A week after Margaret's death, Heaver took John back to Cambridge and stayed with him for the next two weeks. Mr Roderick operated again on the damaged leg and straightened out the effects of the bump sustained while John was being carried into Heavers before Christmas. As time went on, he was able to use the leg more and more, going from crutches to two sticks and then down to one: the leg still had a steel support, with sockets in the shoe heel, and a clamp below the knee. Some persistent ulcers troubled him opening up and discharging in proportion to the amount of use he gave the leg, soaking a dressing in a couple of hours if he overworked it. Heaver thought the ulcers might be due to some spicules of metal from the internal plate that had got lodged in the flesh, but an X-ray revealed nothing. As the summer went on, and his leg improved, John stepped up his activity level, cheerfully going canoeing with Wallis, despite the fact that had he fallen into deep water, the amount of steel attached to his leg would have kept him permanently submerged.A highly disturbed first year at Cambridge did not seem to hinder John's academic progress. In his end of year exams, ('Mays'), he obtained a first class for his Tripos, which included mathematics, physics and chemistry, probably largely as a result of an excellent physics paper. Turning out reams of fair copies of all lecture notes had been sufficiently hard work for the standards required. For his chemistry exam, he had also devised an efficient way of memorising the properties and preparation methods for organic compounds using cards hidden in envelopes to test himself.
In the summer vacation, Heaver paid for John to go on a butterfly-catching holiday in the New Forest with his old friend Ronnie Lahey-Bean. Ronnie was a little concerned at first to see John trotting briskly after Silver Washed Fritillaries on his steel-supported leg, but no harm seemed to be done. They were annoyed every evening by biting insects and Ronnie smoked hard to keep them off. John refused to join him in smoking, but crushed a cigarette in water and rubbed the mixture on his face and neck, which he found very effective. In the evenings he wrote long letters to his father detailing the species he had seen or caught.
Eventually, John had the steel support removed and his leg was declared as good as new by Mr Roderick, although he was occasionally troubled with ulcers on the sites of the holes in his leg for many years afterwards; I remember them as circles half an inch in diameter, highlighted in purple by the ointment he used to use on them. He obtained a new bicycle and it was not long before cycling became John's preferred way of going anywhere and everywhere. The distance between Ryarsh and Cambridge was around seventy-five miles, and John made a regular habit of sending his heavy luggage on by rail and then cycling the whole way at the beginning and end of term. Anyone who cycles has to be very patient with the British weather, and one Easter, when the journey had taken him through five hailstorms, three showers and a number of mixtures of rain, snow and hail, John reported to his father that he had donned his cape and leggings, covered his head with a paper bag to stop the hail melting in his hair and running down his neck, and had then taken no further notice of the weather. That journey took five hours and twenty-four minutes.
In Ryarsh for the holidays, John and Celia used their bicycles to get around together. Celia's friends were most impressed by her gallant brother, for John would help Celia up hills by riding alongside and pushing her. However, this had not started so much from gallantry as from the fact that John, extremely fit as he usually was, disliked having to slow down for hills.
On Armistice Day in 1932, all the students at Cambridge turned out for a day of processions and rags as usual. This year, John and Wallis saw some students riding a bicycle made for four and were much taken by the idea of riding it themselves. They found out where it had been hired and in the following term decided they would use it to cycle to Ely for an anniversary that was being celebrated there. To complete the crew, they tempted another old Berkhamstedian and an American acquaintance called Hank to join them. To get started, it was necessary for the first three to get on, and for number four at the back to keep the bicycle upright until it had gained adequate speed, and then to jump on while it was moving. Wallis and John collected the bicycle the day before the ride, so that Wallis as steersman, and John as number four, could practise until they were able to start reliably.
The next morning they gave their crew the two middle seats, and after a few trials, could start off satisfactorily. Almost immediately they had to cross Chesterton Road to get onto the Ely Road. This was not normally a busy point, but because of the number of cars going to Ely for the anniversary, there was a policeman at the crossing who held up his hand as they arrived. So they made an emergency stop - meaning that they all fell off.
