Oral History Transcript — Dr. Robley D. Evans
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Interview with Dr. Robley D. Evans
Dr. Robert D. Evans; May 2 and 3, 1972
ABSTRACT: Family background; grows up in California; early interest in electronics. Undergraduate and graduate studies at Cal Tech. Strong interest in history of science as undergraduate. Ph.D. in Physics 1932. Berkeley 1932-34. MIT from 1934; founder of the Radioactivity Center. Starts first course designated Nuclear Physics (January 1935). Strong interest in study of radium poisoning. Radium tolerance in humans, cancer research. World War II work, postwar work; establishment of Laboratory for Nuclear Science and Engineering. The Markle Foundation funds for the Radioactivity Centers Cyclotron.
TranscriptSession I | Session II | Session III
Weiner:I want to really start from the beginning I know this much that you were born in University Place, Nebraska, in 1907, which sounds as if it were a university town, I know nothing more.
Evans:Yes, it was a suburb of Lincoln, Nebraska, at the time, and at the present time itís not a separately designated community. Itís just part of Lincoln, Nebraska. My dad was a professor at Nebraska Wesleyan University, which was in University Place. Thatís why I was there. He was in business, shorthand, typing, accounting, things of that sort, and in business law, and he left there and went to California when I was five, so that would have been 1912. We went first to San Bernardino, I think for only about six months, and then went to Hollywood High School, 32 Hollywood, California, and built a small house. I was the only child, and he spent his whole teaching career, the rest of it, at Hollywood High School, 32 years, I think, without ever being tardy or absent once. I asked him once what was the highest fever he ever had, in class. He said 103. He was a really gutsy guy, a farm boy who pulled himself up, taught in the local one-room school and waited on tables down near the university and just pulled himself up.
Weiner:Where did he go to school?
Evans:Well, itís really not clear to me. I doubt that he ever had a college degree. I think it was a one-room school training and his own push and probably some courses at, is it Iowa State thatís in Iowa City? Iím not sure. One or the other, I always get confused which it is. I donít know. Heís dead now, died at the age of 92 a couple of years ago, from an accidental fall. We donít know enough about our parents or their parents. We know almost nothing. And my grandchildren are the same way. They donít know a damned thing about me. Even my children donít know very much. Itís sort of an American habit, Iím afraid. Each generation goes on its own steam, and they know a little bit about their parents and thatís it.
Weiner:Then you spent a good deal of your school years in California?
Evans:Yes, entirely, and first in Hollywood, of course where I went to grammar school, then to Hollywood High School, and I was there the usual four years, You asked in your letter why I went to Cal Tech. I had no difficulty with any of the courses in any studies, and I wasnít much of an athlete. I went out for track and gymnastics, things of that sort, but I was never a first-team type in high school. But I would be president of the Science Club, and in a number of clubs and school activities, and valedictorian of my class and the usual sort of thing, sort of set scholastic records, had teachers who insisted on giving me an A plus on the record, which was forbidden but they were going to do it. So these things accumulated and I accumulated a set of cups, rifle marksmanship and a chemistry cup and a physics cup, which were given each year on the basis of competitive exams, things like that. I think it was the physics teacher rather than the chemistry teacher, though both urged through my dad who was on the faculty, of course, of Hollywood High School, that I should go to a little place over in Pasadena, California, which was nearby, and called the California Institute of Technology. And instead of being top dog academically, I should learn to look up and see the bottom. They thought that would be good for me. So I went over and took the entrance exams, and due to peculiarities of my high school curriculum, I hadnít had either trigonometry or solid geometry, but I took the entrance exams to Cal Tech and came out, I donít know whether first or second or what, but I got immediate scholarships and had scholarships all the rest of the way. I did trigonometry and solid geometry on my own in the summer, took examinations, and they said OK, thatís all right, you may come. So I did.
Weiner:Surely, Cal Tech meant more than choosing a place where your superior scholarship would have an opportunity. It meant specializing, as Cal Tech was known as a scientific school in engineering or science. Among the high school courses, had you a preference in the science area?
