not altogether exempt from caprices; it has certain antipathies and predilections. The fluid chooses that channel which affords the eafieft paffage.' P. 211. vol. ii. When it finds too much refiftance in the space adjacent, it makes an effort to fe cure other paffages.' P. 78. vol. ii. While fuch language is ufed in thefe enlightened times, let us not caft any reproach on the puerile fubtleties of Ariftotle and the myftic dreams of Plato. Mr. Morgan conceives friction to be nothing but fucceffive, preffure, and fuppofes the extrication of the electric fluid to be produced by the approximation of the particles of bodies, in the fame manner as heat is generated in chemical mixtures. This reprefentation feems neither correct nor fatisfactory. Repeated application of preffure differs from friction in being unattended by that general tremor which is probably moft effential. Befides, if this were the true explication, the electricity would proceed from both the substances rubbed against each other; which is contrary to fact, fince these are invariably found to be in opposite states. The figns of electricity discovered in evaporation are not owing to the union or contact of the aqueous and aërial particles, as our author imagines; for the converfion of water into pure fteam, by boiling, affords the fame appear. ances. In all the chemical combinations, there is not merely a condensation; a total change takes place in the internal ftruc ture. Mr. Morgan would fain banish repulfion from the fcience of Electricity. He even endeavours to reduce the phænomena under the general laws of gravitation. Prepofterous attempt! While the electric fluid is leaving the filken thread, it carries the thread to which it is attached towards the excited surface: but when the filken thread receives the fluid, it is apparently repelled by the excited furface; for the courfe of the fluid is then into the furrounding air, and confequently its direction becomes the direction of the thread.' (p. 33, vol. i.) We confefs it is not very eafy to comprehend the author's meaning. Suppose a piece of glafs, which Mr. Morgan admits to be impervious to the electric Aluid, were interpofed between the thread and the excited fubftance: according to this theory, there could then exift neither attraction nor repulfion. Moreover, we should be drawn into this paradoxical conclufion, that the force, with which electrified bodies attract or repel each other, is proportional to the rapidity of the diffipation of their contained fluid. Another confequence of this position still more extraordinary is, that, if the two bodies were equally electrified, the one would recede as fast as the other approached. We have beftowed more words than the occafion deferves, deferves, did it not illuftrate the extreme avidity with which Mr. Morgan propofes fuperficial hypothefes.. Our author afferts that conductors only tranfmit the electric Auid, but are incapable of containing it. They deposit what they receive on the furrounding air, and, as occafion offers, difcharge it inftantaneously. Were this opinion adopted, it would establish an abfolute difcrimination, which does not feem to obtain between conductors and electrics. What fhould we make of thofe fubftances termed imperfect conductors? By what power is the charged air detained on the furface of conductors? Metallic balls can be electrified in vacuo equally as in air; which affords a decifive argument against the opinion advanced. The mode in which the force of attraction (the only force which he vouchfafes to allow) operates, when electrics are charged, is capable, in Mr. Morgan's opinion, of an easy explanation. Unfortunately, this explanation appears fomewhat unintelligible. That the electric fluid is attracted differently by the external and internal portions of a homogeneous fubftance, will not readily be granted. When he talks of a force rendered active by the absence of the particles on which it was exerted, we look in vain for metaphyfical accuracy. Who does not perceive that force invariably implies reciprocity? Yet is this abstract term, this ens rationis, indulged with "a local habitation" and a corporeal vefture. The confequences which Mr. Morgan pretends to draw from his theory are therefore unfounded. Had the views been more precife, we should not have met with this fentence: There are cafes in which a quantity of fluid is, as it were, let loofe, and refts, apparently uncombined, on the furface of electrics.' P.103. vol. i. Such vague language is unfuitable to works of philofophy. The explication given of the discharge of the Leyden jar involves the fame obfcurity of conception: When you connect the outfide and the infide of a phial by a metallic rod, you do nothing more than annihilate all distance between the body which attracts and that which is attracted.' P. 116. vol. i.—‘An opportunity is given for the attractive force to operate upon the accumulation on the pofitive fide; for this is releafed by the contemporaneous action of the negative upon the pofitive." P. III. vol. i. To account for the perforation or bursting of electrics, Mr. Morgan thinks it fufficient that, at a certain height of charge, the invigorated attraction of the negative fide overcomes the adhefion of the fluid to the central mafs. Why fhould this feparation occafion the rupture of the containing fubftance? Muft we acquiefce in the vague and unphilofophical pofition that the elec tric L tric fluid, in the efforts to escape, difpels every obftacle to its. progrefs? It is hard that this æthe real being is completely dependant: it cannot pafs along without the help of fome intermedium. If it burfs the connecting fubftance, no advantage accrues; for air, which must fill up the interruptions, is excluded from the clafs of conductors. Better had the fluid preferred the entire paffage of air to the broken circuit:-but, în fuch inftances, it feems to fail of its wonted fagacity. It gives way to the petulance of paffion, and idly wrecks its vengeance on the substance which, with fuch reluctance, had ferved as the channel of its tranfmiffion. The fracture of electrified bodies, Mr. Morgan juftly observes, is moft apt to enfue when the charge concentrates on a narrow fpot. When the affected furface is large, the oppofite fide cannot be brought into the ftate which precedes rupture, unless the electric fluid be accumulated in proportion to the extent of charge:-but, if the accumulation of fluid be confined to a point, the oppofite point is incapable of affording the requifite quantity before a perforation takes place. Our author employs this principle to explain the noted properties of metallic points, and improves on the idea of Lord Stanhope. Mr. Morgan conceives that these pointed bodies, by confining their impreffion to a fingle spot, overcome the impervious quality of the air. He forgets that, to be