Popular Science Monthly/Volume 72/March 1908/Kelvin in the Sixties
| KELVIN IN THE SIXTIES[1] |
By Professor W. E. AYRTON, F.R.S.
CENTRAL TECHNICAL COLLEGE, SOUTH KENSINGTON
THERE is the stereotyped teacher—the teacher who is like a collection of phonograph records which the human phonograph rolls out before his class in the same order annually—the talking text-book, who instructs his students what it will pay them to read, payment being made in examination marks—the type of teacher whose students, machine-made like himself, will grind out the tune, after the clockwork has been wound up, by due preparation on the candidates' part, the tune required written out by the examiner, and the clockwork started.
And, on the other hand, there is the great teacher, the inspired teacher, he who soars above scientific fashion, whose doxy becomes scientific orthodoxy, who produces thinkers, not mere successful examinees. Such was William Thomson, who became Lord Kelvin.
In the sixties, after the British Association Committee on Standards of Electrical Resistance had been started, but was still in its infancy, I had the rare good fortune to be one of Thomson's students. I, therefore, add to the many memoirs that have recently appeared a loving tribute from one who was at the Glasgow University when the quadrant-electrometer, the syphon recorder, the mouse mill influence machine, and many other instruments that have attained world-wide renown were being developed. Even after his severe illness in 1905 he never lost his keen interest in science, but at the time I am referring to he was not only a giant mentally, but of extraordinary physical activity.
When he came into his class-room, a room festooned with wires and spiral springs hanging from the ceiling like the rigging of a ship, he had hardly given a thought to what he was going to talk about—if it were Monday morning he had just returned from staying the week-end with Tait at Edinburgh, and he gave us an enthusiastic account of their talk, bubbled over with what they had been doing, was full of suggestions about it, told us how the manuscript of "Natural Philosophy" was progressing. We felt that we also had been discussing these points with Tait in his Edinburgh study, and listened with rapt attention to Thomson's narrative.
At that time the advanced proofs of only a fragment of that book had been printed off for the class. We saw the book grow, we felt pride in its growth, we almost felt that we were helping that growth. That book by "T and T'," as is well known, consists of chapters which are more original than the papers usually read before scientific societies. Only one volume has ever appeared—the second, alas! alas! never will now.
To test the power of the Clarendon Press to publish such a book, Tait and he wrote down at random complicated equations, lines of wholly unintelligible reasoning, and then thought it would be a good joke to send out the proofs—as copies of an original paper—to various of their friends. And one day Thomson told me with a twinkle in his eye, "Nobody has yet found any mistakes in that paper."
Every morning, except Mondays and Saturdays, Thomson lectured twice; the first lecture, 9 to 10, was on experimental physics; the second, 11 to 12, on mathematical physics.
Electricity was the subject of the 9 to 10 lecture during a particular session which I have in my mind. But the experiments generally went wrong, and Thomson used modestly to say, "Faraday's result was so and so; mine is just the opposite. But Faraday, with inferior apparatus, divined the truth. Remember his result, not what you have just seen me obtain."
Thomson with all his genius, all his power of advising how an experiment should be made, with all his creative originality in suggesting the details of scientific apparatus and methods, could not make the experiments with his own hands. We all dreaded his touching the apparatus which we had set up and adjusted. He was too impulsive, too full of exuberant energy. After the apparatus was broken when he had touched it he was profoundly sorry. At that time it gave us the feeling that we were able to help him by trying experiments on his behalf. But this feeling resembled that of the calculator who helped Newton when he became too excited to finish the application of his principles to the explanation of Kepler's laws, or the feelings of the sculptor's assistant who transfers to marble his master's inspired creation in clay. We loved him the more that he allowed us to take a part—we felt that we were the soldiers of a great warrior.
In his mathematical physics lectures—aye, even in his elementary lectures—the suggestions that he poured forth were much above the heads of the ordinary undergraduates—over 100 in this class—and they gained little by coming to them except a register of their attendance, necessary for their degrees. For, as soon as he turned round to write on the blackboard, the students row by row began to creep out of the lecture room through a back door behind the benches and steal down-stairs, their bodily presence following their mental presence, which had left as soon as the reading of the roll-call was finished. From time to time Thomson put up his eye-glass, peered at the growing empty space, and remarked on the curious gradual diminution of density in the upper part of the lecture room.