They picked themselves up and restarted. The traffic was not very heavy, but drivers coming up from behind didn't notice at first that the object in front of them was not an ordinary tandem, and each car gave a violent wiggle as the driver drew abreast and saw what he was passing. It also took a while to become accustomed to the three sets of handlebars attached to seats. If someone unthinkingly pulled on his handlebars, the seat in front would move with it, forcing its occupant to pull on his handlebars in turn, and this resulted in several spills (onto a relatively comfortable grass verge) before they all learned to take no notice of the movement of their saddles. It was a lovely sunny day, and all but the American were lightly clothed for an hour or so of vigorous exercise, but Hank, having no faith in the British climate, had on a thick sweater and an enormous overcoat and was sweating heavily, but refused to put the coat on the back carrier.
After watching the Cathedral celebration, they had a large tea at a cafe, and then set off in good humour for home. Now Hank wanted a turn as number four, and, finding a nice quiet road, he started them off and jumped on quite adequately, if not very gracefully, and by the time they had done a few miles, they were feeling very confident and pleased with themselves until a car coming up from behind made the usual wiggle, but instead of accelerating away, ran on for a hundred yards and stopped. Its back door flew open and a man jumped up on the boot and brought out a camera to photograph their approach, which resulted in a spectacular topple at just the right distance for excellent shots. Perhaps somewhere there are some ageing photographs of this event.
Off they went again at a very good speed, but the cameraman and the other passengers shouted and waved vigorously as they went by in their car, and looking back at the road behind, John saw why: Hank had started the bicycle off alright, but had failed to get on himself, and there he was, tearing along behind, with his great overcoat flapping, his anguished shouts smothered by the noise the car's occupants were making. John passed the information up to the front, and they made their usual inelegant stop.
Hank was replaced as number four by John, and as they prepared to move, a couple of friends came up on ordinary semi-racing bicycles, and offered to escort the foursome back to Cambridge 'as they had plenty of time to spare'. There was, as usual, a bit of a head wind, and the bicycle made for four had four times the motive power but little more wind resistance than the single bicycles. After a mile or so, the escorts were struggling to keep up, and quite soon they fell behind and were left out of sight.
During John's second year, Celia was continuing a long battle with her father to be allowed to go to University herself to study classics. The previous summer she had failed to obtain a scholarship to Cambridge, and now her teachers wanted her to try for Oxford, for they believed her to be quite the cleverest girl they had seen for a long time. Her headmistress wondered if her babyish manner had put the Cambridge selectors off at her interview, while Wallis was certain that it was because they did not appreciate Assyrian, Celia's current craze. Ancient languages were becoming an obsession with Celia, and when Heaver attempted to divert her by saying that Greek was not a suitable subject for a woman, she retorted that Greek women must have been able to speak it. Poor Heaver could only resort to his usual escape from his sharp daughter by telling her that he would ask for her opinion when he wanted it. But this was only a side issue: he really did not want Celia to look to higher education of any kind, feeling that she ought to be preparing to return home to Heavers after leaving school to spend her time looking after him. But by the time John started his third year at Cambridge, Celia had been successful both in obtaining an Oxford scholarship and in persuading Heaver to let her take it up. As time went on, Heaver grew to accept her absences during the short Oxford terms and even appeared to be quite proud of his clever daughter.
In John's second year, the Cavendish Professor, Lord Rutherford, was one of his lecturers (Ernest Rutherford became a peer in 1931 after announcing his nuclear theory of the atom in 1911 and going on to split the atom in 1919). His presence at Cambridge had helped to attract John to the University but he found Rutherford to be a dithery lecturer, asking himself where he was and repeating himself at regular intervals. Lack of interest in teaching undergraduates rather than age (he was about sixty-one) was the probable cause of his poor lecturing technique, but, fascinated as John was by the whole subject of nuclear physics, he thoroughly enjoyed these lectures.
After obtaining a first again in his exams at the end of the second year, which completed Part I of his degree course, John was given a Trinity scholarship to cover his third year. After two years in lodgings, he was now expected to spend a year in college, his scholarship allowing him to be one of the first to choose his rooms. He was unsuccessful in trying to get the rooms that Sir Isaac Newton had occupied, but chose K6 New Court, which had a pleasant sitting room and bedroom, with a half-share in a gyp room complete with gas ring, sink and cupboards. He had a 'bedder' and a 'bedder's help' to make his bed and keep his rooms clean.