Evans:I liked the sciences very much. Math was comfortable and chemistry and physics were comfortable, and I enjoyed them. And Iíd always tinkered around. Iíd built radio sets and things like that, mostly receivers. I didnít have the money to buy a transmitter so I was never on the air with a ham station, though I had many friends who could manage it. Iíd go around to their radio shack, as it was called, fool around with their sets, though I dealt only with receivers. But Iíd always been interested in electronics. The kind of books I would hide around the house when I wasnít supposed to be spending my time reading would be a mathematics book or a physics book or something like that, which I tucked down in the back of the davenport so I could grab it and read about Ohmís law.
Weiner:Why did you feel this necessary?
Evans:Iíve forgotten why, but I can distinctly remember that I did. This was some kind of constraint that my mother had on my life. She was a very strong-willed person who insisted that my health was very delicate and that I had to take great care of myself and all of this, which turned out not to be true at all, but that was the atmosphere in which I grew up.
Weiner:She would prefer that you went out into the sunshine, or some athletics or something of that sort, instead of being a bookworm.
Evans:Yes. And yet she didnít want me to be athletic particularly in the sense of football, because she was afraid of bodily injury and all that jazz. When I went to Cal Tech, then I felt on my own to some extent, and then I went out for athletics right away with a vengeance, played on the basketball team, was on the track team and the baseball team. Never played football, but the other sports I enjoyed very much. I never was any outstanding star and it was kind of discouraging, the kind of guys you had to compete with, because the athletic events at Cal Tech then were in Tournament Park, where the old Tournament of Roses first began, right across California Street from the main campus, you know, and Charlie Paddock, the Olympic sprint champion, was the guy I had to run against in training every afternoon. Of course Charlie would run away from me and the rest of us. This was very discouraging to a fellow who could only do 11.2 or something of that sort, and here he was whizzing along at 10 flat. But it was good fun. Then I did a lot of diversified student activities at Cal Tech.
Weiner:You had a scholarship.
Evans:Yes, I had scholarships all the way.
Weiner:So it paid your full tuition. You lived at home though?
Evans:Yes, the first three years. Then I lived at the fraternity house the fourth year, got out from under.
Weiner:Do you recall the source of the scholarship, what fund it was from?
Evans:Cal Tech money. Yes, they had, I donít know how many full scholarships. I had the impression it was not many, like two or three or four maybe.
Weiner:When you were accepted and began your courses, did you have in mind a particular specialty?
Evans:Yes, I think physics, from the beginning. Iím trying to recall the curriculum. I accepted the curriculum as handed out and didnít question the wisdom of the faculty who arranged the courses which we were to take. There were very few, if any, elective courses that one could take, and as I told you earlier, I always felt that the older and wiser heads were the ones to follow. I took the courses without any question. I do remember that in the junior year, physics major had no course in physics at all, and I thought this was a little odd but I didnít go into a student rebellion about it. We had paleontology and geology and lots of history and French and English and German and all that sort of thing.
Weiner:I guess this was part of Hales influence too, the idea that the humanities needed to be included.
Evans:And Iíve always been very glad for it. You learn your profession. You learn your physics later, really. Itís always been said, you only learn a subject by teaching it. Around MIT some decades ago some of us were commenting about what we had specialized in at college, even if it was physics, and what we were actually doing, and there wasnít a single man on the faculty who was doing what he had thought he was going to be doing. Hans Mueller was in optics, and he never dreamed of -- never had had an optics course. But we found this quite generally. Of course, in those days there was no such thing as nuclear physics. No, there were no courses in radioactivity at Cal Tech. This was a new field. It wasnít treated at all. So it was just getting a good general grounding, lots of math and the rest were basic courses, standard curriculum.
Weiner:Whom did you have as instructors? Did Lauritsen come into the picture at all? Or Tolman?
Evans:No, I didnít have Tolman. In undergraduate years, they were in general good men, but they were not world-famous names. There was a mathematician named Weir, I believe, and Smythe taught one of the physics courses. I think that was electricity and magnetism, and -- no, I donít have any strong recollection of these things.
Weiner:I have some of the Cal Tech catalogs for that period with the course breakdown that I havenít studied, but I do have the copies of that.
Evans:Yes. It would be fun to go back. Iíd probably recognize the names, undoubtedly I would, and see who they were. But I felt they were all good. I never thought I had a bad instructor. Of course there was the honors section that we discussed earlier, of a dozen or a dozen and a half fellows who were selected right at entrance time and were in full competition with one another for the first three years, while the prizes were being handed out. The result was that I think it tended to separate us. We didnít tend to become close friends because we were in too tight and ever-present competition in all fields, science and athletics and everything else, student activities, and the whole schmoo. So we were perfectly friendly but never became buddy buddy. And of course everybody was young. We were all in our teens. And Ed McMillan was one that was in the honor section. We called him Christmas because he was always late. He was also quite delayed in getting haircuts, so we cut half of his hair one day, to help him remember to get a haircut. Ed was a very brilliant chap, and troubled some of the people in the honor section I think because he could quite commonly come to class totally unprepared and yet give a perfectly good account of himself, just by being quiet for a while and then speaking up. He was definitely a sharp fellow. That was an interesting group.
Weiner:Who else was in it, do you remember other names?
Evans:Well, Al Lombard was the closest friend as far as my own personal relationships was concerned. We had a good close relationship. Joe Schweinfest, who died in Russia at an early age. You know, Iíd have to go back and look at the catalog and check out who were these dozen guys and identify them.
Weiner:I can get that. Did you have Millikan for any courses?
Evans:I had Millikan for one course, and, I think that was in graduate school. Yes, it was, my first year of graduate school, yes.
Weiner:As an undergraduate did you have any contact with the research work going on, either by faculty or graduate students or visiting research associates?
Evans:Not that I recall at present. The undergraduates were pretty well isolated from research. We got some flavor...
Weiner:We were talking about undergraduate contact with research work and you said you didnít recall.
Evans:Yes. It was very small. I begin to recall a little about it, because this honor section was given a lot of extra chores to do, particularly in the summer time, so that the faculty would award us certain books, and we were supposed to study them during the summer. They would give us like a book on ancient history, and we were supposed to study this, and they gave us Noyes and Sherrillís PHYSICAL CHEMISTRY, and we were supposed to know our physical chemistry on that basis by private study during the summertime and not take a course in it during the regular year. Then during the regular year, in that instance, I remember they substituted a laboratory which was supposed to have to do with research. That is, we were supposed to cook up a demonstration experiment and give a lecture, a short lecture with demonstrations having to do with any topic we chose in physical chemistry. So this was as close as we came as undergraduates to doing research, But at the moment, I donít have any recollections of seeing anything going on in research that undergraduates were aware of.
Weiner:I think you clarified that about the limitations. The next question I had in mind on that was, during that period there were a number of visiting lecturers, especially big names from European institutions. Did you have any contact with them, either in a colloquium or in the public lecture? Were you even conscious of their presence on campus?
Evans:I was as a graduate student, but I donít recall any contact with them as an undergraduate, though it could have happened. And at this moment donít remember whether or not as an undergraduate we attended the Thursday afternoon, if thatís when it was, physics colloquium. It was a weekly event. It certainly became a major factor in my life as a graduate student, but I donít recall ever attending it as an undergraduate. You recall that as a physics major, one in the junior year was not taking any physics courses. You didnít feel as though you were being a professional physicist at all. You were getting a rounded undergraduate education. And physics major simply meant, I think, that in the senior year you took electricity and magnetism and mechanics and courses of that sort, analytical mechanics and what not. While you were on the phone, I was trying to recall what contacts if any we had. I can remember that the travel prize group, this honor section, while the competition was on, would occasionally be taken as a group on some kind of trip, commonly with Arthur Noyes as host. He was a bachelor, you remember, and had come from MIT and was co-author of Noyes and Sherrill, and a really great, marvelous, wonderful warm human being, gentle, but with his eyes and ears open all the time. And he would take us to places like Palm Springs, maybe a dozen of us, and put us up in a hotel there. It was a very small place then. Generally it would be on a weekend, and I think it was only for one night, though it left an impression. The faculty committee on honor students was always there too, people like Ernest Watson and Ike Bowen, and it was perfectly evident to all of us that we were under surveillance every minute, and anything we uttered was being recorded, if that was possible, or noted, for sure, and such things as what were our table manners like in the restaurant, and did you know how to order a meal from a menu, did you know what a taxicab was for.
