BREWSTER, Sir David, natural philosopher, distinguished especially for his original discoveries in the science of optics and his numerous and varied contributions to scientific literature, was born on the llth December ]781 at Jedburgh, where his father, a teacher of high reputation, was rector of the grammar school. At the early age of twelve he was sent to the University of Edinburgh, being intended for the clerical profession. Even before this, however, he had shown a strong inclination for physical inquiries, which had been fostered by his intimacy with a " self-taught philosopher, astronomer, and mathematician," as Sir Walter Scott called him, of great local fame James Veitch of Inchbonny. Veitch was particularly skilful in making telescopes, and may thus have had some influence in determining the precise direction of his young com panion s future researches. Though he duly finished his theological course and was licensed to preach, Brewster s natural preference for other pursuits, combined with a con stitutional nervousness, prevented him from engaging in the active duties of his profession. In 1799 he was induced by his fellow-student, Brougham, to study the inflection of light, repeating Newton s experiments ; and from this date he carried on, almost without interruption, the course of original discovery in the science of physical optics which constitutes one of his chief claims to distinc tion. The results of his investigations were communicated from time to time in papers to the Philosophical Transac tions of London and other scientific journals, and were admirably and impartially summarized by Professor James D. Forbes in his preliminary dissertation to the eighth edition of this Encyclopaedia. The fact that other philoso phers, notably Malus and Fresnel, were pursuing the same investigations contemporaneously in France does not invalidate Brewster s claim to independent discovery, even though in one or two cases the priority must be assigned to others.
The most important subjects of his inquiries are enumerated by Forbes under the following five heads : 1. The laws of polarization by reflection and refraction, and other quantitative laws of phenomena ; 2. The discovery of the polarizing 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, Experi ments on the absorption of light. In this line of investi gation the prime importance belongs to the discovery (1) of the connection between the refractive index and the polarizing angle, (2) of biaxal crystals, and (3) of the production of double refraction by irregular heating. These discoveries were promptly acknowledged by those best qualified to estimate their value. So early as the year 1807 the degree of LL.D. was conferred upon Brewster by Marischal College, Aberdeen; in 1815 he was made a member of the Royal Society of London, and received the Copley medal; in 1818 he received the Rumford medal of the Society; and in 1816 the French Institute awarded him one-half of the prize of three thousand francs for the two most important discoveries in physical science made in Europe during the two preced ing years. Among the non-scientific public his fame was spread more effectually by the invention, in 1816, of the elegant philosophical toy, the kaleidoscope, for which there was so great a demand both in England and America that for some time the supply could not meet it. An instru ment of higher interest, the stereoscope, which, though of much later date (1849-50), may be mentioned here, since along with the kaleidoscope it did more than anything else to popularize his name, was not, as has often been asserted, the invention of Brewster. Whcatstone discovered its principle and applied it as early as 1838 to the con struction of a cumbrous but effective instrument, in which the binocular pictures were made to combine by means of mirrors. To Brewster is due the merit of suggesting the use of lenses for the purpose of uniting the dissimilar pictures ; and, accordingly, the lenticular stereoscope, now in exclusive use, may fairly be said to be his invention. A much more valuable practical result of Brewster s optical researches may be traced in the vast improvement of the lighthouse system during the last half century. It is true that the dioptric apparatus was perfected indepen dently by Fresnel, who had also the satisfaction of being the first to put it into operation, the French Government being in this, as in many other cases, quicker than the English to perceive the value of new scientific discoveries. But it is indisputable that Brewster was earlier in the field than Fresnel; that he described the dioptric apparatus in 1812; that he pressed its adoption on those in authority at least as early as 1820, two years before Fresnel suggested it ; and that it was finally introduced into British light houses mainly by his persistent efforts. The tribute paid to his memory by his successor at the head of the University of Edinburgh was therefore as just as it was graceful : " Every lighthouse that burns round the shores of the British empire is a shining witness to the usefulness of Brewster s life."
Brewster s own discoveries, important though they were, were not his only, perhaps not even his chief, service to science. The extent and variety of his contributions to scientific literature were little short of marvellous. He commenced literary work in 1799 as a regular contributor to the Edinburgh Magazine, of which he acted as editor at the age of twenty. In 1807 he entered on a much larger undertaking, which cost him long continued labour, and, especially towards its close, great vexation and anxiety. The chance suggestion of a friend, who knew his varied powers, led to the projection, under his editorship, of the Edinburgh Encyclopedia, of which the first part appeared in 1808, and the last not until 1830. The work was, as might have been expected, strongest in the scientific department, and many of its most valuable articles were from the pen of its editor. At a later period he was one of the leading scientific contributors to the Encyclopaedia Britannica (seventh and eighth editions), the articles Electricity, Hydrodynamics. Magnetism, Microscope, Optics, Stereoscope, Voltaic Electricity, &c., being from his pen. In 1819 Brewster undertook further editorial work by establishing, in conjunction with Jameson, the Edinburgh Philosophical Journal, which took the place of the Edin burgh Magazine. After a time the title was again changed to the Edinburgh Journal of /Science, sixteen volumes of which appeared under Brewster s sole editor ship, with very many articles from his own pen. To the transactions of various learned societies he contri buted from first to last between three and four hundred papers, and few of his contemporaries wrote so much for the various reviews. In the North British Review alone seventy-five articles of his appeared. A list of his larger separate works will be found below. Special mention, however, must be made of the most important of them all his biography of Newton. In 1831 he published a short popular account of the philosopher s life in Murray s Family Library ; but it was not until 1855 that he was able to issue the much fuller Memoirs of the Life, Writings, and Discoveries of Sir Isaac Neivton, a work which embodied the results of more than twenty years patient investigation of original manuscripts and all other available sources.
communication with the most eminent scientific men, and
he was naturally among the first to recognize the benefit