William Hyde Wollaston, an English natural philosopher, born Aug. 6, 1766, died in London, Dec. 22, 1828. He received the degree of M. D. at the university of Cambridge in 1793, practised medicine for some time at Bury St. Edmunds, and then removed to London, where he devoted himself almost exclusively to chemical and physical investigations. His important researches were mainly embodied in a series of papers published in the "Philosophical Transactions," and embrace almost the entire range of physical science. He early maintained the chemical doctrine of galvanic action, and was the first to demonstrate the identity of galvanism and frictional electricity: As a result of his experiments on the ores of the more refractory metals, he determined a process (known as the Wollaston process) of isolating platinum in a pure state, and in 1803 discovered in association with the ore of that metal palladium and rhodium. He subsequently devised a means of rendering platinum malleable, by which he acquired great wealth, and for which he received the royal medal of the royal society shortly before his death.

To him is due the discovery of the dark or Fraunhofer lines in the solar spectrum, the existence of which he detected in 1802 while viewing a beam of sunlight through an ordinary glass prism. (See Spectrum Analysis.) Among his more important scientific inventions are the double plate and thimble galvanic batteries, the latter so minute as to be embraced in the compass of a thimble; the sliding rule of chemical equivalents; the camera lucida; the reflecting goniometer for measuring the angles of crystals; and the cryophorus, whereby water is frozen by means of its own evaporation. He also improved the construction of the microscope by introducing the Wollaston doublet or compound lens. In 1806 he was elected secretary, and in 1820 president of the royal society.