Weiner:What was the point of this standard which extended to every aspect of your scholarly and personal life? They seemed to work very hard at it, the faculty.
Evans:They certainly did.
Weiner:What was the philosophy behind it?
Evans:I think all we knew about it as competing undergraduates was that we were competing for the highest prizes there were in the place, the highest one being the Junior Travel Prize, the European Travel Prize. That was as high as you could get, and this was a group of boys who would like to have that honor. and it was based on so many factors -- participation in school activities, athletics, physical measurements made once a year, your timing in the 100-yard dash, 440 and mile, how you did the hurdles, high jump, broad jump, all of that. All of these were rated, and as we remarked earlier, personality ratings. Each individual in the group was required to rate each other individual on a large number of personal characteristics, and these were all scored in as part of it. Then we were given oral examinations, as indeed they were oral examinations. As I recall it, one person at a time, with the committee, on the honor students, perhaps three or four faculty members, and we would be quizzed on things concerning which there were no courses. Specifically I recall astronomy and art and ancient history, for which there was no specific course. We were supposed to have been broadening our horizons during these years and they wanted to see how broad weíd made them.
Weiner:Sounds like a Miss America contest.
Evans:I should say. Oh, it was a regime that you just had to get in. We were all in it. There was no escape. You couldnít get out of it if you wanted to. I donít recall that any of us wanted to. We were all pretty eager beavers.
Weiner:You didnít mind the pressure then?
Weiner:It seems to me this would have meant a lot of additional pressure.
Evans:Oh, I suppose it did, but I for one was pretty busy, because I was earning my keep as well, playing in dance bands.
Weiner:You say you were concerned with percussion instruments. Letís get into the background of that a little. When did that start?
Evans:Oh, that started in grammar school, well before 9th grade. I believe I was playing professionally when I was in 8th grade, before I went to high school.
Weiner:In little bands?
Evans:Yes. My drum teacher who operated little bands around the Los Angeles area would have a small dance job for a three or four piece orchestra, and he would select a piano player and whatever number of pieces were involved, and Iíd get the nod on being the drummer, and go all the way across Los Angeles on the street car lugging a bass drum and a snare drum and some cymbals. By the time I got to high school, I was in it deeply in percussion and played in the high school ROTC band and the regular band and orchestra and symphony and Hollywood Bowl and that sort of thing. The symphony stuff was mostly tympani. The military band was snare drum and the night time work was trap drums -- that was for what was called jazz.
Evans:Danceable jazz, yes. These were the days of Paul Whiteman when Paul Whitemanís comment, you remember, was -- how was it? ďAny damn fool can jump up and down and yell Hot Dog but it takes a real musician to play jazzĒ. This we believed in.
Weiner:Werenít you a little young to be at these dances?
Evans:I suppose so.
Weiner:It was no problem.
Weiner:You made extra money that way.
Weiner:You had a scholarship but I suppose you could use some additional funds.
Evans:Oh, yes. I was trying to remember whether I had any budget from my family. It could have been. Somehow or other, I get a little tinkle of $30 a month or $20 a month or something like that, that my Dad and Mother supplied for miscellaneous expenses, and the rest of it I earned in the band.
Weiner:You mentioned that during this period, in your history courses you seemed to do very well and take an interest in the subject, causing your teacher to take an interest in you.
