BREWSTER, SIR DAVID (1781-1868), Scottish physicist, and one of the founders of the British Association, was born at Jedburgh on Dec. I1, 1781, and died on Feb. 1o, 1868, at Allerby, Melrose. He made his name by a series of investigations on the diffraction of light, the results of which he contributed from time to time to Philosophical Transactions and other scientific journals.
The most important subjects of his enquiries are enumerated by J. D. Forbes, in his preliminary dissertation to the 8th ed. of the Encyclopedia Britannica, under the following five heads: (I) The laws of polarization by reflection and refraction, and other quantitative laws of phenomena; (2) the discovery of the polariz ing structure induced by heat and pressure ; (3) the discovery of crystals with two axes of double refraction, and many of the laws of their phenomena, including the connection of optical structure and crystalline forms; (4) the laws of metallic reflection; (5) experiments on the absorption of light. In this investigation the prime importance belongs to the discovery (I) of the connection between the refractive index and the polarizing angle, (2) of bi axial crystals, and (3) of the production of double refraction by irregular heating.
Brewster was elected F.R.S. in 1815, and was awarded the Rum ford gold and silver medal for his discoveries in connection with the polarization of light in 1818. He did not invent the kalei doscope, but he may be said to have rediscovered it. He im proved the stereoscope by suggesting the use of lenses to combine the dissimilar binocular pictures. More important was his work in persuading the British authorities to adopt the dioptric ap paratus, perfected by Fresnel, in their lighthouses. He suggested its use for this purpose as early as 182o. Brewster was one of the group of scientific men who assembled in the archiepiscopal palace at York and developed the idea of a British Association for the Advancement of Science, realized in 1831. (See LEARNED SO CIETIES.) In 1838 Brewster became principal of the united col leges of St. Salvator and St. Leonard, St. Andrews, Scotland, and from 1859 till a short time before his death was principal of Edin burgh university. In 1849 he had the honour of succeeding J. J. Berzelius as one of the eight "foreign associates" of the Institute of France.
In spite of his activity in research and, in his later days, in university life, Brewster accomplished a mass of literary work. He edited the Edinburgh Encyclopaedia (1808-3o), was one of the leading contributors to the 7th and 8th editions of the Ency clopedia Britannica, joint editor (1819-24) of the Edinburgh Philosophic Journal, and then (1824-32) editor of the Edinburgh Journal of Science. Among his many separate publications may be mentioned his Treatise on Optics (1831) and his Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton See Home Life of Brewster (1869) by his daughter, Mrs. Gordon; Ostwald's Klassiker der exacten Wissenschiften, No. 168 (Leipzig, 1908).