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J.J. and the Cavendish

Sir G.P. Thomson

When J.J. was appointed Cavendish Professor at the end of 1884 he had already worked there for four years, though not all of the time he could spare from teaching was spent in the Laboratory. Not only did he gain in this period a Fellowship at Trinity College with a mathematical thesis on the relation of dynamics to physics and chemistry, but also the Adams Prize with his essay on vortex rings in 1882. His early work on Maxwell's theory also comes in this period. In fact, he was regarded primarily as a mathematician, and besides the doubts expressed as to his youth, just 28 - "Matters have come to a pretty pass when they elect mere boys Professors", one senior member of the University remarked - some felt doubts as to his experience as an experimenter. These doubts were perhaps better founded than the first. He was naturally clumsy with his hands, and the absence of any systematic training in a laboratory, such as he would probably have received had he been born even ten years later, allowed him to remain so. He was more dependent than most physicists of his day on mechanical assistants, especially his personal one, E. Everitt.

As is usual with heads of departments, J.J.'s share of the teaching was limited to lecturing, except for one term when a demonstrator was ill. He gave elementary lectures on properties of matter, and magnetism and electricity, as well as others more advanced.

The research work in the Cavendish Laboratory during J.J.'s tenure of office falls rather sharply into two parts, the eleven years up to Rontgen's discovery, and the twenty-two years afterwards. During the first part the subjects studied were very varied, especially considering the relatively small numbers of workers. But this period is best regarded as one of preparation. In particular with J.J.'s work on the passage of electricity through gases and C.T.R. Wilson's early work.

It happened that the crucial year scientifically was also that of an important administrative advance. In 1885 a change was made in the regulations of the University which had a great influence on the fortunes of the Laboratory. This allowed graduates of other Universities (and others in exceptional cases) to receive a B.A. degree after 2 years residence without taking the normal examinations if they submitted a thesis which was judged "of distinction as a record of original research." At the time, of course, the Ph.D. had not been established as a Cambridge, or indeed as a British, degree. This new regulation made it worthwhile for people from abroad, or from other British Universities, to come to Cambridge for research, and in particular to the Cavendish Laboratory.

The effect was immediate. At the beginning of October 1895, when the regulations came into force, two men presented themselves, almost within the hour, at the Cavendish Laboratory. They were Ernest Rutherford from New Zealand and J.E. Townsend from Galway, later Wykeham Professor of Physics at Oxford.

After the discovery of the electron and gaseous conductivity due to X-rays, the work of the Laboratory concentrated on their consequences, but never to the exclusion of work on unrelated or only slightly related topics which happened to appeal to some particular researcher.

This seems a suitable place to describe something of the domestic life of the Cavendish Laboratory in the great days between 1895 and the outbreak of war in 1914.

An extension of the Laboratory was made in 1896 to accommodate elementary demonstration classes, chiefly medical. For some time these had been housed in a disused dissecting room, the odour in which required the most vigorous chemicals available to reduce it to a tolerable level. The new laboratory was to the south of the entrance archway. Half of its cost of £4,000 was paid for by fees saved by the department. The following describes the opening ceremony :

Rutherford to Mary Newton (later Lady Rutherford)
Cambridge, 15th March 1896

"The great event of the last few weeks has come and gone, and was a very great success - the Science Conversazione at the Cavendish Lab. I told you it was to be a very big affair and no pains or expense were spared to make the thing a success. From the entrance to the Free School Lane to the Lab, about 60 yards, was covered in with an awning and lighted with glow lamps, and carpet laid down. Inside the Lab itself carpet was laid down all over the staircases and everything was prettily lighted up... Mrs. J.J. looked very well and dressed very swagger and made a very fine hostess... Mrs. J.J. told anyone she got a chance, that they must go and see the wonderful experiment of Mr. Rutherford and it was the only new thing being shown that night. It is lucky I am of a modest disposition, but these things don't affect me in the way you might expect..."

As the research school prospered, its numbers grew rapidly, as can be seen from the early photographs of the research students preserved in the Lab. By the early years of the century the crowding was excessive, with about thirty research students, not to mention the paid staff, trying to work in a few rooms of moderate size. In 1906 another extension was made, this time to the north, partly paid for by a generous donation of £5,000 from Lord Rayleigh on the occasion of his Nobel Prize. This relieved the pressure until Rutherford returned as Professor after the First World War.

At the turn of the century many students were coming from abroad. One of these, Prof. Bumstead of Yale, wrote his impressions of the Cavendish Laboratory, where he worked in 1904-5.

"The whole social atmosphere of Cambridge is to an American University man most charming and delightful. Its simplicity and lack of ostentation we have kept over here, possibly as a direct influence. But your social life struck me as much richer and fuller than ours; really we seem too busy to enjoy each other's society, and yet we do not get so much done as you. I don't understand it altogether; a laboratory in this country in which nobody worked before 10 am or worked later than 6 in the evening would serve as a terrible example of sloth and indolence. I do not see how you get so much work done and yet have time to live so pleasantly and unhurriedly. We Americans have never discovered that great secret.