Evans:Yes. William Bennett Monroe. Three-Button-Benny. Former Harvard --
Weiner:This led to the suggestion from him to you that perhaps you would specialize in history of science. I think thatís just good to --
Evans:Yes. Good to have this on the record. I made a note to look up for you, because you wanted to know where those scholarships or fellowships or whatever they were that were offered -- I may still have those particular letters from Harvard. I think its Harvard, Columbia and Munich. Iím not positive. I made a note to look for those and see whether Iíve thrown them away, in my home files. If thatís of any interest to you.
Weiner:I think it would be, yes.
Evans:Because I intended to go, at that stage, at the end of my senior year, I intended to go into the history of science. As we remarked when we were talking earlier, I was one of the winners of the Travel Prize at the end of the junior year, and being very much in love with a girl whom I hadnít married yet -- we met in high school and were very fond of each other and didnít want to be separated -- I got permission to postpone the Travel Prize for one year, and we got married and took it as a six months honey-moon, on next to no dollars, but learned a lot and had a very profitable time. I had intended then to stay on in Europe and accept one of the history of science offers, when the economic situation was clarified for me by correspondence with Three-Button-Benny, William Bennett Monroe, that the only way a graduate student in history of science could support himself would be by writing books and having an income from some kind of moonlighting, and it was not perfectly clear how this could possibly mature rapidly enough to pay the grocery bills. So, at the middle of the summer of 1928, having taken my bachelorís degree in absentia, I wrote back to Cal Tech to see if I could come back and stay in physics. They said yes. So I did.
Weiner:You had written to three institutions, Harvard, Columbia and Munich had been accepted at all three and had planned to stay in Europe to continue at Munich.
Evans:Yes, as the selection between the three offers in the history of science.
Weiner:What was the financial arrangement for graduate work in physics at Cal Tech? It seems to me you still faced the same problem.
Evans:Yes, I did, so I took on a number of teaching assistantships and was teaching assistant in the undergraduate physics laboratory and in French and in German, and in the history courses and several others, Iíve forgotten. I held concurrently a large number of teaching assistantships and earned some money -- letís see, as a graduate student was I still playing dances? Iíll have to think that one over. Iím not sure when I sold my trap drums and said, that finishes that career, Iím not going to be a professional musician, Iíll get out of this business.
Weiner:Have you ever taken them up again?
Evans:Iíve played a little in symphonies but I donít own any drums, so generally it has to be tympani where the orchestra owns the drum. So Iíve done a little here. I guess the last time I played in a dancing jazz band was aboard ship on a trans-Atlantic trip maybe around 1941, sat in with the dance band one night, but just for old timeís sake.
Weiner:This extracurricular work, the teaching assistantships simultaneously in several fields, didnít seem to slow you up, though, because you had a masterís in Ď29 and a Ph.D. in Ď32.
Weiner:How many hours a week on the average did the teaching assistantship work require?
Evans:I donít know. In those days, I could schedule my work, and did adhere rigidly to a schedule, so that as an undergraduate in Cal Tech I never studied beyond 9 oíclock at night and never on Saturday and Sunday, and could accomplish all of the assignments complete well ahead of time. So that Friday at 9 oíclock, if I wasnít playing a dance that night, in which case Iíd have to finish it earlier than then -- but Friday evening at 9 oíclock everything was ready for Monday morning and probably for Tuesday morning too, all the assignments finished and done. Knowing how much time the catalog said you were supposed to spend on each subject; I simply laid out a schedule by the hour for the week and said, thatís it. If the two hours or whatever it was that was allocated to physics was up and I hadnít finished the physics assignment, I stopped and did the next thing, the next thing called for. But I seemed always to be able to manage it, so that I would commonly have many more balls in the air than most people would. Thus I could take on a large number of things, and by careful scheduling make it work out. I also did a fair amount in my second and third graduate years. I did outside teaching too. I taught at the Polytechnic Elementary School across the street from Cal Tech and I did private tutoring for, particularly for the son of C.F. Braun at C.F. Braunís request. That was what drew us together and led him to invite me to join his company while I was a graduate student. His son had failed every high school course except freshman English and I tutored him for about ten months, and he in that time covered an entire four year high school curriculum plus the first year of calculus, and passed the Cal Tech entrance examinations.
