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. It concludes with a lively paragraph: