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Interview of Jabez Street by Katherine Sopka on 1976 November 22, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/31112
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This is one of a number of interviews that Katherine Sopka conducted with Harvard physics faculty regarding the history of the Harvard Department of Physics. Street joined the Harvard physics faculty in 1932. The primary themes are the department and his cosmic ray research in the 1930s. Street describes his decision to leave the Bartol Research Foundation in Swarthmore, PA; the salary that Harvard offered; other faculty members, especially Theodore Lyman; conditions in the Physics Department; and the courses that were offered. In the second half of the interview, he focuses on a detailed description of his cosmic ray research and of the colleagues and graduate students who worked with him.
This is Katherine Sopka speaking. Today, November 22, 1976, I am visiting with Professor J. C. Street in his office in the Jefferson Physical Laboratory. In the interest of compiling a history of the physics department in recent decades, Professor Street has kindly consented to share with me some of his recollections of trends and events that have shaped that history since he first came to Harvard as an instructor in 1932. Professor Street, perhaps we can begin by asking you to comment upon the differences that characterize physics at Harvard today from what it was like when you arrived.
Is it running now?
I see. I had been at the Botto [?] Foundation in Swarthmore [?], near Philadelphia. And working on cosmic rays. And I met Professor Kemble [?] at the Washington meeting of that year. What was it, '32?
Thirty-two was when you came.
Thirty-two. And he said they were interested in having me come to Harvard, and would I visit after the meeting. And I agreed. I visited Boston, first time I'd ever been here. The spring weather was cold ??? ??? which is not very encouraging in itself. But the laboratory was, it seemed ??? was ??? ??? ???. I was taken around and shown the Jefferson and the newly built Lymon. It wasn't called the Lymon Laboratories then.
It was called the Research Laboratory of Physics?
Research Laboratory of Physics, that was it. And everyone was most cordial. Looked at from today the department was very small. It was I think six professors in physics. I remember them all very well. Saunders [?], he was chairman, a very tall gentleman and had white hair. He's famous for the Russell Saunders Company. There was Bridgman, who is famous. He occupied the lower floor of the Research Laboratory, and part of the shop, and he had two or three assistants, ??? ??? great. Then there was Kemble [?], who was writing [?], who was the only theorist I think here at the time.
That's right. It was in between then.
And there was Holdenlay [?] who worked in the department of physics and did for many, many years afterwards. There seemed to be a great deal of assistance, technical assistance for the professors. It was Dave Mann, who was an almost famous shop man who operated the machine shops. And there were three or four machinists, almost as many as there were professors. There was a glass floor and there were several sort of assistants. And I didn't forget Lyman, who made the whole thing go. His interest and his money, and his insights, were essential. Lyman had — I didn't learn this until later, but I did see those people. Lyman had hired various people who had been in need of work or in trouble or something — this was in Depression time — and he hired a janitor and he hired two or three men, the Langston [?] brothers. One of them was his assistant and one of them set up the equipment in the laboratory. But in any event, Lyman had picked up from the Boston scene several workers who more or less followed his minute directions in great detail. He hired the two, the Donaldsons, one who operated or at least later operated the photographic end of things. And —
Is that Larry Donaldson?
Larry. He's still here. Later. But he was just a handyman at the time. He had two, Lyman had two laboratory assistants ??? ???. One of them was one of the Langstons. And most of the experimental research was going under Lyman at that time. He had three or four students who became well known, and there probably was many more before I came, but at that time there was Ed Schneider [?], who was quite well known during the war for his work in radar, and Wilson Powell, who later became one of the cosmic ray high-energy people in Berkeley, and there were two or three others whose names I can’t recall. In any event, Lyman’s laboratory was very active. They were breaking in ??? ??? ??? ???, and he was a very, he was way up in that technique in handling the spectroscopy of the ??? ??? ???. It was friends like Crawford, who was not a professor, he was an assistant professor I think ??? ???. Yes, ??? ??? ??? ??? ??? ??? that time change there. And Crawford was interested in spectroscopy, and of course Kemble was very interested in the theory of spectroscopy, wrote a lot of papers at that time on the subject. That’s about all of the professors in physics that I can think of right now. I don’t think I skipped anyone. There were people in the Communications/Physics/Engineering there was Chafee [?] and G. W. Peiss [?] and a young assistant professor, Hunt. And I believe that’s all who were there. Now this doesn’t include the engineering. It was called an Engineering School, and it doesn’t include the people who were over there. I think by that time Kenaly [?], who had been famous for the heavy side ray gun [?], and retired and was not there. But I hear that, you know.
Professor Hall had retired by this time too, I’m sure.
He had retired. But he was still working in the ??? ???. He had retired. I think that — because the people that, Roger Hickman [?] was here as an instructor, and he was given the job of guiding me around the building. Everyone was very cordial. I was interested in the machine shops and the glass blowing because I was majoring [?] in Geiger counters in those days, and there was a glass blower named Layton [?] who became well known later. During the war he went to Dumont [?] and became high up in the company. His skill in glass blowing, he was better educated than for that alone, but he stayed because of Lyman I think. Lyman’s influence kept him around. Chafee was very interested and it also interested me at that time, very interested in the what was called a brown tube that was an early cathode ray oscilloscope. And analyzing circuits for ??? and cosmic ray ???. Micronics was very little developed at the time. I was quite interested in Chafee’s knowledge and interest in cathode ray tubes that he called always the brown tube. I gather later that he was one of the very first fusers of the cathode ray tube.
Oh, that’s interesting.
Of course certainly not the first, but he was the first who made good technical use of the device as of the oscilloscope. Well, I had a hard time deciding to come, because at the Votto [?], as people today recognize, there was no other duties, and you could definitely save until you were well supported. You didn’t get much salary, but your time was your own, and I realize that if I came to Harvard it certainly would be a considerable responsibility for teaching. But Saunders said it really didn’t take much time, and that all I’d have to do is teach a few sections of what was then Physics C. And also the salary for instructors was not particularly impressive. At the Votto, just as a fellow, I had been making $1800 a year, and they were offering $2500. But then with the extra teaching duties, I wasn’t too enthused. They said well, they’d give me a fellowship along with it. And they have such — I don’t know whether you could look up the names, they are all set in a special fellowship. The Cutting [?], that was the name.
So they awarded me the Cutting Fellowship, which made me a member of the Graduate School. So I got, they paid for the literature of the Graduate School from then on for special request for ??? ever since. So that raised my salary to $3000, which is enough, since I was in debt, was enough to attract me, have something attract you. I still owed money from going to Graduate School.
At the Bartol [?] Foundation, could you have stayed on there as long as you wished?
Yes. Swan [?] made it quite clear, W. F. T. Swan was the director then, and Thomas Johnson was the assistant or associate director, I don’t know which one he ???. At any event, they made it quite clear that I could stay on, but Swan said, “Well, this is a good opportunity. I would advise you to take it.” So with that influence and advice, I said I would take it. But I wasn’t sure that I was doing the best, the right thing for me. Anyway, I came to Harvard and after working at Johnson we ??? small cosmic ray expedition to the top of Mt. Washington when we were looking for the so-called — we didn’t know it was the East-West Effect then, but well, any ??? ??? ??? in cosmic rays, with the question of how they charged particles. There was a great argument whether the cosmic rays were gamma rays or charged particles at that time.
What was your own opinion?
We really had no bias. We, Tom Johnson and I, had worked for over a year together, and we were quite sure that what we were observing at sea level was definitely particles, because particles are the only things that make continuous trails of ionization, and that’s what we’d been observing in the counters. But one of the primary things that caused these was charged particles of gamma rays. It was very ???. No one believed Barry Finley [?], and they ??? sort of theories of electrons and photons at that time. You know, everyone believes in it now a hundred percent; it’s really just the Bible. But at that time, it was not very ??? believed in, and ???, who was the strong supporter of gamma rays as cosmic ray origin primaries, was quite sure it was something, enough wrong with that to explain why they could penetrate so deeply. According to ??? ??? theory, electrons and photons would be dissolved in a few centimeters of ???. This was not true. They went to great ??? ??? ??? ??? ???. So we headed out, we were completely open-minded as to — But we did, in the Mt. Washington experiment, although it was a very small effect, we did observe an East-West, an East Mound [?], and we were a little reluctant to push it hard because only a few percent effect in statistics have ??? ??? ??? when you have only a few percent effect. It could be ???.
Was the Mt. Washington experiment before or after you came to Harvard?
Before I came to Harvard. That was the summer. We were doing it in the summer, and that fall I was coming to Harvard.
So I appeared here, and we — I left Tom Johnson on the mountain, and took a duffle bag, walked down and crossed the trail and caught the train there at that hotel over there. I forgot the name. To get to Boston. And ??? ??? ???, with the help of Hickman I guess, or someone in Lyman’s office, found a room at Pagan’s [?] Hall. So I lived in Pagan’s Hall for the first ???. See, I was a graduate student, so that made it alright.
Although you already had your Ph.D. you were —?
Yeah. See, I was registered in the Graduate School as a Cutting Fellow, and so it was not — the rules didn’t forbid me ??? ??? ??? time. I think Batol [?] was most interesting to me because of my best friends were the graduate students. Not just in physics. I had a friend in geology and two friends, two good friends in geology, and one who was in the engineering school, Dick ???, who later became my first graduate student. And I had the services of, without any limitation of this, of the shop and the glass blower and — Lyman, there wasn’t much money, you weren’t given a budget or anything to call on, but Lyman always said if you wanted anything you tell him about it and he’d see you get it, get it to make it possible.
Funding was certainly handled differently in those days.
Oh, it was very a sort of personal almost exchange with Lyman. And there was no formal you could spend so much money. And most everything was made here, because — and the way I was doing, you didn’t, there was nothing you could buy with it, it was — other than normal materials. You could buy vacuum tubes and transformers. But most of it was made in the shops. It was a pretty good electronics shop for that day in the Croft [?] Laboratory. And you could get that help through ??? Hickman, who was always friendly, and I never had to go to Chafee because it never went to that high a level. And the glass blower had been told to make anything I wanted, within reason. And Dave Mann [?], in the big shop, had plenty of help, plenty of time, so there was really no problem in getting stuff made. So I started at once and had counters and ??? and recording systems made according to the style that we had at Barteau [?]. And that occupied me most of that year, was building up equipment. I have forgotten whether it was the end of that year or the end of the next year when through Lyman’s influence I was offered Carnegie support to go on this ??? expedition. The idea was to check up, again was the ???, was the charged particle aspect of the cosmic rays, which is a big point in those days. Dave Mann’s outfit, I think it was through that year that, and not one year later, I think it was at that time that we built up the equipment. There was a young man, Jim Dunham [?], who was a theoretical [?] student working, who had worked at Kemble, who was very bright and full of good ideas, who was going to go with me on the expedition. Not long before summer however he had a case of appendicitis. It was operated on and he seemed to be getting along fine, and hospitals kept people longer then. He was there about a week, and he got up and the next day he died from an aneurism [?] or something. So I had no one to accompany me on this. It was a difficult trip to make because of the transportation and all the equipment that was going to be really something to keep up with. I could tell by that time I was going to have many boxes. So I hadn’t mentioned him before, but Mennos [?] was in the division, and he was working on ??? ??? ???, and he volunteered to accompany me. Not as anyone very interested in the experiment, but as a traveling companion and as a help, as an aide. And offering some help on the equipment ???. But he really said he wasn’t interested in the equipment, and if I didn’t need him why he was going to be traveling, tourism ???. So that was agreed to, and we — I don’t think there’s anything — Well, I shouldn’t, this is not history of the department. It’s been my own story. I should say something more about the department, the teaching. Now Saunders was in charge of the largest and the main physics course for science concentrated. It’s Physics C, which would now correspond to Physics 12 or something like that. And there were two other physics courses, Physics D which was for pre-medical students, and Crawford at that time was in charge of that. That was still scientific enough to serve the medical purposes, and it be Physics B for people who were really frightened by physics but they had to take it for some reason.
Well, also people who didn’t have physics in high school had to take Physics B.
That really didn’t make so much difference as whether they had in high school or never had it made all that difference, but the ones who felt that it was going to be the new level in ??? ??? doubtful about getting on well took Physics B. With Black, who did not, who didn’t enter into the department much except for this operation in teaching these people. A very pleasant gentleman. He was nice to associate with, but he didn’t take too much interest in ??? ???.
Physics B was given at Radcliffe, and that was where I was introduced to physics with Professor Black.
Oh, so you knew him as well. Well, he was a fine gentleman. He didn’t know much physics. At least that was the impression I ??? ??? ???. He was a good teacher, and he knew Physics B well enough.
I don’t mean that. Crawford’s Physics B was a good cut more turnaround [?] and a ??? more physics. Physics C was really I think a splendid course. Of course the teaching of physics has changed a lot now and we teach many more advanced topics in the first course, but still I don’t think Lyman could have improved certainly for that day on the course that Saunders taught. And Saunders was the sort of man who taught physics from the point of view of you look around and you see the things that happen and you explain all of the physics that’s connected with it. I mean he was interested in ??? ??? ???, how the ponds froze, and so on. Not at a low level, though. I mean you had to understand it thoroughly. How do you roll hoops by the gyroscopic effect, rope ??? ??? boys playing with yellow roll hoops [?]. In any event, the questions in his course always made him explain those things. He was also very good at keeping up with the things that were then active. I remember Langley had a lecture on the physics of surfaces [?], and Saunders had thoroughly included that in some of his lectures, he gave the same demonstrations that Langley had given — how you would determine the size of a molecule by measuring the thickness of a nonmolecular [?] ??? on the surface, things of that sort. And there’s a lot of delicate chemistry involved in doing experiments of that sort. He worked them up to the point where he could see them and understand them. So his course, Physics C, was really outstanding. I, as he promised, for the first few years anyway, taught two or three sections in Physics C. That consisted of teaching a conference section with problems and answer questions and teaching the laboratories.
The laboratories would be frowned on today as too elementary and technical enough but not modern enough. But at the time they seemed to me fairly good, and they were again aimed in this direction of explaining the world around you, even as ??? heat conduction of a mark or you’d measure the interference of sound, sound waves, and measure the speed of sound, ??? ??? and that sort of thing. These are now old hat experiments that have been largely abandoned. Nonetheless at that time they seemed alright. The more advanced courses certainly didn’t have very much of a burden at that time. They had a lot problems they look up the figures in some of these reports, but my memory is that perhaps they were maybe 50 concentrators in all years. Maybe less. So that none of the classes were very big, and an intermediate class might have 10, 12 students typically. And Kemble taught the quantum mechanics course which was Physics 40 in those days, and there might be six or eight students in a class like that. And then there was — there were just a few of the so-called advanced graduate courses. There was an introduction to theoretical physics, which friends of [?] Crawford taught. It certainly wouldn’t be more than eight or ten students. The number of graduate students I think was probably about 20 in all total. Again, you could check the figures. I had felt — I went to the University of Virginia — that my formal physics education was probably not very outstanding, so I decided I would try to see what they had ???, so for two or three years I attended at least one of the classes. I attended Kemble’s quantum mechanics, and I went to hear Bridgman lecture in thermodynamics for a year, and I listened to one or two other things. I forget now.
Did you indeed find these significantly differently from your —?
??? ??? ??? far more, much more mathematical than had been my training, and didn’t find that there was a lot of what I call physics that was new, but there was a lot of difference in the thoroughness of the mathematical training. I mean, such things as existence theorems and so on had not been pressed on me very hard before that.
With whom did you take your own doctoral degree?
With Jess Deans at the University of Virginia.
Yes. And it would have been an experimental physics, so —
??? ??? theory spiral was, his name was in theoretical physics in Virginia. He was a very capable man, and I had had a course in quantum mechanics, although it was just about the time people began to teach quantum mechanics. In the smaller places like Virginia for instance, there hadn’t been any ???. That was the first year it was taught I think that I took it. And we used Sonnefeld’s [?] supplement and we had gone through —
Oh yes. The one that’s called wave mechanics.
Wave mechanics, yeah. I had had Sonnefeld’s old ??? ??? ???, and then we, in the quantum mechanics course in Virginia the first time it was taught ??? said well we’ll try to work through this book of Sonnefeld’s. It was quite confusing, because that book is quite confusing. It all seems to begin in the middle and doesn’t tell you very much how one arrived at those conclusions.
Well, I think that characterized quantum mechanics in the early days — the teaching of it, at any rate.
