ELECTRICITY.

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tinguisbed by die names of vitreous and resinous, and afterwardsby those of plus and minus, or positive and negative, lie formedthe idea of two distinct electric fluids. Both of these were supposedto have a repulsive power with respect to themselves, but an at-tractive one with regard to one another. As long as electrical at-traction and repulsion were the only phenomena to be accountedfor, this theory served the purpose well enough. To account fcrattraction and repulsion by an attractive and repulsive power, wasindeed no explication at all; but it afforded a change of terms,which is too frequently mistaken for an explanation both in elec-tricity and other parts of philosophy. At last, however, M. DuFay dropped his opinion concerning the existence of two tlectricfluids, and thought that ail the phamomena might be accountedfor from the action of a single one. The vitreous or positive elec-tricity, which was supposed to be the stronger, he thought mightattract the negative, or weaker electricity. It is indeed true, thatin many experiments, the positive electricity doth manifest a su-periority in strength over the negative, something like that supe-rior degree of vigour which is observed in one of the poles of aloadstone over the other. According to M. Du Fay’s own prin-ciples, hdwever, had this been the case, a body positively elec-trified ought to have attracted one electrified negatively moreweakly than one not electrified at all; which is contrary toexperience. During all this time, it was imagined that theelectric matter, whether it consisted of one or more fluids, wasproduced from the electric body by friction ; but by a disco-very of Dr. Watson ’s, it became universally believed that theglass globes and tubes served only to set the fluid in motion, butby no means to produce it. He was led to this discovery by ob-serving, that, upon rubbing the glass tube, while he was standingupon cakes of wax or rosin (in order, , as he expected, to preventany discharge of the electric matter upon the floor), the powerwas, contrary to his expectation, so much lessened, that no snap-pingcould beobserved upon another person’s touching any part of hisbody ; but that, if a person not electrified held his hand near thetube while it was rubbed, the snapping was very sensible. Theevent was the same when the globe was whirled in similar circum-stances. For, if the man who turned the wheel, and who, toge-ther with the machine, was suspended upon silk, touched the floorwith one foot, the electric fire appeared upon the conductor; butif he kept himself free from any communication with the floor,little or no fire was produced. He observed, that only a spark or twowould appear between the hand and the insulated machine, unlesshe at thesame time formed a communication between the conductorand the floor ; but that then there was a constant and copious fluxof theelectric matter observed between them. From these, and someother experiments of a similar kind, Dr. Watson discovered what liecalls the complete circulation of the electric matter. When hefound, that by cutting off the communication of the glass globewith the floor, all electric operations were stopped, he concludedthat the electric fluid was conveyed from the floor to the rubber,and from thence to the globe. For the same reason, seeing therubber, or the man who had a communication with it, gave nosparks but when the conductor was connected with the floor, heas naturally concluded that the globe was supplied from the con-ductor, as he had before concluded that it was supplied from therubber. From all this he was at last led to form a new theory ofelectricity, namely, that, inelectricoperations, there was both an af-flux of electric matter to the globe and the conductor, and like-wise an elllux of the same electric matter from them. Some timeafter, however, the doctor retracted this opinion concerning theafflux and efflux, and supposed that all the electric phamomenamight be accounted for by the excess or diminution of the quan-tity of electric matter contained in different bodies. This theorywas afterwards adopted by Dr. Franklin, and continues to be ge-nerally received. One great difficulty with which the first elec-tricians were embarrassed (and which is yet scarcely removed),was to ascertain the direction of the fluid. At first, all electricpowers were supposed to reside in the excited globe or glass tube.The electric spark, therefore, was imagined to proceed from theelectrified body towards any conductor that was presented to it.It was never imagined that {here could be any difference in thisrespect, whether it was amber, glass, sealing-wax, or any thingelse that was excited. This progress of the electric matter wasthought to be quite evident to the senses ; and, therefore, the ob-

