YOUNG, THOMAS English man of science, belonged to a Quaker family of Milverton, Somerset, where he was born on June 13, 1773. At the age of fourteen he was acquainted with Latin, Greek, French, Italian, Hebrew, Arabic and Persian. He studied medicine in London, Edinburgh and GOttingen. In 1797 he entered Emmanuel College, Cambridge, and in 1799 he established himself as a physician in London. Appointed in i8or professor of physics at the Royal Institution, in two years he delivered ninety-one lectures, which contain a remarkable number of anticipations of later theories. He resigned in 1803. In the previous year he was appointed foreign secretary of the Royal Society of which he had been elected a fellow in 1794. In 1816 he was secretary of a commission charged with ascertaining the length of the seconds pendulum, and in 1818 he became secretary to the Board of Longitude and superintendent of the National Almanac. He died in London on May io, 1829. Young is perhaps best known for his work in physical optics, as the author of a remarkable series of researches which did much to establish the undulatory theory of light, and as the dis coverer of the principle of interference of light. (See INTERFER ENCE.) He gave the word "energy" its present scientific signifi cance and gave his name to Young's modulus. In 1793 he ex plained the mode in which the eye accommodates itself to vision at different distances; in 180i he described the defect known as astigmatism; and in his lectures he put forward the hypothesis, afterwards developed by H. von Helmholtz, that colour perception depends on the presence in the retina of three kinds of nerve fibres which respond respectively to red, green and violet light. In physiology he made an important con tribution to haemadynamics in the Croonian lecture for 1808 on the "Functions of the Heart and Arteries." In another field of research, he was one of the first successful workers at the decipherment of Egyptian hieroglyphic inscriptions. Some of his
conclusions appeared in the famous article on Egypt which he wrote in 1818 for the Encyclopedia Britannica.
His works were collected, with a Life by G. Peacock, in 1855. YOUNGHUSBAND, SIR FRANCIS (EDWARD) ), British soldier, explorer and author, was born at Murree, India, on May 31, 1863, and educated at Clifton and Sandhurst. He entered the army in 1882, and rose to the rank of lieutenant-colonel in 1908. In 1886 he crossed the heart of Central Asia, by crossing the Murtagh, the great mountain bar rier between China and Kashmir. In 1890 he was transferred to the Indian political department, and in 1902 accompanied the British mission to Tibet, sent out to counteract the Russian influence on the Dalai Lama. The mission was ended by the treaty of Sept. 7, 1904, and Younghusband was made K.C.I.E. in the same year. His work during this period resulted in an extension of the Indian system of triangulation which finally determined the geographical position of Lhasa. He also proved that the Murtagh is the true water-divide west of the Tibetan plateau. Sir Francis returned to England in 1905 and was ap pointed Bede lecturer at Cambridge, but in 1906 he went to Kashmir as resident, remaining there until 1909. From the time when he first went to India he travelled widely in India and also ill Manchuria, China, Turkistan and South Africa. He was made K.C.S.I. in 1917.