This class consisted mainly of divinity, medical and law students, who, of course, should have been taught the elements of natural philosophy by some assistant provided by the university. To waste the time, energy and extraordinary original power of a genius like Thomson on such teaching was like using a razor to chop firewood. The junior clerks in Downing Street require instruction, but the prime minister is not expected to personally hold daily classes for them. And yet, during the past eighty years, there have been many prime ministers, but only one William Thomson.
But to those, like myself, who, after receiving some scientific training, had come from other countries to hear Thomson's talks, his suggestions, his buoyancy, were like the rays of brilliant May sunshine following April showers. The ideas of those students sprouted as never had they done before. The more thoughful gazed with eyes of wonder at Thomson developing an original paper during a lecture on anything that he might be talking about, we knowing that any notes or calculations that he might previously have made were on the back of some old envelope and left probably with his great-coat in the hall. "If you want to know what's in books go and read them for yourselves. I am telling you what is not in books," he used to remark at those lectures at the old University of Glasgow (now a railway goods station), the "Academia Glasgnana," founded by a bull of Pope Nicholas V., and built on the east side of the High Street in 1450 under the authority of Gulielmus Turnbull, Bishop of Glasgow.
The present university did not exist in my student days; in fact the classic stream Kelvin, although beginning to show signs of the drainage from manufactories spreading to the northwest of the city, flowed through a park and a dale still of a sufficiently sylvan character to make the words of the old song, "Oh! let us haste to Kelvin grove," not absolutely inapplicable.
To my question, "What books on electricity shall I read?" he replied "None! there are none. But you might read some of my papers in the Philosophical Magazine." Clerk Maxwell's classical treatise, Fleeming Jenkin's "Electricity and Magnetism," and the reprint of Thomson's own papers did not appear until some years afterwards. Fleeming Jenkin, who with Cromwell Varley became a partner in that famous firm of consulting telegraph engineers, "Thomson, Varley and Jenkin," was the first person to write a text-book which brought together disconnected and disjointed experiments and gave the elementary mathematical theory underlying them. In the preface of this book, which first appeared in 1873, the author said:
Among Thomson's early discoveries was the fact that it was good for students to do laboratory work. So almost immediately he was appointed the professor of physics, at Glasgow, in 1846, at the age of twenty-two, he "organized a laboratory corps from volunteer students," and about 1849 he "established an incipient laboratory in the wine cellar of an old professor's house," so his successor, Professor A. Gray, tells me. In my time Thomson's laboratory consisted of one room and the adjoining coal cellar, the latter being the birthplace of the syphon-recorder. To avoid friction with the capillary glass syphon, which was moved to the right or left by the electric signals coming through the submarine cable, the end of the syphon was not allowed to touch the strip of paper, but a continuous stream of ink spurted out of the syphon on to this paper in consequence of the reservoir of ink, into which the other end of the syphon dipped, being kept highly electrified.
To find out what sort of electrical machine should be used for this purpose Thomson suggested that we should measure the efficiency of frictional electric machines. We did so, and brought him the result—viz., efficiency equals some small fraction of unity. He replied, "I can not degrade a man by asking him to use his energy so wastefully; I must design something better." And he did—viz., the influence machine; then when, by carrying out his suggestions, a fellow student and I had constructed an influence machine and got it to work, he sent us to the Glasgow Patent Office to see whether any one had thought of that principle before. And we found Varley's and other anticipations, with, however, this difference—that the earlier patentees proposed giving to the arrangement an initial charge to start its action, whereas Thomson's was a machine that worked on the compound interest law, starting with an infinitely small initial capital. This led not only to the "mouse mill" and the "replenisher," but to the class working all kinds of problems on investments at compound interest. "Now, suppose the interest is one one-thousandth per cent., paid every one one-hundredth of a second, etc.," and we who had never invested any money in our lives, indeed, possessed no money to invest, might have been mistaken for budding pupils of a stock broker had any visitor chanced to come into the lecture room.