Well, we learned a few of the rules, and we learned to do some of the problems. But of course Kimbell’s course, Kimbell was a leader in the field, and he was working on his textbook then which ??? been some years later. He was doing everything most thoroughly. I could tell that what I had was a very skimpy ??? Kimbell’s course [?]. I didn’t work at it as hard of course as the students who had to pass exams on it, but like any just listener, why you could let that part go. And later of course, when many textbooks came out on quantum mechanics, I had to study again much harder. But when you had Langley teach it, then you had to learn certain — Well, I thought that the greatest experience in the first few years I had at Harvard was as much contact with the graduate students and their problems as it was with my colleagues and professors. As I say, I mentioned Wilson Powell, who worked with Lymon, and Ed Schneider [?], and I followed their research pretty much, and it was very, stuff that — Lymon had a very good program going. He had almost retired then, not quite. He taught one course. And I think he taught a course in optics, sort of an introductory course in optics for the undergraduates.
I believe he formally retired in 1937 from the teaching, but then continued to be director of the laboratory until ‘47.
But he didn’t take as much responsibility for the teaching then. He just taught this one course which was so familiar to him I’m sure that he didn’t worry much about it. He did take a tremendous interest and didn’t neglect in any way the work with these graduate students. He supported them. He had the most graduate students and the most active research program of that period. There had been a course — and I didn’t know much about it, never looked into it, and that may be the reason I don’t emphasize it — this band spectrum study of Crawford’s that Kimbell was also interested in had been very active before I came. But spectroscopy was losing interest at a great rate in that period. And the nuclear physics and cosmic rays and things of that sort, and electronics [?], were becoming much more interesting.
I expect that’s why the department was interested in having someone with your interests and background added to the department.
I suppose. Now, in the ‘30s I was not a voting member of the faculty, so I didn’t attend faculty meetings and know nothing about the plans and what they were trying to do. Although it was quite clear that there was a tremendous effort being made to build up the department. I’m quite sure — this is guesswork, but I’m quite sure they felt the department had been great but was, people who ??? were getting old, older, and they needed new people.
Well, both Professor Van Dyke [?] and Professor Flurrey [?] came two years after you did.
Well, Bainbridge came two years later.
And Bainbridge. Yes.
Because he was young when I ???. I had known him before, but he wasn’t there when I was ???. So they asked me about Bainbridge, and of course I wasn’t asked about any ???. I remember Bridgeman asking me what sort of fellow is Bainbridge. The brought in, as you say, they brought in Bainbridge, Flurrey. Van Dyke came two years after I came. I think it was ‘34 or ‘35.
Yes, it was ‘34.
‘34. I used to play tennis with Van Dyke. You didn’t realize that he played tennis.
Oh, no, I didn’t.
He played a good game of tennis. Of course these people, the new people, they replaced Barry Anderson [?]. I had worked with, at Virginia as a graduate student I had known Edward Stevenson [?] very well. And he went to the Naval Research Lab I think at the same time I went to ???. And he and I were very close friends and had written back and forth. Then he, I recommended him to Swan, and Swan asked him to come to Novato [?]. He had gotten, he was more in chemistry, he was a physical chemist, and he went to the Barteau the year after I left, not while I was there. And I ??? Saunders and Lymon to get Stevenson. And so he came, and I can’t remember whether it was in ‘33 or ‘34, and worked with me during the ‘30s. We worked very closely together for about six or eight years, until the war. And that made a great difference, because having someone to talk to on a subject that’s entirely open when you don’t know anything about it, and it looks contradictory, it’s a great help. So he was a key figure, and so I mentioned Woodward, who was a friend in Pagan’s Hall. By talking with him, he became interested in cosmic rays. And although he was enrolled as a graduate student in what we would now call a division, then the engineering school, he asked if he by special arrangement be allowed to work with me on a thesis, and they said alright, go ahead. So he worked with me. He didn’t get a physics degree. He got a doctor of science degree in engineering.
Oh, that’s interesting.
Some years later. And I think he got his degree in about ‘36 or ‘37. But he worked with me during that period, mainly on caplets. I had another graduate student named Young, R. T. Young, and he was a very able student, and he worked with me on ionization changes. These are the things I mentioned those, that I took on that expedition to Peru. I took a set of ??? which had been thoroughly built up. I only had that one year to build up equipment. And a small ionization chamber which had been built up in Dave Mann’s shop, and recording equipment. To go on expedition is very different from experimenting in the lab, because you can’t go and get any parts to fix anything. So everything has to run. And then my fellow who was going to collaborate with me that totally died that ???. So I was quite alone on trying to prepare this. I felt that I was really not as well prepared as I would like. But we set out on the expedition. The ionization chamber worked beautifully, so that we got latitude effects and the interesting thing about cosmic rays in those days was the fact that you knew that there were these ??? particles that came as singles — you could count them in calendar [?] space, and those ionizations, you measure them in an ionization chamber, but there were also the unknowns were the fact that you could set up two or three counters out of line and they would go off every now and then. So it was a shower of some sort. More than one ray associated in time. And then the part of that that you saw in an ionization chamber was the fact that you got a base; the ionization didn’t come smoothly. Every so often you would get a big kick. So the recorder had to show not only the amount of average ionization, which you just view ??? ??? ???, but you had to have a continuous record to see — if you wanted, you can get a whole picture — what these bases look like. And I was quite interested in how the bases [?] and the so-called soft absorbable radiation, how that varied with latitude and altitude and was ??? ???. Well, I was very unhappy with the counter system, because we had 900 [?], our counters went bad in time. They changed their rates, and they would start hissing, and you couldn’t have dependence on them. Now I must say the counters that I took with me I thought were fine, but when I started working with them down there I was completely dissatisfied with them. I said well, we just have to give this up.
Were the problems with the counters involved with maintaining the vacuum in the chamber, or were they electrical problems?
