Part 14 (2/2)

12 Zinc appears to be the best exciter when applied to gold, silver, molybdena, steel, or copper The latter metals, however, excite but feeble contractions when applied to each other Next to zinc, in contact with these metals, tin and lead, and silver and lead, appear to be the most powerful exciters

At least two kinds of fishes, the _torpedo_ and the _electrical eel_, have a voluntary power of giving so strong a shock to the water in which they swim, as to affect fishes and other ani communication between different parts of these fishes, an electric shock iven exactly like that of the Leyden phial, which will be described hereafter; and if the coht will be perceived

The growth of vegetables is also quickened by electricity

LECTURE xxxV

_The same Subject continued_

No electric can be excited without producing electric appearances in the body hich it is excited, provided that body be insulated; for this insulated rubber will attract light bodies, give sparks, andnoise, upon the approach of a conductor, as well as the excited electric

If an insulated conductor be pointed, or if a pointed conductor, co with the earth, be held pretty near it, little or no electric appearance will be exhibited, only a light will appear at each of the points during the act of excitation, and a current of air will be sensible from off them both

The effect of pointed bodies is best explained on the supposition of the electricthat in another; and consequently the electricity belonging to a body with a large surface n electricity than that belonging to a smaller

These two electricities, viz that of the excited electric, and that of the rubber, though similar to, are the reverse of, one another A body attracted by the one will be repelled by the other, and they will attract, and in all respects act upon, one another lass or silk possessed of contrary electricities will cohere firether, and require a considerable force to separate the been first discovered by producing one of the-wax, sulphur, rosin, &c first obtained the na afterwards iined that one of them was a redundancy, and the other a deficiency, of a supposed electric fluid, the former has obtained the naative_, electricity; and these terative electricity uished from each other by the manner in which they appear at the points of bodies From a pointed body electrified positively, there issues a streaht, divided into denser streams, at the extreatively, the light is more minutely divided, and diffused equally The former of these is called a _brush_, and the latter a _star_

If a conductor not insulated be brought within the atmosphere (that is the sphere of action) of any electrified body, it acquires the electricity opposite to that of the electrified body, and the nearer it is brought, the stronger opposite electricity does it acquire, till the one receive a spark froed

The electric substance which separates the two conductors possessing these two opposite kinds of electricity, is said to be _charged_

Plates of glass are the most convenient for this purpose, and the thinner the plate the greater is the charge it is capable of holding

The conductors contiguous to each side of the glass are called their _coating_

Agreeably to the above-eneral principle, it is necessary that one side of the charged glass have a communication with the rubber, while the other receives the electricity from the conductor, or with the conductor, while the other receives from the rubber

It follows also, that the two sides of the plate thus charged are always possessed of the two opposite electricities; that side which co the electricity of the electric, and that which communicates with the rubber, that of the rubber

There is, consequently, a very eager attraction between these two electricities hich the different sides of the plate are charged, and when a proper communication is ht, attended with a report (which is greater or less in proportion to the quantity of electricity cooodness of the conductors) is perceived between theed

The substance of the glass itself in, or upon, which these electricities exist, is impervious to electricity, and does not per, and the plate of glass very thin, they will force a passage through the glass This, however, always breaks the glass, and renders it incapable of another charge

The flash of light, together with the explosion between the two opposite sides of a charged electric, is generally called the _electric shock_, on account of the disagreeable sensation it gives any animal whose body is made use of to form the communication been them

The electric shock is always found to perforlass to the other by the shortest passage through the best conductors Common communicated electricity also observes the same rule in its transmission from one body to another