Weiner:What was the problem? Iím sure you were a great teacher but there must have been another problem. (Interval) You made the point that he was a good student. This led to an offer from C.F. Braun to come to work in his company which was involved in oil refinery equipment.
Weiner:Was there a particular vacancy or did he create something for you?
Evans:I donít think there was a particularly vacancy, no. He had a thing he called the research laboratory with a small number of people in it, and it didnít seem to have any operating head. Well, yes, it did, but he was remote. It was Professor Eckart formerly of Stanford University
Weiner:Carl Eckart who did some work in quantum physics in the Ď20s?
Evans:It wouldnít be that. No, this would be not that Eckart, this would be a mechanical or petroleum or chemical engineer type of early vintage. So I became a chemical engineer for I suppose a couple of years there. I worked full time at the laboratory. It wasnít a big laboratory, three or four or five guyís maybe, working in theoretical and experimental heat transfer for heat transfer devices in oil refineries and in cooling towers. Carl Braun would say heíd like to have certain thing done. For example, he wanted a spray nozzle which would spray uniformly in a square rather than a circle and would have a uniform area deposition over a square; say, 10, 12 feet on a side. So I did that and got the patent issued assigned to the C.F. Braun Company.
Weiner:That was about Ď33 that the patent was issued.
Evans:Yes, for which I signed the receipt for a dollar but never received the dollar. That was my first experience with patents. And I havenít earned a dollar from one since although I have several patents. Iím very interested in the American patent system. Thereís much more to it than what one would naively think. I learned a good deal about it. Itís a good sink for money, even where you have a good idea. Youíve got to be able to pursue it yourself economically and go on through. So I essentially was a practicing chemical engineer, studying. Walker, Lewis and McAdamsí book, the great Bible from MIT, and going beyond it, considerably beyond it, because industrial practice I found was well beyond what was in the textbooks. Yet I found that in terms of the physics, which was all-important of course, physics and mathematics, I didnít need to use anything beyond middle type undergraduate Cal Tech physics and mathematics to solve any of the industrial problems that came up. So I thought I was going to be an industrialist, and then came the great Depression. There were 700 people in the company when I joined it, and I think 14 or 15 when I was finally called in and told, ďWe have to cut our force and itís your turn next.Ē They advised me to go back into teaching. I had at the same time continued my graduate work.
Weiner:How did you manage to do that?
Evans:I did that by careful scheduling again, and with a very supportive and cooperative and loyal wife, and youngster. We had one child. There would be a few classes which I felt I needed to attend. The plant of C.P. Braun and Company is in Alhambra, so that it was only a few minutes from Cal Tech, and I could take an hour off from time to time and dash up and attend a class and back. Then after dinner Iíd go to the research lab at Cal Tech and work on my thesis, generally till about 11 or so. But I had a cot in the laboratory, and if there were some very late night readings that I had to continue to take manually, because in those days we didnít even have an Esterline-Angus recorder, you see, -- you looked down the electroscope or whatever it was with your eyeball, and wrote the number down. You had to be there and awake or there werenít any measurements going on. So I had a cot in the lab and could rest that way, and I got so I could tell within probably 15 minutes of collapse time, when I was going to fold, and stop about 15 minutes before that and scoot home. So after the third graduate year, my thesis adviser said, ďYouíve got plenty here for a PhD, why donít you turn it in and finish up?Ē And I said, ďIím not contented with it yet. Thereís a great deal more that I can do and that I know how to do, and it will be very, very much better if I donít turn it in now but work on it some more,Ē so I spent another year.
Wiener:Who was the adviser?
