Electrostatic machine used by Joseph Priestley, 1775. The glass globe (upper right) was rotated by the handle against a fixed 'rubber' (such as fur) and the charge collected by wires (top right) sweeping the globe. The voltage was soon high enough to spark across the gap (upper left). Joseph Priestley (1733-1804) was an English chemist. His most famous scientific research was on the nature and properties of gases. By clever design of apparatus and careful manipulation, Priestley isolated and characterized eight gases, including oxygen, and out of this work emerged his most important scientific texts: the six volumes of Experiments and Observations on Different Kinds of Air (1774-86), from which this image is taken. He also contributed to the understanding of photosynthesis and respiration.