Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/679

M A X M A Y 647 with this branch of physics ; one is an extension and simplification of some of Bolzmann s chief results, the other treats of the kinetic theory as applied to the motion of the radiometer. He has written an admirable text-book of the Theory of Heat, which has already (1882) gone through several editions, and a very excellent elementary treatise on Matter and Motion. Even this, like his other and larger works, is full of valuable matter, worthy of the most attentive perusal not of students alone but of the very foremost scientific men. But the great work of his life was devoted to electricity. He began by reading with the most profound admiration and attention the whole of Faraday s extraordinary self- revelations, and proceeded to translate the ideas of that master into the succinct and expressive notation of the mathematicians. A considerable part of this translation was accomplished during his career as an undergraduate in Cambridge. The writer had the opportunity of perusing the MS. on Faraday s Lines of Force, in a form little different from the final one, a year before Maxwell took his degree. His great object, as it was also the great object of Faraday, was to overturn the idea of action at a distance. The splendid researches of Poisson and Gauss had shown how to reduce all the phenomena of statical electricity to mere attractions and repulsions exerted at a distance by particles of an imponderable on one another. Sir W. Thomson had, in 1846, shown that a totally different assumption, based upon other analogies, led (by its own special mathematical methods) to precisely the same results. He treated the resultant electric force at any point as analogous to the flux of heat from sources distri buted in the same manner as the supposed electric particles. This paper of Thomson s, whose ideas Maxwell afterwards developed in an extraordinary manner, seems to have given the first hint that there are at least two perfectly distinct methods of arriving at the known formulas of statical electricity. The step to magnetic phenomena was compara tively simple ; but it was otherwise as regards electro magnetic phenomena, where current electricity is essentially involved. An exceedingly ingenious, but highly artificial, theory had been devised by Weber, which was found capable of explaining all the phenomena investigated by Ampere, as well as the induction currents of Faraday. But this was based upon the assumption of a distance-action between electric particles, whose intensity depended on their relative motion as well as on their position. This was, of course, even more repugnant to Maxwell s mind than the statical distance-action developed by Poisson. The first paper of Maxwell s in which an attempt at an admissible physical theory of electromagnetism was made was communi cated to the Royal Society in 1867. But the theory, in a fully developed form, first appeared in his great treatise on Electricity and Magnetism (1873). This work, already in a second edition, is one of the most splendid monuments ever raised by the genius of a single individual. Availing himself of the admirable generalized coordinate system of Lagrange, Maxwell has shown how to reduce all electric and magnetic phenomena to stresses and motions of a material medium, and, as one preliminary, but excessively severe, test of the truth of his theory, has shown that (if the electromagnetic medium be that which is required for the explanation of the phenomena of light) the velocity of light in vacuo should be numerically the same as the ratio of the electromagnetic and electrostatic units. We do not as yet certainly know either of these quantities very exactly, but the means of the best determinations of each separately agree with one another more closely than do the various values of either. There seems to be no longer any possibility of doubt that Maxwell has taken the first grand step towards the discovery of the true nature of electrical phenomena. Had he done nothing but this, his fame would have been secured for all time. But, striking as it is, this forms only one small part of the contents of his truly marvellous work. One of his last great contributions to science was his editing (with copious original notes) the Electrical Researches of the Hon. Henry Cavendish, which had been altogether unappreciated by the witlings to whom they had previously been confided. It now appears that Cavendish, already famous by many other researches (such as the mean density of the earth, the composition of water, <fec.), must be looked on as, in his day, a man of Maxwell s own stamp as a theorist, and an experimenter of the very first rank. This encyclopaedia has been, in its scientific aspects, greatly indebted to Clerk Maxwell. The articles ATOM, ATTRACTION, CAPILLARITY, DIFFUSION, ETHER, &c., were intended as parts merely of one comprehensive system, in which a general resumd of all that is known of the pro perties of matter should be given in simple yet profound completeness. The reader of these articles cannot but feel how much has been lost when this splendid series cannot be completed by its initiator. In private life Clerk Maxwell was one of the most lovable of men, a sincere and unostentatious Christian. Though perfectly free fro v m any trace of envy or ill-will, he yet showed on fit occasion his contempt for that pseudo-science which seeks for the applause of the ignorant by professing to reduce the whole system of the universe to a fortuitous sequence of uncaused events. His collected works will shortly be issued from the Pitt press ; and an extended biography, by his former school fellow and lifelong friend Professor Campbell, has just been published (1882). (p. G. T.) MAXWELL, SIR WILLIAM STIRLING-, BART. (1818- 1878), man of letters, the only son of Mr Archibald Stirling of Keir, Perthshire, and of Elizabeth, second daughter of Sir John Maxwell, seventh baronet of Pollok, Renfrewshire, was born at Kenmure, near Glasgow, in 1818. William Stirling was educated at Trinity College, Cam bridge, where he graduated in 1839, and afterwards he spent some years on the Continent chiefly in France and Spain. Having succeeded his father as proprietor of Keir in 1846 (when he was made vice-lieutenant of Perthshire), he in 1852 entered parliament as member for that county ; and he was several times re-elected. On the death of his uncle in 1865 he succeeded to the baronetcy and estates of Pollok, in respect of which he assumed the additional name of Maxwell. In the same year he became deputy- lieutenant of Lanarkshire, and a like office was conferred on him in Renfrewshire in 1870. The services which his talent, energy, and wealth enabled him to render to literature were recognized in a great variety of ways by numerous universities; in 1863 he was chosen lord rector of St Andrews, in 1871 the same honour was conferred by Edinburgh, and in 1875 he became chancellor of Glasgow. In the following year he was created a Knight of the Thistle, being the only commoner of the order. He died at Venice on January 15, 1878. Sir W. Stirling-Maxwell s works, which are invariably character ized by thoroughness of workmanship and refinement of literary taste, were in some cases issued for private circulation only, and almost all of them are now exceedingly rare. They include an early volume of verse (Songs of the Holy Land, 1847), and several volumes containing costly reproductions of old engravings, along with valuable explanatory matter. His best-known publications are Annals of the Artists of Spain (1848 ; 2d ed. , 1853), The Cloister Life of Charles V. (1852; 3d ed., 1853), and Velazquez and his Works (1855). A life of Don John of Austria, from his post humous papers, is now (1882) in the press. MAY, the fifth month of our modern year, was the third of the old Roman calendar. The name is of doubtful origin.

Ovid (Fasti, v. 483-90) suggests the three derivations of