Evans:I guess it was Millikan himself. Yes, it was. Millikan was my thesis adviser. Itís interesting that I have to stop to recall who it was, because he would select a person and then simply turn him loose, and I would see him about twice a year. Heíd come over in my lab and sit down. I had a couple of comfortable wicker chairs, a table and a lamp, at one end of the lab, so that it looked a little bit comfortable and homey alongside my cot, and a couple of times a year heíd come over and spend a whole afternoon. And weíd chew the rag about the research and about whether Radio City was going to succeed in getting tenants and what the board of trustees was doing and things of this type. Then I might not see him again for months. But he was my thesis adviser, and he did this on the basis of the examination in the one course that I took from him, which was out of his book, and then heíd put some fancy types of questions on the exam, which were out of the ordinary and from which he selected the people whose theses or future careers he wanted personally to direct. To the rest of them heíd give a grade, but that guy, heíd scratch his name and call him in. It was a very short conversation. He said, ďI like the examination paper you wrote very much. Now, for your thesis you will do the followingĒ. Exactly that.
Weiner:He did select the topic.
Evans:Oh, youíre darned right, he selected the topic.
Weiner:Why that topic? It seems to me it was rather remote from the kinds of things he was doing.
Evans:No, it was right down the alley for his cosmic ray studies. You see at that time he didnít know how to correct for local gamma radiation in the cosmic ray high pressure electroscope that Vic Neher was building and Ike Bowen was helping calibrate, and Robert Millikan was carrying all over the world on field trips. And he didnít know how to correct for the local gamma radiation on the basis of the absorption in lead. So he did this and went ahead and produced his cosmic ray results, without benefit of my results, so that what I then was able to do, so far as the result side of the thesis was concerned, was to have from his electroscope readings the ionization per cubic centimeter of air and from my own measurements of the radioactivity of the rock, in terms of radium, but not of the thorium series. We had to make assumptions about that. And not of potassium 40 because potassium 40ís gamma activity had not yet been discovered. So my paper on that point has one small error in it towards the end, when weíre trying to figure out where the rest of the gamma rays come from, and I had to ascribe them all to the thorium series because thatís the only other radioactivity anybody knew about besides the radium series. The fact is, they were in part due to potassium 40 in the rocks. Naturally we chased that down in some detail later when we found out about potassium 40.
Weiner:Was anyone else working on radioactivity at Cal Tech at the time?
Evans:No, I think I was the only one. I was the radioactivity guy.
Weiner:Had you known anything about the subject before you were assigned that as a thesis topic?
Evans:No. Not a thing.
Weiner:Had you had any particular interest?
Evans:Nothing at all.
Weiner:He could just as well have put you to measuring cosmic rays directly, for example.
Weiner:-- or doing some ionization thing --
Evans:Yes, perfectly. Just as he had Vic Neher do the ionization chambers, and told Carl Anderson to make cloud chambers, and make those measurements. Of course in Carl Andersonís case, Carl had understudied Don Lockridge, and was a cloud chamber super-expert. Carlís techniques with the cloud chamber were absolutely superb. He was a master at it. So Millikan had told him and Vic Neher -- as I recall they finished one year before I did -- and he told them, ďDonít apply for a National Research Fellowship or anything of that sort. Iíll fund you with the same amount of money that youíd get from a National Research Fellowship,Ē $1800 I think it was in those days.
Weiner:If you were single. I think married people got $2400.
Evans:Maybe the second year, if you were married with two children or something. Anyhow, in terms of the kind of money that you hand out to graduate students today of course, the numbers are appalling. Yes, he just said, ďMake these measurements.Ē So of course in seeing what techniques had been available in the past for measuring radioactivity in rocks, I felt that those could be greatly improved. So the essential part, I think, of my thesis was the development of completely new methods of getting radon, for example, out of rocks with the direct fusion furnace which boiled the rock in less than five minutes, boiled all the radon out of it, and then very sensitive detecting equipment which measured the radon. And thatís how I got into radioactivity.
