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In footnotes or endnotes please cite AIP interviews like this:
Interview of Norman Feather by Charles Weiner on 1971 February 25,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Undergraduate atmosphere at University of Cambridge: course work, lecturers, extra-curricular groups, training experiments in radioactivity and scintillation-counting; obtains old radon tubes for neutron experiments while doing radioactivity work with Robert W. Woods at Johns Hopkins University in 1929; discussions with James Chadwick of Joliot papers, 1932; move with Chadwick to University of Liverpool, 1935; return to University of Cambridge 1936; reaction to selection of William Bragg as Ernest Rutherford's successor; shift in Cavendish Laboratory's world role in nuclear physics; World War II service at Cambridge: administration, teaching, measurement of fission cross-sections; move to University of Edinburgh to replace Charles D. Barkla, 1945.
It is the 25th of February, 1971 and, just to identify the tape this is Charles Weiner asking some questions and making some comments in an interview with Professor Norman Feather in his —
— his sulking room (a name given, light- heartedly by Dr. A.F. Brown a senior member of staff of the department) —
His sulking room or retreat office at the University of Edinburgh. I’d like to start by going back really to the beginning, in terms of your work in Cambridge, about your choice of science as a career, and perhaps as part of the explanation, it might be good to go a bit into your family background and to your earlier education, to set some of the stage for this ultimate decision that took place.
Yes. Well, my family background has no science in it at all, as far as I know. My father and mother were both teachers in primary schools, in the country. I went as early as the age of 10 to attend a boarding school, where it so happened the headmaster was himself a scientist. Over eight years there, there were not a great many boys I think who really became close to the headmaster intellectually, but I was one of them, and because he was a scientist I was set to be a scientist. Then I went up to Cambridge and never had any other intention except to be a scientist.
Scientist is a broad term. Did you have any specific interest within it?
Well, he was a mathematician, a physicist and an astronomer, an amateur astronomer, and so I was going to be a physicist. That was it. He had J.J. Thomson as one of his heroes, and so I had J.J. Thomson as one of my heroes, and went up to Trinity College, Cambridge, where J.J. was master. I never had any intention of being other than a physicist myself.
Had the headmaster gone all the way through Cambridge?
He had been in Cambridge, yes. He’d taken mathematics and science in the 1880s, I suppose, and in those days it was perhaps unusual for anyone to take a double degree in mathematics and science. I think he was more of a mathematician than a scientist himself, but he was interested enough to give young folk an enthusiasm for the subject. I said he was an astronomer, an amateur astronomer. I’m talking now of, say, 1920. And I remember, with his encouragement we set up a four-inch refractor with an equatorial mounting, just a rough equatorial mounting, and with the aid of tables in Whittaker’s Almanac, we ‘rediscovered’ Neptune (that is we observed the motion of the planet against the background of stars).
What was his name, the headmaster?
Arthur Thornton. Incidentally, this was at school in Bridlington in East Yorkshire. It was not a very large or well known school, an old school. But before he came there as headmaster he had been senior science master at Bradford Grammar School, which was of course in a fairly large industrial city, a wealthy city, a school with quite a reputation; and there he had entertained as lecturers all the big scientists of the day, and acted as chairman to public lectures for them. And incidentally at that time, 1896, he had become so interested in the discovery of X- rays that the first book in English, or first book published in England on the new discovery, was his own short book on X- rays published in August, 1896.
That’s very close after the discovery.
The discovery was December, 1895.
Did he do experiments?
Yes, he made his own X- rays sets, and even in my day at school, he always had an X- ray set in the background.
Fascinating man. Just a word about your family backround, as far as the professional background, their occupation and their education. Was there any connection or lack of it?
No, as I say my father and mother were primary school teachers. They went to teachers’ training colleges. They were both Yorkshire- born. My mother went to college at Ripon, my father in Leeds, and that was the extent of their education. On each side they came from families — large families usually in those days and theirs were large families — families where the tradition of turning out primary teachers was a strong tradition. I don’t know, at one time or another I should think six members of my mother’s family were teachers in primary schools. Certainly my father had a sister who was also a primary school teacher.
That’s a long tradition. When you came to go to Cambridge, this was 1920?
I went up to Cambridge in 1923.
You were 18 years old then. I’m really not familiar with the procedures, as far as how one decides not only to go to Cambridge, but to follow through and to in fact enroll.
In those days, you see, for people without any financial backing, such as my family, the only way to go was on scholarships. And the only way to obtain complete cover on the basis of scholarships was to take a lot of individual scholarships examinations — you know, scholarships awarded by the county, by the college in Cambridge and so on — in order to put the money together bit by bit. Well, I managed to cover the complete cost in that way, you see. The important thing in such a situation is to get an entrance scholarship at the college of one’s choice, and then to supplement it with scholarships from other bodies. I was successful in getting an entrance scholarship at Trinity College, Cambridge. And I had, as I’ve just said, set my heart on going there, for purely emotional reasons, because J.J. Thomson was my hero, which I had inherited from my headmaster.
He was very much a presence there.
Oh yes, of course. By that time, his force was more or less spent as a pioneering physicist, but as you know he didn’t die until after Rutherford died. He didn’t die until 1940. Except in the last year or so, when he was hardly ever seen, he was a real presence. In fact, I remember vividly being one of the delegation of three, led by Rutherford himself, to present an address to J.J. on his 80th birthday.
That would have been in the ‘30s?
J.J.s 80th birthday was one the 18th of December, 1936.
Just a year before Rutherford died.
Enrolling at Cambridge, starting in 1923, there was about three years —
Three- year degree course, yes.
In the course of that, what exposure did you have to physics and in what form, and further what understanding did you have of the kind of research that was going on at the Cavendish?
Well, it was really, I suppose, towards the end of the second year and during the third year that one became exposed to the real atmosphere of the Cavendish. I attended some of Rutherford’s lectures in my second year. Rutherford wasn’t a good lecturer, I think, as far as the ordinary run of students was concerned. He was a very enthusiastic lecturer and he was capable of generating enthusiasm, but — J.J. Thomson was no longer a regular lecturer but he gave some short special course. I attended that too. In Trinity I had as my director of studies C.D. Ellis, who was of course active in research in the Cavendish at that time. Living in college and seeing these people about and having some contact with them, one got to know what was good. I mean, during my third year I had already become sufficiently interested in problems of nuclear physics to spend or even waste a lot of time in idle speculation as to how nuclei might be put together. I remember handing Rutherford, with some temerity, a document during my third year as an undergraduate containing lists of possible nuclear constitutions in terms of protons and electrons and other particles. Rutherford took it all in good part. I mean, he didn’t say to me what he wrote to W.B. Harkins, in Chicago, in 1920 or ‘21, in relation to notions of the neutron, that all these matters have been common knowledge, “particularly to myself, for the last five years”.
So you did certainly get the flavor. You mentioned C.D. Ellis was supervisor in a sense at Trinity. Were there other people on the staff of the laboratory who had responsibilities in teaching physics, with whom you came in contact?
Oh yes. Not of course so directly, because the private tuition, the tuition in small groups, was organized then by colleges and Ellis was my supervisor. So once a week in a group of two or three I would have a session with him. But as I say, I attended lectures from Rutherford, from J.J., from Aston — was a most uninspiring lecturer. He just read his book. Wonderful man, but quite uninspiring as a lecturer to the young. Chadwick didn’t do any lecturing regularly. He was entirely concerned with organizing the research. So I didn’t come in any contact with Chadwick to speak of until I had started research. In the practical classes, the undergraduate practical classes, of course we came in contact with the younger people, who were active in research at the time.
I’d be interested to know who they are and what kinds of subject matter you covered. I have a few names, I’m not clear whether they did —
You mean who were involved, who were the younger people at the time?
Who took over the practical classes, yes.
Blackett was very active in the advanced practical class at that time. The practical classes in the earlier years, the outstanding figure was G.F.C. Searle. Now, does that name mean anything to you?
Yes, I have a record of him being there, at least from the time Rutherford was there.
Oh, much before. He collaborated with J.J. right from the l890s.
His position was lecturer.
Yes. And I did attend lectures from him, on electromagnetism and heat in my third year, but his main contribution to the undergraduate teaching was in the laboratory of the first and second years. That was organized in an old- fashioned authoritarian way. Searle, as you probably know, lived on to be 90, and during the Second War, at the age of 80, he had been brought back into the department to take over again the kind of teaching that he had been doing until he retired at 70 or so. No, I think he went on over 70. Anyhow I think he had been appointed before there was any retiring age. But he had been retired a number of years, and he was brought back during the wartime, and spent three or four years in his old haunts. He was a remarkable man. Died at the age of 90.
Fascinating. You mentioned that he would take over the laboratory work. Was this in the Cavendish or in a separate course?
Oh no, it was in the Cavendish.
So even in your three- year course of study —
Oh yes, the lecture theatres, the laboratories were in the same building as the research activities. Oh yes.
I knew that. I thought perhaps they were for the more advanced students only.
No, no. In those days everyone was taught in the same place.
But the undergraduates —
Yes, the undergraduates.
Their practical work there was in a different room from the advanced research students?
Oh yes, of course. The research students were spread about in small rooms all over the place. The undergraduates’ work was done in large classes.
This was similar to my experience, I guess. This was done with routine setups - - — were you measuring?
In the first and second years, yes, we were working with setups — not necessarily with everybody, no, in fact certainly not with the whole class doing the same experiments all at one time, but with standard setups which you inherited from the last person, the electrical connections having been broken and that kind of thing, and with a standard document saying how is should be done. That was in the first two years. In the third year, in the final year, it was rather different. One assembled one’s own equipment, and it was more like small research — well, not so much a research problem, but an unseen problem, to a larger extent.
Did people like Thirkill and Bedford play any role?
Thirkill was at some time in charge of the advanced laboratory, yes. Bedford, no. I knew him, but he ran the laboratory for the premedical students.
I see. And I understand that Edward Victor Appleton was assistant demonstrator as well for a period?
He was there my first year as an undergraduate. I was due to go into the electrical laboratory which he looked after, in my second year, but by the time that I went in he had just moved to Kings College, London. J.A. Crowther, who was thereafter professor in Reading, had the laboratory the year I was in it.
Was it Crowther who was associated with PHYSICS ABSTRACTS. or I guess it was SCIENCE ABSTRACTS, in the mid- thirties?
The other was more a popular science worker?
The Crowther I’m speaking of was the one who wrote IONS, ELECTRON, AND IONIZING RADIATIONS.
Vernon Crowther I think was the one on SCIENCE ABSTRACTS.
That’s right. He was a research student at Cambridge. He was a year or two younger than I was. The Popular Science writer was J.G. Crowker - different again.
Are there any others you can think of who played a role in the experimental —
Well, there were many members of staff. There was Alex Wood, who lectured on sound and optics, and there was J.A. Ratcliffe, who lectured on electromagnetic theory and radio. Wood is dead, Ratcliffe is retired and is still alive. Ellis lectured — I attended his lectures. I attended some lectures by Thirkill. I’m sure there must have been others.
These lectures, the ones you refer to as the practical classes, this was the core of your physics education — I mean, lectures by J.J. and Rutherford were sort of special?
The lectures by J.J. were entirely optional and special, but there was a standard course of lectures which it was essential to take. Now, Rutherford’s lectures — Rutherford had some part in the standard course. I mean, the standard course as I took it involved Alex Wood in the first year, and in the second Ellis, and — oh dear, at this length of time it’s difficult. But there was a regular course of lectures going through the whole period, which was standard, and there were certainly plenty of additional lectures one could go to if one were so disposed. But no, I would say the core of one’s education was in the lectures rather than in the practical work.
The practical work would involve doing problems and turning them in?
No, we wouldn’t call that practical work. You mean numerical problems?
No, we wouldn’t — that wouldn’t be called practical. We would use the term practical work just for what happened in the laboratory: the laboratory exercise. Handing in of problems, doing problems of that kind, was the responsibility, kind of the task one’s supervisors, one’s tutors set one, you see, for these weekly sessions I was speaking of. One didn’t accumulate any credit that way, of course. There was no real system of accumulating credits towards a degree. It was entirely a matter of the supervisor and the bunch of students concerned whether the operation was conducted by that kind of process or a more informal process. I didn’t in fact do many problems in that way, except in mathematics.
For mathematics, did you have any work with people from the mathematics department? They were quite separate.
Quite separate, and the amount of mathematics, as mathematics, which we did in those days was really rather small. In fact, one could get through, one could get the degree without having taken any formal courses in mathematics at all. Regulations were so flexible. I have a very good friend (Dr. N.A. de Brunye) from my year in Cambridge, my undergraduate year, who in his own words gave up mathematics after the first year because he found it too difficult, and at the end he got his first class honors in physics, because a Fellow of the Royal Society, and all that. Without mathematics, as such.
How far did you get in mathematics in your case?
