"Two cannon balls, when suspened by long cords, so as to hang quite near each other, are found to exert…
"If an excited substance be brought near a ball made of pith, or cork, suspended by a silk thread, the…
"b is a glass tube in water and c is a glass tube in mercury. The surface of the water in the tube b…
"Pith ball pendulum or electroscope; the figures illustrate also electrical attraction and repulsion."…
"Mutual action of solenoids. When two solenoids traversed by a current are allows to act on each other...attraction…