"As for the Lab itself, it is difficult to describe the (almost paradoxical) combination of qualities which I thought I observed there. It is obviously dominated by the personality of J.J. and yet I have never seen a lab in which there seemed to be so much independence and so little restraint on the man with ideas. The friendliness and mutual helpfulness of the research students was obvious and one of the finest things about the place, and it appeared to be a part of this friendly service to jump into a fellow-student, if you thought him wrong, and to prove him wrong. In a good many places friendship does not stand that strain, but it usually does at the Cavendish.

"Another thing which struck me as paradoxically fine was the relation between the Professor and his students. The great admiration and reliance with which J.J. was regarded by everybody was unquestionable; yet in matters of detail there was no subservience. I saw a good many men, while I was there, following their own causes, and I remember well the frank tone prevailing at the meetings of the Cavendish Society, where the Prof's theories or experiments were not spared in the general criticisms."

Each man working in the Cavendish Laboratory had as a rule his own problem and apparatus, a good part of which he had probably made himself. Sometimes, but rather rarely, two men worked together. There was no teamwork in the sense of a group all working on the same apparatus. On the other hand, even when there were 30 men working, each knew more of what the others were doing than would be usual in a modern laboratory. This was partly because the great majority were working on interlocking problems and it was important to know what results the others were getting.

In the early 'nineties J.J. started the Cavendish Physical Society. It was an unusual society, with no rules and no subscription. It met about once a fortnight in term, and one, or sometimes two, pieces of work, experimental or theoretical, were described each by one of the research students, or, more rarely, by one of the staff. The paper did not necessarily contain the speaker's own work, though a man would be asked to give an account of what he himself had been doing at least once in his time as a research student. There was a discussion after each paper. The Cavendish appears to have been the first lab in this country to adopt this custom, at least in Physics, but it was by then common in Germany and known as a seminar or colloquium. Tea was provided by Mrs. Thomson and one or two other ladies connected with the lab, before the serious work was started.

J.J. did most of his theoretical work at home, sitting in a chair that had been Maxwell's, and mostly on scrap paper until it had reached the stage of being written up. He wrote a clear and beautiful hand, his one manual accomplishment. Unless he was lecturing - all lectures to undergraduates were then in the morning - he stayed at work till nearly one o'clock, till lunch was nearly ready in fact, and then hurriedly walked to the laboratory. There he walked about, visiting research students and giving advice. I never quite knew why he was so late, whether that he kept hoping that his problem would come out and only left it when his conscience forced him, or whether he argued that a man who really needed help would wait into the lunch hour and the others could be missed without loss. This, however, was not the only time he was accessible if needed. The afternoons were spent on experimental work, except for a few lectures to advanced students.

J.J. was extremely untidy with papers and bad at answering letters, not at all the copybook administrator, but in fact the Cavendish Laboratory in his day ran with smoothness and efficiency. This was partly because he gave his subordinates a great deal of freedom, within certain financial limits, and perhaps even more because they were an outstanding group of men as devoted as he was to physics and the Cavendish.

The finances of the laboratory were remarkable. In those days before Government grants and the University Grants Committee, Cambridge University was very poor, though some of the colleges were very rich. The University paid the Professor and most of the more senior staff, but the salaries of the latter, even allowing for the change in the value of money, were very small by present standards. This was somewhat alleviated by many of them having College Fellowships, worth about £250, and in this way the Colleges contributed indirectly to the lab. The University contributed £270 (sic) per annum to the running expenses. Everything else, including paying the workshop staff and supplementary demonstrators, had to come from fees earned by teaching and examining. Yet the lab contributed £2,000 from savings to the extension made in 1896 and another £2,000 to add to Rayleigh's generous gift and so pay for the extension of 1906. Naturally the expenditure on apparatus was low. J.J. reckoned that the extra cost of nearly 40 research students in the year 1913-4 was only £550 in all. The only source of outside grants was the Royal Society's £4000 per annum, which had to cover all the sciences and the whole country. As far as apparatus made on the spot went there was enough, but galvanometers, ammeters, pumps, even resistances, were very short.

Once a year, a little before Christmas, the Cavendish Research Students held a dinner to which J.J. and one or two other guests were invited. It had a musical tradition. At the end of what must have been the first dinner, Langevin sang the Marseillaise with such fervour that one of the waiters, a Frenchman, fell on his shoulder and kissed him. Later, special songs were written, many by A.A. Robb, a mathematical physicist. A collection called the Post Prandial Proceedings of the Cavendish Society was printed and went into 6 editions, the last in 1926.