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By Root 985 0

to the cork as well as to the glass. The "attractive Virtue," as he put it, had been "communicated" from the glass to the cork. Curious to see how far this communication would extend, Gray attached ordinary thread to the cork, tied a shilling to the string, and found that the coin attracted feathers. He extended the string and tied on more objects—a piece of tin, an iron poker, a copper teakettle, various vegetables—and found that all became electrified. Gray attached thirty-two feet of thread to the corked end of the glass tube, tied a billiard ball to the other end of the string, and dangled it out a window. When he rubbed the glass, he found that the billiard ball still proved attractive.

Abandoning a plan to drop a string from the cupola of St. Paul's Cathedral, Gray decided to proceed horizontally. He snaked a long piece of iron wire along the ceiling of his workroom, suspending it from the beams with pieces of string. When he touched the wire with the rubbed glass wand, however, the attractive virtue did not communicate to the far end. Gray thought the string suspenders might be too thick, so he tried silk, which worked beautifully. Equally thin brass, however, failed, leading Gray to conclude that success depended upon the supports "being Silk, and not upon their being small." The differences between silk and brass wire raised the question of which objects could be supports and which receivers. (Before long another experimenter started calling these two classes conductors and insulators.) To test the electrical properties of the human body, Gray persuaded an orphan boy to allow himself to be suspended horizontally from the ceiling, supported at his chest and thighs by stout loops of silk. Gray rubbed his glass tube, touched it to the lad's feet, and found that he attracted feathers to his fingers.2

Philosophers at the time believed that electricity—as well as light, heat, and magnetism—consisted of exquisitely fine "fluids" that passed through ordinary matter. The electrical phenomena of attraction and repulsion were thought to be caused by jets of subtle fluids blowing into and out of tiny pores in larger objects. The public, however, was less concerned with theories of electricity than with the thrilling effects it produced. Members of polite society in the eighteenth century flocked to scientific lecture-demonstrations, where they learned about planetary motion, the shape of the Earth, and the size of the solar system. Newtonian physics could be a bit dull, but a suspended human body attracting objects to its fingers—that was magic. Electrical displays swept Europe in the 1740s, and a French entrepreneur sold electrical kits that included a glass wand for rubbing, light objects for attracting, and thick silk cords for hanging human conductors. In darkened rooms lecturers drew sparks—"electrical fire"—from the noses of suspended men.

In the electrical craze of the 1740s, "human conductors" were sometimes suspended from the ceiling by silk cords and charged with electricity.

Experimenters in Germany produced more flamboyant effects. They replaced the glass wand with a spinning globe and used a "rubber" of leather or paper to excite it. They also suspended prime conductors—usually a sword or gun barrel—near the globe to collect the charge. Experimenters were soon killing flies with shocks from their fingers and showcasing the "Venus electrificata," a woman whose kisses threw sparks. When a glass of brandy was lifted toward the lips of a charged man, the spark from his nose set the liquor aflame.3

Human conductors began to complain that these shocks were unpleasant, but they did not know true pain until they experienced another new device. In 1746 Pieter van Musschenbroek of the University of Leyden attempted to produce electricity with a glass globe and then store it in a jar of water. He attached a wire to the gun barrel that served as his prime conductor and placed the wire's end in a water-filled glass jar. While an assistant spun and rubbed the glass globe, Musschenbroek held the water jar in his hand and