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height, with cold water, and let them be placed upon a foot with glafs legs, near the conductor of the electrical machine, and as far apart as the ftool will admit. Let a chain, or rod, be fixed to the conductor, and put into the jar which contains the cold water, and then turn the cylinder to electrify the cold water. If a perfon prefents any conducting fubftance to the knob of the coated jar, ftanding in the veffel filled with hot water, it will give a fpark; and if a communication be formed between the knob of the coated vial, and the cold water in the other veffel, there will be a difcharge, a fpark, and a fhock. In this experiment the electric fluid muft pafs from the denfer to the rarer medium, i, e. from the vessel with cold water to the jar with hot water; and if it does not pafs, through the pores, or over the surface of the glass, I must leave it to the friends of the Franklinian theory to fhew, how the knob, of the coated vial can acquire a fufficient quantity of the electric fluid to give a fpark.

This ftrange experiment, which is followed by another nearly of the fame kind, is more likely to puzzle than to entertain the reader who furely will not readily comprehend the defign for which it was made.' It is indeed a circumftance peculiarly. characteristic of this work, that, while other philofophers aim at the greateft fimplicity in the planning of their experiments, the Author feems to delight in throwing an air of obfcurity over the fimpleft phenomena, by employing the most complicated apparatus. One would think, that his principal defign in this performance was not to overturn a particular theory, or to eftablifh any other; but to perplex the Franklinist with a fet of electricale enigmas, to exercife his wits upon them; so as to puzzle him to find which fide of a jar or flafk, which he has put into fome ftrange fituation or other, is pofitive, and which is negative. A great part of his apparatus is certainly better adapted to confound than to convert him: and in fact, we rather fufpect that the Author himself has been often bewildered in the mazes into which he has been led by his own machinery.

A variety of other fubje&s is treated of in the prefent work ;> fuch as Signor Voita's Electrophorus; where the Author conti-. nues to maintain the doctrine of electric permeability:-the electric phenomena produced by the friction of filk, and other bodies of a rare texture; as firft obferved by Mr. Symner, and afterwards particularly attended to by M. Cigna, and Signor Beccaria-electrical cohefion, and various other phenomena relative both, to natural and artificial electricity. On all these fubjects the Author produces a great number of original experi→ ments, In this, as well as in the preceding parts of the work, we cannot help obferving, and indeed commending the Au

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thor's industry; not, however, without remarking, that his inquiries in this branch of philofophy would undoubtedly have been more fuccefsful, had he not evidently prosecuted many of them under the influence of prejudice; or had he more carefully ftudied the fyftem which he oppofes, and imitated the fimplicity of its inventor. We mean no difrefpect to the Author, even when we recommend to his perufal the following fhort article, or rather the little manual which is the subject of it; the leading doctrine of which he opposes, particularly in his 4th chapter, and in his eleventh, when he treats of the Electropho rus, as well as elsewhere.

ART. II. A Short View of Elearicity: By Benj. Wilfon, F. R. S. and Member of the Imperial Academy of Sciences at Petersburgh, 4to. 2 s. Nourfe. 1780.

&c. &c.

WH

7HATEVER may be thought of Mr. Wilfon's peculiar opinions, with refpect to the controverfy concerning the comparative utility of blunt and pointed conductors; he has in this little tract performed an acceptable fervice to those who would undertake the ftudy of electricity. The experiments contained in it, which are in general extremely fimple, and of course easily to be comprehended, are contrived with a view to explain fome of the principal phenomena presented by electrified bodies. The principle on which the greater part of thefe experiments depends, though not particularly fpecified by the Author, is one of the most fertile and important in the whole science; and we think, that the Author would have done right to have inferted it among his General Obfervations" prefixed to the experiments. The propofition to which we allude is, in fhort, this ;-that electrified bodies, without parting with their own electricity, act upon other bodies in their neighbourhood, in fuch a manner as to produce in them an electricity contrary to their own.

We have frequently taken occafion to fpeak of this principle; particularly in our Review for December 1779, pag. 408, and in the other parts of our Journal there referred to. The principal. phenomena of the Leyden vial, and of the Electrophorus, as well as thofe exhibited by thunder clouds, receive from this principle the moft fatisfactory explanation. And though it be. difficult to conceive in what manner one body can act upon. another, at a diftance, through glass, or air, without actually paffing through thefe fubftances (which are affirmed to be impervious to it, except when it forces its way through the former by perforating it, or through the latter in the form of a spark, or blaft); yet the truth of the principle is too well established by experiment to admit of doubt.

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With refpect, however, to the impermeability of glass, we fhould observe that, from an expreffion that occurs in this treatife, where the Author applies the results of the preceding experiments to the explanation of the phenomena of the Leyden vial, the Reader is led to fuppofe, that he allows that glafs is permeable to the electric fluid; and that he confiders it as differing from metals, wood, &c. only in the circumstance of refiftance. More time,' he fays, is required for the electric fluid to pass through a given length, or thickness of glass, than through metal or wood of the fame length or thickness.'Though we recollect, that the Author formerly maintained the opinion, that glafs was permeable to the electric matter; we are rather inclined to fufpect only an inaccuracy of expreffion in this quotation. For if, in the charging of a Leyden vial, the electric matter paffes through the thickness of the glass' at all; it moft undoubtedly paffes through it with the greatest freedom and celerity: for, during the process of charging it, fparks fucceffively appear at its outfide furface, equal both in number and. in ftrength to thofe feen at the wire that communicates with its infide. On the whole, whether the electric fluid can pafs through glafs, under certain circumftances, or no; it appears evident, that it does not pafs through it in the Leyden experiment: at least no theory has yet been imagined, by which the charging of the vial has been accounted for, on the hypothefis of the permeability of glass.

