William Hyde Wollaston (1766-1828), English chemist. Wollaston was born at East Dereham, Norfolk, and was educated at Cambridge where he graduated as a physician. In 1800, having given up a medical practice, Wollaston devised an improved method for processing platimun ore. This led to the discovery of the elements palladium (1802) and rhodium (1804), and to a significant private income. He also pioneered powder metallurgy, the use of heat and pressure to convert powders into metal articles. He did useful work in physics, showing that electricity caused by friction is identical to that from a voltaic pile ('battery'). In optics he invented the camera lucida as a drawing aid for artists, the reflecting goniometer for precise determination of angles and the Wollaston prism that seperates a light beam into two divergent polarised light beams.