures on the component parts of the electric Auid, as they discover themselves in its decomposition. When the quantity surrounding the largest conductor passes off at once in a small thread, its density and velocity must be amazingly increased, and the deferent fluid itself appears to be decom poled, the light, which is the general principle of all the deferents, being disengaged. Some curious bints are added respecting magnetism, and the probable existence of some other fuids as yet unknown. But we must take leave, for the present, of this pleasing, as well as instructive, writer; and hope to meet him again soon, in the second volume.

Ch; Art. VI. The Fair Syrian, a Novel. By the Author of Mount Henneth *, and Barham Duwns t.

2 Vols. 6s. sewed. Walter. 1787 Tis unquestionably the business both of the dramatic writer

and the novelist, "to hold as 't were the mirror up to nature; to lhew virtue her own feature, vice her own image, and the very age and body of the time his form and pressure.” The man of genius, therefore, who writes with the view of affording amusement to his readers, will, when selecting materials for his work, make choice of such particular incidents and scenes in life as may be somewhat familiar to the people in general, but which are still of such a nature as to admit of amplification, and which will allow him to exercile his inventive faculty in a certain and Jimited degree; that is, in such a degree as that he do not 'o'erstep the modesty of nature,' or in all events, that probability do not receive from it any great or violent shock.

Our three great novel-writers are Richardson, Fielding, and Smollet; and there,-to illustrate one art or profession by another,—we would compare with Reynolds, Le Brun, and Hogarth. The first for truth and beauty of colouring, the second for a lively display of the pasions, and the third for caricatura. We almost despair of seeing them equalled. It is, however, no little satisfaction to us to find, amid the multitude of unfinished things,' which are continually illuing from the press under the denomination of novels, or romances; and which we should really be at a loss to characterize, were it not that the writers of them have kindly, and in imiration of the showman, let down in the title-pages of their respective performances - this is a noveľmie is no little satisfaction to us, we say, to meet with

# See Rev. vol. Ixvi. p. 129.

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+ Ib. vol. Ixxi. p. 223.

a writer

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