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burgh, 1868.
- 'Burns in Drama, together with Saved Leaves,' Edinburgh, 1878, a collection of literary writings.
- 'Darwinianism: Workmen and Work,' Edinburgh, 1894, an acute criticism of the Darwinian theory of evolution.
- 'What is Thought? ' Edinburgh, 1900.
- 'The Categories,' Edinburgh, 1903; 2nd edit. 1907; an appendix to the former book, both further elucidating the Hegelian position.
A painted portrait by Stirling's daughter Florence is in the possession of the family. There is also a black-and-white drawing, of which a replica is in the philosophy classroom of St. Andrews University.
[A biography of Stirling, by his daughter Amelia, is in course of publication.]
STOKES, Sir GEORGE GABRIEL, first baronet (1819–1903), mathematician and physicist, born at Skreen, co. Sligo, 13 Aug. 1819, was youngest son of Gabriel Stokes, rector of Skreen, by his wife Elizabeth, daughter of John Haughton, rector of Kilrea, co. Derry. First educated at Dr. Wall's school in Dublin from 1831, he proceeded in 1835 to Bristol college under Dr. Jerrard, the mathematician, and entered Pembroke College, Cambridge, in 1837, becoming senior wrangler, first Smith's prizeman, and fellow of his college in 1841.
In his early Cambridge years he established a close scientific friendship with William Thomson (afterwards Lord Kelvin) [q. v. Suppl. II], which gathered force throughout their long lives. Both were impelled by the keenest interest in the advance of scientific discovery, but their endowments were in some respects complementary. Stokes remained a student throughout has life, closely pondering over mathematical questions and the causes of natural phenomena, perhaps over-cautious in drawing conclusions and in publication of his work, remarkable for his silence and abstraction even in crowded assemblies, but an excellent man of affairs, inspiring universal confidence for directness and impartiality in such administration as came to him. Thomson, during all his career, took Stokes as his mentor in the problems of pure science which he could not find leisure to probe fully for himself; and, though their opinions sometimes clashed, yet in the main no authority was with him more decisive or more venerated than that of his friend. In 1845, at the end of his undergraduate course, Thomson took over the editorship of the 'Cambridge Mathematical Journal' from Robert Leslie Ellis [q. v.], and for the following ten years his own contributions and those which he obtained from Stokes made that journal a classic. In 1849 Stokes was appointed Lucasian professor of mathematics at Cambridge, and he held the post till his death.
In his early years of residence as a graduate Stokes promoted most conspicuously the development of advanced mathematical knowledge at Cambridge. His own earliest work was mainly on the science of the motion of fluids, which he found in the preliminary stage in which it had been left by Lagrange, notwithstanding some sporadic work done by George Green [q. v.], then resident at Cambridge; in a few years he developed it into an ordered mathematical and experimental theory. To this end, in addition to a very complete discussion of the phenomena of waves on water, he created, in two great memoirs of dates 1845 and 1850, the modern theory of the motion of viscous fluids, a subject in which some beginnings had been made by Navier. In the later of these memoirs the practical applications, especially to the important subject of the correction of standard pendulum observations for aerial friction, led him into refined extensions of mathematical procedure, necessary for the discussion of fluid motion around spheres and cylinders; these, though now included under wider developments in pure analysis, have remained models for physical discussion, and have been since extensively applied to acoustics and other branches of physical science.
In the science of optics he had already in 1849 published two memoirs on Newton's coloured rings, treated always with dynamical implications; one appeared in 1851 establishing on a firm physical basis the explanation of Newton's colours of thick plates; and he had elucidated the principles of interference and polarisation in many directions. In 1849 a new path was opened in the great memoir on 'The Dynamical Theory of Diffraction,' which deals with the general problem of propagation of disturbances spreading from vibrating centres through an elastic æther, and in which mathematical expressions were developed wide enough to include the Hertzian theory of electrical vibrations and other more recent extensions of the theory of radiation. A side problem was the experimental investigation of the displacement of the plane of polarisation of light by diffraction, in order, by comparison with the theory, to ascertain the relation