No, no. They were surface electrical chemistry. They were really a complicated — A counter operates by sparks, by regeneration by this method that a spark develops. The electrons which collected have to multiply in some way, and as a spark they go to a ??? incident ??? ??? limitations in the circuit, and so that procedures by which one electron makes many more electrons, that’s a simple avalanche, but the, something goes back to the — what is it? — cathode. And produces another avalanche behind it. And if this is unstable, the thing will just go into an arc, and won’t quit. And that was the way the counters were behaving. And they worked fine for a while, but then they would do this. Now later on it was found everyone took on the technique that was discovered somewhere in Germany, that if you put a little alcohol of some heavy, some terrible substance, complicated substance in the counter, that it would clear all this up. And what it does, is it prevents energy from being exchange from molecular form to release more electrons. If you’ve got complicated molecules so that the vibrations are very, all sorts are possible, then the energies divided gets to a low enough level where it can’t eject more electron. The counter ??? ???. So these quenching agents, so to speak. But I didn’t know about that, and the counters that I took — Is ??? ????
Yes, I just was —
The counters that I took on the expedition didn’t have this nice treatment with ???. The nicest thing turned out to be later pure ethyl alcohol, as little ??? ??? as possible.
Oh, I see.
The water vapor causes trouble, because electrons attach to it, and that reduces the main avalanche effect, the thing that you want that you are registering, the sharp pulse, the efficiency of the counter is reduced if you have an electron attachment. Because even the one or two electrons that are formed, it first may be captured and you won’t record the thing at all. So you want to keep out oxygen and ??? ??? which are a negative of electromagnetism and try to attach electrons. But you do want to have some complicated molecule which will divide the available energy going back to reproduce more electrons and not have it keep happening. You want it to stop. Anyway, well I gave up the counterpart. I had some data that indicated that there was still an East-West Effect and it was bigger than we had gotten out on Mt. Washington, but it wasn’t reliable. I couldn’t depend on it, so I didn’t use it. The ionization chamber, though, worked beautifully and it showed that the thing that was beginning to be realized at that time, that there was a soft component of the radiation, and there was a hard component. Soft component had a large number of these bases [?] mixed up in it. The soft component at high elevation changed latitude effect much more than the sea level latitude. It was only about 6 percent latitude in fact between the Equator and this place, and for the hard component it was about 30 percent latitude effect for the soft component. Many people about that time observed that, and this was just one of the many — Compton, other people. [inaudible phrase]
This trip to Peru was just you and Mimno.
You weren’t part of a larger expedition.
No, no. And Mimno, I should say, was a tremendous help. Without him I’d never been able to — We had 20 boxes. And we had a great joke about it, because the ionization chamber had to have lead shields, and that was one of our experiments was that we had heavy lead shields on the side, and then we had these variable shields we built up on top. And so we would build these up and take readings at various lead decances [?], and that was how we steadied the absorption of the soft component in lead; we compared it with the add-on [inaudible phrase]. Well, that’s enough on that. I think that probably you should ask questions [inaudible phrase]. Perhaps you could help me by indicating what sort of things would be best to talk about. My research in the ‘30s remained in cosmic rays, and we — and I saw “we” advisedly, because these graduate students that I mentioned, and Young, together with Edward Stevenson who came as a colleague, and later I had another graduate student who is not on the normal list, Lee Fussel [?], who was at MIT, and in one of the lectures he became quite interested in cosmic rays and came as he could come up to Harvard and work on the exchange. It was some sort of exchange with MIT, so that he was a graduate student with me.
After the first two years, the argument — we haven’t had a personal [?] detailed argument, but the physics argument with Millikin [?] over one of the Kaiser brother gamma rays, they argued ??? cosmics or not, which remained strong, and we had read Rossi [?], who did the first, some of the first coincidence experiments after Geiger’s [?] originally, and wanted to check out his observations that if you put any centimeters or even a meter or two of lead between counters, you have still got counts. This was explained by Millikin as due to some regeneration of energy from some gamma ray that was much more penetrating than the theory said she [?] would be. So we became interested in the cloud chambers due to the ??? details of this. And we built a system which had a Geiger counter on the two sides of the cloud chamber, so that we’d set the cloud chamber off with the counters, and look in the chamber to see what really happened, what you could see. And we found that invariably there were always a few that you couldn’t explain, but invariably for the average picture there was a single thinly ??? icing [?] track going from one counter to the other, and these went through lead and chamber and so on. And they do, anyone can do this experiment ??? ??? ???. You see these penetrating braids [?]. Those were later found to be the mesons. We thought they were electrons or protons at that time, didn’t know. But it was a thinly ionizing tract. As you know, all very high-energy particles ionize ??? ??? extend tracks of about the same route. You couldn’t tell a proton from an electron from a meson by looking at the thin track.
If you believe the theory, electrons just couldn’t possibly do that. That is if you believe the theory of Baylor and Hackman [?]. And past 1934 and ‘35 came along, people began to take these theories more seriously. Quantum mechanics was more strongly believed, and relativistic quantum mechanics was beginning to be believed a little bit. So we really wondered, because here are beautifully demonstrated in the cloud chamber between the counters one could see these continuous tracks, and they went right on through 15 centimeters of lead, no trouble. And if it were an electron, it should lose by radiation at least half its energy and any half centimeter, ??? ??? millimeters of lead. So how in the world could it ever get through 50 centimeters if it were losing half its energy if the mean path was only a few millimeters of lead? So most people said, “Well, it’s just something wrong with their ???. We just can’t believe that.” Others said, “Well, they’re probably protons at very high energy.” So with the aid of my colleagues, Stevenson and the graduate students and Fussel, we set up a whole program to try to understand the thing further. Now, the behavior of electrons is such that it loses like an exponential thing, it loses the ??? ???, roughly half of its energy every mean ??? path is so-called in lead, so that you would expect a tremendous shower to develop; that is, it would produce radiation, radiation would produce a pair, and the pair would produce more radiation, ??? ??? rays would produce more paths. And so instead of seeing a single track going down you ought to see a great pile of tracks. Well, we had seen these clouds of tracks in the cloud chamber not set up with this penetrating thing. We just set up a ??? ??? ???. We’d seen shadows [?] alright. So I devised an experiment for which Fussel carried out in which the cloud chamber was a very big chamber, and we didn’t have the kind of money to buy big things made of metal when it was too hard to do it, so we devised — I thought it was very clever at the time — we devised a cloud chamber made of wood! And we had a fine carpenter. That was probably the reason for the ??? ???. ??? ??? was the carpenter.
