In order to succeed in these experiments, it is requisite that the two bodies which are put near each other, to find out the nature of their electricity, be rendered as electrical as possible, for if one of them was not at all or but weakly electrical, it would be attracted by the other, though it be of that sort that should naturally be repelled by it.

But the experiment will always succeed perfectly well if both bodies are sufficiently electrical."(1) As we now know, Dufay was wrong in supposing that there were two different kinds of electricity, vitreous and resinous.

A little later the matter was explained by calling one "positive" electricity and the other "negative," and it was believed that certain substances produced only the one kind peculiar to that particular substance.

We shall see presently, however, that some twenty years later an English scientist dispelled this illusion by producing both positive (or vitreous) and negative (or resinous) electricity on the same tube of glass at the same time.
After the death of Dufay his work was continued by his fellow-countryman Dr.Joseph Desaguliers, who was the first experimenter to electrify running water, and who was probably the first to suggest that clouds might be electrified bodies.

But about, this time--that is, just before the middle of the eighteenth century--the field of greatest experimental activity was transferred to Germany, although both England and France were still active.