CONCLUSION
The imperfect sketch of Lord Kelvin's scientific life and work which this book contains can only give a faint notion of the great achievements of the long life that has now ended. Beyond the researches which he carried out and the discoveries he made, there is the inspiration which his work and example gave to others. Inspired himself by Lagrange, Laplace, Ampère, and Fourier, and led to experimental research by the necessity for answers to the questions which his mathematical expression of the discoveries of the twenty-five years which preceded the establishment of his laboratory had suggested—the theories of electricity and magnetism, of heat, of elasticity, his discoveries in general dynamics and in fluid motion, the publication of "Thomson and Tait," all made him the inspirer of others; and there was no one, however eminent, who was not proud to acknowledge his obligations to his genius. Clerk Maxwell, before he wrote the most original treatise on electricity that has ever appeared, gave himself to the study of Faraday's Experimental Researches and to the papers of Thomson. And if some, like FitzGerald and others, have regretted that the electromagnetic theory of light to which Maxwell was led by Faraday, and, indeed, by Thomson himself, did not meet with a more sympathetic reception at his hands, they have not been unmindful of the source from which much of their illumination has come.
He has founded a school of thought in mathematical physics, of men in whose minds the symbol is always the servant of the ideas, whose motto is interpretation by dynamical processes and models as far as that is possible, who shirk no mathematical difficulties when they have to be encountered, but are never led away from the straight road to the goal which they seek to reach—the systematic and clear formulation of the course of physical action.
And in Lord Kelvin's mind there was blended with a clear physical instinct which put aside all that was extraneous and unessential to the main issue an extraordinary power of concentration on the problem in hand, and a determination that was never daunted by failure, which consented to postponement but never to relinquishment, and which led often after long intervals of time to success in the end. He believed that light would come at last on the most baffling of problems, if only it were looked at from every point of view and its conditions were completely formulated; but he could put what was for the time impossible aside, and devote himself to the immediately possible and realisable. And as often happens with every thinker, his mind, released from the task, returned to it of itself, and what before appeared shrouded in impenetrable mist stood out suddenly sharp and distinct like a mountain-top before a climber who has at last risen above the clouds.
With the great mathematical power and sure instinct which led him to success in physical research was combined a keen perception of the importance of practical applications. Sometimes the practical question suggested the theoretical and experimental research, as when the needs of submarine telegraphy led to the discussion of the speed of signalling and the evolution of the reflecting galvanometer and the siphon recorder. On the other hand, the mathematical theory of electricity and magnetism had led to quantitative measurement and absolute units at an earlier time, when the need for these was beginning to be felt clearly by scientific workers and dimly by those far-sighted practical men who dreamed—for a dream it was thought at the time—of linking the Old World with the New by a submarine cable. But the quantitative study of electricity in the laboratory threw light on economic conditions, and the mass of data already obtained, mainly as a mere matter of experimental investigation of the properties of matter, became at once a valuable asset of the race of submarine cable engineers which suddenly sprang into existence.
And so it has been with the more recent applications of electricity. The induction of currents discovered by Faraday could not become of practical importance until its laws had been quantitatively discussed, a much longer process than that of discovery; and we have seen how the British Association Committee, led by Thomson and Maxwell, brought the ideas and quantities of this new branch of science into numerical relation with the units of already existing practical enterprise. The electrical measuring instruments—first the electrometers, and more recently the electric current balances and other beautiful instruments for the dynamo-room and the workshop—which Lord Kelvin invented have brought the precision of the laboratory into the everyday duties of the secondary battery attendant and the wireman.
And as to methods of measurement, those who remember the haziness of even telegraph engineers as to the measurement of the efficiency of electrical currents and electromotive forces in the circuits of lamps and dynamos, in the early days of electric lighting, know how much the world is indebted to Thomson.[26] He it was who showed at first how cables were to be tested, as well as how they were to be worked; it was his task, again, to show how instruments were to be calibrated for practical measurement of current and energy supplied by the early contractors to consumers. He had in the quiet of his laboratory long before elaborated methods of comparing resistances, and given the Wheatstone balance its secondary conductors for the comparison of low resistances; he now showed how the same principles could be applied to measure the efficiencies of dynamos and to make up the account of charge and discharge for a secondary battery.
