THE

MONTHLY REVIEW,

For JANUARY, 1781.

ART. I. Experiments and Obfervations made with a View 10 point out the Errors of the prefent received Theory of Electricity; and which tend in their Progress to establish a new Syftem, on Principles more conformable to the fimple Operations of Nature. By the Rev. John Lyon, of Dover, Kent. 4to. 12 s. Boards. Dodiley. 1780.

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7HEN a Writer, who has evidently taken confiderable pains to investigate a particular fubject by a great variety of experiments, and who has, in general, expreffed their refults without arrogance, fails in his purpose of informing the world; we feel a fincere pain in difcharging our duty to the Public, by pointing out his defects. That duty, however, must be performed by us on the prefent occafion; not as partifans of Dr. Franklin, but as friends to truth, and well-wishers to the progrefs of real science.

If the Franklinian fyftem of electricity is to be overturned; its demolition must be effected by means very different from thofe employed by the prefent Author. It undoubtedly has its difficulties:-but what fubject of human investigation is free from them? It may have its errors, as is afferted in the title-page of the prefent work: but this publication, we may fafely affirm, is better fitted to exhibit the errors and overfights of its Author, than those of Dr. Franklin. But let us hear what the Writer himself fays, in his Introduction.

He there informs us, that, above ten years ago, he had reafon to believe, that the prefent received hypothetical fyftem of electricity could not be founded on truth.' An apprehenfion, however, that he might be miftaken, prevented his offering his obfervations to the public. Returning afterwards to his first purfuit, he found more convincing proofs to confirm his. forVol. LXIV.

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mer opinion, that the received theory, as established by Dr. Franklin, is erroneous; and has fince profecuted this study

with an unwearied zeal.'

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He was foon fatisfied of the permeability of glafs to the electric fluid.' He drew up his opinion on this fubject, grounded upon and confirmed by experiments, and offered it to a learned fociety: but as I happened, adds Mr. Lyon, to differ from the popular theory, the perfons to whom my paper was addreffed, did not deign to fubmit it to the infpection of the Public.'-On this occafion, the Author formed the refolution of compiling the prefent work; which fhould not only contain his proofs of the erroneoufness of the popular theory; but likewife fuch an account of the principles of electricity, as would be fufficient to initiate a young beginner in the elements of this branch of fcience.

He accordingly firft undertakes to explain the general properties of the electric fluid, according to the prefent received theory; but does not proceed far in this explanation, before he denies the impermeability of glafs to the electric matter. Paff ing over fome frivolous experiments, brought in proof of his doctrine on this head; we fhall attend to his 6th Experiment, which we fhall give in his own words:

• Exper. VI. To fhew that a large far may be discharged through a Pane of Glafs, without injuring it in the leaft Degree.”

Take a pane of glass 10 or 12 inches diameter, more or lefs, according to the fize of your jar, and place it upon a wire under the end of the conductor, where you fix your jar. Let the end of the wire be hooked to a fharp pin, placed perpendicularly to the horizon, with the point close to the under-furface of the pane, and oppofite to another sharp point upon the upper furface of the glafs, upon which alfo the vial or jar is to be placed; fo as to be in contact with the laft-mentioned point. Fix one end of a large conducting bow, with a glafs handle, to the other end of the wire lying under the glafs; and when the jar is charged, if you fuddenly touch the knob of the jar with the other end of the conducting bow, the jar will be discharged with a fpark, and a fnap.'

This experiment is defcribed rather obfcurely; but the meaning of it we apprehend to be this :-that a charged jar may be difcharged, though the circuit be interrupted by a pane of glafs interpofed the electric matter, that iffues from the infide of the jar, paffing from the point of one pin, through the fubftance of the pane, and without cracking or perforating it, to the point of another pin placed directly oppofite to it, and which is connected with the outfide of the jar.

Were there no error in the relation of this experiment, it would afford a moft decifive proof against the fuppofed impermeability

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permeability of glafs, at leaft with refpect to an electric charge; and would, in fact, thake the Franklinian fyftem to its very foundation. Though we might content ourselves with giving this experiment, as here related, a flat contradiction; we can not help expreffing our furprife, that the Author fhould not dwell more particularly on a refult fo very decifive against the Franklinian doctrine; though he could not but be confcious, that the generality of electricians confider a pane of glafs as an impenetrable barrier to the courfe of an electrical discharge. He must be fenfible, that they would be anxious to know, whether the experiment fucceeds invariably, or how often, and what are the circumftances that contribute to its failure or fuccefs. On these particulars, however, as well as every other refpecting fo remarkable an experiment, the Author obferves the moft profound filence. He afterwards, indeed, diverfifies it, only by making a man's body a part of the circuit; and then adds an observation which he needed not to have made, had he related all that he knew concerning this matter *.

If, fays he, the operator does not receive the fhock in his arms, notwithstanding the intervening of the glafs pane, I am much deceived: adding, "If thefe experiments will stand the teft of a fair examination, is it poffible not to conclude, that glafs is permeable to the electric fluid ?'

In our Review of this performance, our remarks are neceffarily confined to fuch parts of it as do not require the affiftance of plates. Even under this reftriction, we meet with abundant matter for animadverfion. The following experiment is produced by the Author, with a view to fhew the infufficiency of the Franklinian theory to account for the principle upon which the Leyden vial acts.' In our apprehenfion, it only fhews, that the Author has not fufficiently ftudied the theory which he attempts to demolish; without fubftituting a better, or any other, in its room.

