Examples of this are his work on lubrication, which has led to important practical inventions; on the laws of the flow of water in pipes, with the recognition of the ‘critical velocity’, now universally known by his name, at which the flow changes its character; and on the ‘dilatancy’, as he called it, of granular media. The same peculiar insight is shown in his papers on atmospheric refraction of sound, and on the ‘group-velocity’ of water waves, where, in both cases, he made important additions to the work of Sir George Gabriel Stokes [q.v.].
Although Reynolds made valuable contributions to engineering practice, as in the design of turbine pumps, and in the study of the laws of communication of heat from a metal surface to a fluid, his scientific reputation will probably rest mainly on his work in general physics, although this, it may be said, was suggested often by some practical question of engineering. The most extensive piece of experimental work which he carried out was a determination of the mechanical equivalent of heat from a novel point of view. The object here was the direct measurement of the amount of heat required to raise a pound of water from the freezing to the boiling point, the result being thus independent of the thermometric properties of any particular substance, such as mercury or glass. This must always rank as a classical instance of the determination of a physical constant.
The scientific papers of Reynolds were published in a collected form, Papers on Mechanical and Physical Subjects, in three volumes (1900–1903). Of their originality and value there is no question, but it cannot be said that they are always easy to follow. The leading idea is in most cases simple; indeed, Reynolds's bias was always to look for a simple explanation, rather than for one which depended on the concurrence of a number of independent causes. But the involved style of exposition which he adopted had a tendency to perplex all but determined students, with the result that much of his work, especially his theoretical work, was long in gaining general acceptance. By his scientific compeers his worth was early recognized. He was elected a fellow of the Royal Society in 1877, and was awarded its gold medal in 1888.
The character of Reynolds was, like his writings, strongly individual. Somewhat reserved in serious or personal matters, and occasionally combative and tenacious in matters of university politics, he was kindly and generous in all ordinary relations of life. He had a keen sense of humour, and delighted in starting paradoxes, which he would maintain, half seriously and half playfully, with great ingenuity and resource. After his retirement (1905) he lived at St. Decuman's, Somerset, where he died 21 February 1912. An admirable portrait by the Hon. John Collier hangs in the hall of Manchester University.
Reynolds married twice: first, in 1868 Charlotte (died 1869), daughter of Dr. Chadwick, of Leeds; secondly, in 1881 Annie Charlotte, daughter of the Rev. Henry Wilkinson, rector of Otley, Suffolk. By his second marriage he left three sons and a daughter.
[Proceedings of the Royal Society, vol. lxxxviii, A, 1912–1913; private information; personal knowledge.]
RHONDDA, first Viscount (1856-1918), statesman, colliery proprietor, and financier. [See Thomas, David Alfred.]
RHŶS, Sir JOHN (1840–1915), Celtic scholar, was born at Aber Ceirio Fach, Cardiganshire, 21 June 1840, the eldest son of Hugh Rhŷs, yeoman farmer of Ponterwyd, Cardiganshire, by his wife, Jane Mason, who, according to family tradition, was of Scottish extraction. John Rhŷs received his elementary education at Brynhwyth (as he insisted on writing the name), Pant-y-ffynon, and at the British school at Penllwyn, near Aberystwyth. After a course of study at the Bangor Normal College he was appointed master of a school at Rhos-y-bòl in Anglesey. In 1865 he was introduced by Chancellor James Williams, of Llanfairynghornwy, Anglesey, to Dr. Charles Williams, principal of Jesus College, Oxford, who, after a brief oral examination, offered him an exhibition at that college on the spot. Rhŷs went up to Oxford in the same year, obtained a second class in classical moderations in 1867, and a first class in literae humaniores in 1869. Towards the end of the latter year he was elected to a fellowship at Merton College.
Visits to French and German universities in the long vacations of 1868 and 1869, and again in 1870–1871 when he matriculated at Leipzig and attended the lectures of, among others, Georg Curtius and August Leskien, turned Rhŷs's attention definitely towards linguistic research. He contributed to the first volume of the Revue Celtique (1870), and in the course
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