ELECTRICITY.

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•alls almo-t all that is known of (lie subject; the passage of thisvirtue from one body to another is what causes its light; by beingcommunicated to other bodies, we see its attraction ; by its quicktransition it melts metals, destroys animal and vegetable life ; andin short it is by this communication, that the science is at allknown and cultivated.” When electricity is induced on a body,it is contined there by electrics alone; and for a longer or shorter,time as these are more or less perfect. A glass tube rubbed ac-'quires a quantity of electricity, which remains, in the glass, be-cause it is surrounded by the air, which is an electric, lint as theair is never a perfect electric, the glass tube cannot retain the c-lectrical virtue perpetually, but only for a longer or shorter time,as the air happens to be in a more or less perfect electric state. Ittherefore imparts some of this virtue to the air, or to the conduct-ing particles in it, gradually, till it loses it altogether. A finger orany other conductor presented to an excited electric, w'lll re-ceive a greater or less part of its electricity ; but cannot receivethe whole because the excited electric, being a non-conductor,•cannot convey all its electricity to that side to which the conductorlias been applied. Ilence a conductor, presented to differentparts of an excited electric, will receive at every approach a spark,w ithout repeating the excitation, till the whole power excited is.exhausted. W hen a conductor which communicates with theearth, is exhibited to an excited electric, at a proper distance, itacquires an electricity, on that tide, contrary to that of the elec-tric, and which increases the nearer they approach, till by theeager attraction betw een the tw o electricities, the conductor re-ceives a spark from the electric, and thus the equilibrium is re-stored. If the conductor be insulated, both sides will appearelectrified, but with different electricities: the side next the elec-tric having acquired the electricity contrary to that of the electric,-and the opposite side one of the same kind. These electricitiesincrease as 1 be conductor approaches the electric, but upon re-ceiving the spark, the electricity of the conductor becomes thesame with that of the electric throughout. All these effects aresimilar, though some other electric, as glass, rosin, wax, &e. lie'interposed between the excited electrics and the conductor; forthe spark forces through the interposed electric, as it always doesthrough the air, when it causes the snapping noise, that attends it.When an in-ulaled conductor lias received the electricity from an•excited electric, it is said to be electrified by communication. Itthen acts like the excited electric ; excepting that w hen touchedbv another conductor, that communicates with the earth, it dis-charges its whole surplus of electricity at once. The reason is, be-cause the electricity belonging to the whole of the conductor iseasily communicated through its own substance to the other con-ductor. Hence tlie electricity discharged from an electrified con-ductor is much more powerful than that discharged from an electric.•If an insulated conductor be touched with another electrified con-ductor, it will acquire part of its electricity, and eacli will shewsigns of it. It will not, however, be equally divided between■them, unless they arc equal in respect to their surfaces and situa-tions. The quantity of electricity in each will be in proportion-to their surfaces, and not to the quantity of matter in each. Mr.(.'avallo, specifies these proportions very accurately in his Com-plete Treatise, voi. i, p. 40, 41. Edit. 4th. The distance to whichan electric spark will go through the air, to reach a conductor, isin proportion to its quantity of electricity, the perfection of the■conductor, and to the sharpness of the parts from which it (lies off,and on which it strikes. The noise attending it also is in propor-tion to all these. A sharp-pointed body w ill throw oft’ the elec-tricity to, and receive it from, a greater distance, than a body ofany other shape, hut the comrmmicution is attended with iftlletight and no noise, as the electricity comes by little and little, notin a large body. A current of air is sensibly felt in these cases atan ele.ctr.tied point, and always in the direction of the point. Anelectric spark, taken upon any part of a living body, otcasionsa■disagreeable sensation, and more or less proportion to the

strength of the spark. Electric^; strongly communicated to in-sulated ammal bodies, quickens tiie pulse anil promotes perspira-tion. It the face or any part of the body be presented to an ex-cited electric, or an electrified conductor, it will feel as if a w indwas blowing, or rather a spider's web drawn over it. If an excit-ed electric is presentedgo the nose, a si all will b- perceived likethat ot phosphorus; but communicated electricity does not occa-tion any such sensation, unless a large quantity passes suddenly