In my case I took the standard course for physics students, provided by lecturers from the department of mathematics, for two years, and it provides, you know, a reasonable working knowledge of simple mathematics, but nothing really elaborate.
Would you get into calculus, differential equations?
You had some of that before you came to Cambridge.
Yes. Of course, in those days one did, much more than now. Yes.
What about theoretical work?
Theoretical physics, as such, we got none.
None at all.
Not even through the mathematics? The mathematics wasn’t oriented —
Well, if you like, but one would not call it theoretical physics, one would call it applied mathematics. I did have a course on electrical theory given by a mathematician in my first or second year. There was nothing sophisticated about it. We’re talking of the time 1923- 36, and there was no formal quantum theory of any kind. I mean, one got a few quantum theory notions, but having taken my degree in 1926, I had never heard of wave mechanics, essentially. After all it was only two years old. I’d never heard of it. Oh, we knew a little bit about Bohr’s theory of the atom, you see, but as it came through on the physics lectures, not give by theorists.
There was no one then trained in theoretical physics.
There was no one trained in theoretical physics in the Cavendish, in Rutherford’s department. At Cambridge, no, hardly. R.H. Fowler had a chair in the subject. But let’s see, that would be after 1926, I think.
That would be in mathematics.
Yes, it was in the department of mathematics. Yes, it would be after 1926, because Fowler lectured to me in my first year on geometry. He was a geometer to begin with, and he only went over to theoretical physics somewhat later.
I think I have a record of Fowler’s appointment that will establish the year. About the other students, you mentioned two or three that would be in the group with Ellis — who were they? and what happened to them?
Well, in my last year it was a group of two, and the person I was teamed up with was a man called Bullard, no relation to Sir Edward Bullard — a man called Bullard who had taken a good first in mathematics, and was just doing a year of physics for the purpose of having a wider spread of subjects in order to take the civil service examination for top grade, you know, for civil service jobs — the old civil service competition in which everyone came out in order of merit and the top people went to the Treasury and so forth. Actually Bullard came out top of the national list and went to the Treasury, but unfortunately he died in his early fifties.
Who were some of the others, do you remember?
You mean the one I was in groups with in earlier years? I don’t think I could remember now. I remember plenty of the other people who were in the same final year as I was in physics, but they weren’t associated with me in small tutorial groups.
I see. Ellis was the supervisor of your tutorial group. Do you recall who else from the Cavendish was supervising others?
The arrangement was effectively that everybody in the Cavendish in those days, everybody of any seniority, had a college affiliation and duties in college as well, those duties being the duties of taking these people in tutorial groups, duties of acting as college supervisor. So every member of the teaching staff in the Cavendish acted in that way, and many of the graduate students also had undergraduates farmed out to them for tutorial work. Otherwise there wouldn’t have been enough to go around. So when you ask who else, the answer is, everybody, at one college or another.
I’m in the process of trying to construct the list of the entire staff for each year in an official way, and this must be done through the materials at Cambridge.
I think I can do it, after several attempts, I think I know where all the pieces are. Unfortunately I’ve found no single list already made.
Well, now, in that connection, perhaps you may know, this is the centenary, — and for the purpose of distributing information, about the centenary Dr. Schoenberg of Cambridge has been drawing up a list of people who’ve been through the Cavendish. But I think his list is not a list of research students. It’s a list of staff.
I want that as well. I spent a long time with Mr. Deakin talking about his problems and he didn’t recall that at the same time, of course, right outside his office are the yearly photographs of research students.
And of course the staff too.
And then the university REPORTER and so forth.
Of course, you’ll find the end product no doubt in the lists of PhD’s awarded, with the titles of the theses.
That I’ve found in bits and pieces in the university REPORTER.
At one stage, I think it was about the time I took my PhD, they introduced the method of publishing abstracts of PhDs, all PhDs awarded in an annual publication.
If it was complete for the ‘30s that would be very helpful. That’s a good lead. I ask this, as you can gather, about the various responsibilities of different people in the groups just to help me in that larger project. How large would you estimate the group of final year physics students was in your year, ‘26?
About 30. And generally they came from other English universities?
Oh, no, no. These were all first timers, people for whom Cambridge was the first university.
I was projecting it into research students. But they were British, probably all from various schools in England?
How many of them, do you recall, went on to graduate students? Not necessarily at Cambridge.
Oh, I should think, a dozen. 10 or 12.
What happened to the rest? Did they take the civil service exam?
Some of them would. In those days a few would go into teaching, school teaching, and there were a few young men of means amongst them, not many, who would go back into financial or other business.
When you say 30, you’re referring to 30 at Trinity or the university?
At the University; possibly at Trinity.
Was there any time in which you came in contact with all of them through discussion groups or seminars, or would it be just the larger lectures of Rutherford that you’d be in the same location with them?
We should be there as a class for all the formal lectures, all the standard lectures, yes. But there was no formal seminar arranged exclusively for them. There were weekly meetings with speakers on research topics, from within the Cavendish, which were attended quite voluntarily by, oh, at least half the class each time, and sometimes if it was an interesting subject, pretty well the whole class. They were late afternoon meetings which were entirely voluntary. Then there was a student- organized physical society [which met in the evenings] in college rooms. I mean, we took turns to present our own papers.
I see. This was strictly without any staff?
Oh yes, entirely without.
It was strictly informal — but there was a society. It would be interesting if any records were kept of these subjects of discussion, the attendance.
Well, now, perhaps I’m confusing matters a little. I think what I’ve just said relates, in my own experience, to the postgraduate students, the research students. Certainly they organized their own physics society. I think at the undergraduate stage, we were all pretty much too busy. There was certainly the rather exclusive university Science Society, which I was never a member of and I don’t know anything about it. I think I should correct, and say that I’m thinking of evening meetings, of young first and second year graduate students, rather than undergraduates.
Then, in addition to that there would be the Cavendish Physical Society itself, as separate
Yes. Those were the late afternoon meetings that I was speaking of, though they alternated between Cavendish Physical Society once a fortnight which was a little more formal — the speakers were from outside usually — and the departmental research colloquim, which took the alternate weeks, in which the speakers were almost entirely within the department. For the Cavendish Physical Society, Rutherford took the chair. The other, he very rarely turned up at all and it was organized by Chadwick or someone like that.
Do you recall — this of course should probably span the entire period, from your first arrival in Cambridge to your PhD — do you recall any outside guests and speakers of special importance? Not importance in terms of today, but in terms of making an impression at the time.
It’s very difficult for me to recall, in that period, particularly, because you see I was three years at Cambridge as an undergraduate, I was three years at Cambridge as a research student. I had a year then in America. Then I was back in Cambridge for another long period. Although it was broken by the year in America, it’s not very easy for me, you know, on a snap answer like that, to identify what happened before I went off and what happened after I came back. Your question was, up to the time I took my PhD, do I remember anyone like that? It’s hard to say. I attended most of the meetings of the Cavendish Physical Society, and I must have been at many lectures by distinguished people from outside, but to fix one in time as occuring during that three- year period would be very difficult.
Let me get on to something else, then. When you completed your three years, and successfully completed them, was it clear to you that the next step would be to do advanced research? Then of course what steps did you have to take to make this possible.
I think so. Well, you see, in those days one went up to a college at Cambridge. If one does some research, there’s always the possibility, there’s always the ambition, that at the end of that time, one can get a college fellowship on the basis of it. That provides another three years or four years of stipend without any obligation except to do research — not enough to live on, but at any rate a beginning, you see. I got a college fellowship at the end of the three years research so there it was, the possibility extended on, and by the time that was over I found I had a fairly secure place as a teacher.
By the time it was over you had your PhD as well.
Oh, yes. Yes.
What was required for the PhD? I know there was a three- year research commitment, unless you came in with a year from outside. Was there anything else?
An oral examination.
Both the thesis itself and the oral.
Let’s take it from the beginning. Did you consult anyone regarding your continuing as a research student? Who would you have consulted with - Rutherford or Chadwick?
Oh yes. You see, towards the end of the final year at the undergraduate stage, those who wanted to go on to research were interviewed. Of course the financial support at that stage came and still does come from grants from the treasury — you know, studentships from (in those days) the Department of Scientific and Industrial Research. Now it’s call the Science Research Council. They’re the main suppliers of funds for support. And so it all depended upon whether the authorities in the Cavendish were prepared to support my case as an applicant for a research grant from the DSIR, Department of Scientific and Industrial Research. If they had declined to do so, well, that would have been the end of the story. But they did not, you see. And having the grant I went on to do research.
The grant wouldn’t come to you as a DSIR grant?
Oh yes, it came to me. I mean, this was merely a maintenance grant - to provide the necessities of life.
This was to supplement the fellowship?
No, no. The fellowship came later. The rules are or were that from the date of first arriving at the college, a person can be awarded a fellowship in his fourth, fifth or sixth year, to continue for another four years, you see.
That would be after the PhD.
Oh, yes. It’s very unusual that one gets it before one’s fifth year. I didn’t get it until my sixth. That was 1929. So I was supported by the DSIR research grant for three years, and then got my college fellowship.
Was it the usual procedure for someone to take a PhD and then continue on a research fellowship? Was it a desirable thing, or was it that once you had your degree, then you would try to get a post at some other university?
Well, the situation has changed enormously since that time. The number of universities in the country, you know, has multiplied by a factor of three since then. The number of posts at universities wasn’t large. The tradition of moving from one university to another wasn’t a very strong tradition at any stage in those days. No, I think that by and large, in the 1930s the people who took PhDs either then went out into the wide world — I mean, out of the academic field - or remained at the same university in a junior teaching post or with a continuing research grant for a year or two and then a junior teaching post. By and large, I think, the transfer from one university teaching post to another took place a little later on in one’s career.
So when Rutherford would accept you as a research student, a graduate student, he was buying you for a long term, in a sense.
Well, he was buying me for three years, until I got my PhD; of course he was hoping, in the group he would take in in any one year, to pick up one person who was going to remain on his staff for quite a long time.
But he had no obligation and no responsibility to you beyond the three years?
At any rate, he wouldn’t have been able to take people on unless they brought their own funds with them through the DSIR grant or supplementary fellowship?
Yes. Put it that way, true. All the applications for DSIR grants were channeled through him. It was very unlikely that someone would arrive saying “I’ve got the DSIR grant, will you take me in”? You know, they were all channeled through him, so he would know what he was bidding for, what he was letting himself in for. And by the time that they’d been around for a while, he would know who was likely to get a college fellowship, and might even have a slight degree of leverage, you know, in seeing who did get a college fellowship.
Who else could judge them better? That makes a lot of sense. [Laughter] What about the selection of research problems when the DSIR grant came through? Was this for research training in general, or did someone have to specify that it would be certain specific — ?
No, it was research training in general. Although the problem that one was being put onto had to be notified to the DSIR, in those days at any rate there was no pressure put on the head of the department to assign one kind of problem rather than another.
When did it come up that you were assigned a problem, or made a choice on your own?
Well, I would know in the late summer of 1926 that I had got a DSIR grant, and after a period of a couple of months or so, doing a few training experiments, as all new research entrants were put through, than I was assigned the problem. I suppose I started, oh, sometime in October or November actually assembling to do it.
These training experiments — was this part of the relatively formal orientation?
We’re talking now, you remember, of the 1926 period, when nuclear disintegration studies using alpha particles were to the fore, and cloud chamber work was another general line of approach. It was merely a set of training experiments using gold leaf electroscopes, scintillation screens, zinc sulphide screens and so forth — a few things like that, just largely I think to give Chadwick and those concerned the chance to sort people out. Everyone for example had to do some scintillation counting, to be tested in relation to actual ability to do it. You know, looking through a microscope and counting scintillations, it’s not everyone whose eyesight is up to it or show phychological attitude to life is up to it, you see. So everyone was put through this in order to pick out those who could count scintillations if necessary. And the other things were experiments in radioactivity and so forth, just to give people — the authorities — time to shake us down.
I think people have used the term, “Chadwick’s attic course”.
Yes, that’s exactly right. It was all set up in the attic of the building.
And Chadwick was in charge.
Yes, he was in charge.
He would sort of conduct the drills, and supervise things.
And this was a process, I imagine, not only of screening but of self- selection too, where you developed some interest.
Yes. He would walk around and talk to us.
Was it quite clear that he was an important figure in the life of the laboratory, in terms of student’s impressions? You’ve come in contact with the Rutherford course, you understand who he is —
Oh yes, I think it was quite clear that we should be dealing largely with Chadwick from now on, you know, after this.
And in fact was that the case?
Oh yes, it was, more so with some than with others, but it was pretty much the case with most people.
— I notice you’re watching your watch —
Yes, I think perhaps we should move up to lunch pretty soon.
Well, perhaps at this point. I just want to remind ourselves for later that this takes us to the beginning of your research work. Perhaps I’ll ask one other more general question now, and then we can break. That is, the approximate number and the origins of the research students who came in the same time that you did.
