Lord Kelvin's written work consists of the Electrostatics and Magnetism, three volumes of Collected Mathematical and Physical Papers, three of Popular Lectures and Addresses, the Baltimore Lectures, a very considerable number of papers as yet uncollected, and the Natural Philosophy. But this, great as it was, represented only a relatively small part of his activities. He advised public companies on special engineering and electrical questions, served on Royal Commissions, acted as consulting engineer to cable companies and other corporations, was employed as arbiter in disputes when scientific questions were involved, advocated distinctive signalling for lighthouses and devised apparatus for this purpose, and he was, above all, a great inventor. His patents are many and important. One of them was for a water-tap warranted not to drip, another, for electrical generating machines, meters, etc., was perhaps the patent of largest extent ever granted.
To Lord Kelvin's class teaching reference has been made in an earlier chapter. He was certainly inspiring to the best students. At meetings of the British Association his luminous remarks in discussion helped and encouraged younger workers, and his enthusiasm was infectious. But with the ordinary student who cannot receive or retain his mental nutriment except by a carefully studied mode of presentation, he was not so successful. He saw too much while he spoke; new ideas or novel modes of viewing old ones presented themselves unexpectedly, associations crowded upon his mind, and he was apt to be discursive, to the perplexity of all except those whose minds were endued also with something of the same kind of physical instinct or perception. Then he was so busy with many things that he did not find time to ponder over and arrange the matter of his elementary lectures, from the point of view of the presentment most suitable to the capacity of his hearers. To the suggestion which has lately been made, that he should not have been obliged to lecture to elementary students, he would have been the first to object. As a matter of fact, in his later years he lectured to the ordinary class only twice a week, and to the higher class once. The remainder of the lectures were given by his nephew, Dr. J. T. Bottomley, who for nearly thirty years acted as his deputy as regards a great part of the routine work of the chair.
It is hardly worth while to refute the statement often made that Lord Kelvin could not perform the operations of simple arithmetic. The truth is, that in the class-room he was too eager in the anticipation of the results of a calculation, or too busy with thoughts of what lay beyond, to be troubled with the multiplication table, and so he often appealed to his assistants for elementary information which at the moment his rapidly working mind could not be made to supply for itself.
To sum up, Lord Kelvin's scientific activity had lasted for nearly seventy years. He was born four years after Oersted made his famous discovery of the action of an electric current on a magnet, and two years before Ampère, founding on this experiment, brought forth the first great memoir on electromagnetism. Thus his life had seen the growth of modern electrical science from its real infancy to its now vigorous youth. The discoveries of Faraday in electrical induction were given to the world when Lord Kelvin was a boy, and one of the great tasks which he accomplished was to weave these discoveries together in a uniform web of mathematical theory. This theory suggested, as we have seen, new problems to be solved by experiment, which he attacked with the aid of his students in the small and meagrely equipped laboratory established sixty years ago in the Old College in the High Street. It was his lot to live to see his presentations of theory lead to new developments in his own hands and the hands of other men of genius—Helmholtz and Clerk Maxwell, for example—and to survive until these developments had led to practical applications throughout our industries, and in all the affairs of present-day life and work. His true monument will be his work and its results, and to only a few men in the world's history has such a massive and majestic memorial been reared.
He was a tireless worker. In every day of his life he was occupied with many things, but he was never cumbered. The problems of nature were ever in his mind, but he could put them aside in the press of affairs, and take them up again immediately to push them forward another stage towards solution. His "green book" was at hand on his table or in his pocket; and whenever a moment's leisure occurred he had pencil in hand, and was deep in triple integrals and applications of Green's Theorem, that unfailing resource of physical mathematicians.
Saepe stilum vertas quae digna legi sint Scripturus,
the motto which Horace recommends, was his, and he would playfully quote it, pointing to the eraser-pad in the top of his gold pencil-case. He erased, corrected, amended, and rewrote with unceasing diligence, to the dismay of his shorthand-writing secretary.
The theories and facts of electricity and magnetism, the production and propagation of waves in water or in the luminiferous ether, the structure and density of the ether itself, the relations of heat and work, the motions of the heavenly bodies, the constitution of crystals, the theory of music, the practical problems of navigation, of telegraphing under the sea, and of the electric lighting of cities—all these and more came before his mind in turn, and sometimes most of them in the course of a single day. He could turn from one thing to another, and find mental rest in diversity of mental occupation.
He would lecture from nine to ten o'clock in the morning to his ordinary class, though generally this was by no means the first scientific work of the day. At ten o'clock he passed through his laboratory and spoke to his laboratory students or to any one who might be waiting to consult him, answered some urgent letter, or gave directions to his secretary; then he walked or drove to White's workshop to immerse himself in the details of instrument construction until he was again due at the university for luncheon, or to lecture to his higher mathematical class on some such subject as the theory of the tides or the Fourier analysis.
As scientific adviser to submarine telegraph companies and other public bodies, and more recently as President of the Royal Society of London, he made frequent journeys to London. These were arranged so as to involve the minimum expenditure of time. He travelled by night when alone, and could do so with comfort, for he possessed the gift of being able to sleep well in almost any circumstances. Thus he would go to London one night, spend a busy day in all kinds of business—scientific, practical, or political—and return the next night to Glasgow, fresh and eager for work on his arrival. Here may be noticed his power of detaching himself from his environment, and of putting aside things which might well have been anxieties, and of becoming again absorbed in the problem which circumstances had made him temporarily abandon.