A disadvantage of being a Trinity scholar was that he was expected to take his turn for a week reading the lesson at the daily morning service in the College Chapel. When he first discovered this, he was tempted to try and exempt himself on the grounds that he wasn't a Christian, but decided that doing the readings would please his father. To be sure to get up at quarter past seven, which would be necessary to get there in time, he got his bedder to call him every five minutes until he was out of bed. The first session was not easy: he arrived at the Chapel to find that his total congregation consisted of the Dean and Chaplain, and that he had to read Malachi 2, which spelled out a detailed list of the ways priests were failing in their duties. Fortunately, later readings were slightly better attended.
Apart from this, College life suited John extremely well. He now had a number of friends, although Wallis was still the only one he referred to by his Christian name, and they all called in at each other's rooms for a relaxed chat over tea, coffee or a scratch supper at regular intervals. Some of these friends were idealistic communists; all discussed politics with the greatest enthusiasm. Once or twice a week, John would go with someone to the cinema. He often criticised what he saw, sometimes claiming to prefer the Mickey Mouse cartoon to the feature film, but he thoroughly enjoyed 'The Good Companions', particularly admiring the lack of affectation of one of the leading actresses. He ran with the Hare and Hounds whenever he could, and cycled the countryside with Wallis who led John to a number of turf mazes and old churches, two of Wallis's special interests. John attended debates, and further developed his strong, though as yet unspoken, opinions. He began tentatively to attend College anti-war group meetings and demonstrations.
After returning to his rooms in the evenings, John spent his time reading, often continuing into the small hours. He chided himself for this habit, but the truth was that he had never needed a lot of sleep. He also felt guilty about how little work he was doing, having given up the habit of copying out lecture notes, but his quick understanding of all that he was told meant that constant swotting was not necessary.
Women barely figured in this life. There were only two in the Part II physics course among twenty-eight men, and an assumption that neither of them would look at him prevented him from even imagining approaching one of them. John said later that this did no harm: many of his activities really depended on his male companions, and he would have missed a great deal had he spent his time chasing women. He did take an interest in his cousins, Betty and Frances, Aunt Freda's children. Of the two, he actually liked Frances better, although she was still a child to be romped and played with, but was attracted to the older Betty. He exchanged letters with Betty, and when he stayed with Aunt Freda's family that Christmas, spent a lot of time plucking up the courage to kiss her under the mistletoe, and although his polite request was rejected on Christmas Eve, he finally succeeded on Boxing Day.A unique relationship was started at this time, with the Robertshaws. Joe and Peggy Robertshaw were friends of the Chapman family and when John was introduced to them by Wallis as someone who had just lost his mother, he was taken firmly into their hearts. The Robertshaw family moved to Letchworth, which was within cycling distance of Cambridge, soon after John first met them and so he and Wallis visited frequently, finding the atmosphere agreeably different from that of Cambridge and lapping up the kindness that was always offered to them.
There were two Robertshaw children, Frank, who was then about fifteen, and Nancy who was about eleven. John was intrigued by the non-repressive scheme that was being followed for their upbringing and was surprised that children should be allowed to interrupt adults. But he was delighted by their resulting lack of shyness and pleased by Nancy's Frances-like desire to climb and romp almost at once. Peggy and Joe were Quakers, and to please them and to learn more about the Society of Friends, John and Wallis went to a number of Quaker Meetings in Cambridge. They were impressed by the unembarrassed silences, broken only by individuals getting up to say something sensible about current matters.
The Part II course lasted for one year, and consisted of physics only. As John described his life from this time to me, he included more and more details of the physics he learnt and what he had thought about it. Letters to his father were full of regurgitated information from lectures and practicals. He was deeply interested in the work and the physics itself became an integral part of his life. Outside the lecture halls, he thought over the facts and theories he had heard and sometimes produced novel ideas of his own. In a biography of a writer or a politician, any reader can be reasonably expected to understand an outline of the subject's work, but this is not necessarily the case for the story of a scientist. Because his science was of such immense importance to John it cannot be left out, so I have tried to explain as much as possible by means of short footnotes together with a slightly more detailed Glossary. I hope these will be sufficient to get an interested reader through passages describing John's studies and his later research work.
The practical part of the course used two days a week from ten to five and John thoroughly enjoyed most of it. He noticed that the neat machine-made apparatus of Part I had given way to constructions put together by the laboratory assistants, or even the students, with much recourse to plasticine and string, but building apparatus gave John more opportunities to exercise his practical skills and increased his sense of achievement when an experiment turned out well. A large part of the course consisted of a series of gold-leaf electroscope-1- experiments on various radioactive materials and he was thrilled to be involved in a field that had fascinated him for several years.