Yes. Well, I said that probably no more than a dozen at most of the final year went forward to research, not all of them at Cambridge perhaps, but most of them. Then another half dozen perhaps came in from overseas at the same time. I remember E.E. Watson from Canada was in that year, and a young Russian called Chariton who is now an academician. Perhaps not as many as six from overseas, but something like that. Massey came later.
That’s something I’m trying to track down, the ratio of Cambridge continuing people and so-called outsiders’ coming in, to establish something of the international flavor. It’s very hard to pin down. People have different impressions and of course what I’m going to do is compile these lists. Your impression was, it was mostly Cambridge?
Oh no, not when you got into the advanced research field. Of course, there were those who came in to get their Cambridge doctorate, and they came largely from Commonwealth countries, on scholarships which were funded by the profits from the 1851 Exhibition. They were the 1851 Exhibition scholars. Those scholarships were available to overseas students to come to this country for research, anywhere in this country, and I suppose each year brought about two or three to the Cavendish. Then there were a few people who came from non-Commonwealth countries, also to get a doctorate. Chariton was one, for example. There were slightly senior people who came on some postdoctoral award and would get involved in some research problem for a year or two. When all those were taken into account at any one time, I should think that if one did not include the teaching staff of the laboratory, that the rest of the research personnel would be — oh, between 30 and 40 percent from overseas, I should think, at any one time. Of course, if you put in the teaching staff, again you would reduce that fraction.
I’m concerned not only with the surface things but with the total atmosphere, and there of course the visitors, the teachers, everything would contribute to that, and it would be good to know all these categories. Well, I think this is the time to break.
We’re resuming now after a very pleasant lunch break, and we are at the point of getting you onto your research problem, after the initial orientation training period at the Cavendish.
Yes. Well, it was decided that I should work along with a New Zealander who’d just come in the same time as I did, Robert R. (now Professor) Nimmo of Christ Church, New Zealand. And that we should operate the cloud chamber and, to begin with, study the distribution of ionization along the path of an individual alpha particle. It was thought possible that the amount of light scattered from well formed particle tracks might be directly proportional or have some close relationship to the amount of ionization as it varied along the track. So it turned out, and in a period of a year or 18 months we had obtained quite interesting information about the distribution of ionization near the end of the alpha particle tracks in different gases. Then, having an expansion chamber in good working order, we were given a more serious problem, a problem having more fundamental interest to the nuclear physicist, the problem of the long- range alpha particles. The rest of our three- year period as candidates for the doctorate was spent on finishing that one off, which we did, in the three- year period.
I asked about how you got started on the problem in terms of the available apparatus and instruments. Was it just a question of putting together components?
Well, there was nothing together to begin with. We built the whole thing up from scratch. I mean, we didn’t build the expansion chamber out of scrap metal or anything like that; I think we got an expansion chamber bought for us off the shelf. But for the rest we put it together bit by bit — the lighting circuits, the expansion valve and all that, either made ourselves or had made in the shop.
Was there any difficulty in getting parts that you needed?
No, not at that time, not really, except it was slow as it always is when you have to assemble apparatus for the first time.
The first work you did, if you were to break it down in terms of the amount of time in gathering pieces and putting them together, and the actual amount of time where you had useful runs, how would you — ?
Oh, the useful runs in the light-scattering experiment could be compressed into a very short time. We only needed to take, under good conditions, photographs of a hundred of so alpha particle tracks. When that was done, the larger problem, the time- consuming problem, was putting these all through a densitometer, and finding the distribution of scattered light along the track lengths for all the tracks concerned. This was all done manually, and the results worked out without even a calculating machine for the purpose.
Let me switch the tape now.
During the various stages of the experimental work, what contact did you have with the staff of the laboratory, or were you pretty much on your own?
By that I take it you mean the academic staff, or the technical staff?
I meant both.
Well, we had some contacts with the workshop staff at the early stage, not a great deal because there was no very complicated mechanism involved. We had quite a lot of contact with Chadwick as the thing was developing. By the time we got our photographs taken and we were at the measuring stage, we were left to ourselves, more or less, as far as I remember, until we came up with the results.
Did Rutherford take an interest?
At that stage, except for popping in once a fortnight and just passing the time of day, no, not really
Was there anyone you could go to for advice on a difficult point?
I don’t really think it was the kind of exercise that brought any of those problems out. It was a fairly straightforward problem, and once we’d learned the trick of taking good photographs, and that was a matter of experience, the thing was done, except just for measuring them up.
On the work that ultimately became your PhD, was it a question of having a problem assigned that could fit into the specific time period? Did you feel this was the question? I often wonder when people say they had three years, how can you — ?
Well, the three year period of course was not sharply defined by any university regulations. Three years was the minimum period, and three years was the normal period for which one could get DSIR support. It was only a matter of balancing the one against the other which decided what was the actual period for any particular research student. Many of them took a little more than three years, and some additional support was obtained somehow or by that time they had managed to get a college award of some kind or other. In fact, myself, I didn’t actually submit my PhD thesis until I’d had a year in the States and was back again. The work was finished in three years, but the thesis wasn’t submitted for another year.
I see. On the choice of the original problem, I may have missed this — just who suggested this?
Well, i’th sure it was agreed between Rutherford and Chadwick. That is to say, Chadwick had the responsibility for seeing everything done, but the problems that he set people, or that were set to people, were agreed between him and Rutherford.
This is pretty consistent in his account.
You see, take this problem that we were given, the long range alpha particles. This was 1927, and Rutherford had first discovered these in 1916. He and Chadwick had made a rather serious investigation of them in 1924, by the scintillation method, and this was the first time within the Cavendish at any rate that they had been investigated by the more objective method of the cloud chamber. It was a problem which had been developing over eight years, and this was the stage it had reached, and here it was handed over to us at this stage.
So it was very much in their interest as well. In other words, this was not just a random problem, but it was
Oh, it was not a training exercise, in any sense of the word.
It was original research but I mean it was research that was consistent with the interests of the laboratory.
I’d like to ask some general questions about your impressions of the orientation of the laboratory at that time. We were talking at lunch about the fact that the Cavendish was focusing on certain problems and there were very few other institutions interested in them. I’d like to know whether there was a consciousness at the time of the orientation of the laboratory, if the participants thought of it as a so- called radioactivity (leading to a nuclear physics) laboratory, or if there was enough diversity so that you didn’t think of it as specializing in any particular subject.
Speaking only for myself, I was so thoroughly interested in this branch of physics that it didn’t matter to me whether the laboratory had a wide spread of interests or not. I think there were many others, young people, in the same situation. I think there were a few, obviously, there must have been a few, even young people, for whom radioactivity, nuclear physics, didn’t arouse any great enthusiasm. And they might have liked the department to have had other activities developed on a similar scale. I mean, there were a few people certainly interested in optical spectroscopy, and they no doubt thought themselves tolerated rather than supported actively. There was a colleague of mine (de Brunye, whom I mentioned earlier) who was interested in cold electron emission, who certainly didn’t think Rutherford gave him any support. There were one or two people like that. But it was quite wrong to say that they got no support. They had places in the laboratory. They didn’t really lack the basic facilities for their particular investigation. And of course there was Kapitza and his group, who had the most active support from Rutherford, in a field which was not nuclear physics, although it is sometimes forgotten (it shouldn’t be) that Kapitza’s first investigation when he came to the Cavendish from Russia was in the field of nuclear physics.
It’s interesting that the large- scale funding was developed for low- temperature physics in the absence of large- scale funding for basic nuclear physics work.
That’s something I found difficult to understand. For example, the DSIR made a special grant (first the Royal Society, then the DSIR) to Kapitza’s work to establish a laboratory, and during the same period I see no evidence of large- scale support to existing nuclear physics activities, and I’m puzzled about that — activites very close to his heart.
Well, yes. You see, I think that’s rather in line with what I was saying at lunch time. There was so much of interest still to be won, using this inexpensive equipment, that Rutherford was happy to go on winning in this way. It was not until a definite need arose within the nuclear physics field — that he was prepared to seek financial support on a larger scale. That need arose partly in 1926- 27, when electrical detection of particles became necessary and he supported Wynn- Williams and his group who developed the electrical counting technique. Then on a larger scale, when people began to build accelerators, cautiously to begin with, he supported building accelerators in Cambridge. Well, even that I think is perhaps doing Rutherford an injustice implying that he was following. He wasn’t really following. From 1929- 30 onwards, he was supporting some work on acceleration of particles. Unfortunately, on not quite a large enough scale. I don’t know whether it’s generally accepted or even known, but I think a case can be made that Cambridge missed the betatron. I’m talking about the first work that Walton did in the Cavendish, before he joined forces with Cockcroft on the cascade generator. So that —
That would be interesting to explore for a minute, what you mean by that.
Well, I’m not an accelerator expert, but I think I’m right in saying that the antecedents of the betatron go back to Widerse on the one hand, and I think they equally could be held to go back to Walton on the other, except that technically Walton hadn’t quite the support to establish his case.
Do you know if it ever came to the issue of Walton desiring support and not being able to obtain it? Because of a conscious decision?
I don’t think so. I don’t think, first of all, that Walton was the kind of person to have made a fuss about extra money. At any rate, I never heard of any conscious decision not to put any more money into that particular experiment.
This is part of the question you mentioned before about support, with some people doing certain subjects who felt perhaps there could be more support. If they were given laboratory space and had access to the same apparatus as others had, then what do you mean by support? I don’t know what you mean.
Well, I don’t entirely mean financial support, because in those days there were very few pieces of equipment that came into the department which were bought whole and cost large sums of money. It was as you say mostly access to the same stores and the same workshop facilities. Possibly one went to see Chadwick and he would agree to buy one some special material to be made up, I mean some tungsten or this or that which isn’t usually in the stores. But by support, I perhaps mean, you know, encouragement to expand the group. or something like that.
I see. So it’s a question of priorities in terms of grouping and concentration.
Weren’t there research groups formed within the laboratory where it was known that so and so was doing something? I was under the impression that most experiments were two research students working together.
Now, I know under certain circumstances research students would be assigned to a group — maybe it’s the word word, assigned, but assigned to a problem which would fit them into an existing group.
Yes, well, true, Ellis had — I mean, all the beta ray spectroscopy was under Ellis’s direction. Chadwick supplied him with research students, and agreed with him on the problems that they were going to do. But any new research student who got into Ellis’s group, was assigned to Ellis’s group, wouldn’t see as much of Chadwick, for example, for the rest of his time, as Ninmo and I saw, who were a pair of people doing a job which, although it fitted into the general scheme of interest of the laboratory, didn’t fit into a larger group. The number of identifiable larger groups was not big. On the whole, they were well- defined problems of general interest, to Rutherford and the laboratory generally, as essential nuclear radioactivity research.
Well, perhaps one interpretation of the groups would be, those problems which were not in that central area would therefore have groups formed around them?
Well, that is true of Kapitza, of course.
That’s almost organizational.
Or they gathered them around an experimental facility, which was shared. I think that’s the only real type of grouping, you see.
For example, there might be a cloud chamber group working on the improvement of the cloud chamber?
Well, hardly, I think. There were two or three cloud chambers at any one time working. Blackett of course had a lot of use of the cloud chamber. I started with one in 1926 and continued to use cloud chambers until 1935. There were others which had smaller degrees of continuity.
I was thinking of C.T.R. Wilson for example.
C.T.R. Wilson was not strictly in the Cavendish. He was Jacksonian Professor, which didn’t assign him any particular teaching duties. Incidentally, he had, before that time, certainly all through the First World War, been responsible for the advanced practical third year laboratory, and a large part of the final honors teaching. He was an extremely poor lecturer in a technical sense, but an extremely good physicist. But in my time, for very good reasons, his cloud chamber was set up in the Solar Physics Laboratory out on Madingly Road, the best part of a couple of miles from the Cavendish. It was out there of course to get away from all radioactive contamination for one thing, and because C.T.R. was a recluse, it was congenial to him to have it out there. He did take one or two research students or collaborators. In my year, Philip Dee, who’s my opposite number at Glasgow, went out to GTR, and a year or two later, J.G. Wilson, [now] head of department at Leeds, was with CTR. and C.F. Powell, who got the Nobel Prize and how he’s dead, unfortunately, was one of CTR.’s people. But they were very few in number all told. They did their work with Wilson out at the Solar Laboratory and we only saw them occasionally. Aston, of course, never had any collaborator at all.
That’s interesting. A young man came to Cambridge last week when I was there, doing some work on the development of mass spectrometry, and wanting to know who the research students were who worked with Aston, trying to establish the idea of a group around this. It’s interesting you say Aston didn’t have them. Why is that?
