Thomas Young, an English physicist, born of Quaker parents at Milverton, Somersetshire, June 13, 1773, died in London, May 10, 1829. He was able to read fluently at the age of two, learned surveying at eight, studied at school, besides the classical and modern languages, Hebrew, Persian, and Arabic, and in order to construct a microscope mastered the differential calculus. After seven years spent in private study, he studied medicine in London, Edinburgh, and Göttingen, and in February, 1797, returned to England. To qualify himself for membership in the college of physicians, he entered Emmanuel college, Cambridge, as a matter of form, and graduated in 1799. In 1801 he was appointed professor of natural philosophy at the royal institution; but he was not a popular lecturer, and in 1803 he resigned. In 1802 he published a "Syllabus of a Course of Lectures on Natural and Experimental Philosophy," containing the announcement of the discovery of the law of interference of light, which contributed largely to the establishment of the undulatory theory. (See Light, vol. x., pp. 436 and 442.) In 1808 he became a fellow of the college of physicians, in 1810 was elected one of the physicians of St. George's hospital, and in 1818 was appointed secretary of the board of longitude, on the dissolution of which he became sole conductor of the "Nautical Almanac." From 1802 till his death he was foreign secretary of the royal society, and during the latter years of his life was a member of the advisory scientific committee of the admiralty.

Dr. Young also engaged in the study of Egyptian hieroglyphics, and held several controversies with Champollion. His conclusions were published in the article "Egypt" in the supplement to the "Encyclopaedia Britannica" in 1819, and show that he first determined that the wings on the Rosetta stone contain the name of Ptolemy, and that the characters are phonetic. His other works include "A Course of Lectures on Natural Philosophy and the Mechanical Arts" (2 vols. 4to, 1807; new ed. by Prof. Kelland, 2 vols, royal 8vo, 1845); "A System of Practical Nosology, with an Introduction to Medical Literature" (1813); "A Practical and Historical Treatise on Consumptive Diseases " (1815); "Elementary Illustrations of the Celestial Mechanics of Laplace" (1821); and "Rudiments of an Egyptian Dictionary" (1830). His miscellaneous works have been collected by Dean Peacock and John Leitch (4 vols. 8vo, London, 1855), by the former of whom his life was written (8vo, 1855).