There were also experiments in physical optics. Towards the end of the second term, one of these experiments was to measure the polarisation of light-2- produced by a pile of glass plates. When light strikes a glass plate, part is reflected and part transmitted, and if the plate is at an angle to the direction of the beam, both reflected and transmitted beams will be partially polarised. With several plates at the same angle, one behind the other, the transmitted light will be further polarised by each plate, and the experiment consisted of measuring the total degree of polarisation for various numbers of plates.
John compared his results with the theory given by the standard text book and was disturbed to find that his results did not fit the theory. The divergence from the theory increased smoothly with the number of plates and repetition of the experiment gave the same result. After a cycling and camping holiday with Wallis in Wales, he spent a large part of the remaining Easter vacation puzzling over this, trying to find an explanation from the electromagnetic theory of light, instead of revising for his final examinations. About three days before the end of the vacation, he suddenly realised that the existing theory did not consider multiple reflections inside the pile of plates. He worked out a theory to allow for this for any given number of plates and found complete agreement with his earlier experimental results. He was delighted with this, and on his return to Cambridge, told the research student who was his laboratory demonstrator who seemed quite pleased but not especially impressed. It did not occur to John to tell Dr P I Dee who was the head of the laboratory.
On another occasion, John told his supervisor about an idea he had had for a particle accelerator. Excited by news of Cockcroft and Walton's recent experiments with some of the earliest particle accelerators, his idea had come after he had attended some lectures on the theory of alternating current. John imagined a series of metal tubes of increasing length each charged by an alternating current, such that positively charged sub-atomic particles spent half an alternating current cycle inside one tube while accelerating fast across the gap towards the next (temporarily) negatively charged tube in the other half cycle. Thus, he thought, a number of small accelerations added together would eventually produce particles moving with very high energies.
The supervisor told John it wouldn't work, and John took the idea no further, but he had in fact invented a linear accelerator. Unknown to him at the time, Rolph Wideröe had built just such a machine in 1928 and Lawrence and Sloan had developed a similar one in 1931 but neither attempt was particularly useful in producing material for nuclear research at a time when a frantic hunt was on to find ways of producing radioactive particles artificially. Later, successful linear accelerators were built to produce particles with very high energies in systems some miles long.
When the finals started, John's revision may have been lacking but his enquiring mind was developing fast. One of the assignments in the physics practical exam was an experiment in which an alpha-particle-3- source could be moved along guides over a distance of about three centimetres towards a gold leaf electroscope. The instructions were to record the time it took for the gold leaf to fall through a standard range on its scale and John plotted the required shape of curve without difficulty. The results of the experiment showed that the range of the given alpha-particle source was nearly nine centimetres. Having effortlessly absorbed much of the available information on radioactive materials, John knew the ranges of all the main natural sources of alpha-particles, and eight and a half centimetres was that of a material then called Thorium C (now known as Polonium-212) so that at first sight it would appear that this had been the material provided for the experiment. But he also knew that Thorium C had a half life-4- of a tiny fraction of a second, and so the actual material given must have consisted mainly of some longer-lived precursor with a shorter range, which was constantly renewing the Thorium C. Losing sight of the fact that he had already done the work required for the exam, John managed to rebuild the apparatus, reducing the distance between the moveable source and the gold leaf electroscope. Sure enough, he was able to plot a second, shorter curve, corresponding to the expected shorter range of the longer-lived precursor.
The supervisor, Dr Chadwick (who later discovered the neutron), came round to his bench, and asked John why he had changed the apparatus. As he started to explain, Dr Chadwick shushed him, saying that there was no need to tell everyone, but was clearly pleased. John discovered many years later that Dr Chadwick had left the room in a state of excitement and told Dr Dee that they had a genius in the class.
Everyone was a little disappointed when John got only an upper second instead of a first class honours degree. Regular pricks from his conscience when he found himself reading in bed until two in the morning had tried unsuccessfully to warn him to work harder, and the polarised plates problem had interfered with some weeks' worth of revision time. Moreover, for the last year, what work he had done had tended to be selective: those parts of the syllabus he found less interesting had been effectively ignored while he had absorbed anything and everything about radioactivity with no conscious effort. John's friend Bamford, who did get a first asked what had happened to him which John found flattering rather than critical. That he was intelligent enough to get a first, and known to be so, may not have been more important than actually getting one, but it certainly made him feel better.