That is just a matter of individual psychology. Aston was a perfectionist as a manipulator. He really was an extremely gifted experimenter. He had been JJ’s assistant, collaborator. Then the First War intervened, and he came back, after having been mixed up at Farnborough with Fowler and a lot of other scientists, at the experimental station there, and came back with this new idea of a mass spectrograph of the focusing type. And he got a couple going. Of course, I didn’t see the beginnings of it. I saw it halfway through. I got the impression, and still have the impression, that he thought and probably quite rightly that nobody could keep this bit of equipment in going order except himself. And certainly nobody else could extract from this, by paying minute attention to detail, results as accurate as he could extract himself. In those respects no doubt he was justified. But I also have the suspicion that, unconsciously or otherwise he told everyone how difficult it is. And he was in a small corner in the Cavendish where there wasn’t much room to take in any collaborators anyhow. The result was that when distinguished visitors came, or even less distinguished visitors who might like to have joined him, it was still, “Sorry, it’s much too difficult really, you wouldn’t make a go of it”. By the time that that bluff had been called, he’d done the job. He’d had ten years and he’d done the job effectively. He’d exhausted the instrument as far as that particular type of instrument would go, and there was nothing more to do.
Maybe he was correct.
Maybe he was correct. I think he probably was. But you see, he was not a subtle man. In some sense it was doubtful whether he was a scientist, in my view. When he died, he directed I think in his will that the two rooms in which he’d worked in the Cavendish — and as far as I know, he had no authority to direct what should be done with them, but perhaps he only expressed the wish in his will — that they should be left just as they were when he left them, in perpetuity. Odd, isn’t it?
He had rather a unique relationship with this instrument.
There you are. Who would grudge him his Nobel Prize? But I honestly don’t think he was a scientist.
You mean he was rather simpleminded, his approach and orientation was — you know...
Well, a scientist, but an an intellectual level, I really do not think he was a first- rate physicist. He knew what he was after. He knew how to design the apparatus. He knew how to keep it running, when it was being very temperamental.
Let me ask now — we’ve talked about groups, what we mean by them, how different problems jelled. Something we talked about at lunch, about the relations with theorists, how extensive they were if they existed at all, how people in the laboratory felt about them, whether there was a need for such relationships, what the influence was in this respect?
Well, I think probably anything I say on this matter is very much an account of my personal development. As I said, I never had any advanced mathematics. I had enough to get on with; I have enough to get on with. I never had any theory, theoretical physics of any pretension, when I was young. I escaped wave mechanics throughout the whole of my early research career. It had very little impact on what I was doing, and after all there were no courses on it in the Cavendish. And I continued to find that there were still bits of nuclear physics where one can get along with intuitive ideas. So you’re asking someone who has, for better or worse, I suppose for worse, got along in the Rutherford tradition even for another 30 years, although I think most people would say, and I think they’re right, that that tradiation had not that length of life in it 30 years ago. I mean, I think I would have been a better physicist over the last 30 years — in fact, I doubt whether I’ve been a physicist over the last 15 — if I’d been exposed, young, to a good deal more theoretical physics. On the other hand, I think it does take all types to make a world, and even in the forefront of physics it takes all types to make an advance. Now, those are generalities. When you come to a particular — Rutherford’s own attitude — I think you said, and I agree, that he kept his ear very close to the ground, with Fowler’s help. I think also that he was not as innocent of training, mathematical training, as he sometimes made out. After all, his own undergraduate career in New Zealand had been essentially in mathematics, with a bit of physics tacked on at the end. And when it came to it, for example, he did the mathematics for the alpha particle scattering without any help, on the basis of an infinitely massive nucleus. He got CC. Darwin to help when he wanted to take the central mass motion into account. Also, he was sufficiently interested to attend, I think regularly throughout the course, Horace Lamb’s lectures on probability theory, when he (Rutherford) was already professor in Manchester. And even as late as 1927, he wrote a paper on his own, admittedly quite out of the stream of theoretical thinking at the time, but a paper which involved quite a bit of mathematical manipulation. So he could be a reasonable amount of mathematics when it was necessary. But he had a distrust of theorists, as a class, or he professed a distrust of theorists as a class publicly. One would imagine with a mixture of reasons: first of all, to warn the young not to be dazzled by the glamor of it. Two, because the theorists at that time were quite prone to change their ground fairly rapidly. Thirdly, as antidote to the view of the other camp, which of course the really good theorists never countenanced but which might seem to show through sometimes — that they could get on without experimental results. Having said all that — in a sense I would think, you know, it might be held that Rutherford’s attitude was quite a healthy one — I think I should also say that when it turned out that someone who’d been accepted for experimental research in the Cavendish, when it turned out that he had leanings to theory, he did not necessarily go up in Rutherford’s estimation. He had a blind spot, I would have thought, in this connection. For example, to mention two people of my own generation, both of whom are sadly dead, E.J. Williams and Ronald Gurney — you’ll probably know both of them by repute. Well, they both died experimental PhDs at Cambridge, Gurney a little before me, Williams a little after, and Rutherford regarded both of them I think as second- rate.
You made the point earlier, a point that covers two things, one that covers his attitude toward expensive equipment, another that covers his attitude on theory. He ‘thought there was enough one could do, with simple apparatus, that hadn’t been done.
And this would account for reluctance to get involved with a new type of large- scale expensive physics equipment, and also a reluctance to sort of stop with the basic experimental work in order to get greater theoretical input. I’m just repeating our conversation to give some perspective.
And you see, I think it comes out in his writing a little. Talking about the last ten years of his life, he was becoming more and more aware that nationally the Cavendish was being looked to to train young men in research, you see. And there was just not the manpower to set up some large piece of hardware to embark on the new large scale physics, you know. You couldn’t set research students onto it as sweated labor. No, I think you’ll find it somewhere in his Royal Institution lectures or somewhere, more or less said in so many words — that really you owe these people an obligation to give them a training in physical research. You can’t use them as sweated labor. So I think perhaps that was partly it.
That’s consistent, because it relates many things. How would you explain his attitude toward the considerable expense involved even in Cockcroft and Walton’s work?
You see, there were no research students involved there, not in the strict sense. Cockcroft was a member of the teaching staff at the time. Walton had already done his PhD, and was supported by a senior award of some kind, not a college fellowship, probably a senior DSIR award, I think. No, there were no research students involved.
Here’s a letter Rutherford wrote to Bohr, when the first successful results came from Cockroft’s and Walton’s setup. In his final paragraph he said, “It seems to be worth the expense and the effort”.
Well, it was more effort than expense.
He mentioned specifically expense. To him this was expensive physics, and it was an exception, that’s why I asked about it. It was an exception but you feel it’s not inconsistent with his attitude toward the students — this wasn’t diverting resources.
Also it wasn’t taking students away from the basic training of students. This raises another question regarding the criticism that Rutherford was supposed to have received from other members of the British scientific community, although it’s not clear to me who they were, and I’d like to know. Regarding the orientation of the Cavendish.
Well, I don’t know who they might have been. Rutherford was president of the Royal Society from 1925 to 1930. From then on he was the preeminent figure in British physics.
He was chairman of the advisory committee.
He was chairman of the advisory committee and all that. He was very successful in getting what national funds there were into the Cavendish at that time. There might well have been people who were a little critical of this degree of concentration of national funds. I had not heard any serious criticism of the lines on which Rutherford chose to run his own laboratory.
Chadwick felt, on several occasions Rutherford had returned from London and been momentarily depressed by this kind of discussion, comments he’d heard from other people, who felt that nuclear physics, as it was developing in the ‘20s, was a rather unproductive, unpromising field.
Well, there was a very slack period, of course, between about 1925 and 1932. It began to look up again perhaps a little earlier than 1932, with the introduction of the electrical counting devices. They began to be useful about 1929. But it is conceivable that I was too young, at that stage, to know that during that period there were people who were saying that Rutherford was backing the wrong horse.
It was that Chadwick calls a very frustrating period in nuclear physics because there wasn’t much to show.
You feel that during the last ten years of his life, during the period when you had association with him, that his orientation and attitude toward the laboratory was as a training institution.
Yes, that he would hope to organize it so that new knowledge came out of this process, but that he couldn’t overlook the fact that the had this responsibility for the training of the students.
Did he say that? You mentioned the Royal Institution lectures, but ordinarily did he say —
— no, I didn’t get that impression from his day- to-day talk. I think that he always gave us the impression that we were finding out new knowledge.
In his administrative role you feel this was his orientation — that’s interesting, that’s what Chadwick felt, that it was rather a source of a problem. What happened when a theorist would come? For example, Gamow came in 1929 — do you recall maybe, or you had no particular contact with him?
No. I saw him about; I didn’t have really any contact with him. Of course Fowler would look after him, and he’d have contact with Mott. I don’t think he had much contact with Mott, perhaps, but certainly Fowler. Well, of course, that was the first time it became clear to people like myself that in the field of nuclear physics, wave mechanics had to be taken seriously.
How did you know this? He was there. Did he have talks, private conversations? Was it related to you by other people?
I think probably he gave one or two talks. I can’t recall attending more than one, perhaps, but it was relayed, of course, if I didn’t read it. I saw all the things that were published in those days. I mean, it was one of my regular exercises to go into the Cambridge Philosophical Society Library, which was just next door, where all the journals of any importance were on the shelves in the current numbers, and to look through all the journals, monthly at least, and not titles and read those that I could understand and even those that I couldn’t understand, to try to assess what they were getting at. So at that time I had a full conspectus of the literature on nuclear physics.
So despite the lack of it in a formal way in the laboratory, that didn’t prevent you from getting an awareness anyway —
— oh yes, I knew what was going on, but I could neither contribute to it nor assess it critically.
In your particular line of work, it didn’t influence it very much.
I think this gives me a very good background. I’d like to know how the Johns Hopkins journey came about, what was the motivation.
Well, you see — you’ve no doubt read about R.W. Wood.
Oh, yes. We have some of his letters in our archives.
As you know then, he used to come to Europe almost every year, in the summer with Alfred Loomis —
— you knew Loomis?
Oh yes. Wood came over in the early summer of ‘29 and came up to Cambridge, and he said he was recruiting three new associates, young men who would start out new lines of work in his laboratory. He was going to Groningen where he was scouting Dieke, and he was scouting Beardon from Chicago, and he was appealing to us to find someone to start up some radio- activity. I was sold not exactly you know, but Rutherford said, “I think I could fix you up with a fellow, if he’s prepared to come with you, with Feather there, so what about it”? I confess to slight duplicity, if you like, in this whole exercise, because it was toward the end of my third year. I was writing the fellowship dissertation for Trinity. I had reasonable hopes that I would get a fellowship. I knew that if I did get a fellowship, I had one year free, in which I could draw the stipend and do just what I wanted. Those were the rules at that time. It was a four- year award. You could just have a holiday for one year if you liked and draw the stipend. If you didn’t come back and research after that, then period. You could take one year out of the four in fact at any time as a sabbatical year. So although I was young and innocent and very cautious, I think, at the time, I thought this was a gamble which was sound. If I got my fellowship, I needn’t stay more than a year, but I was quite prepared to go, and if I didn’t get my fellowship, well, I might land up in the States for the rest of my life. So I went with Wood, and I got my fellowship. That was announced just before I left England in October, so I knew right in the beginning that I could come back if I wanted. Wood of course was very pleased to bring a youngster into the department and say that he had a fellowship from Trinity College, Cambridge, you see. And I decided to come back. I published three short papers while I was there. I didn’t really get any work going which other people carried on afterwards, and the slump came at the end of the year. In fact, the slump was already on the way. Although, as Wood said, he kept my name on the door for quite a while, they didn’t fill the post again. But Beardon and Dieke stayed. On the other hand, all kinds of things came out of that visit, as I’ll tell you in a moment, but I would like to tell you one more story to add to your Wood collection. This was 1929, in the summer, and the automobile industry in this country had not long before brought out the Austin 7, you know, one of these baby cars. I’d arranged to go up to London to meet Wood at the Artillery Mansions Hotel on Victoria Street, have lunch with him and be introduced to his wife, and he’d take me along to the American Embassy to get all my travel documents fixed up. So I did, and he did, and we were in Grosvenor Square and just stepping off the pavement to go across to the embassy, and an Austin 7 came around the corner. He jumped back and he said, “Gee — there’s nothing more disrespectful to humankind than to be run down by Austin 7, unless it is to be converted by a child evangelist”!
Quite a sense of humor. This was a good introduction for you, I think. I’m curious about the Hopkins experience, about what was going on there, what your impressions were of this department. After all it was your first time away from Cambridge, first time in that country, I assume the first time in the U.S.
I’m curious to know what you found in the department, what your impressions were of the total scene?