There was no special apparatus for students' use in the laboratory, no contrivances such as would to-day be found in any polytechnic, no laboratory course, no special hours for the students to attend, no assistants to supervise or explain, no marks given for laboratory work, no workshop and even no fee to be paid. But the six or eight students who worked in that laboratory felt that the entrée was a great privilege. College laboratories for any branch of physics did not, as far as I remember, exist anywhere in London during my student days. Principal Carey Foster started one in 1866 shortly after his appointment as professor of physics at University College, since he realized that making experiments was as great a necessity for students of physics as for students of chemistry. And it was Carey Foster's pioneering efforts to have a students' physical laboratory at University College, and his description of what Thomson had done at Glasgow, which made my mouth water and turned my attention northwards. Of course, the accommodation in Gower Street for physical work in 1866 did not differ much from what had existed at Glasgow since 1846, and certainly even in 1879, thirteen years later, Professor Cornu's students at the Ecole Polytechnique, Paris, never touched a piece of physical apparatus, although the cabinet de physique there contained all the originals of Regnault's classical apparatus, or facsimiles of the apparatus that Regnault had used in his investigations.
Thomson's students experimented in his one room and the adjoining coal cellar, in spite of the atmosphere of coal dust, which settled on everything, produced by a boy coming periodically to shovel up coal for the fires. If for some test a student wanted a resistance coil, or a Wheatstone's bridge, he had to find some wire, wind the coil, and adjust it for himself.
It is difficult to make the electrical student of to-day realize what were the difficulties, but what also were the splendid compensating advantages of the electrical students under Thomson in the sixties. We were like a band of emigrants following our leader in wagons across the prairies and the Rockies on the way into California in 1848. While his far greater genius, perseverance, and endurance would enable him to find nuggets, we perhaps might find specks of scientific gold. We were proud to follow him, we did not expect or even know what the laboratory luxuries of to-day would be, we did not need an Empire State Express train to hurry us in Pullman cars along a line of smooth level rails.
If the instrument given us by Thomson to work with had never been described to us—if its theory or even its use was entirely unknown to us—well, there were no maps for the early emigrants going westward to fall back on, they had to ford the streams for themselves, and did not expect to find bridges already built to enable them to step over every difficulty.
The fact that the students of to-day have such a wealth of apparatus at their hands, printed instructions supplied them, text-books galore, has made them globe-trotters in the region of science. They lack the self-reliance, the initiative to devise expedients for accomplishing ends which the emigrant pioneers in science fifty years ago had to employ. Indeed, it is becoming a question whether using a dictionary to translate a Latin or Greek play is not a better training for the inquiring faculty than working in a modern physical laboratory, since at any rate the translator has to use some thought.
Thomson openly expressed his contempt for a university that spent its time merely in holding examinations, as did the Burlington House University of London at that time. One day I was in his lecture room puzzling over an examination paper that he had set, when he advised me to take the paper home to my lodgings, as I should be much more comfortable there. Such a permission was an upheaval of all my ideas about scholarship examinations; so, boy like, I asked him how he would know that I should not look at books. But he only replied, "When you bring me your answers to-morrow I shall know what you have got out of books." I expect he sent me to my lodgings partly to impress on me the important lesson that all the books that exist will not solve a new problem.
The incident left a deep, lasting impression on me, partly because at the public announcement of the examination results he referred to his method, and jokingly ended with the remark: "This course was on hydrodynamics, and when we got into deep water there was only one student who was still in his depth." What a young engineer can do, using all existing knowledge, is, of course, what an examiner should try to test, not what the examinee can remember and reproduce.
He had great belief that one of the main uses of a university was to form character. He, Rankine, Tait and some other professors had a long discussion in his house one evening after dinner. Would he have been justified in asking that the student who had that day thrown a paper dart at the blackboard when he himself was writing on it should declare himself. Thomson thought no! As a matter of fact the student owned up. He was asked to absent himself from the class, but, on the other students pointing out that he would lose his degree by not attending, Thomson readmitted him.