And if the siphon-recorder and the mariners' compass and the sounding machine proved pecuniarily profitable, the reward was that of the inventor, who has an indefeasible right to the fruit of his brain and his hand. But Lord Kelvin's activity was not confined merely to those practical things which have, to use the ordinary phrase, "money in them"; he gave his time and energies freely to the perfecting of the harmonic analysis of the tides, undertook again, for a Committee of the British Association, the investigation of the tides for different parts of the world, superintended the analysis of tidal records, and invented tide-predicting machines and improved tide-gauges.
Lord Kelvin's work in the theory of heat and in the science of energy generally would have given him a title to immortality even if it had stood alone; and there can be no doubt, even in the mind of the most determined practical contemner of the Carnot cycle, of the enormous importance of these achievements. Here he was a pioneer, and yet his papers, theoretical and yet practical, written one after another in pencil and despatched, rough as they were, to be printed by the Royal Society of Edinburgh, form, as they are collected in volume i of his Mathematical and Physical Papers, in some respects the best treatise on thermodynamics at the present time! There are treatises written from a more general standpoint, which deal with complex problems of chemical and physical change of means of thermodynamic potentials, and processes which are not to be found set forth in this volume of papers; but even these are to a great extent an outcome of his "Thermoelastic, Thermomagnetic and Thermoelectric Properties of Matter."
In hydrodynamics also Lord Kelvin never lost sight of practical applications, even while pursuing the most intensely theoretical researches into the action of vortices or the propagation of waves. In his later years he worked out the theory of ship-waves with a power which has made more than one skilful and successful cultivator of this branch of science say that he was no mere mathematician, but a man who, like the prophets of old, could divine what is hid from the eyes of ordinary mortals. Of the ultimate importance of these for practical questions of the construction of ships, and the economy of fuel in their propulsion, there can be little doubt. Unhappily, the applications will have now to be made by others.
It is interesting to note that the investigation of waves in canals with which Lord Kelvin recently enriched the Proceedings of the Royal Society of Edinburgh have been carried out by a strikingly ingenious adaptation of the Fourier solution of the differential equation of the diffusion of heat along a bar, or of electricity along a slowly worked cable. Thus, beginning with Fourier mathematics in his earliest researches, he has in some of his last work applied the special exponential form of Fourier solution of the diffusion equation to a case, that of wave propagation, essentially different in physical nature, and distinct in mathematical signification, from that for which it was originally given.
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.
Genius has been said to be the power of taking infinite pains: it is that indeed, but it is also far more. Genius means ideas, intuition, a faculty of seizing by thought the hidden relations of things, and withal the power of proceeding step by step to their clear and full expression, whether in the language of mathematical analysis or in the diction of daily life. Such was the genius of Lord Kelvin; it was lofty and it was practical. He understood—for he had felt—the fascination of knowledge apart from its application to mechanical devices; he did not disdain to devote his great powers to the service of mankind. His objects of daily contemplation were the play of forces, the actions of bodies in all their varied manifestations, or, as he preferred to sum up the realm of physics, the observation and discussion of properties of matter. But his eyes were ever open to the bearing of all that he saw or discovered on the improvement of industrial appliances, to the possibility of using it to increase the comfort and safety of men, and so to augment the sum total of human happiness.
His statement, which has been so often quoted, that after fifty-five years of constant study he knew little more of electricity and magnetism than he did at the beginning of his career, is not to be taken as a confession of failure. It was, like Newton's famous declaration, an indication of his sense of the vastness of the ocean of truth and the manifoldness of the treasures which still lie within its "deep unfathomed caves." Like Newton, he had merely wandered along the shore of that great ocean, and here and there sounded its accessible depths, while its infinite expanse lay unexplored. And also like Newton—indeed like all great men—he stood with deep reverence before the great problems of the soul and destiny of man. He believed that Nature, which he had sought all his life to know and understand, showed everywhere the handiwork of an infinite and beneficent intelligence, and he had faith that in the end all that appeared dark and perplexing would stand forth in fulness of light.