Well, of course it was still in the time when Hopkins was essentially a postgraduate institution. There was an undergraduate background but it was quite small. I did a reasonable amount of lecturing to young graduate students, in a field that they hadn’t been lectured on before, nuclear physics. I found them very interested. I got on quite well with the staff and with people generally. In that group — well, not in the group that I was lecturing to particularly, but John Wheeler was just starting, and with the flexibility of regulations which they had then he had been accepted at the age of about 17 as a graduate student. There were one or two other people who were just starting research who are still in the picture. There was G.B. Collins, and J.D. Hardy, and R.B. Barnes, all of whom for some years at least came on, and I think some of them are still going strong.
There are spectroscopy people, aren’t they?
Yes. Dieke and I had just arrived together, you see, from Europe.
Wasn’t Dieke in the US earlier? Cal Tech? Berkeley? He went to the West Coast?
No, no — I don’t know for certain, but I think he hadn’t spent any expensive time in the States before.
I’ll check on it, because I think I recall letters that he wrote to Goudsmit.
Perhaps so, but certainly this was the first post that looked like being permanent for him.
The others were fellowships - a Rockefeller fellowship I think.
We struck up quite a pleasant friendship over that short time, and you know, I quite enjoyed it. I got about a bit to American Physical Society meetings. I didn’t get West at all. I was still young, and innocent, and it was the days of Prohibition. You know, I came away I think without really having understood what the States was all doing. Wood was very good to me, and I spent essentially the last month of my year at Loomis’s lab in Tuxedo Park, enjoying all the lavish entertainment that there was there and the last couple of days or three days with Wood at Easthampton on Long Island. He waved me away, on the train, and referring to Rutherford, and with a glint in his eye, and a cynical view of the hierarchy in Britain, said, “The Lord hath given and the Lord hath taken away, blessed be the name of the Lord”.
He must have been a delight to be around, a constant threat in the sense of being unprepared for what would happen next. You mentioned Loomis. I know quite a bit, from other people about Loomis, and would like to know your impressions of him and his laboratory.
Well, of course, I think it wouldn’t have happened but for Wood.
Wood was an influence on him?
I think so, yes. Loomis had obviously a lot of spare cash, and was I imagine a reasonable engineer. I don’t know whether he was trained as a physicist or an engineer.
He had a number of patents on ballistic devices in World War I.
But you know, I think [his laboratory) was organized on the basis of taking the catalogs and ordering one of each, you know. There was an enormous amount of equipment, quite a bit of it never used. On the other hand, there were one or two things which were more continuing researches or continuing exercises. You see, the business of ordering one of each — they went a little better to some purpose in ordering three Shortt clocks when the Shortt clock first came on the market. Then they had a continuous record on a long paraffin tape, several yards long, you know, slowly moving, in which the timing of the beats of these clocks were recorded. I think that was the first time really that is was established that mechanical clocks could be more accurate than the earth. I mean, there was a greater agreement between these three clocks than there was between any one clock and the rotation of the earth. So it was not entirely without scientific merit. But you know, it was a pleasant place to go for a spell, and meet other people scientifically. I only spent a month there, so my particular final verdict is obviously not —
Were other people there with you at the time? Was Wood with you?
Wood was there part of the time only. I met E. Newton Harvey the physiologist from Princeton, was it? He was an expert on glow worms.
Yes, E. Newton Harvey. And I met Bill Richards, the son of the atomic- weight physical chemist. Those were the two whom I remember. I played tennis with both of them quite a bit.
It was a rather relaxed atmosphere — you ate well.
Oh yes. You see, this large house, it was the second house that Loomis had in Tuxedo Park. He had his own residence. This second house was run as a Laboratory and guest house. There was a flat at the top and installed in this flat was an English gentleman, slightly down at the heels perhaps, but a genuine Percy of Northumberland, you know, and his wife and family, with collaterals to the dukes of Northumberland. And they fed us in that way, you know. We had everything free except charges for postage and laundry, I think.
Loomis is still —
— still around?
Still around, off on a Mediterranean cruise last year, I think. Someone else told me they saw him. Getting back to Hopkins for a moment, Herzfeld was there at the time, and was Gregory Breit there at the time?
Did you have any contact with Merle Tuve?
In Washington I went to visit him one day, that’s all.
Did you see any of his work, in terms of the high- voltage work?
Not in any purposeful way, no. I just dropped in. One person — well, there were two visits which were a little more serious than that. One was to Bergen Davis in New York, at Chadwick’s instigation. Bergen Davis and one of his students had published some work that we couldn’t make head or tail of in the Cavendish. I think the first publication had come out before I left. There was a second one which came out later on. Now, 40 years on it’s difficult to remember precisely.
X- ray phenomena?
No. Of course, Bergen Davis was an expert on that. But here they were entering a field that they knew nothing about. It was an experiment on alpha particles — I think I’m right, the capture of electrons by alpha particles, although I don’t know just how it happened that they were doing it this way. But they claimed that there were discrete velocities of alpha particle motion when the alpha particles were more prone to capture electrons, or something of that order, you see, and it had been done by observing scintillations. As I say, we couldn’t make head or tail of it at Cambridge. There seemed to be no theoretical justification, and although no one had ever done similar experiments at Cambridge, it just wasn’t believed. Knowing how tricky the visual observation of scintillations is if you want to get accurate results, we thought, obviously, they didn’t know the drill. So I was sent up to Columbia to have a talk with these people and see if I could make anything out of it, and of course I didn’t penetrate into the sanctum, so to speak, to see the thing in operation. There was nothing much to see. But I did discover that this young research student had been counting scintillations six or eight hours a day. That’s enough to say, no go, to anyone who knows the business. You see, all Rutherford’s work on scintillations, using human counters, was done on the basis of ten or fifteen minute counting periods, and 20 minutes or half an hour’s rest in between, and unless you do that, your reliability goes absolutely haywire.
It was enough for you to find out their routines to discredit it?
To have them say that really they had been counting scintillations all morning and part of the afternoon, you know, was enough to say, “I don’t believe a word they’re saying”.
Do you remember whether they recognized this later?
I forget the final result of all that. I think they withdrew later, but I wouldn’t be absolutely certain.
This brings up a question regarding the problems of the Vienna people, with Pettersson and so on — were you involved in that?
No. Chadwick spent some months in Vienna in 1926. That was the year in which I took my first degree. I came under his charge in the autumn of ‘26. He’d already been to Vienna.
Some months? That long?
Yes. Well, I may be wrong... (off tape)
So that was a little early for you to get involved in the thing. One other related question — I gather from things that I’ve seen and from what you tell me about the experience with the Columbia people, that Rutherford felt a certain responsibility as far as standards in this field, and that very often he tried to reconcile differences by first-hand observation and by personal communication. I don’t know if there’s anything more to say on it, but I’ve seen several letters where he felt that this was better to handle personally — my interpretation is, so we don’t muddy up the literature with a lot of —
Yes, that was his general point of view, yes. You see, he and Ellis had a bit of cross-purpose publication, just for a year or so, about 1924.
And Briggs too I think, on the straggling business. But this was his characteristic approach.
Yes. The other contact I made at that time was quite different. As I say, Wood asked me to go over there and start up some radioactivity, and at least to keep myself busy, I wanted to do some simple experiments, and so I thought I’d like a source of radium E, which is one of the final decay products of radium. You get a lot of old dead emanation tubes, radon tubes, and you extract it. So I was put in contact with the Kelly Hospital in Baltimore. I don’t think I ever met Kelly who was already quite old, and I think he was out of town most of that year. But his deputy was a man called Burnam, C.F. Burnam, and I made myself known to him. He turned me over to the man who had charge of all their radium, Dr. West, initial F. — I forget whether it was Fred or Frank. I said, if he had any old radon tubes I’d be interested. They had lots, and it turned out that probably at that time their supply of radium was the largest of any in the world — the largest amount of radium in solution in one pot. The radon that they took off every day was not put into lots of ‘needles’ but what they did was to put it into one single bulb. They had five grams of radium in solution. It was Kelly’s private property. And they took off 700 millicuries of radon every day into one bulb, which they used for massive dosage, you see. And West had lots of these used bulbs, lots of them. So I got some hundred — did I get some hundred at that time? No, I got enough for what I wanted at that time. Then it turned out that Dr. West was Yorkshireman, as I am. And so when I was proceeding to go back to Cambridge, I thought I might as well go back with my hands full as with my hands empty. So I got in touch with Dr. West with Burnam’s knowledge again, and said, “Look here, in the dead bulbs that you have, there is more polonium than anyone else in the world has, except perhaps the Curie-Joliots in Paris, and the difference between Cambridge and Paris just now is a factor of ten in relation to polonium. What about letting me have some of this, you see”? And he handed over about 300 of these dead bulbs, which represented in polonium terms, what, a factor of 30 — oh, getting on for 100 millicuries of polonium.
No charge. I just took it back to Cambridge.
How did you take back that much? I know they’re small, but still
But there’s no gamma rays. They’re quite innocuous, within an aluminum box. They just went into a box, you see. Well, the polonium sources with which the neutron experiments were done [in 1932] were made out of this material. And when I got back to Cambridge, and the neutron was discovered, I wrote to West and said, “Look what we’ve done, would you like to send us some more bulbs”? And they sent us some more.
I see. They became your regular supplier.
Well, that was the end of it. We just had a second issue, and that was it.
So you used it in your own work.
Well, I handed it over to the Cavendish, and Chadwick and I and one or two others who were doing that kind of experiment had a go from it.
I would say, if there was no other result of the trip, that one —
Oh yes. I think it is incontrovertible that without having found another source of the material, the yield, the sensitivity of the experiments by which Chadwick discovered the neutron would have been down by a factor of ten below what actually he was able to deploy.
This goes to a problem I’ve noticed, a very limited supply of sources —
Well, you see, this is an interesting thing too, and perhaps Chadwick has told you. There was about half a gram of radium in solution at the Cavendish. I forget whether that was in two quarters or in one half, but they had altogether at one time or another about half a gram of radium in solution. Now, up to 1929, pretty well all their experiments had been done with active deposit sources, mostly or radium, some of thorium. Of course no one had that kind of strength of source of thorium, but thorium is more energetic in alpha particles, and so with the greater energy and the less intensity you can sometimes get things that you couldn’t otherwise. Pretty well all the work in Cambridge had been done with radium active deposit sources up to 1929. This controversy with Vienna largely centered on the fact that they said, “We can get artificial transmutations with polonium source alpha particles of 5.4 million electron volts”, radium active deposit 7.7 million, They were saying, “We can get disintegration with alpha particles with much lower energies than you can”. And by and large, they were shown to be wrong. In fact, it was almost an article of faith in 1926 at Cambridge that you can’t get artificial transmutations worth speaking of, with polonium sources. Well, both sides were wrong. I mean, Vienna was very seriously wrong because their experiments were at fault. Cambridge essentially had never tried. Because they hadn’t had the polonium sources, for one thing. They’d done the experiments with the others and certainly the yield was going down very quickly as the energy was reduced and all that. Then of course, when the Gamow picture came along, just the same way as the Cockcroft-Walton machine succeeding when other people thought it might not (for lack of energy), then this issue became open again. And in any case, if you are going to study nuclear gamma rays with light elements, as Bothe and Becker were beginning to do in 1930, it’s no use using a radium active deposit source, because the transmutations were occurring only once in every million alpha particles. The active deposit source itself is giving one gamma ray for every alpha particle, roughly, and if you’re looking for some gamma rays going with the transmutations, you’ll never find them. You have to use a radioactive source which gives no gamma rays to begin with, and polonium is about the only source they had available at that time which fills that bill, you see. So that if you want to study gamma rays associated with these processes, you must use polonium, and you must confine yourself to those cases in which polonium does produce disintegrations. So of course, when it was a question of deciding whether what you get from beryllium was gamma rays or neutrons, you had to use a polonium source. Luckily beryllium being a very light element does go with polonium. In fact it’s now known of course that the heavy ones do too, the alpha particles going through the barrier, to a small extent. So about 1930, Cambridge had to switch to polonium to continue the story, you see, into the gamma ray field, and by 1932, when it came to deciding whether there was a neutron there, it so happened that they had a strong polonium source in the laboratory.
What would have happened, would there have been a way to get that same source, had you not been there?
Not easily. Because you see, although throughout the world there were probably five-gram radium units, no one, as far as I know, except Kelly, was putting the radon all in a single seed. They were distributing it through a hundred needles every day instead of bringing it to one seed. That means it’s more difficult. In Paris, you see, they had a large quantity or radium. They got their polonium by a laborious radiochemical process. They really separated it out chemically. That was the Paris tradition. For ten years previously they’d always had a large source of polonium, but they got it the messy radiochemical way - — but they were expert at it. But the other method, you see, involves nothing. You just pump the radon off every day and let it decay, and then you grind up a few thin glass bulbs, and essentially there you have it. You know, just dissolve them in HNO3 and plate it out.
