Popular Science Monthly/Volume 10/January 1877/Sketch of Sir William Thomson

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THIS distinguished physicist and mathematician was born in Belfast, in June, 1824. His father, Dr. James Thomson, was a man of large capacity and culture, who studied in the Glasgow University, became head-master of the Belfast Academical Institution, and in 1832 was appointed Professor of Mathematics in the University of Glasgow. He made various improvements in mathematics, and wrote books upon education. William passed through the Glasgow University early, and then entered St. Peter's College, Cambridge, from which he graduated as second wrangler in 1845, and he was immediately elected Fellow of his college. He afterward went to Paris, and worked in the laboratory of Regnault. In 1846, at the early age of twenty-two, he was appointed Professor of Natural Philosophy in the University of Glasgow, a position which he has filled with distinction, and still occupies.

Sir William Thomson's earliest contributions to physical science were on the subject of heat, the laws of its motions being treated mathematically. A remarkable paper on "The Uniform Motion of Heat in Homogeneous Solid Bodies," written at the age of seventeen, was full of original conceptions, but it was afterward found that Thomson had been anticipated in his ideas by Gauss, Chasles, and George Green, of Nottingham. In 1842 he published an important paper on "The Linear Motion of Heat," which contained a method of deriving % geological dates from underground temperatures, a subject which he treated in his inaugural address, in entering upon his professorship at the university.

It will be impossible here to give any account of the numerous contributions to science made, by Sir William Thomson, as they were generally of so mathematical a cast as to be unintelligible to ordinary readers. His papers on "Electro-Statics" and on "Magnetism" were collected and published in 1872, in a valuable volume of six hundred pages. The more interesting aspects of his work have been well described by a writer in Nature, and we cannot do better than to quote some passages from his notice:

"His electrostatic researches led Thomson to the invention of very beautiful instruments for electrostatic measurement. The subject of electrostatic measurement occupied much of his attention from the very earliest, when he was obliged to call attention to the defects of the electrometers of Snow Harris. His labors in this direction have produced the quadrant electrometer, which is employed for all kinds of electric testing in telegraph construction, and for the registration of atmospheric electricity at Kew Observatory; the portable electrometer, for atmospheric electricity and for other purposes, in which the extreme sensitiveness of the quadrant-electrometer is not required; and the

absolute electrometer, which serves for reducing the scale-readings of other instruments to absolute measure, and which was used by Thomson in his measurement of the electrostatic force producible by a Daniell's battery and in many other investigations. Those who have seen the collection of electrometers in the Loan Collection at South Kensington will not think it too much to say that to Sir W. Thomson is due our present system of practical electrometry.

"But while thus engaged in investigations in electrostatics and magnetism, there were many other branches of science that were receiving from him advancement in a not less remarkable way. There is no part of his work of higher importance than his investigations on the Dynamical Theory of Heat. These were communicated in a series of papers to the Royal Society of Edinburgh, the first of which was given in 1849. It was a critical account of Carnot's memoir of 1824, 'Réflexions sur la Puissance Motrice du Feu.' Though Rumford and Davy had, in the beginning of this century, experimentally disproved the material theory of heat, their experiments and arguments were unheeded and nearly unknown; and it was only after 1843, when Joule actually determined the dynamical equivalent of heat, that the great truth that heat is a mode of motion was admitted and appreciated. Thus Carnot, although dissatisfied with it, was obliged to adopt the material theory of heat in 1824; and, regarding heat as indestructible, spoke of the letting down of the heat from a higher to a lower temperature, and looked on the production of work by the heat-engine as a phenomenon analogous to that in which water, descending from a higher to a lower level, does work by means of a water-wheel. Thomson, among the first to appreciate the importance of Joule's results, set himself to alter the theory given by Carnot into agreement with the true theory; and in the series of papers referred to, placed the whole science of thermodynamics on a thoroughly scientific basis. In 1846 he first suggested the reckoning of temperature on an absolute thermodynamic scale independent of the properties of any particular substance. Subsequently, in consequence of experimental investigations of the thermodynamic properties of air, and other gases, made in conjunction with Joule, he showed how to define a thermodynamic scale of temperature having the convenient property that air-thermometers and other gas-thermometers agree with it as closely as they agree with one another. This system of reckoning temperature gives great facility for the simple expression of thermodynamic principles and results.

"Having here mentioned Joule and Thomson together, we cannot omit to remark that some of the most admirable researches in thermodynamics were those undertaken in conjunction by these two attached friends.

"Among the many important results of Sir W. Thomson's investigations in thermodynamics, one of the most remarkable was his discovery of the principle of dissipation of energy, announced by him in 1852. During any transformation of energy of one form into energy of another form there is always a certain amount of energy rendered unavailable for further useful application. No known process in Nature is exactly reversible, that is to say, there is no known process by which we can convert a given amount of energy of one form into energy of another form, and then, reversing the process, reconvert the energy of the second form thus obtained into the original quantity of energy of the first form. In fact, during any transformation of energy from one form into another, there is always a certain portion of the energy changed into heat in the process of conversion; and the heat thus produced becomes dissipated and diffused by radiation and conduction.