Thomson always began his nine-o'clock lecture by devoutly repeating the General Confession from the Church of England Morning Service. I do not know whether the other Glasgow professors did. There was never the slightest interruption; the Scotch student is naturally reverent, besides, the prayer was said by Thomson with such fervor and impressiveness that the most stanch freethinker, the most frisky dart-thrower, could not but respect the convictions of the teacher whom they all loved and honored. They might not be able to follow the lecture; but the affecting appeal which preceded it touched their hearts.
When he described to us how Joule in 1840 had experimentally proved that the rate of production of heat was directly proportional to the square of the electric current, and not to the first power, he used to add, "And Joule had the honor to have his paper rejected by the Royal Society. For it was an honor in those days." The rejection of the results of experimental work, although scrupulously accurate, because the experimenter was not already well known, filled Thomson with indignation. For example, the assertion of Sir William Snow Harris (Phil. Trans., Roy. Soc., 1834, p. 225) that the heating power of electricity was simply as the charge, as well as many other electrical errors which Thomson used to dilate on, was held up to scorn before the class as "fashion versus truth in science." In the Philosophical Magazine for 1851 Thomson published an article explaining and defending Joule's work on the heating of conductors.
This ability to sift the wheat from the chaff, the courage to champion what he believed to be true, even if it were not the fashion, and the readiness to give up a theory when speculation lacked accurate experimental corroboration were marked features in Thomson's character.
During the sixties the world was very much interested in the possibility of an Atlantic cable. The 1857 cable had broken while being laid; the 1858 one had failed after one short month of existence; the 1865 cable snapped after 1,186 miles had been laid, and, although nine days were spent in trying to pick it up, and, although it was grappled many times, the rope broke; and this cable, like its predecessors, had to be abandoned. A few yards of this 1865 cable that had been picked up lay on the floor of the Glasgow laboratory and was often pointed to by Thomson as being what had given them heart and kept off despair. Then a prize of over three quarters of a million sterling was offered to the Telegraph Construction and Maintenance Company if they could complete the 1865 cable and lay an 1866 one. And they won it.
While it was remaining doubtful whether the two sides of the Atlantic would ever be coupled electrically, Thomson's secretary not unfrequently used to be sent to the Glasgow railway station a few minutes before the mail train started with this urgent message from Thomson: "I have gone to White's to hurry on an instrument. The London mail train must on no account start to-night until I come." And such was the national importance of the problem, and such the honor in which Thomson was held, that the station-master obeyed.
Many have used a Thomson's reflecting galvanometer and have regarded it merely as an extremely sensitive galvanometer without knowing how it came into existence. It was devised by Thomson to enable him to utilize his mathematical solution of signaling through a long submarine cable, and was regarded of such national importance that a private act of Parliament was sanctioned by the Privy Council to extend the normal life of fourteen years for the patent of this cable "speaking instrument," as it was originally called. The invention of this instrument marks the theoretical solution of a most important problem, which solution Thomson found great difficulty in getting the electrician of that day to accept.
As early as 1855—before any long submarine cable had been constructed—Thomson published in the Proceedings of the Royal Society the theory of the propagation of signals through a cable based on a correspondence which he had had with the late Sir Gabriel Stokes, and he showed that the book "Fourier de la Chaleur"—that "mathematical poem," as he used to call it—contained, in Fourier's mathematical equations of the flow of heat, the entire mathematical solution of the propagation of electric waves through a cable. From "Fourier's series" he deduced that, whereas on a short overhead telegraph line the signal reaches its full strength at the distant end practically as soon as the signaler at the near end of the line begins to send it, with a submarine cable it is retarded, spreads out, and blurs the next signal. There is a past history effect as in politics and in many natural phenomena. The passing of an act of Parliament can not suddenly change a people; indeed, it is well known that the actual effect of an act of Parliament promoted by well-wishers is often gradually found to be most harmful, and has to be repealed or curbed in its action.
Herbert Spencer in his "Sociology" strongly advocated legislators to study the science of politics. Thomson would perhaps have said, "Study Fourier's mathematical poem."