confiftent with his principle, it would require the ftratum of intervening air to be very narrow. fides, the fame phænomena might be expected when the point is immersed in oils and other fluid electrics. As a radical error, however, affects the general principle, it were fuperfluous to examine its various applications. Be The pertinacity with which the author perfifts in excluding repulfion from the fcience of electricity, and in denying the aptitude of conductors to contain the electric fluid, colours the whole train of his fpeculations. His incorrect defire to attain fimplicity again draws him into obscurity and error. Inftead of viewing the phænomenon of the Leyden jar as the refult of the particular application of a more general law, he endeavours to extend its principles to the explication of the properties of the Electrophorus and Doubler. It is no wonder that the attempt appears violently ftrained, and that the comparisons inftituted fail in all the effential points. Rather than abandon his hypothesis, he would account for the neceffity of rubbing the furfaces of the electric before its contact with the plate of the Electrophorus, by fuppofing that the attraction he has alluded to fo frequently may be helped by an accumulation of the fluid on the furfaces, just as a small drop of water or oil, expanded on their furface, promotes the adhesion of two pieces of REV. JAN. 1795. D glass. glass.' (vol. i. p. 161.) If the hafty fuggeftions of fancy may thus be called in at every turn, it will always be easy to devise plaufible explications.-The mode in which Mr. Bennet accounts for the operation of his Doubler is indeed liable to fome objections, fince it prefuppofes principles which, although highly probable, have not yet been demonftrated. The experiment, related in page 188, which Mr. Morgan urges in oppofition, is not ftrictly applicable, and fome of his objections are not well founded. That the electricity exhibited by the Doubler fhould not increafe in a geometrical ratio, as the theory prefumes, is very confiftent; for, after it has gained a certain degree of intenfity, it diffipates among the contiguous matter as fast as it collects.-Mr. Morgan's idea, that the Doubler is only a double Electrophorus, appears to deserve at tention. Annexed to the first volume, is an essay containing obfervations on electric light, which, with a few exceptions, are ingenious and important: but, as thefe have been publifhed in the Philofophical Tranfactions, we shall not detain our readers with an abstract of them. Mr. Morgan next proceeds to inveftigate the conducting qualities poffeffed by different fubitances, and affected by their different forms and dimenfions. This important inquiry, we have already obferved, is attempted in five different ways; yet the refults are not always confiftent and fatisfactory. The first which he employs is, by means of an inftrument of a peculiar conftruction, to prefent two circuits to the paffage of the electric fluid, with the view of afcertaining which is preferred. It is evident that this felection implies in his darling fluid an unfurmountable principle of union. Yet he maintains that fome bodies permit only a partial difcharge, or afford a difficult paffage. This last epithet, fo often mifapplied, refers properly to the exertions of animated agents. What becomes of the reft of the charge? If two conductors be prefented in all circumftances alike, Mr. Morgan would be puzzled to determine on which the choice would fall. He will certainly allow that every portion of a conductor must perform its office. No matter whether this conductor be compound, or confift of feveral branches: each of them will convey a quantity of the fluid correfponding to the degree of its conducting quality. The fame argument will extend to conductors of different kinds. The fecond method propofed is to meafure the momentary expanfion of certain fluids, particularly air, confined in a tube through which an electric fhock is fent. The apparatus used for this purpose appears to want neatness and accuracy. The raifing of weights, and the application of pulleys and stop cocks The cocks, are not fuited to the rapid motion examined. manner in which the author would account for this expanfion is unfatisfactory. He afcribes it to the adhesion between the elec tric fluid and the connecting medium, which thereby partakes of its motion. If fuch were the true explanation, the expanfion could only happen in the longitudinal dimenfions. Adhesion and attraction are likewife fynonymous terms, or the force with which one body unites to another is equal to that neceffary to detach it; and, if the electric fluid ftrongly attracts fuch fubftances as air, it will diffuse itself through them with inconceivable rapidity. Here then is the logical argument, reductio ad abfurdum. The third method for difcovering the conducting quality of bodies is to meafure the ftriking diftance, or the interval of air through which a given charge can be fent. This plan is liable to inaccuracy, for the electric fluid notably escapes before the general explofion takes place; nor is it eafy to affign the point of principal effect, which will alfo depend on the celerity of the conductor's approach. The refult varies, too, according to the figure and magnitude of the knobs by which the conduc tor is terminated. The fourth method employed is founded on the estimation of the breaking or luminous distance. It is applicable chiefly to fluids. If these be inclofed in a glafs tube, and oppofite wires inferted and approximated within a certain limit, an electric explofion will be attended with great brilliancy and the violent difperfion of the glafs. Why this effect is produced Mr. Morgan does not explain: but he conceives the interval between the metallic points to be a measure of the conducting quality of the fluid fubmitted to examination. It is clear, however, that this mode of trial must be very imperfect, fince the width and ftrength of the tube are not taken into the account:-not to mention the infuperable difficulty of distinguishing the precife limit of fonorous explofion. In proportion as the ends of the wires are separated, the fharp found of the difcharge will pass by imperceptible degrees into a faint whifper. Mr. Morgan alleges that when the points are at certain diftances from each other, a part only of the charge paffes through:' (p. 64. vol. ii.)· will he maintain, in oppofition to the law of continuity, that an inftantaneous tranfition is made? The fifth method is furnished from the measures of the refiduum of electrical charges. The more perfect conductors may be prefumed to accomplish a more complete difcharge. Yet here alfo is a fource of error. The quantity of refiduum will depend on the shortness of the time elapfed during the applica tion of the conductor. If, instead of approaching this dif D 2 charger |