"Consequently, there is a tendency in Nature for all the energy in the universe, of whatever kind it be, gradually to assume the form of heat, and, having done so, to become equally diffused. Now, were all the energy of the universe converted into uniformly-diffused heat, it would cease to be available for producing mechanical effect, since for that purpose we must have a hot source and a cooler condenser. This gradual degradation of energy is perpetually going on; and sooner or later, unless there be some restorative power, of which we at present have no knowledge whatever, the present state of things must come to an end.

"In 1854 Faraday, with an experimental cable, investigated the cause of the retardation of signals first observed in the working of the cable between Harwich and the Hague. Thomson, taking up the question, published an investigation of the nature of the phenomenon, one practical result of which was that with cables similar in lateral dimensions the retardations are proportional to the squares of the lengths. This law is now commonly referred to as the 'law of squares.' About this time it was proposed to construct a cable to connect England with America; and it became obvious that the discovery of the retardation of signals raised a question whether the transatlantic cable would not prove a commercial failure. Whitehouse, experimenting with 1,125 miles of cable, found the transmission of an instantaneous signal to the farther end of the cable to occupy one second and a half. The length of a cable required to connect Ireland with Newfoundland is twice that of the experimental cable of Whitehouse; and thus, according to the law of squares, the time taken to transmit an instantaneous signal through a cable similar in lateral dimensions to that of Whitehouse, and joining those two places, would be no less than six seconds. In 1856 Whitehouse read a paper before the British Association, in which he described experiments by which he hoped to disprove the law of squares. Thomson replied in the Athenæum (November 1, 1856); and subsequent experiments have established the correctness of his law.

"Fortunately a true understanding of the nature of the phenomenon of retardation led Prof. Thomson to the method of overcoming the difficulties presented. The disturbance produced at the extremity of a long submarine cable by the application for an instant of electromotive force at the other end is not, as in the case of a signal through an overhead land-line, a pulse, practically infinitely short, and received only a minute fraction of a second after it was communicated. Instead of this, a long wave is observed at the farther extremity, gradually swelling in intensity, and as gradually dying away. Its duration for such a cable as we have been speaking of would be the whole six seconds, calculated from the experiments of Whitehouse. Prof. Thomson perceived that an instrument was required which should give an indication of a signal received long before the wave has acquired its maximum intensity, and in which the subsequent rising to maximum intensity should not render unreadable a fresh signal sent quickly after the previous one. This was effected by his 'mirror galvanometer;' and it was by means of it that the messages transmitted through the 1858 Atlantic cable were read.

"The 1858 cable, submerged under difficulties that many times threatened to be insurmountable, soon failed. Several important messages were, however, transmitted through it; and it served to prove the feasibility of the project which many eminent engineers up till that time regarded as chimerical. Before another attempt was made the labors of Prof. Thomson and others, to all of whom the world owes a deep debt of gratitude, had so improved the construction of the cables and the mechanical arrangements for submersion, that though many difficulties presented themselves they were all, in 1866, triumphantly overcome. It was on his return from the submersion of the 1866 cable, and the raising and the completion of the 1865 cable, that the honor of knighthood was conferred on him along with others of his distinguished fellow workers.

"Recently Sir William Thomson has invented a new and very beautiful instrument, the 'siphon recorder,' for recording signals on long submarine lines. It is in use at all the telegraph-stations along the submarine line connecting England with India. It is also used on the French Atlantic Cable, and on the direct United States line. Sir W. Thomson, Mr. Varley, and Prof. Jenkin, combining their inventions together, have given the only system by which submarine telegraphy on long lines has been carried on up to the present time.

"Sir William Thomson is an enthusiastic yachtsman and a skillful navigator. His recently-published popular lecture on 'Navigation' proves this; and, with that bright genius which enriches all with which it comes in contact, his improvements in navigation are of very high importance. The general adoption of Sumner's method, now made simple for the navigator, would be a reform in navigation almost amounting to a revolution, and is one most highly to be desired. Sir William Thomson has also invented a new form of mariner's compass of exquisite construction. It possesses many advantages over the best of those in general use, not excluding the Standard Admiralty Compass; but its special feature is that it permits of the practical application of Sir George Airy's method of correcting compasses for the permanent and temporary magnetism of iron ships. He has also invented an apparatus for deep-sea sounding by piano-forte wire. This apparatus is so simple and easily managed that he has brought up 'bottom' from a depth of nearly three nautical miles, sounding from his own yacht, without aid of steam or any of the ordinary requisites for such depths. His method was much employed in taking rapid soundings during the laying of telegraph-cables along the Brazilian coast to the West Indies. It has also been used with great success on the United States Submarine Survey. Recently, while on his way to Philadelphia, Sir W. Thomson himself was able to take flying soundings, reaching the bottom in sixty-eight fathoms, from a Cunard Line steamship going at full speed.

"Sir William Thomson is a Fellow of the Royal Society of London and of the Royal Society of Edinburgh. He has received the Royal Medal of the former and the Keith Medal of the latter. He is also an honorary member of several foreign societies. The Universities of Dublin, of Cambridge, and of Edinburgh, have each conferred upon him the honorary degree of LL. D., and that of Oxford the honorary degree of D. C. L. On his marriage in 1852 he gave up his fellowship at St. Peter's College, Cambridge; but in 1871 his college again elected him to a fellowship, which he now holds."