du Fay and the Two Field Theory of Electricity
Charles du Fay was the first to state the 'two fluid' theory of electricity. According to this theory there were two different types of electricity. One type was 'vitreous electricity', the type of electricity that appeared when a glass rod rubbed with silk. The other type was 'resinous electricity', appearing on a rubber rod rubbed with wool – notice that rubber is formed of resin..
Du Fay observed that when electricity was passed from a charged to an uncharged object, both objects would be charged with the sa same type of charge as one on the charged object originally.
He observed that objects charged with the same type of electricity repelled each other, while objects charged with different types of charge repelled each other and from this he deduced that electric charge came in two types. Today his observations are summarised in the phrase, 'like charges repel, unlike charges attract'. He failed to find any link between the two types of electricity, or to find any insight into their nature.