Static electricity device. 18th century engraving of a device for demonstrating static electricity and its ability to produce light. A glass sphere (at top centre) could be rotated by means of the handle at lower right. The static was generated by the operator holding their hand against the sphere as it rotated, and it caused an electric discharge glow in the partial vacuum within the sphere. Image taken from Physico-mechanical Experiments on Various Subjects (1709) by Francis Hauksbee.