Caption:
Hauksbee's electrical machines in which two glass vessels were independently rotated, one within the other. A dry hand applied o the outer revolving vessel produced a glow in the inner one. Turning both in a common or in opposite directions gave a more brilliant light. Francis Hauksbee the Elder (1660-1713) was an English scientist. In 1705 Hauksbee discovered that if he placed a small amount of mercury in the glass of his modified version of von Guericke's generator, evacuated the air from it to create a mild vacuum and rubbed the ball in order to build up a charge, a glow was visible if he placed his hand on the outside of the ball. The glow was bright enough to read by. This effect became the basis of the gas-discharge lamp, which led to neon lighting and mercury vapor lamps. In 1706 he produced an "Influence machine" to generate this effect. In 1709 he published Physico-Mechanical Experiments on Various Subjects which summarized much of his scientific work. This image has been color enhanced.