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In the first fet of experiments given in this fhort tract, one, two, or more cylinders of wood, to which pith balls are annexed, are infulated by refting on a wine glass; and an excited glafs cylinder is held at a fmall diftance. The cylinders are either rounded or pointed at the ends, and are fucceffively placed, end to end, in different fituations with refpect to each other: and the effect of the excited glafs, in producing a change in the electric ftate of the wooden cylinders, is readily afcertained by an examination of the balls fufpended to each.-Thus, to give only one inftance exemplifying the principle above mentioned; -four wooden cylinders, round at both ends, are placed in contact with each other, in the order of the letters, A, B, C, D. The excited glafs cylinder is held at a fmall diftance over A, from which it forces out a part of its natural quantity of electricity into B. This additional quantity, accumulated in B, in its turn forces out part of the natural quantity belonging to C, into D. That these changes have been produced is rendered evident, on feparating the cylinders juft before the excited glafs is removed from A: for A is found to be in a negative, B in a pofitive, C in a negative, and D in a pofitive state.

The Author makes a practical application of the refult of one of his experiments to the celebrated trials formerly made

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by him, on a larger fcale, at the Pantheon; in order to determine the much litigated question, whether a point or a ball will be ftruck at a greater diftance. To afcertain this matter more precisely, he proposes that a broad and fufficiently thick plate of glafs or wax fhould be interpofed between the great infulated conductor, or artificial cloud, and the pointed or blunt conductor which is to receive the ftroke: and when the artificial cloud is fufficiently charged, the interpofed plate may be fuddenly removed, either by means of a spring, or fome other fimple me

chanical contrivance.

The Author next gives a fimilar fet of experiments made with folid glass cylinders, either pointed or rounded at the extremities, and which, like the wooden cylinders above mentioned, perform the office of conductors of the electric fluid. The phenomena are here fomewhat different, because the fluid meets with more refiftance in glass,' (or rather over its furface, as we are inclined to fuppofe) than in metal or wood; and its motion accordingly is flower. Thofe experiments, confidered together with thofe of the preceding fet, very fatisfactorily illuftrate the phenomena of the Leyden vial.

Thefe trials are fucceeded by others, made with a plain glass, on which is laid a plano-convex glafs, with its convex surface in contact with it, after they have both been feparately charged; in order to obferve the alterations that might be produced in the appearance of the coloured rings, in confequence of the pofitive or negative state of the two furfaces. Thefe experiments cannot eafily be rendered intelligible, without the affistance of the plate annexed to them; nor indeed to any one who is not previously acquainted with the Author's former publications: particularly with his attempts to explain the phenomena of electrieity by the ether of Sir Ifaac Newton, or the action of a fubtile medium at the furface of bodies, which is fupposed to refift the entrance and exit of this ether. We must refer the mathematical Reader likewife to the pamphlet itself for the Author's theorems and demonftrations relative to the denfity of the elec tric fluid at the furfaces of bodies, the action of pointed bodies, and the cafes in which the electric current is accelerated, or

not.

ART. III. Obfervations on Fevers, especially thofe of the continued Type; and on the Scarlet Fever attended with Ulcerated Sore Throat, as it appeared at Newcastle upon Tyne in the Year 1778, &c. By John Clark, M. D. &c. 8vo. 5 s. Boards. Cadell. 1780.

HE Author of this performance formerly published a work of merit, entitled, Obfervations on the Difeafes in long Voyages to bot Countries; a particular account of which was given in our 49th Volume,

Volume, September 1773, pag. 173. In the prefent work, he confines himself wholly to the confideration of fevers, particuJarly thofe which fell under his own obfervation at Newcastle, in the years 1777 and 1778, where he kept a regular and daily account of the particular cafes, and of the effects of the medicines which he prefcribed.

In a preliminary fection, treating of the difference of fevers, he admits of only one genus; the only fpecies of which, that can be well afcertained are, the intermittent, the remittent, and the continued, confidering even the latter, as he had obferved in bis former performance, as being liable to alleviations and exacerbations. He accordingly affirms, that it is the nature of every fever to remit, if not accompanied with local inflammation and that all primary fevers are attended with the fame effential fymptoms; the only difference being, that in fome of them, the intermiffions and remiffions are perfect; in others to obfcure, as juftly to entitle them to the name of continued.' The genera into which thefe laft are ufually divided, under the titles of inflammatory, nervous, and putrid, he confiders as only proper to express different states of fever; as the fymptoms which characterize them equally attend fevers of the intermittent and remittent type.

The peculiarity which principally diftinguishes the Author's treatment of continued fevers, confifts in the early and liberal exhibition of the Peruvian bark. The ufe of this remedy in intermittent and remittent fevers, in all their varieties, is univerfally acknowledged. In his former publication, the Author bad maintained, that this noble febrifuge may be given, with the greatest fuccefs, not only in the remiffions of fevers, in bot climates, but even when they become continued. In confequence of his fubfequent experience in this country, he declares, that here likewife, as foon as the ftrong action of the veffels has been reduced, by means of antimonials, aperients, and diluents, we ought not to wait till fymptoms of debility enfue, but immediately proceed to exhibit the bark, in as large dofes as the stomach of the patient will admit, without regard to the remiffions or exacerbations. If this method be timely employed, he declares, with confidence, that the difeafe will feldom terminate in the other states of fever; or in other words, become nervous or putrid.

He further obferves, that in fome cafes of continued fever, after the use of antimonials, the affair may be trufted to nature. I have frequently done fo,' he adds, when the difease has shewn no diforder of the nervous fyftem; and where there has been no fufpicion of its having arifen from contagion. But, in doubtful cafes, after the fever has continued to the end of the fourth day, it is the safest method to commence immediately

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