The question of sources and availability seems to loom large in the whole development of the field. You mentioned Vienna. That was a source for Rutherford. I forget the exact date, but I know he insisted on paying them for it and finally was able to get the money and pay, the Vienna Academy of Science, $1000. — though it could have been regarded as a gift. I think that’s fascinating, that whole transition. I’d forgotten that the polonium story was connected with your trip. Now, I think we’re ready for the return to Cambridge. You returned to your fellowship. At the same time, you hadn’t turned in your thesis.
Which I did very soon after I got back.
What procedure did you face then? You mentioned an oral. Whom did you have to face on this oral?
Rutherford and Chadwick. You see, those oral examinations are not taken as formally as they are on the Continent, say. They are — or were in those days — entirely run by internal examiners. I don’t know whether they have external examiners now. They’re within reasonable limits, adjusted to the situation. I mean, if a man has got his college fellowship already, it’s very unlikely he would be turned down on his PhD oral, you see what I mean? So I had a pleasant three-quarters of an hour with Rutherford and Chadwick. I think they embarrassed me just once or twice, you know, that was all.
This would cover your general knowledge in physics, not only the specific piece of work?
No, general knowledge of physics.
Was it the procedure then for you to write to one of the university boards applying for a degree? I noticed such letters, when I worked in the archives, saying, “This is what I’ve done, these are my publications, this is an abstract of the work I’m submitting.”
No, no. In those days, and I think it’s still the case, for the PhD, one writes a thesis for the occasion. That is, one describes one’s experimental work at some length — I suppose it might have been on the order of 25,000 words — longer than you’d have in a published paper. You turn that in. If some of it has already been published, you attach reprints. That has been read and reported on. And then you have your oral examination, and the examiners report to the appropriate university authority, “Yes, this man is worth his PhD”, and then it’s announced. No, apart from filling in an application form at the beginning, you don’t do anything. But there’s the other degree of ScD, Dr. of Science, where a man of a specified number of years’ standing can really submit his published work and say, “Look here, I’ve published all this, will you give me an ScD for it”?
Perhaps that was the kind I saw. It was almost routine by that time, because your fellowship had been established your work had been done, and they knew your work. Then you got involved in cloud chamber work more?
Yes, I continued with cloud chamber work on my own. First of all, the primary thing was to try to take some cloud chamber photographs of disintegration — collisions — involving fluorine. I’m talking now, shall we say, of January 1931; the time from October to Christmas, 1930, was taken up with formalities about the PhD. Shall we say January, 1931, I started with the cloud chamber, trying to get photographs of alpha-produced disintegrations in fluorine. At that time, the only pictures of disintegration produced by alpha particles in a gas in a cloud chamber were those of Blackett in nitrogen. Well, I may not be quite right in saying that. One or two other people around the world may have got some more. I think Harkins’ people in Chicago perhaps had, by that time. Anyhow, I think by and large I’m right in saying that nitrogen had been the only gas in which anything had been found of significance. Although one couldn’t use fluorine in an expansion chamber, of course. So I got in touch with a man in Germany who had been a physical chemist, who’d been examining carbon tetrafluoride as to its physical chemical properties. Carbon tetrafluoride (CF4) is a very well- behaved gas, it’s quite saturated, it’s a perfectly inert gas, very well behaved. I got a few litres of carbon tetrafluoride from — I ought to remember his name but I forget, but in the published paper he’s thanked for it — and mixed it with helium and observed about a quarter of a million alpha particle tracks in it, photographed them. And didn’t find anything. I had I think just about done statistically all right, as it turned out. I couldn’t have hoped for anything much better, Blackett was statistically very much [ahead) actually, as it afterwards turned out, with his experiments in nitrogen. His yield of about a dozen cases I think was almost twice the value that he might reasonably have expected. But I didn’t find any. On the other hand, of course I found many interesting things, because at that time I was interested in the range- velocity relation for heavy particles, such as fluorine nuclei of carbon nuclei, so this was the first information about the range-velocity relation for carbon and fluorine nuclei. And it was that research which was just coming to an end when the excitement about neutrons boiled up, you see. So I had quite a good cloud chamber, mostly automatic by that time, ready to go for the neutron investigation as it happened.
When you returned, during the two years you’re describing now, from 1930 to the beginning of 1932, what were your responsibilities? Did you have students who worked with you?
No, I was still working on my own.
Was that the year of the fellowship?
Yes, I still had the fellowship, but I was under no obligation to work on my own. The fellowship didn’t enjoin me to work on my own.
You refer to the one out of the four years on a fellowship.
The one that I took free was the one in the States. That counted.
Who paid for that year in that case?
Oh, I got a salary from Hopkins. Then I got the other free. At that time the fellowship dividend, so called, was £300 a year, so you see, it wasn’t a living wage, it was just an additional emolument, but I got 300 pounds that year over and above my Hopkins salary of whatever it was, $3500.
And they paid for the trip.
So you worked pretty much on your own with the cloud chamber, the fluorine work and so forth, and had no tutorials?
Oh yes, I did, but I did those because everybody does, or did in that situation. My fellowship didn’t require me to do it. But as I was saying earlier on, all able bodies, so to speak, in the college are recruited for this kind of exercise.
Before we get onto this next stage of work, which is very rich — just two other points, as far as meetings. There are two that I’m particularly interested in. Chadwick mentioned the 1928 group, and some of the radioactivity people were involved in it. I wonder if you remember anything of that meeting, whether you participated?
Oh yes, I participated.
I have no description. He’s very vague on this. I have some documents, but it would be nice to know, first of all, if you know anything about the specific occasion, the reason for it, what precipitated it?
— it was on beta rays the relation of beta to gamma rays?
Yes, that’s right. And the date was 1928. And that means that people had just begun accurate experiments on gamma- ray scattering which were tying up quite closely with the wave-mechanical predictions, the Klein-Nishina formula. 1928 would be just a little early for the discrepancies to begin, I don’t think they began to appear until 1929 or ‘30. And if it had been the discrepancies which were chiefly important for bringing the conference together, it wouldn’t have been called beta and gamma rays. No, I think the title of the conference really described the area of doubt at that time, namely, what was then nature of the conservation laws, or lack of conservation laws, in relation to energy, in beta and gamma ray processes? You see, Ellis and Wooster had just for the first time done the experiments to show that the absorbed energy from beta rays is given by the average taking over the energy spectrum, the problem being that the beta ray energy spectrum is not a single line, it’s a continuous spectrum, that you have over a large number of identical nuclei, when they emit beta particles, they don’t emit beta particles with the same energy but the energy spectrum is continuous. He appears as if no conservation of energy in that process, and yet you get afterwards gamma rays of quite discrete energy. Ellis and Wooster had done a crucial experiment in relation to that only the previous year, ‘27. They’d done a crucial experiment just a year or two before, to decide whether it was the beta ray or the gamma ray that comes first. There was a lot of new material about that time. I was too junior to be involved in the organization of it, so I really don’t know where the initiative came from and what was the essential problem which sparked it off. I would think that was largely it. On the other hand, you see, there were one or two people there who were not involved in this field at all but in the cosmic ray field — Skobelzyn, for example.
There were two fellows who read papers on the program.
See, in those days I used to be rather free with a pencil, and I have at home somewhere two sheets of drawings of participants, and I remember I have a sketch of Kohlhorster taken from behind, showing the baldness in the middle of his German head, I have one of Skobelzyn and I have one of Auger and one of Francis Perrin. One of Lise Meitner, and one of Irene Curie and so on.
Was Joliot there?
Joliot wasn’t, no.
In Chadwick’s literature he mentioned Joliot’s coming, but then when I talked with him he definitely remembered Joliot was not there.
No. I don’t remember much about the sessions, but I obviously took part in them — or I spent my time doodling. No, I didn’t, because in those days I always drew all these things from memory. But I spent my time taking these people’s visual appearance in. I do remember sitting next to Geiger at the dinner. Yes, I think I sat next to Geiger.
Did Lise Meitner make any remarks at dinner, do you recall? I’m trying to piece this together, because Chadwick wrote to her, “Since you’re one of the most important guests you might be called upon to make a few informal remarks at the dinner, let me know that it’s to your liking, or I’ll make sure you’re not called on”.
I don’t know.
As far as the effect of this, do you recall this as doing anything special in terms of bringing people in the field together and assessing things, or was it just a specific problem that came up and had to be dealt with?
It came up, and I’m sure it was a healthy exercise, but for my own part, there was no lasting effect of it, because I wasn’t closely involved in the beta- gamma ray field.
Now, about another meeting, one in 1931 that’s more well-known, the Rome Congress of Nuclear Physics. There were some people from the Cavendish there. Rutherford wasn’t there, Chadwick wasn’t, I don’t think you attended.
I think you find Fowler there, perhaps Ellis and Aston, I’m not sure. Do you recall anything about that, any discussions afterwards? The significance of it
In October, in Rome.
No, I don’t. [It was in October 1931 that the Maxwell centenary celebrations brought an international gathering to the Cavendish].
An interesting meeting, nothing happened, probably the last of the international meetings — it was called by the Rome group. Well, now we’re back to the very interesting spot that we left off on, where you were really tooled up in pursuit of your own work, and at the same time the polonium was at the laboratory as a result of this trip to the US. We talked about this in Ithaca, but I would like to go into some of the informal circumstances. I don’t know where to start. I could start with typical historical questions — how did you first hear of it in the laboratory? Maybe that’s the way to start. How did you first hear about the work in Paris which led to a new line of work?
Well, I didn’t hear about it, I read about it. Just by this — at least weekly, more often every other day — ten minutes’ visit to the library of the Cambridge Philosophical Society. I mean, I would pop in for ten minutes or a quarter of an hour every other day, or twice a week or so, and skim through the journals and read anything that was obviously of interest. I knew of the Bothe and Becker experiments, and I knew that Chadwick had some experiments going on, on gamma rays, of beryllium I would assume it to be at that time. These were being done by Webster, as I referred to in my article. Then there were these papers from Curie and Joliot, saying that they got a much smaller absorption coefficient than Bothe and Becker had done. They thought the radiation was more penetrating. One was immediately slightly disturbed that two quite expert experimenters should get such different values for an absorption coefficient — although that is a field where the number one gets out at the end of the day depends very much on one’s experimental arrangement. Then you see, when these people got an effect out of paraffin wax, and when they said that that put up the quantum energy that they had to assume for their gamma rays by another factor of at least five, you know, one just on the spot couldn’t believe it. There were no two ways about it, one just couldn’t believe it. I happened to see Chadwick the same morning or that afternoon — “Have you seen this paper from Paris? Just nonsense, isn’t it”? “Yes, just nonsense”. It was simple — I had no thoughts of neutrons. Perhaps Chadwick had, even at that stage, but we were both thinking that it was just nonsense, their interpretation.
Immediately without any further discussion.
Yes. So Chadwick began assembling his equipment as quickly as he could — I think obviously, although he never said so at that moment in time, with neutron notions in the back of his mind. I think he must have had it in the back of his mind, because these experiments that Webster had been doing had been going on slowly, and they had been giving funny effects. He was using two different kinds of detectors, and in the results he was getting, the two hadn’t matched completely. And it appeared that the penetrating radiation was more penetrating in the forwards direction than the backwards direction, and that doesn’t tie up with gamma rays, you know. In fact, Chadwick had I suppose at that time not — no, Webster at that time, knowing that Chadwick didn’t really think that it all tied together, Webster had asked a colleague, another research student, to put the polonium - beryllimum source near an expansion chamber he was working and see if he saw anything surprising. And he didn’t. I don’t think Webster pressed him hard enough to persevere, and if he took any photographs he didn’t keep them. Anyhow, that was all a month or two before, so I think Chadwick really knew what he was expecting to find. But he was obviously looking to see whether you got similar effects with other substances besides hydrogen. While he was getting this ready — or perhaps as soon as he had got the first indication from his own equipment that yes, he was getting some effects in nitrogen which were heavily ionizing particles, to match with the protons from the hydrogen - he brought this source along to me. It was the same polonium- beryllium that we were both using alternatively. And we didn’t do anything with my big cloud chamber, which would have taken a day or two to get tooled up, so to speak, but there was somewhere in the laboratory the demonstration cloud chamber. It had been once a saleable object produced by the Cambridge Instrument Company designed by the Japanese Shimitsu who came to work with Blackett in 1922, where you turned the handle and you got a reciprocating motion. You didn’t get sudden expansions, but anyway enough of an expansion to produce a cloud. A small chamber about so big, you see about 8 or 10 cm. diameters]. So we dug this thing out, and I turned the handle and he held the source near it. Of course it’s a very messy thing, but we convinced ourselves in the first half hour that we saw little stubby tracks about two or three millimeters long in the air in that cloud chamber, and that would just about match up with the ionization pulses that he was getting from his nitrogen chamber. So then we knew that there was something up, and I got the big chamber ready and took several hundred feet of film, 35 mm by 25 mm pictures. It all went quite well. Things were there, and then we saw these tracks, these forked tracks, you see, which I took along to show him the first time I got any reasonable picture. Again he didn’t say anything, very much. By that time it was clear that we were talking about the neutron, and I went away and measured them up and analyzed them. It all fitted in, and within two or three weeks we were ready to announce. Rutherford was no longer president of the Royal Society. There was a third person involved. Dee, as I told you, was in the same year as I was working with C.T.R. Wilson out in his physics laboratory where there was no radioactive background. He was particularly concerned with cloud chamber operations, the actual formation of drops, and getting a really clean cloud chamber so that if you saw a drop, one drop, you knew that it was one ion, you see, and you might have some hope in saying how it came there. So Dee had the cleanest cloud chamber in the world. I make that claim for him without any doubt. And there was here, very soon or course, some collaboration with the theorists. Massey was already sufficient of a theorist to talk to Chadwick about it. I think even before Massey started talking, it became evident that the theorists would predict that if there was a particle like this, it should not interact with electrons to any appreciable extent. And they were fairly soon on the ball there. From the experimental side, it was an obvious question to ask, does it interact with electrons, you see? Oppenheimer had speculated about neutral particles before this, and talked about particles of small mass and magnetic moment, and thought that they might ionize, sparsely, a good deal more sparsely than electrons. So of course it was an obvious question to ask. So Dee had the cleanest cloud chamber in the world. The source had to be taken out to Dee, at night time, and he had to run his thing, and see if he got any tracks due to electron interactions. So, no, he was able to account for every drop in his cloud chamber without involving electron tracks. So there were three papers to be written. There was Chadwick’s and mine and Dee’s, and we got down to it and we wrote them. Rutherford saw to it — those three papers were published together in the PROCEEDINGS of the Royal Society within 17 or was it 21 days, I’m not sure which, from the date of submission. You can check it up. The date is on the document. Fifty pages of Royal Society PROCEEDINGS print, with halftone photographs, in 21 days. Rutherford might not have been interested in the neutron any more in 1930 — I mean, that is a moot point — but as soon as he saw it was there, he also saw that that thing was in the Royal Society in the quickest time that 50 pages of the Royal Society had ever been done before.