What was his name.
Oh, I see.
I suppose some people would call it Kennaly [?], but he called Kanee [?]. And so he was very interested in the proposition, and so we bought rubber patching equipment for vulcanizing and patching together rubber, and we had him make a wooden cloud chamber, and we lined it with rubber so it wouldn’t leak, and we managed to seal the rubber to the glass in the front, and in the method of expanding the chamber came from reading ???, happily just current with our ??? reading C. T. R. Wilson, who had invented the first cloud chamber, but invented a still more practical and usable form of cloud chamber by noting that you could, instead of having a piston you could have a rubber diaphragm to cause the expansion. The rubber diaphragm in our wooden cloud chamber moved between two things we called “hole plates,” which is just, it’s not a gauze, because you have to have strength to make it stay flat and level and not move. We get brass plates about a sixteenth of an inch thick and drilled many holes in them, very fine holes, thousands of holes. We spent a whole week doing holes. Everybody did this for himself in the machine shop, and then we made these hole plates be in front and behind the moving rubber diaphragm so that when you boom that in from the back, which wouldn’t have to be purified air, just a driving source, pressure from behind to push the rubber diaphragm against the front hole plate, then when you reached the pressure from behind ??? ??? ??? where the ??? pile, then it would fly back and hit the back hole plate. And then you could control the expansion very accurately by being able to screws to adjust the spacing from the hole plate. So we made a wooden — so very cheaply then for probably less than fifty dollars we made big cloud chambers which were a foot by oh, even as big as 18 inches. And you had to have big ones to see these showers properly.
Do you still have one of these wooden cloud chambers?
No, I’m afraid we destroyed them.
That’s too bad.
But they were easy to make, and we made two or three wooden cloud chambers, made of staunch oak. And Fussel, ??? Fussel to carry out the experiment to try to examine these showers that we thought — The theory of electrons and ??? said that there should be showers, so I asked Fussel to try to investigate these showers. The trouble with the first or the single cloud chambers we showed and put a plate of lead across them, you would see a shower, you would see a, either no track going in and just a little five, ten, as many as fifty rays coming out as though they came from single ???. They looked like they came ???. Of course the technique rather crude, and not absolutely free of distortion, but still it looked pretty good ??? section. And the point was, if these showers were developing according to the electron theory they shouldn’t do it all at one place. There should be this succession, a little dance [?] ??? radiation, and then the pair, and then more radiation, then pair, and so it ought to be spread out a bit. So Fussel’s job was to put free ??? of ??? across his big wooden cloud chamber, and we decided to make the layers, two of them quite thin, only a millimeter thick, so that the chances of them doing this progressive then in that kind of piece would be two-sided [?]. Or at least you could ???. And he had one thicker piece ??? ??? ??? and then he was going to take lots of shower pictures with that. He’d take shower pictures by putting counters to trigger the cloud chamber, which are not in line, so you don’t have things going straight through so he can select showers with the device. And so Fussel contributed greatly too, because he invented the prize [?] hot valve.
We’d had a lot of mechanical trouble with hot valves control the expansion in the chamber. The reason being that you didn’t, you couldn’t buy these things ??? ??? ???, but then the only kind of valves that we had for setting up this device was something that you went in with a powerful lever and cocked the hot valve behind it with a little prop on it so — and then electromagnet would eject the top [?] loose and the chamber would fly open. But to get another ??? you’d have to go back and get a hold of this lever and so you’d have to sit there by the hour while the thing went, and it was about anywhere from five to ten minutes between [?], most boring. And just interrupted you enough to where you couldn’t study. Well Fussel, you know the mother of invention, he was tired of this so invented a pop lab [?], which was ??? ??? used ever since. He invented it by paying attention to Bridgeman. Bridgeman made what he called a non-supported area of vacuum — not vacuum, but a seal, which he used in his high pressure work so it wouldn’t leak, and the greater the pressure of the ??? it wouldn’t leak because it seals itself by a non-supported area. I won’t go into detail on that, but the main point was that when it pops off, we used an electromagnet of the sort that when you turned the cork off the magnet, you no longer held the top of the seal. The seal ??? ??? would give way ??? ???. But now the pressure is off, and if you don’t build it up too fast you can have the electromagnet reset it without any great strength because until the gas pressure builds up the ceiling strength on this type of valve is not great, you see, no great forces. So Fussel invented the valve so you could go in, leave the equipment, it’ll take care of itself.
A great step forward.
