Charles Francois de Cisternay du Fay

The Discovery of Electricity (Charles Francois de Cisternay du Fay)

In 1733 Charles Francois de Cisternay du Fay noticed that objects that had been rubbed sometimes attracted and sometimes repelled each other. He explained this by proposing two different kinds of electricity. Vitreous electricity (from the Latin for "glass") is produced when glass or gems were rubbed. Resinous electricity (from the Latin for "resin," or "amber") is obtained by rubbing amber, silk, or paper. Du Fay argued that objects with different kinds of electricity attract each other, whereas those with the same kind of electricity repel.

Du Fay's discovery led to a theory of electricity that assumed the existence of two fluids. Objects that are not electrified were assumed to have equal amounts of these fluids, which neutralize each other. Rubbing an object was assumed to remove one of the fluids, leaving an excess of the other.