Dufay, Charles François De Cisternay

Born Sept. 14, 1698, in Paris; died there July 16, 1739. French physicist. Member of the Paris Academy of Sciences (1723).

Beginning in 1732, Dufay was director of the Botanical Gardens. He was the first (1733-34) to arrive at the conclusion of the existence of two types of electricity, and he determined that similarly charged bodies repel each other, whereas oppositely charged bodies attract each other. He observed electrical sparks from an electrified, human body. Dufay designed the first electric measuring instrument—a prototype of the electroscope. He was the first to attempt to measure magnetic force with the aid of a magnetized needle, fastened by means of a spring (magnetometer).