That’s fascinating. Prior to that time, the letter went out to NATURE, the Chadwick letter, about the 17th of February. About how many days elapsed before that letter went in? From the first time that Chadwick started picking this up?
Well, I think the dates are given in my article — the publication date of the three full papers, and the publication date of Chadwick’s letter is there. I don’t think I was able to record the actual date on which this “don’t believe it” episode occurred.
By the way, Deacon showed me some Cavendish account books that he’d found. Maybe Thirkill was the one that kept them, according to what Chadwick said, and they go only to February 13, 1932. Although there’s an entire blank notebook... I asked Chadwick, but he had no explanation. It seems that thoughts stopped at an appropriate moment. After these three papers in the PROCEEDINGS of the Royal Society appeared, on such short notice, through Rutherford’s help, it seems to me that it was quite clear what the research program would be. It would be clear for Chadwick and for you. Did it effect very many other people at the laboratory?
No, at that stage I don’t think it did. I went on in a rather a systematic, rather a pedestrian way, just taking photographs of other gases and being interested more in the disintegrations produced by neutrons than in anything else. Of course, it quickly became clear once the accelerators had started working, that neutrons were produced in reactions in accelerators too. But Chadwick and I continued to work with alpha- particle produced reactions for a little while. As you know Chadwick in the following year gave a Bakerian Lecture on the subject, which — I haven’t a very clear picture of this, but I imagine represents about as far as he took the subject individually himself. I mean, he had other groups still investigating the alpha particle reactions which produced protons rather than neutrons, and studying the energy groups of the protons. You see, the work in the laboratory over the previous three years, the work in Chadwick’s groups, had been a detailed investigation of the reactions in which protons are produced — directly, you know, alpha in, proton out. In various energy groups, and the protons correlate with the gamma rays, which Bothe and Becker had been finding. Then of course there was this new work in which the neutrons came out as an alternative type of reaction. And then it became clear that in some cases, from the same target, say aluminum, you could get neutrons or protons. If you bombarded an aluminum target with alpha particles, you’d get some protons and some neutrons, and it was the correlation of those two reactions which was interesting. And here we missed, I think quite clearly missed, full realization that we ought to have been looking at that time for artificially produced radioactivity. You will see there is a remark in the 1933 Bakerian Lecture, — I haven’t done any homework for this interview, this is all first recall — there is a remark in Chadwick’s 1933 Bakerian Lecture with a footnote saying that I also said the same thing, which gets pretty near to saying that electrons should be involved too somehow, you see, and setting limits about energy. But we should have said, but did not, that there ought to be produced some artificially radioactive bodies here. And as you know, those were discovered almost by accident by Curie and Joliot next year, 1934. So my experiments on various collisions, disintegrations of various gases, and Chadwick’s further experiments using his proportional counter detector, I think roughly came to an end in the summer of 1933 or something on that order. Though we did go on running the expansion chamber later than that. WT. Davies (who’s now at Oxford) came in as a research student, and we did a little more, and began to get some three-pronged disintegrations as well as two-pronged disintegrations. I think the first of those which was actually published in the literature was by Chadwick, Feather and Davies; that was probably 1934, too. By that time Goldhaber had arrived, and Chadwick and Goldhaber got teamed up. Their interests became concentrated on disintegrations produced by gamma rays, you know, photo- disintegration of nuclei. Because of course you can produce neutrons that way from hydrogen and beryllium. And they became interested in the fundamental problem of the constitution of the deuteron- the heavy hydrogen nucleus — one neutron, one proton, held together — how strongly is it held together? So I think Chadwick’s interest became focused on this, the simplest situation in which the neutron is involved. I got roped into that too, because with Bretscher I did some expansion chamber work on the photo-disintegration of the deuteron.
When had Bretscher come? He was in Zurich before, wasn’t he?
Yes. You met him personally?
Well, at Churchill [College], in a crowd, someone told me to shake his hand. I’ve never talked with him really.
He’s a Swiss. As you say, he came from Zurich.
I came across his name in the Meitner papers because he was connected with some conference in Switzerland.
He hates that you should call him a chemist, but as a matter of fact, he took a PhD in chemistry here in Edinburgh in his young days. He was trained as a chemist. And during the wartime he allowed himself to operate as a chemist quite a bit in the atomic energy group to begin with. But he quite rightly regards himself as a physicist, or did throughout his more mature years. I suppose he must have come in 1934, would it be, to the Cavendish — I suppose so, because the experiment was done with the cloud chamber before I went off to Liverpool, at the end of September, 1935. We’d actually taken the photographs, with the heavy hydrogen gas in the cloud chamber and the gamma ray source, photographing the photo- protons produced by the photo- disintegration of the deuteron. Now, Bretscher again allowed himself to operate partly as a chemist in that situation. We had of course a small supply of heavy water, and we wanted to make a gas mixture for cloud chamber use which would contain as much heavy hydrogen as possible, and not be too dense, and so we compromised in the end to use a mixture of acetylene and helium; I’d previously compromised in the fluorine experiments to use a mixture of carbon tetrafluoride and helium, to get the right kind of stopping power for the cloud chamber experiments. And so Brestscher generated heavy acetylene from heavy water, you see, and fed that into the cloud chamber and mixed it with helium. And we did this experiment, photographing the tracks of about some 50 or 60 photo-protons, measuring ranges — they’re only very small energy, only about 180 key, which gives them a range in air of a couple of millimeters or three millimeters, something like that. Those plates were measured up once in Cambridge just before we went off, and measured up a second time in Liverpool, and the published paper was written after the second measuring in Liverpool.
In August of ‘35.
No, more like August 1936. Of course, this is essentially the neutron story, because it involves the binding of the neutron and proton. We had a brush with Bethe over this which is interesting, you see. As you know one of Bethe’s early claims to fame as a theorist was the theory of the loss of energy of charged particles passing through matter, which he goes into in great detail. So you see, we had this situation in which, having measured the range, we had to deduce the energy. There was our gas mixture of known composition, heavy acetylene and helium. We did this just by calibrating it with alpha particles, and then translating from aipha particles to these particles on the basis of empirical results, in which you have collisions of alpha particles with others and measure their ranges, you see. And if you remember, I said I’d done this in fluorine and Blackett and Lees had done it in hydrogen and other gases. This calibration of our measured ranges to energies — I had myself been entirely responsible for it. It was entirely empirical, very much intuitive, taking what one gets as the right way of looking at a rather complicated set of data gathered from here and there and everywhere. And on the basis of this we concluded that the energy was such and such, and we quoted the value of the binding energy of the neutron as 2.25, plus or minus .05 MeV. Bethe wrote a letter to NATURE, I think it was to NATURE, effectively saying, “I know how to calculate energies from ranges”, you see, “these people really don’t, and from their ranges the energy should be such and such and the binding energy should be 2.17 MeV”.
Was he in Manchester at the time? He was still in England, yes, ‘35.
This was ‘36. It may have been ‘37, when he —
Was it something he did alone or with Peierls?
Yes, in those days he was collaborating with Peierls. I think that this was a letter in which he was the sole signatory. He said the binding energy had to be 2.17MeV. Well, I mean, we had given plus or minus .05 on it, that didn’t overlap to 2.17. Of course the currently accepted value is 2.223MeV, so I’ve always felt that this purely empirical approach to the situation was the right one, and the theorist didn’t know what he was talking about. I’ve never sat down and talked to Bethe about this one, but I think he would have agreed, if he’d been tackled, that he really was extrapolating his theory into a very dangerous energy range. Because when you get right to the end of the path of any fast-moving particle, the situation is getting a bit fluffy. You can’t theorize about it very precisely. I thought at the time, the only way to deal with this was to compare it with comparable situations and take the best evidence you have, and theories couldn’t help. I was always very surprised that Bethe thought it worthwhile to write to NATURE about it.
Did you ever communicate with him at the time about it?
No, we just let it go.
I see. But you knew he was wrong. Or, that you were right.
Put it this way. I felt that his theory couldn’t be trusted in the range where he was attempting to apply it. I mean, if I thought it could, I’d have used it myself right from the beginning.
There was no basis for publishing another article. You didn’t have any results?
Oh no. After all, later it was done more accurately, and there you are, within our value; we were entirely vindicated.
Some theorists don’t even come close to being concerned with experiments.
Oh yes. We were encouraged that he was reading his literature rather closely.
A general question, about this productive period before you left for Liverpool. At the same time the Cockcroft- Walton work produced some dramatic results. I’m interested in the internal reaction of the Cavendish, how Chadwick felt about his work. We both understand certain personality characteristics of his. I’m just curious, how this surfaced, what reaction you noticed, in terms of his own feelings?
You mean, did I notice any real feeling that he’d achieved something? Well, yes. Just a flicker of it, now and again. Now you see, Rutherford — there was this letter in NATURE. I’m not sure of this, you must check the dates, but very shortly afterwards, and I think before the papers had appeared in the Royal Society, Rutherford was giving a Royal Institution lecture, and he took the opportunity to speak publicly about our results.
I think it was the Royal Society - it may have been Royal Institution, but it was in April. I know that he did give a talk on the nucleus.
I’m fairly convinced that this was the Royal Institution, because I remember a seat high up, not on the floor of the Royal Society, which is quite a different room. So of course Chadwick and I went up to be there, to hear it, and he (Chadwick) was sufficiently enthused for us to have a meal at the Cafe Royal, you see, to celebrate. That was a flicker of satisfaction and achievement. Then, to take it a little later, November 1935, when we were both in Liverpool — we’ll come onto the general situation in Liverpool later on, but we were both in Liverpool and by and large, there weren’t many other people there who could talk together on nuclear physics. In November 1935, when I returned early from lunch one day the departmental secretary had been in early after her lunch, and she came out and she said to me, “Oh, there’s been a telephone call for the professor from Stockholm”. Chadwick came in, and I said, “Oh, Miss Lloyd- Jones has been telling me there’s been a call from Stockholm for you”. He said, “Darn it, they’ve been worrying me for my photograph for ever so long”. That’s all he said. So I hadn’t even a chance to congratulate him. If he’d taken it as congratulations.
That’s characteristic. Well, it was quite apparent —
Yes. Then of course he was pleased. But I mean, he was also extremely delighted with the Cockeroft- Walton success. There was no sense that he felt, you know, that he would have had more of a show if the two things had happened a couple of years apart.
That’s right, very much so. Well, these things came fast and furious during those few months. What about the general atmosphere? Now, here you have a number of research students. You showed me the picture of the group assembled — these things coming out, world attention. Was there any feeling in the laboratory of a new stage, or elation, or what?
