born June 13, 1773, Milverton, Somerset, Eng.
died May 10, 1829, London
English physicist.
Trained as a physician, he practiced medicine at St. George's Hospital (from 1811 until his death) but spent much of his time on scientific research. He was the first to describe and measure astigmatism (180001) and the first to explain colour sensation in terms of retinal structures corresponding to red, green, and violet (1801). He established the principle of interference of light, thus resurrecting the century-old wave theory of light (1801). He explained capillarity independently of Pierre-Simon Laplace . Investigating elasticity, he proposed Young's modulus, a numerical constant that describes the elastic properties of a solid undergoing tension or compression. His other work included measuring the size of molecule s and surface tension in liquids. With J.-F. Champollion , he helped decipher the inscriptions on the Rosetta Stone (181314).