Dufay, Charles

[düfay] (1698–1739) French chemist: discovered positive and negative charges of static electricity.

Dufay came from an influential family, which secured an army career for him; he left as a captain to become a chemist at the Académie des Sciences when he was 25. He had no training in science, but he began to study electricity in 1733. He showed that there are two kinds of electricity (and only two) generated by friction; he called them vitreous and resinous because they were obtained by rubbing glass (or rock crystal, hair or wool) or resin (or amber, silk or paper) respectively; they are the positive and negative charges of today. Dufay showed that like types repelled and unlike kinds attracted one another. The ‘two-fluid’ theory of electricity was linked with these results in opposition to later one-fluid theory. Dufay’s experiments included suspending a boy by silk cords, electrifying him by friction and drawing sparks from him in London had done similar experiments, and had also distinguished conductors from insulators (eg silk from metal wire).