If it were attempted to send a series of electric signals through an Atlantic cable with the same apparatus and at the same speed as messages are sent between London and Brighton, the signaler at the far end would not have the slightest knowledge that the signaler at this end was trying to send a message, whatever were the strength of the current sent into the cable. To work a long submarine cable, either time must be allowed for each signal to grow at the distant end, or, as this would make the sending of messages very slow, the receiving instrument and the signaler receiving the message must, like a clever doctor diagnosing a disease, be able to interpret mere indications. Sending the letter "e," for example, produces at the other end of a long cable a totally different result, depending on what has preceded it. In no case, at a speed of, say, thirty words a minute with a 3,000-mile cable, will it be more than a suggestion, even at the beginning of a word; but in the syllable "toe" the "e" is as indistinct as the hurriedly written scrawl that you are very glad to get some one else to read for you.
Thomson wanted a receiving instrument which, unlike the ordinary telegraph instruments used in post-offices and railway stations, could render the interpretation of such suggestions possible in the hands of an expert signaler, and he devised the mirror galvanometer speaking instrument to obtain this result.
Another most important fact that his theoretical investigation brought out was that no increase of battery power could counteract the retardation in the signals produced by an impurity existing in the copper conductor of a cable, and hence that every yard of copper wire used in the thousands of miles of a long cable must be electrically tested for resistance before being used.
But all this appeared to the electrician as arising from the ignorance of an inexperienced young man who had never erected a mile of telegraph line in his life, and would not have been given a job in any telegraph office. And so when signals through the 1858 Atlantic cable became weak, and a message from the president to our queen took thirty hours in transmission, although containing only 150 words, and which would need only three or four minutes to transmit through any one of the good Atlantic cables of to-day, the only remedy of those who looked down on the theories of the young Glasgow professor was to use Whitehouse's "thunder pump," a magneto-electric machine which produced a sudden large electromotive force when the armature of the permanent magnet was jerked off the poles of the magnet. But these shocks only sent sparks through the gutta-percha insulating coating and hurried the poor cable to its doom, so that even the three words per minute which would have been the utmost limit of speed possible had this cable been entirely uninjured, were replaced by absolute silence.
But Thomson energetically struggled on and, pursuing (as he told me afterwards) a "Parnell-Biggar policy" at the board meetings of the Atlantic Cable Company, obstructed all business until the directors promised to have all the copper wire tested for resistance before being made into cable; and thanks to Thomson for his theory of signaling, to that engineer of energy and surprising resource, even when quite a lad, Sir Charles Bright, to Captain Anderson of the Great Eastern, and to all those who have followed in the history of submarine cable development the London Stock Exchange is by cable to-day within thirty seconds of Wall Street.
Thomson's work in connection with submarine telegraphy has been epoch-making. But thirty-three years ago it was associated with what I felt was a national loss. I give it in an extract from a long letter which he wrote to me in Japan, December, 1874: "My dear Ayrton—You will be very sorry to learn of the terrible loss which has befallen us in the loss of La Plata, cable ship, with my nephew David King on board...." David King and I had worked together for Thomson. I had seen them much in company with one another. In appearance, independence of thought, and in many ways there was great resemblance between uncle and nephew, so that I used to hope that a corner of the mantle of William Thomson might rest on David King.
Thomson has been called an engineer. In creative power, yes—a great engineer. But not in the forties, nay, even in the sixties, could a university student at either London, Glasgow or Cambridge learn what to-day is called even college engineering. Thomson had never learned to make a working drawing; he designed in metal. We students could not help him with the T square and drawing-board as we might have done had we received the college engineering training of to-day. He thought of a new instrument, a new method of accomplishing some result flashed on him, and he sketched in his pocket-book a rough indication of what he wanted constructed; I took the idea, or what I understood of it, in my head to Messrs. White, so it was not to be wondered at that alteration after alteration was necessary before the thing that was in Thomson's mind's-eye became realized in metal.
But oh! the delight of those days! Would we have exchanged them, had the choice been given us, for days passed in the most perfectly designed laboratory of the twentieth century without him? No! for the inspiration of our lives would have been wanting. As pathetically said, since his death, in the Electrical Review, "Le roi est mort," but we can not add, "Vive le roi," for were the whole world summoned, "no successor would there be."
- ↑ From the Engineering Supplement of the London Times.