servation of electric appearances at an insulated rubber occasionedthe greatest astonishment. In tills case the current could, not besupposed to flow both from Iherubberand the conductor,and yet thefirst appearances were the same. To provide a supply of the elec-tric matter, therefore, philosophers were obliged to suppose, that,notwithstanding appearances were in both cases much the same,the electric fluid was really emitted in one case by the electrifiedbody, and received by it in the other. But now being obliged togive up the evidence from sight for Ihe manner of its progress,they were at a loss, whether, in the usual method of electrifyingby excited glass, the fluid proceeded from the rubber to the con-ductor, or from the conductor to the rubber. It was, however,soon found that the electricity at the rubber was the reverse of thatat the conductor, and in all respects the same with that which hadbefore been produced by the friction of sealing-wax, sulphur, ro-sin, &c. Seeing, theretore, that both the electricities were pro-duced at the same time, by one and the same electric, and by thesamefriction, all philosophers were naturally led to conclude, that bothwere modifications of me fluid ; though in what manner that fluidwas modified throughout the immense variety of electric pheno-mena, was a matter not easily to be determined. On this subjectthe Abb6 Nollet adopted the doctrine of afflux and efflux. liesupposed, that, in all electrical operations, the fluid is thrown intotwo opposite motions ; that the aillux of this matter drives all lightbodies before it by impulse upon the electrified body, and its effluxcarries them back again. He was, however, very much embar-rassed in accounting for facts where both these currents must beconsidered ; as in the quick alternate attraction and repulsion oflight bodies by an excited glass tube, or other excited electric.To obviate this difficulty, he supposes that every excited electric,and likewise every body to which electricity is communicated, hastw'O orders of pores, one for the emission of the effluvia, and an-other for the reception of them. M. De Tour improved uponNollet’s hypothesis, and supposed that there was a difference be-tween the affluent and effluent current, and that the particles of thefluid are thrown into vibrations of different qualities, which makesone of these currents more copious than the other, according assulphur or glass is used. It is impossible, however, that suppo-sitions so very arbitrary could be at all satisfactory, or receivedas proper solutions of electric phamomena. Various othertheories were proposed and maintained by different philosophers,but the theory invented by Dr. Franklin, and which had beenfirst suggested by Dr. Watson , is generally received, as it is moresimple than any- other which has been proposed, and better ac-counts for the most remarkable electrical phenomena. ThisIheorv may be resolved into the following axioms ;

1st.’ The electric matter is one and the same in all bodies, andis not of two distinct kinds.

2d. All terrestrial bodies contain a quantity of this matter.

3d. The electric matter violently repels itself, but attracts allother matter.

4th. Glass and other substances, denominated electrics, containa large portion of this matter, hut are not to he penetrated bv it.

5th. Conducting substances are permeable by it, and Jo notconduct it merely over their surface.

6th. A body may contain a superfluous quantity of the electri-cal fluid, when it is said, according to this theory, to be in a posi-tive state, or electrified plus; and when it contains less than itsproper share, it is said to be negative, or electrified minus.

7th. By excitingan electric, the equilibrium of the fluid is brok-en, and the one body becomes overloaded with electricity, whilethe other is deprived of its natural share.

Thus, ace !'■ ling to the Frauklinean theory, that electricity,which was before called vitreous, is now called positive electricity ;and that winch was termed the resinous, is now denominated ne-gative electricity. This theory, however, is not without its de-tects, and many electrical appearances remain as yet unexplained.Wc shall here propose another theory more simple even than thatof Dr. Franklin, tliough in some things agreeing with it. And wehope to shew tiie cause of several electrical phamomena hithertoreckoned among the arcana of electricity, 'i he theory which wehere speak of, may be expressed in the five following articles,which mas he considered as axioms in electricity.

1. 'Fhe phamomena of electricity depend on one extremely sub-tile fluid, called the electric fluid.

a. The