TO CADWALLADER COLDEN,* AT NEW YORK

COMMUNICATED TO MR. COLLINSON.

Unlimited Nature of the Electric Force.

SIR,

Philadelphia, 1751.

I enclose you answers, such as my present hurry of business will permit me to make, to the principal queries contained in yours of the 28th instant, and beg leave to refer you to the latter piece in the printed collection of my papers, for farther explanation of the difference between what are called electrics per se and non-electrics. When you have had time to read and consider these papers, I will endeavour to make any new experiments you shall propose, that you think may af ford farther light or satisfaction to either of us; and shall be much obliged to you for such remarks, objections, &c., as may occur to you.

I forget whether I wrote to you, that I have melted brass pins and steel needles, inverted the poles of the magnetic needle, given a magnetism and polarity to needles that had none, and fired dry gunpowder by the electric spark. I have five bottles that contain eight or nine gallons each, two of which charged are sufficient for those purposes; but I can charge and discharge them altogether. There are no bounds (but what expense and labor give) to the force man may raise and use in the electrical way; for bottle may be added to

Afterwards lieutenant-governor of New York. He was highly distinguished for his attainments in medicine, the mathematics, botany, and the philosophical sciences, and wrote several papers on those subjects, which were published in Europe. He also wrote a history of the Five Nations of Indians. He lived to an advanced age, and died at the beginning of the American Revolution. — EDITOR.

bottle in infinitum, and all united and discharged together as one, the force and effect proportioned to their number and size. The greatest known effects of common lightning may, I think, without much difficulty, be exceeded in this way, which a few years since could not have been believed, and even now may seem to many a little extravagant to suppose. So we are got beyond the skill of Rabelais's devils of two years old, who, he humorously says, had only learned to thunder and lighten a little round the head of a cabbage.

I am, with sincere respect,

Your most obliged humble servant,

B. FRANKLIN.

QUERIES AND ANSWERS REFERRED TO IN THE FORE

GOING LETTER.

The Terms "Electric per se and "Non-electric" improper.-New Relation between Metals and Water. - Effects of Air in Electrical Experiments. - Experiment for discovering more of the Qualities of the Electric Fluid.

Query. Wherein consists the difference between an electric and a non-electric body?

Answer. The terms electric per se and non-electric, were first used to distinguish bodies, on a mistaken supposition, that those called electrics per se alone contained electric matter in their substance, which was capable of being excited by friction, and of being produced or drawn from them, and communicated to those called non-electrics, supposed to be destitute of it; for the glass, &c., being rubbed, discovered signs of having it, by snapping to the finger, attracting, repelling, &c.,

and could communicate those signs to metals and water. Afterwards it was found, that rubbing of glass would not produce the electric matter, unless a communication was preserved between the rubber and the floor; and subsequent experiments proved, that the electric matter was really drawn from those bodies that at first were thought to have none in them. Then it was doubted whether glass, and other bodies called electrics per se, had really any electric matter in them, since they apparently afforded none but what they first extracted from those which had been called non-electrics. But some of my experiments show, that glass contains it in great quantity, and I now suspect it to be pretty equally diffused in all the matter of this terraqueous globe. If so, the terms electric per se and non-electric should be laid aside as improper; and (the only difference being this, that some bodies will conduct electric matter, and others will not,) the terms conductor and non-conductor may supply their place. If any portion of electric matter is applied to a piece of conducting matter, it penetrates and flows through it, or spreads equally on its surface; if applied to a piece of non-conducting matter, it will do neither. Perfect conductors of electric matter are only metals and water; other bodies conducting only as they contain a mixture of those, without more or less of which they will not conduct at all.* This (by the way) shows a new relation between metals and water heretofore unknown.

To illustrate this by a comparison, which, however, can only give a faint resemblance. Electric matter passes through conductors, as water passes through a porous stone, or spreads on their surfaces as water spreads on a wet stone; but, when applied to non

• This proposition is since found to be too general; Mr. Wilson having discovered, that melted wax and rosin will also conduct.

conductors, it is like water dropped on a greasy stone, it neither penetrates, passes through, nor spreads on the surface, but remains in drops where it falls. See farther on this head, in my last printed piece, entitled Opinions and Conjectures, &c. 1749.

Query. What are the effects of air in electrical experiments?

Answer. All I have hitherto observed are these. Moist air receives and conducts the electrical matter in proportion to its moisture, quite dry air not at all; air is therefore to be classed with the non-conductors. Dry air assists in confining the electrical atmosphere to the body it surrounds, and prevents its dissipating; for in vacuo it quits easily, and points operate stronger, that is, they throw off or attract the electrical matter more freely, and at greater distances; so that air intervening obstructs its passage from body to body in some degree. A clean electrical phial and wire, containing air instead of water, will not be charged, nor give a shock, any more than if it was filled with powder of glass; but exhausted of air, it operates as well as if filled with

Yet an electric atmosphere and air do not seem to exclude each other, for we breathe freely in such an atmosphere, and dry air will blow through it without displacing or driving it away. I question whether the strongest dry north-wester would dissipate it. I once electrified a large cork ball at the end of a silk thread three feet long, the other end of which I held in my fingers, and whirled it round, like a sling, one hundred times in the air, with the swiftest motion I could possibly give it; yet it retained its electric atmosphere, though it must have passed through eight hundred yards of air, allowing my arm in giving the motion to

A cold dry wind of North America.

add a foot to the semidiameter of the circle. By quite dry air, I mean the dryest we have; for perhaps we never have any perfectly free from moisture. An electrical atmosphere raised round a thick wire, inserted in a phial of air, drives out none of the air, nor on withdrawing that atmosphere will any air rush in, as I have found by a curious experiment* accurately made, whence we concluded that the air's elasticity was not affected thereby.

An Experiment towards discovering more of the Qualities of the Electric Fluid.

FROM the prime conductor, hang a bullet by a wire hook; under the bullet, at half an inch distance, place a bright piece of silver to receive the sparks; then let the wheel be turned, and in a few minutes (if the repeated sparks continually strike in the same spot) the silver will receive a blue stain, nearly the color of a watch-spring.

The experiment here mentioned was thus made. An empty phial was stopped with a cork. Through the cork passed a thick wire, as usual in the Leyden experiment, which wire almost reached the bottom. Through another part of the cork passed one leg of a small glass siphon, the other leg on the outside came down almost to the bottom of the phial. This phial was first held a short time in the hand, which, warming and of course rarefying the air within, drove a small part of it out throngh the siphon. Then a little red ink in a tea-spoon was applied to the opening of the outer leg of the siphon; so that as the air within cooled, a little of the ink might rise in that leg. When the air within the bottle came to be of the same temperature of that without, the drop of red ink would rest in a certain part of the leg. But the warmth of a finger applied to the phial would cause that drop to descend, as the least outward coolness applied would make it ascend. When it had found its situation, and was at rest, the wire was electrified by a communication from the prime conductor. This was supposed to give an electric atmosphere to the wire within the bottle, which might likewise rarefy the included air, and of course depress the drop of ink in the siphon. But no such effect followed.