Take two jars, and charge them by their knobs, at the pofitive conductor. While they are ftanding with their knobs in contact with the conductor, and at fome diftance from each other, form a communication between the outfide of one of the jars, and the infide of both of them (for the conductor connecting the two jars together by their knobs, their internal furfaces become as one), and there will be a fpark, a shock, and a

• We entertain not the least doubt of Mr. Lyon's veracity; but fuppofe that he may have been deceived; and that the electric matter may have paffed over the surface of the glafs. If, however, he will tranfmit to our Editor any further explanation of this fingular experiment, we fhall take a pleasure in communicating his obfervas tions to the Public, in our CORRESPONDENCE.

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discharge of both the jars, notwithstanding the outside coatings are at a confiderable diftance from each other.

If the charging of glafs depends upon repelling as much of the electric fluid from one fide, as is condenfed upon the other, and the difcbarging upon reftoring the equilibrium; then the external furface of one jar could not contain the electric fluid condensed upon the internal furfaces of two jars. Besides, how is the equilibrium reftored to that jar which has no communication with the infide? The jars are both apparently in the fame ftate after the difcharge is made, as they were before they were charged.'

It is fufficient to ask the Author how it is poffible-fuppofing both jars to be placed on the table, or their outfides to communicate with the earth-that the second jar, or that to the outfide of which the discharging rod is not applied, can fail of being discharged; when, at the time of the discharge, the discharging rod forms a communication between its infide coating and the earth. It would be ftrange, indeed, if the fecond jar were not discharged, when its infide coating communicates with the prime conductor; and when one end of the difcharging rod touches the prime conductor, while its other end touches the outfide coating of the first jar, which stands on the table, and confequently communicates with the earth.-Were the jars infulated, a complete difcharge would not take place.

We forgot to mention, in their proper place, fome particular cafes which the Author produces at pag. 58, 59, &c. to fhew, that glafs is permeable to the electric fluid; which are all very eafily to be accounted for on the Franklinian fyftem. With refpect to the remark at pag. 61, we need only to obferve, granting the facts, that it is well known, that, when a vial is highly charged, and the electrization continued, and vigorous, the electric fluid will pafs over the furface of glafs and other electrics, how dry foever, to a confiderable diftance. The Author himself, in the 2d experiment related in this work, fhews that it will pafs to the distance of four feet.

The Author, fuppofing that he has proved the permeability of glafs to the electric fluid, and confequently that he has overturned the Franklinian theory, proceeds, in his 10th chapter, to give us An Analysis of the Leyden Vial.' But though, in the course of this chapter, he very frequently gives the Reader hints, that he is explaining the myfteries of this wonderful bottle, by a better hypothefis; we have more than once studied it from beginning to end, without being able to discover in it any thing that carries the most diftant appearance of a fatisfac tory analyfis. We here meet indeed with feveral experiments which, fo far as we understand them, do not tend to throw the leaft additional light on the Leyden vial: much lefs are they adapted

adapted to overturn Dr. Franklin's fimple and luminous explanation of its fingular properties.

The Author, indeed, here, as well as elfewhere, carries on an analogy between electricity and magnetism, as others have done before him; and afcribes a kind of polar virtue to the particles of the electric matter. Electrical attractions and repulfions have an undoubted refemblance to certain phenomena of magnetism: but the Reader, who is kept in continual expectation that the myfteries of the Leyden vial are about to be explained by the Author's polar fyftem, arrives at the end of the chapter, and afterwards at the end of the book, without learning how the polar virtues of the electric matter are employed, either in the charging or in the discharging of the vial. And yet, perhaps, it might not be difficult, on this head, to frame a plaufible hypothefis, on the fuppofition that the electric particles are endowed with poles: but not without adopting the Franklinian doctrine of the impermeability of glass, as an indifpenfable poftulatum. The Author, however, has not only given up the advantage he might have derived from the adoption of this principle; but has taken pains to confute it, and has accordingly, as might be expected, left the Leyden vial as big with mystery and contradiction as it stood above 30 years ago; when Dr. Franklin explained all its feeming anomalies, by a fimple hypothefis founded on this very principle. In fhort, the Author, by maintaining the permeability of glafs, has undertaken to fhew, how a veffel becomes the better adapted to receive and contain a fluid poured into it, because it is full of holes, which permit just as much of the fluid to run out, or through its fides, as is poured into it; whereas, if the veffel were perfectly found, or impenetrable, it would neither receive or retain a drop of it :and his fuccefs is fuch as might be expected in fo hopeful an enterprize.

The greater part of the Author's experiments requires the having a recourse to the two plates which he has given; in which is delineated a most complex apparatus, confifting of fuch a variety of members, that in fome cafes, it is not very easy to comprehend their structure, or the purport for which they are put together. As a fpecimen however of fuch of his experiments as do not require the affiftance of figures, we fhall transcribe the first of a particular fet; which, as perhaps having novelty to recommend them,' he recites for the entertainment of the practical electrician, without taking any notice of the design for which they were made.'

Fill a coated jar with boiling water as high as the top of the infide coating, and place it in a glafs veffel, and then fill the veffel with boiling water, till it rifes to a level with the water in the coated jar. Fill another jar of glass, to the fame

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height,