Benjamin Franklin; Self-Revealed, Volume 2 (of 2) / A Biographical and Critical Study Based Mainly on his own Writings

by Wiliam Cabell Bruce

Purposing [he said] to analyze the electrified bottle, in order to find wherein its strength lay, we placed it on glass, and drew out the cork and wire, which for that purpose had been loosely put in. Then taking the bottle in one hand, and bringing a finger of the other near its mouth, a strong spark came from the water, and the shock was as violent as if the wire had remained in it, which shewed that the force did not lie in the wire. Then, to find if it resided in the water, being crouded into and condensed in it, as confin'd by the glass, which had been our former opinion, we electrified the bottle again, and, placing it on glass, drew out the wire and cork as before; then, taking up the bottle, we decanted all its water into an empty bottle, which likewise stood on glass; and taking up that other bottle, we expected, if the force resided in the water, to find a shock from it; but there was none. We judged then, that it must either be lost in decanting, or remain in the first bottle. The latter we found to be true; for that bottle on trial gave the shock, though filled up as it stood with fresh unelectrified water from a teapot.

By a similar course of experimentation with sash glass and lead plates, he also demonstrated that the form of the glass in the bottle was immaterial, that the power resided in the glass as glass, and that the non-electrics in contact served only like the armature of a loadstone to unite the force of the several parts, and to bring them at once to any point desired; it being the property of a non-electric that the whole body instantly receives or gives what electric fire is given to, or taken from, anyone of its parts. These experiments suggested the idea of intensifying the application of electrical forces by grouping numerous electrical centres.

We made [he said] what we called an electrical battery, consisting of eleven panes of large sash-glass, arm'd with thin leaden plates, pasted on each side, placed vertically, and supported at two inches distance on silk cords, with thick hooks of leaden wire, one from each side, standing upright, distant from each other, and convenient communications of wire and chain, from the giving side of one pane, to the receiving side of the other; that so the whole might be charged together, and with the same labour as one single pane; and another contrivance to bring the giving sides, after charging, in contact with one long wire, and the receivers with another, which two long wires would give the force of all the plates of glass at once through the body of any animal forming the circle with them. The plates may also be discharged separately, or any number together that is required.

When the idea of the electrical battery was formed by him, Franklin was not aware that Smeaton and Bains had previously assembled panes of glass for the purpose of giving an electrical shock.

At the time that this letter was written, Franklin had added to his electrical exploits that of electrifying a mezzotint of the King in such a manner that, if anyone attempted to take the crown off his head, he would receive a "terrible blow."

If the picture were highly charged [he said], the consequence might perhaps be as fatal as that of high treason.

The operator [he continues], who holds the picture by the upper end, where the inside of the frame is not gilt, to prevent its falling, feels nothing of the shock, and may touch the face of the picture without danger, which he pretends is a test of his loyalty. If a ring of persons take the shock among them, the experiment is called The Conspirators.

Another far more significant exploit was the application of electrical energy in such a way as to set an electrical Jack revolving with such force and swiftness as to carry a spitted fowl around before a fire with a motion fit for roasting.

This wheel was driven by an electrical battery, but Franklin also devised what he called a self-moving wheel that was, by a different electrical method, revolved with so much force and rapidity that he thought that it might be used for the ringing of chimes and the movement of light-made orreries. And after observing that a thin glass bubble, about an inch in diameter, weighing only six grains, being half filled with water, partly gilt on the outside, and furnished with a wire hook, gave, when electrified, as great a shock as a man can well bear, Franklin exclaims, "How great must be the quantity (of electrical fire) in this small portion of glass! It seems as if it were of its very substance and essence. Perhaps if that due quantity of electrical fire so obstinately retained by glass, could be separated from it, it would no longer be glass; it might lose its transparency, or its brittleness, or its elasticity."

This letter also reaches the conclusion that bodies, having less than the common quantity of electricity, repel each other, as well as those that have none.