Physicist, born in Somersetshire, of Quaker parents; studied medicine at home and abroad; renounced Quakerism, and began practice in London in 1800; was next year appointed professor of Natural Philosophy in the Royal Institution, 1802; made Secretary of the Royal Society, and was afterwards nominated for other important appointments; his principal work is a "Course of Lectures on Natural Philosophy and the Mechanical Arts," published in 1807, in which he propounded the undulatory theory of light, and the principle of the interference of rays; the hieroglyphic inscriptions of Egypt occupied much of his attention, and he is credited with having anticipated Champollion in discovering the key to them (1773-1829).