And of course there were many other technical details. Some of the people worked on the type of light we used for the cloud chambers. We didn’t have then the lovely lights you can now buy on the market invented by Edgington. We had to make our own flash lamps, and they weren’t very good, but we did get things that would work and so on. Well, ??? ??? ???, so Fussel studied ??? ??? ??? that if you took, if you did statistics this way, if you look at his pictures and if you took, set the counter so that you saw single tracks going through his arrangement of plates, then the chances of there being another shower anywhere in the chamber or visible at all was very small, I mean like 1 percent, or smaller than that. If you just took single tracks, then the single track would go through, nothing, there was no shower. But if you selected a shower with his device, if there was a shower anywhere in the chamber the chance of it being the only one was negligible; there almost always was a shower over here and a shower over there, so that things that were associated was very likely to be associated with still more. If they were not associated with anything, why it just wasn’t ???. So this led us to believe — and I think it was the first, I’ll tell you the truth, first good argument that there were really two beasts, you are dealing with two beasts, and these shower things were really very different from the single ???. And that’s why we began to think about where there’s no particle ???. These things all ??? is true, they all look alike as far as each track goes. But they are not all electrons. And they are not all this, the other thing. And I managed then to do an experiment in which we wanted to test out the general argument that was made that the theory broke down as the energy got very high. It is the electron theory of this radiation was, was just wrong if you got beyond a certain energy. That was an argument made at the time. So we set up the combination of cloud chambers. One, we were getting very fancy. We set up a magnetic cloud chamber, and this was a case where Lymon’s money helped us out. He raised the money to build that little shed we call the Annex. Have you seen the Annex next to Bainbridge’s old laboratory?
I’m not sure that I do know it.
There’s a little red house that sticks out from the Lymon Laboratory along the other side. We, all we did was we were doing cosmic ray experiments, we didn’t want to have an argument that it had something to do with going through all the building above us. So we’d rather have light roof so it would simplify interpretation of anything we saw. So Lymon got money to build us this house, and Billy Kaneeda [?] to come and practically build it. And he also, we wanted a magnetic measuring energy. We’d have to have a magnetic field, and that’s always, costs ??? ??? ???. So Lymon raised the money — at least, he must have raised it, I don’t know why else they would have gotten it. They knew Wesley [?] wouldn’t give it, to build us an electromagnet. And Mimno helped me design the magnet. He did most of the designing. You couldn’t buy tubing with a hole in it in great lengths in those days. That was before the days ??? extruded, before they built many magnets. And so you couldn’t buy extruded copper type with a thick wall. So we had to buy ??? copper pipes, and they weren’t very efficient. They didn’t have a thick enough copper wall. But we still made the magnet ??? ??? ???, and we got about five, six, seven gauss, not nearly as high as we would like. And we built a magnetic cloud chamber. And this we used in conjunction with a chamber down below, so we had a counter, a counter above, magnetic cloud chamber, a counter below ??? ??? cloud chamber, then a bigger cloud chamber with lead plates in it and ??? ???. Of course the space to put extra lead in it.
So we were going to make what turned out to be the most accurate way, and still is the most accurate way of measuring the mass and ??? of this sort. We never gave good measurement, but we didn’t invent the best method. And that is, you first measure the ??? by measuring the deflection in the magnetic cloud chamber, then you measure the rainage [?] by seeing how far the sparkle [?] goes in a series of lead plates down below. In this chamber we had I think about four or five ??? and lead plates. And we convinced ourselves that these ionizing particles, these thin particles that had no showers along with them lost their energy and only by just the ionization along the track ??? ??? ???. And we convinced ourselves, we saw, we had enough data of a statistical nature to measure the momentum above and you could make a prediction of where it ought to stop. And this worked out. Occasionally you’d get a shower in there of course, and this is something else. So now you can improve on this if you get good data, even off one particle. If you can measure the momentum accurately and tell when it stopped accurately, and you’re sure it didn’t scatter out but really stopped, you get this combination of range and initial momentum gives you, allows you to view the facts [?]. Well, as I say, we never got good enough data about that method to get a good measurement for the mass [?], but we were quite convinced that the mass was a hundred or two hundred, a few hundred times as much as the electrons — but not as much as the proton. Because we had a few proton facts, and we saw what they did. As the proton track would come near to stopping in this ??? cloud chamber, its track would thicken up. Because when a proton goes slow, or any particle going slow ??? more density. Remember the ionization problem?
It’s ??? with the velocity. And so we were quite convinced there were no electrons; we were quite convinced they were not protons. And so that was our first evidence for a meson. It was something independent. It was not myself alone. It was a whole group of people that ???. It was Fussel and his shower chamber, started us to thinking in the right direction, and ??? ??? we listened and got every way we could from the theorists. We, Oppenheimer visited here once and we talked to him at great length, and he was quite sure the theory was alright by that time and we didn’t have to worry about it breaking ???. And then Stevenson worked as hard as I did. He was always in it. And some of the, uh, Dick Woodward [?] and some of the other graduate students worked along with us and really helped. Schneider [?] worked with us. They didn’t work with us enough to want to say that they worked on the experiment, put their names on it and so on, but they were very interested and they helped out.
Was this then very promptly reported at a Physics Society meeting?
Well, in 1937 we wrote, we reported it at the Washington meeting and wrote it up in ??? those abstracts ??? ??? ???. We didn’t feel — we were very anxious to improve on our data. We were having a lot of apparatus trouble, so we didn’t report it in a full paper as we should have. We set up, we felt we could make, we could do a better job. We were wrong, because this method turned out to be the most accurate method of measuring any mass. But we did another experiment. We put our energy in doing another experiment. We tried to get mesons who had stopped. We wanted to show that, like the protons, if we got just the right conditions we could show the increase in ionization of the meson. So we set up the chamber in which we had the, going through the magnetic chamber with a plate across the middle, we would see the particle which was then going to stop in not a lot of lead but just in a thin lead. And so you have to wait until you get one just right. See, most of them go on through or never get done, and ones which will just stop in the right thickness and therefore be in the right range to thicken up are hard to find, because there aren’t many that are in that particular — It’s just selecting a narrow energy rate is what it is. And we did get one or two, and we were the first to report on that. And from that measurement, which is in a sense a similar, similar thing except now you are measuring the increase in ionization instead of the range. You are measuring momentum and the increased ionization as your tube. And the reason this method isn’t good is ??? what I’m getting. Stevenson and I worked on that for a year or two, rather than pursuing the other method, which was a mistake. The narrow measure was a great mistake. We continued with ??? ??? ??? we would have had a lot more data, easy. But we did succeed in getting a few tracks like that — one or two with ??? ???. We did reach an estimate of the mass as being about, we’d said about 135 ???, and we made an error in our calculation, in our use of the theory, a slight error. It should have been 165. Well, the mass turned out to be, I’ve forgotten now, about 190 [?] ??? ???.