Somehow I didn’t experience it. No, in a sense I thought it was aim a day’s work, having been to some extent involved in it. Rutherford I’m sure felt that he knew Chadwick had it in him to jump in at some stage and make a big discovery. Those people in the laboratory who weren’t so directly concerned without putting anything more than a factual gloss on it — had been used to living with Nobel Prize winners all their lives. The fact that something should happen, that there was likely to be another one in a year or two, you know, didn’t cause all that much change in the atmosphere. After all, people were about the place with that kind of international fame, and Cambridge was about the only place — over a period of years, I mean, others were beginning to crop up — nuclear physics happened in Cambridge. That was the general attitude. Quite an unconscious attitude, I think. But it didn’t make any great climactic change of direction or change — I don’t think so.
That’s internal. What about the attitudes of other institutions toward the Cavendish? We talked before about the relative special role, and relative isolation in some cases.
Well, one got invitations to go and talk about it in various places. I went to talk about it at Oxford and Nottingham and one or two other places, I should think. Yes, there were those. Shortly a period of intense interest, yes.
Rutherford wrote a letter to Bohr at this time, by May, when all results were in, saying that he feels that this really opens up the field, Bohr replied with equal enthusiasm, broad new avenues were opened. I guess it’s really my task to try to assess what changes it made, but we know that there were some fundamental changes. Anyway, from your point of view inside the lab, it didn’t change the direction of the work.
That’s really the point of the question. I’m sure we’re skipping things but perhaps we’ll have an opportunity to get back — I’d like to get to the decision of Chadwick to leave, to go to Liverpool, and also your decision to join him. What do you think the background of his decision was, and what you know was the background of your own.
Well, of course, he was what — 43, 44 — and I don’t know whether he’d had any previous offers of posts. Things in those days mostly went by a few people being invited to apply. Oliphant certainly was invited to apply for Birmingham. I think Ellis may have put himself forward for Kings College. He went just afterwards, in ‘36, so there was Oliphant going to Birmingham — he went just before Chadwick, didn’t he?
Yes, I think so.
I wouldn’t be sure. Blackett had gone to Birkbeck some years before. Of course, Liverpool was near Chadwick’s home. Chadwick was a Manchester man himself. I never heard and he never gave me any information about his reasons for taking this seriously. I think there was as much local loyalties as anything else. Certainly the department at Liverpool had run down quite a bit. Wilberforce was well turned 70. He was one of JJ. [Thomson]’s nominees from many years before. And I suppose there was a slight feeling — but I must be quite clear that Chadwick never indicated this to me — in the laboratory generally, it was thought that there was a slight feeling that Rutherford in the past few years had relied more on Oliphant than on Chadwick for direction of work. Chadwick still had his official position as director of research. In fact, Oliphant was very good at it, and certainly as an Australian had, I suppose, appeal to Rutherford — perhaps there was just a little of that in it too. But I have no basis on which to give you any indication of reasons which Chadwick has probably himself declined to disclose.
I don’t know. I only know that he must have said that he wouldn’t go unless he could take someone with him. He had in fact got Liverpool to agree to establish a post which they called at that time the Leverhulme Fellowship and Lectureship. I mean, he’d got them to acquire some money from Leverhulme to finance this post, and it was indicated in the title that it was partly a research post. The first I knew about it was that he came along and said he was being pressed to consider going to Liverpool, and it would help him very much to look upon the proposal favorably if I’d say I’d go with him. Again, quite illogically I said I would. The financial outlook was certainly not very attractive. Admittedly in Cambridge I was still on the lowest rung of the ladder in the hierarchy of university posts. My college fellowship had expired, although I was still getting some work and some support from the college. At that time I only held the university demonstratorship. So I said I’d go. Whereas I’ve confessed to a slight reservation, mental reservation, about joining Wood at the Hopkins, it would be wrong to suggest I had a similar reservation about going with Chadwick to Liverpool, because that looked as if it might — apart from the financial considerations — be a very fruitful collaboration. But then, you see, Ellis went to Kings College, London, in the following year, and vacated at Trinity, the one position which would fall vacant once every ten years or so, which was just the position which I was waiting for, the vacancy, you see. So it was either go back to Cambridge after one year, or never. So whereas I’d gone to Baltimore hoping almost that I could go back to Cambridge the next year, I went to Liverpool and had to make the choice whether to go back to a permanent job in Cambridge after one year, or no.
What was the outlook at Liverpool? There was no assurance —
Oh, it would have taken quite a time to get things going. It did take quite a time. Chadwick eventually got the cyclotron built, but that took four years or so.
Is this where Kinsey and Holt C?) worked?
Letters I’ve seen say there was not much going there.
But you did some teaching, I assume.
Oh yes, I did some teaching. I knew that I would be doing some teaching in any case. Yes, I had almost a normal teaching load.
Did you have the opportunity for research in that first year that you had hoped for?
Well, I didn’t get any experiments done. I wrote up and measured up the effectsagain, and I wrote my first book, INTRODUCTION TO NUCLEAR PHYSICS.
Yes. I remember in the introduction to the book, you mentioned Gamow’s work which you had the privilege of working through. I’m curious to know how that came about, and also, why the timing of that book, why you felt things were ripe for it.
Well, I think the Cambridge press, before I left Cambridge, had put the proposition generally about that it was time for a book on nuclear physics, and specifically to me. And I said yes, I’d consider it. I mean, they didn’t commission it. They could have turned the thing down when they saw it, but they took it when it was written. The other one, which came at the same time — you see, Gamow had published in 1931 a short tract with the Oxford Press, and they apparently at the same time were persuading him to expand it and give it a different title, which he did. So I think when the first bit of copy came in, it was more than ever evident that they couldn’t hand it over to the printer as it was. Oxford Press approached me and said, would I put this into English? It was written in English, of course, but would I put it out of Gamow-ese into English, you see. So I said I would. Well, I don’t think that I felt any necessity to quieten my conscience. I mean, Gamow knew. I told Gamow right away that I would do it but he must know that I was writing a book myself. I had no need to quieten my conscience really, because the two books were written for completely different purposes. In fact, the only thing I had to quieten my conscience about was that I was even sufficiently knowledgeable about the theoretical language to do the job that I’d been asked to do. However, I said I’d do it, and I even wrote a bit in the preface in which he thanks me for doing it, you see. You read that last bit of the preface. You’ll see quite clearly that it isn’t the translation of anything that Gamow could have written. But that was a most remarkable job. The thing came along in his quite unpredictable hand, for one thing. Sometimes it was legible and sometimes it wasn’t. And with all these marginal drawings of ‘Heisenbergs’ and so forth — and talking about pet dogs — once an anguished letter from him saying, “Sorry chapter 3 wasn’t sent on the date promised, because the dog had eaten it”. That was the kind of Marx Brothers situation in which that was done. I didn’t of course prune everything. There was a footnote there, “Proceedings of S.S. Aquitania”, such and such a date, you see, and things like that — of course all the marginal drawings went, and it is fairly readable.
Did you retain the original manuscript? It would be fascinating if you could lay your hands on it, just as an example of his style.
I had it for a long time. I may still have some. There are all kinds of tea chests at home which haven’t been opened for a long time, and I may have some of Gamow’s manuscript.
May I urge you to take a look in Pandora’s box? It would be quite interesting. Well, then, the thing that precipitated your book was that Cambridge Press felt the time was ripe. It’s interesting — Rasetti about that time writes a book, and Bethe, Bather, Livingston, and yours start coming out, which was really bringing the field to a focus. From my point of view it’s very interesting. Your book I find very useful, for me, to understand the state of the field at the time. It covers it concisely with historical insight, although not avowedly historical. You’re getting a review of the book some 30 odd years later, from one who wasn’t intended to read it. I hate to run short of time like this, but there are a couple of major questions. One is, on returning to the Cavendish, it seems to me that you returned just at the time when the large Austin gift came, and a time when there seems to be the change in the policy. There was in fact a cyclotron built. I’d like to explore those two things, especially Rutherford’s attitude toward the cyclotron, toward the building of this, whether this was something he was sort of forced into or just accepted. Secondly, the gift itself, whether this was sought or just happened, and how Rutherford would respond to that. The third category is the effect of Rutherford’s death on the laboratory itself and on its direction. Now, I think the three are all bound up together. You’ve indicated partially that the group had already started disbanding, and so I’m fully aware that just because Rutherford died, it didn’t mean everything else happened all of a sudden. There were lots of complex things going on. That’s what’s on my mind.
Yes. Well, you see, the Cockcroft- Walton thing had produced the goods in ‘32. The Phillips set was bought — I can’t place a date on it precisely. Before very long there were two Phillips sets, you know, a one million, and another with two million volts, straight accelerator, cascade generator, the same Cockcroft-Walton type. The Austin money put up the building that housed those two sets. And then there was the cyclotron. Now, Rutherford I don’t think had to be persuaded against his judgment to do any of these things. I think he was quite happy to do them. You see, Cockcroft had an enormous span of technical knowledge, and Rutherford was quite prepared to rely on it. If Cockcroft said the thing could be done for 20,000 pounds, it would be done for 20,000 pounds and it would work. Dee had now become a fairly mid-senior member of the departmental staff, and he was happy to take over full charge of the Phillips sets and Cockcroft- Walton type sets, and Cockcroft himself was there desirous of having a go at the cyclotron. Rutherford was fully content on Cockcroft’s recommendation to agree to both of these developments, and to take a major share of looking for the money on it. It was I think through Baldwin, who was chancellor of the university at the time, that a good deal of the corning and going with Austin was arranged.
I did talk with Cockcroft on that.
I don’t know much about the details on all that. Except I would, I hope, be confirming what other people have said, that in my view at least Rutherford was not reluctant in any sense.
Well, there is obviously some difference of opinion on that. The question of the scale of physics — the cyclotron does change the relationship of an individual to a specific experiment and interferes perhaps with the teaching role of the laboratory, and it’s problematic, and I don’t think anyone can really make a statement — I wouldn’t be satisfied to say that he resisted it or supported it without some other kinds of documentation. I’m very much interested in your impressions. There’s nothing you know of that could work against it, unless you interpret the things that I said just now as working against it, then perhaps that’s evidence against it.
No, really, I take your point about the teaching, the training — I think Rutherford would have that in mind and would wait.
Well, we can get this out of the work that Cockcroft and Walton are doing, and the work that he I guess had involved with Oliphant on the other device.
— related to the cyclotron —
— yes, specifically the cyclotron. When Cockcroft went over to the US in 1933, he looked at cyclotrons and I think would have been willing to convince Rutherford of it, but I think again with some reluctance. I wouldn’t be surprised if this was among Chadwick’s problems, as far as seeing the future. After all, first he has to build a cyclotron at Liverpool —
— quite, quite, yes —
— and it’s not at all obvious to me that he could have built one and had the freedom to operate that way at the Cavendish, not because of — I’m sorry, here I’m giving opinions on certain interpretations and I’m supposed to be asking you — but not because of the obstinacy of any individual, but because there was so much else involved at the Cavendish, which was already established. That’s interpretation.
Yes. See, I was away for the long year and lost the thread of development a little at that stage.
That’s interesting. That was a critical year. By the time you came back...
Yes, in relation to policy perhaps it was the critical year.
That could very well have been. Well, you did come back, and there was a two million volt, and the one million the original Cockcroft- Walton, and the cyclotron in the works. That already represents in a sense a continuity, but certain change taking place. Within I guess a year of your return, Rutherford died — is that right?
Yes, in October of ‘37.
When you came back, were there many people left? Of course Ellis had left, that’s why you were there. Who was left of the original team?
Dee and Cockcroft. Oliphant had gone — they were really the senior people in the research line, in the nuclear physics line. Ratcliffe was still around but he was doing his radio research, you see, didn’t work in the Cavendish itself but out in the field. Kapitza, of course, had failed to return from Russia, but Schoenberg and his people were continuing the low- temperature work. In the nuclear field, no, it was Cockcroft and Dee, the teams working on the cyclotron project and on the high- voltage sets. There was nobody else.
I guess Oliphant took over Chadwick’s position at first. Was that filled when Oliphant left?
No, not in the sense of putting anybody in with the same research interests, no.
I meant as director of research with responsibility for running the laboratory.
No. There was no overall responsibility of that kind. Rutherford, you know, had a new team, and he was going to see how to divide authority between them, I think. Meanwhile each one was running his own group. They hadn’t of course the freedom to hire and fire or decide just how research students should be divided among them. Rutherford was chairman throughout. I hadn’t got any large machine. In fact, by that time I’d become interested for a while in beta ray work that’s another matter. But Rutherford had begun to say that I could have responsibility for all the publications of the department, which should be channeled through me, and I should act as papers editor effectively for the department. But that never got off the ground before he died, really. It all happened so quickly. We hadn’t really shaken down into a regular way of running.
Yes, that’s right — to find a routine — get organized —
That was the situation in 1937.
Fowler held the Plummer professorship of applied mathematics from 1932.
Joliot and Irene Curie also extracted polonium from used radon bulbs - ed (SW).