Two Kinds of Electrical Fluid: Vitreous and Resinous - 1733
Charles François de Cisternay DuFay (1698 - 1739)

Charles François de Cisternay DuFay, French scientist and superintendent of the Jardin du Roi of Paris, made the important discovery that there are two kinds of electricity, one produced by glass (vitreous) and the other by resin (resinous). These terms were used for fifteen years until they were replaced with positive and negative  - coined independently by William Watson and Benjamin Franklin.³   This discovery, along with Dufay's other observations on electricity, were reported in a paper written in December of 1733 and printed in Volume 38 of the Philosophical Transactions of the Royal Society in the following year (see excerpt below).

Dufay's work clarified many of the unexplained phenomena associated with electricity.  His outstanding contributions to the knowledge of electrical art include:

1) All bodies can be electrically charged by heating and rubbing, except metals and soft /liquid bodies.
2) All bodies, including metal and liquid, can be charged by influence (induction).
3) The electrical properties of an object unique to color are affected by the dye, not the color itself.
4) Glass is as satisfactory as silk as an insulator.
5) Thread conducts better wet than dry.
6) There are two states of electrification, Vitreous and Resinous.
7) Bodies electrified (charged) with vitreous electricity attract bodies electrified with resinous electricity and repel other bodies electrified with vitreous electricity.

Additional Excerpts from Dufay's "A Discourse concerning Electricity"