STEWART, BALFOUR (1828-1887), Scottish physicist, was born in Edinburgh on the 1st of November 1828, and was educated at the university of that city. The son of a tea merchant, he was for some time engaged in business in Leith and in Australia, but, returning to his studies of physics at Edinburgh, he became assistant to J. D. Forbes in 1856. Forbes was especially interested in questions of heat, meteorology, and terrestrial magnetism, and It was to these that Stewart also mainly devoted himself. Radiant heat first claimed his attention, and by 1858 he had completed his first investigations into the subject. These yielded a remarkable extension of Pierre Prevost's " Law of Exchanges," and enabled him to establish the fact that radiation is not a surface phenomenon, but takes place throughout the interior of the radiating body, and that the radiative and absorptive powers of a substance must be equal, not only for the radiation as a whole, but also for every constituent of it. In recognition of this work he received in 1868 the Rumford medal of the Royal Society, into which he had been elected six years before. Of other papers in which he dealt with this and kindred branches of physics may be mentioned " Observations with a Rigid Spectroscope," " Heating of a Disc by Rapid Motion in Vacuo," " Thermal Equilibrium in an Enclosure Containing Matter in Visible Motion," and " Internal Radiation in Uniaxal Crystals." In 1859 he was appointed director of Kew Observatory, and there naturally became interested in problems of meteorology and terrestrial magnetism. In 1870, the year in which he was very seriously injured in a railway accident, he was elected professor of physics at Owens 1 On the 6th of November 1 878 his body was stolen from St Mark's churchyard in New York, but recovered in 1881 upon the payment of $20,000, and buried in the crypt of the cathedral in Garden City.
2 Upon her death she left a small part of her estate to her other relatives and her servants, about $4,631,000 to Charles J. Clinch, a kinsman, and about $9,262,000 to Judge Henry Hilton (1824-1899), a business associate of Stewart, who had received a legacy of $1,000,000 from Stewart, and who managed Mrs Stewart's business affairs after her husband's death. Clinch and Hilton were executors, and it was understood that Hilton should complete the cathedral at Garden City and endow schools there. A nephew of Mrs Stewart in 1887 sued to break the will on the ground that Hilton had unduly influenced her; the case was compromised out of court in 1890 and Mrs Stewart's relatives received more of her estate than they would have got under the terms of the testament.
College, Manchester, and retained that chair until his death, which happened near Drogheda, in Ireland, on the 19th of December 1887. He was the author of several successful textbooks of science, and also of the article on " Terrestrial Magnetism " in the ninth edition of this Encyclopaedia. In conjunction with Professor P. G. Tait he wrote The Unseen Universe, at first published anonymously, which was intended to combat the common notion of the incompatibility of science and religion.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)