MAXWELL, J,ums CLERK-, one of the greatest of modern natural philosophers, was the only son of John Clerk-Maxwell of Middlebie, a, cadet of the old Scottish family of Clerk of Penicuick. He was b. in 1831 and died in November, 1879. He was educated in boyhood at the Edinburgh academy. His first published scientific paper was read Col him by prof. Forbes to the Royal society- of Edinburgh before lie xvas fifteen, and when he had received no instruction in mathematics beyond a few books of Euclid, and the merest elements of algebra. He spent thre,e years at the university of Edinburgh, work ing with physical and-chemical apparatus, and devouring all sorts of scientific works in the library. During this period he wrote two valuable papers, Oa the Theory of Rolling Curves, and On the Equilibrium of Elastic Solids. Thus he brought to Cambridge, in the autumn of 18'50, a mass of knowledge which was really immense for so young a man, but in a state of disorder appalling to his private tutor. But by slier strength of intel lect, though with the very minimum of knowledge how to use it to advantage under the conditions of the examination, he obtained in 1854 the position of second wrangler, and. was equal with the senior wrangler in the higher ordeal of the Smith's prize.
In 1856 lie became professor of natural philosophy in Marischal college, Aberdeen; in 1860 professor of physics and astronomy in King's college, London. He was succes sively scholar and fellow of Trinity; and was elected an honorary fellow of Trinity xvlien he finally became, in 1871, professor of experimental physics in the university of Cambridge. There can be no doubt that the post to which be was ultimately cAlled was one for which he was in every way pre-eminently qualified; and the Cavendish laboratory, erected and furnished under his supervision, remains as remarkable a monument to his wide-ranging practical knowledge and theoretical skill as it is to the well-directed munifi cence of its noble founder. In clearness of mental vision, iu power of penetration, and in the possession of that patient determination to which Newton ascribed all his success, 'Maxwell is to be ranked with Faraday. He was too rapid a thinker to be a good lecturer, except for the very highest class of students. The great work of his life is undoubtedly his treatise on Electricity and Magnetism (2 vols. 1873). He had previously, from 1856. onward, published various papers on these subjects, following very closely the experi mental procedure of Faraday. His great object was to construct a theory of electricity in which " action at a distance" should have no place; and his success was truly wonder ful. There can be little doubt that lie has succeeded in laying the basis of a physical theory of electric and magnetic phenomena, quite as securely founded as in the undula tory theory of light: and the luminiferous ether, which is required for the one series of phenomena, is shown to be capable of accounting for the others also. One grand test is found in the fact that, if his hypothesis be correct, the velocity of light ought to be equal to the ratio of the electrokinetic unit to the electrostatic unit. We are not yet sure of
either quantity to within two or three per cent; but the most probable values of each agree so well as almost to put the hypothesis beyond doubt. In Nature, vol. vii. p. 478, the reader will find an account of the more remarkable discoveries in this extraordinary book, which suffices of itself to put Maxwell in the very front rank of scientific men.
Another subject to which he devoted much attention, and in which his numerous dis coveries were acknowledged by the award of the Rumford medal, was the perception of color, the three primary color sensations, and the cause of color-blindness. He was the first to make color-sensation the subject of actual measurement.
He obtained the Adams prize from the university of Cambridge for his splendid dis cussion of the dynamical conditions of stability of the ring-system of Saturn, in which he aaowed that the only hypothesis consistent with the continued existence of these rings is that they consist of discrete particles of matter, each independently a satellite.
He was perhaps best known to the public by his investigations on the kinetic theory of gases, with their singular results as to the nature of gaseous friction, the laws of dif fusion, the length of the average free path of a particle, and the dimensions of the parti cles of various gases. His Bradford " Discourse on -Molecules" is a classic in science.
Besides a great number of papers on various subjects, mathematical, optical, dynami cal, he published ATI extraordinary text-book of the Theoky of Heat (which has already gone through several editions) and an exceedingly suggestive little treatise on Matter and _Motion. In 1879 lie edited, with copious aud very valuable original notes, The ElectricaC Researches of the Hon. Henry Cavewlish, a work which shows that that remarkable man had (a hundred years ago) made out for himself much of what was till very lately looked upon as one of the chief triumphs of the present century.
Maxwell obtained the Keith prize of the royal society of Edinburgh for a valuable investigation of stresses and strains in girders and frames; he took a prominent part in the .construction of the British association unit of electrical resistance, and in the writing of its admirable reports on the subject; and he discovered that viscous fluids, while yielding to stress, possess double refraction. He was excessively ingenious in illustration, especially by means of diagrams; and possessed a singular power of epigrammatic versi fication, as the reader of Nature and Blackwood cannot fail to remember. Some of his last and very best scientific work adorns and enriches the new edition of the Encyclopadia Britannica. In these days of materialism it is not superfluous to record that he was, in the full sense of the word, a Christian; and that he asserted that he had examined every form of atheism which he had met, with the result of finding that all ultimately required the recognition of a personal God.