from one body to another. A prelty large quantity of electricitypervades a long conductor with an astonishing, though impercep-tible velocity, but a small quantity takes more time. Substancespossessed ot the same electricity repel, ami those possessed ot theopposite electricities attract each other. Them is no electric at-traction but between bodies possessed ot different electricities;nor any electrical repulsion but between those possessed of thesame electricity, Electricity communicated to insulated limits,fluids, and other bodies in a state ot evaporation, increases thatevaporation. Electricity promotes vegetation by increasing theperspiration of vegetables. Plants often and long electrified,have shewn a more lively appearance Ilian others that w ere not.Mr. Koestlin, however, says, that negative electrization retardsboth animal and vegetable’life. When electricity is communi-cated to insulated ve sels containing water that is running from apipe, the electrified stream is hut little accelerated, unless the tubebe capillary, in which it is accelerated with an impetuousness andvelocity, which is increased in proportion to the smallness ot tin?tune. The electric power is neither affected by heat nor cold,lor an iron bar made red hot, and any conducting fluid bard fro-zen, when electrified, exhibit sparks, attract or repel nearly aswell is in their natural temperature. Ami it neither affects, noris affected bv the magnet. Electricity can be communicated toelectrics, although it is done with difficulty, as their substance isimpervious to it in a great degree. To make ail electric acquireelectricity, it must be touched several times, and in different parts,with tlie electrified body.

Of Charged Electrics, and fa- ficulaiu.y of the LeydenPhial.

*' If to one side of an electric (says M. Cavallo) sufficientlythin, as for instance a pane of common window glass, a plate ofsealing-wax, &c."be communicated one electricity , and to tlie op-posite side tlie contrary, that plate in that case is said lo he charg-ed; and tlie two electricities can never come together, except acommunication of conducting substances be made between bothsides, or tlie electric lie broken by the power of electric attrac-tion. When the two electricities o'f a charged electric are by anymeans united, and therefore their power destroyed, that electric isthen said to lie discharged, ami the act of union of these two op-posite powers is called tlie electric shock. “ To avoid the diffi-culty of communicating electricity to an electric plate, it is custo-mary to coat the sides of it with some conducting substance, as tin-foil,* gilt paper, &c. by which means tlie charging and dischargingbecomes very easy; for w lien (lie electricity is communicated toone part of the coating, it is immediately spread through all tin:parts of tlie electric that are in contai t'witli that coating; andwhen the electric is to be discharged, it h sufficient to make a con-ducting communication between tlie coatings ot both sides, todischarge entirely the electricities of that electric.” lie adds,that “ the coatings of both sides of an electric should not comevery near one another tow ards tlie edge of the plate ; lor althoughthey do not absolutely touch one another, yet when they are elec-trified, the electricity will easily force a passage through the air,and by passing over the surface'ot tlie electric, from one coatingto tlie other, render it incapable of receiving any charge.” It isby means of charged electrics, that we become acquainted withthe greatest powers of electricity, as we can accumulate thesepowers, and use tlieni in various experiments with advantage. Ifa glass plate he properly coated on both sides with a conductingsubstance, ami if to one of these coatings be communicated someelectricity, tlie other coating, while communicating with tlieearth, or with a sufficient quantity of conducting bodies, acquiresbv itself an equal quantity of tlie contrary electricity; but if, w bileone side is acquiring electricity, the opposite side does not com-municate with the earth, or tile conducting substances, the glasscannot he charged. The reason why, while one side of the glassreceives (lie one electricity, the opposite side acquires tlie other,is, tlie property of bodies to acquire an electricity, contrary tothat possessed by a contiguous electrified body; and tlie cause thathinders these two electricities from mixing, is tin* attraction be-tween the glass plate and the fluid, it is of little consequence ofwhat form the charged electric or Leyden jar lie, provided theglass be suffirtenlly thin. “ The tliinnei it is, (says M. (_ avallo,)the greater charge it is capable of receiving; for the stronger inproportion is tlie power of tlie electricity ol one side, to cause a

contrary