It’s close to 200 now.
Close to 200.
Lessy [?] pointed out our mistake in ??? ???. [laughs] Well, that was our particular business in the ‘30s, so as far as the rest of the lab, there were very exciting programs going on. Now Bainbridge’s mass spectra work was most interesting to me. The work with Bridgeman was very interesting. He always had exciting people working on interesting things. The theorists I didn’t keep up with too well. Kimbell’s students were calculating ??? at that time. It seemed like an awful lot of calculating on a hand calculator. I think ??? ??? ??? was calculating these spectroscopic values for helium.
And the hydrogen molecule.
And the hydrogen molecule. And I didn’t find that very exciting to me. Although I realized they were good, I would try to get them to speculate on all these new particles and so on. But after all they didn’t have any more speculation to make at that time. We didn’t have enough data. I taught, continued to teach in Physics C, and Bainbridge and I taught a course, started a course in nuclear physics, X-rays, and that sort of thing, for undergraduates. And I think beginning in about 1936 and running until the war. So we were very excited about that, and we had a course in which you could demonstrate with our equipment. So you could use your equipment for some laboratory ???. I still continued to be very interested in the work that was going on in Lymon’s Laboratory, ??? ??? ???, and the techniques they developed. They learned to — it turned out to be useful to me personally later on — they developed techniques for growing single crystals, especially Sneider [?]. There’s a crystal, and lest I be in error I won’t say exactly what it is, which was very transparent in the ??? ??? ???. And if you, especially if you grow a single crystal. And this is the thing that Sneider was working on. It’s some kind of a fluoride and crystal. Do you know?
I don’t remember it, but I’m sure we could look in one of the —
Find out. Right. Anyway, it was a tour de force to grow this crystal, and this was being used where you needed to pass the old ??? through windows, but for mass spectroscopy. Great rivalry with MIT. There was a fellow at MIT who was also growing these crystals, and everybody said that he grows [?] that crystal.
Horticulture of crystals.
Well, growing single crystals is sort of an art. A fellow later, named Kennedy, at Harvard here, made a living at it for awhile. He was in a society of fellows, and he’d developed every known method of growing crystals. I used it because we became interested in the so-called crystal counter after the war ??? ??? ??? had grown — A silver halide crystal made a crystal counter ring [?] in this sense, that if you release, if you let it stay warm and exposed to light it develops centers, you know, photographic centers and it turns light [?]. But if you keep it cold, where the ionic conduction, where there is no ionic conduction, then it becomes a conductor for any free electrons that get formed. So if a particle such as X-rays or electrons or ??? any ??? ??? particle passes through, the electrons that are released will travel through the crystal and you get a count, a pulse through. It’s really a conduction ionization chamber.
In other words, the crystal becomes an equivalent to the behavior of the gas ionization chamber in which electrons released in a gas will move across under a field and you can collect your pulse. And similarly in this ionic crystal, which must be cold so that you’re not messed up by the chemical conduction —
How do you keep it cold?
Well, we put it in at liquid nitrogen temperature by having it in contact with a piece of copper which was in contact with liquid nitrogen. And you had to have single crystals or else the ions freed in it are tracked, so they get tracked in mechanical faults and things of that sort. But the ??? ionization chamber is quite useful because it’s such a dense thing, you see. In a gas you don’t have any ions form. That is, if the thing goes through it doesn’t make — it makes 20 or 30 or 40 collisions per centimeter, same atmospheric pressure they normally have. But in this other thing you ??? ??? ??? so that you have a thousand times more effective ionization chamber. And after the war, I became interested in Van Halen’s [?] — he did this kind of ionization chamber. ??? ??? very nice device for cosmic rays, a wonderful device for detecting these bursts.
Well, the tail of the ‘30s was still interesting in cosmic rays, because now that we had the clear separation and we were convinced, and other people quite independent of me someone discovered — Anderson gets a lot of the credit, and Blackett [?] gets a lot of the credit — nonetheless, having straightened out that there were electrons that make up the soft component, and mesons, what we call a “mesatron” in those days, an awful name ??? ??? ???, they make up this penetrating part of the radiation. That couldn’t be all of our ???, because Fussel in his chamber, his 3-plate chamber, found that that wasn’t a hundred percent right, but every now and then in a great while, but not many, you got some showers that did come from a point. Even these 1-millimeter-thick things show — not only did they come from a point, but they had dense stripes among them; that is, they had slowly moving protons coming out of them. So this was something new and different and altogether exciting, because this was over and above the mesons that we, mesatrons we’d call them, and the electrons, all in these chance protons that would come in from above. This was stuff looking like protons, or something of that sort, being formed right there. It was happening all in one point, and Fussel had a meson or two, maybe more than that, maybe ??? ??? ??? all together, because he took thousands of pictures. And we were trying to, we were going to investigate those, and those were the beginnings of the modern business you know of nuclear collisions with showers from a nuclear hit, and with pi mesons we didn’t recognize, didn’t know about it, was certainly among these showers. And if fact if we’d been smart enough, we had one that I’d gone back to and realized was a pi mu e-decay [?] among Howard Fussel’s pictures.
Oh. And it was only years later that —
Only years later that we knew what —
— we were sophisticated enough to determine it.
Yeah. So that, if we’d been visionary enough or smart enough, we would have been able to see that.
Well, that’s —