Weiner:Was this supported by Millikanís cosmic ray research grant? I notice the publications that came out of it for a number of years acknowledged that fund source, his grant from Carnegie Corporation for cosmic rays. I wonder then, why is it that you didnít get some kind of fellowship or something that would support your work without having to take on these teaching jobs or the industrial research job or, earlier, the assistantships?
Evans:Well, I didnít have my doctorate yet, you see. This was my doctoral thesis.
Weiner:In other words, his grant couldnít have paid for your salary.
Evans:I never asked. I donít think so. I think it only applied after the doctorate. The recipients like Vic Neher and Carl Anderson were post-doc.
Weiner:During this period, when you were so busy with the thesis research and then when that hit bottom, the teaching, there were lots of things going on at Cal Tech and in the larger scientific world. Letís talk specifically about the colloquia. Were there outside speakers? What subjects seemed to be of interest?
Evans:Well, I always found them interesting, and I always attended them because I found the talks interesting, and some of them I couldnít understand at all, and this seemed to be shared by a good fraction of the audience so I didnít feel any embarrassment about it. At those colloquia, Millikan always stood up at the end of the speech -- if it was Heisenberg or whoever it might be talking, and summarized in two or three sentences as to what had happened during the past hour. And I remember once he got up and said, ďWell, as I understand it, these guys talk Chinese to each other for a while, and then they come up with the following results. PeriodĒ. This was all he could say. I always felt that Millikan was a person who worked about three hours or four hours longer per day than anybody else I knew, and that one didnít necessarily have to be brighter than anybody else if you worked real hard and kept at it, but you worked up an impossible lead by this additional expenditure of effort. And I felt that that was the key to Millikanís success. Iíve always been willing myself to put in the extra hours too. In my case, not -- I would be the first to deny it -- for the sake of leadership, but rather for the sake of getting very interesting things done. So Iíve been accustomed to long hours for a long, long time.
Weiner:In the colloquia, there was one particular meeting of the American Physical Society in Pasadena in where Pauli was present, the summer of Ď31. Do you recall that meeting?
Evans:Just that he was present.
Weiner:That was the meeting where he advanced the idea of the neutrino. It didnít have that particular name on it, but it was first mentioned at that meeting.
Weiner:-- it comes out later, you know, if you think back on it, but he did announce the idea then.
Evans:No, I wasnít aware of that.
Weiner:Did you get much theoretical physics in your graduate work?
Evans:Well, just the classical theoretical physics.
Weiner:No quantum mechanics?
Evans:No, no quantum mechanics.
Weiner:No exposure to Oppenheimer on his visits?
Evans:No, Oppie came while I was a graduate student, you remember. He came back and taught, was it one term? Cal Tech had three terms a year, and the summer. He taught one of them, I think, and one at Berkeley which, by the calendar, worked out all right. I signed up for one that he was giving, and went the first few days. He had a large attendance the first day, and went to the blackboard and wrote the Hamiltonian and apologized for starting at such a low level -- and then he took off. The second day there was about half as many people there. The third day, there were a few left. And shortly after that I too disappeared from the class, because I didnít know what was going on at all.
Weiner:Carl Anderson I guess was in the same class. Do you remember if he was in that one? I guess he said that Oppenheimer pleaded with him not to drop it. He needed someone there.
Evans:I think Charlie Lauritsenís wife was one who attended, at least the first day, and maybe for a while, but she also disappeared.
Weiner:But most of time your graduate work was actual research? You sat in on some courses but you did a lot of the work on your own.
Weiner:Were you required to take formal examinations in certain subjects in order to qualify?
Evans:Oh yes. The rules for passing the PhD exams were just as rigid as those which had been in the undergraduate school. They had some flexibility in that if you had taken the course in electricity and magnetism, letís say, using Jeansí book and solving all the homework problems, if you had taken the course and had satisfactory grades, then you didnít have to take a written doctoral examination in electricity and magnetism. Otherwise you did take such an examination, and as I recall it, it was a nine-hour examination in the one topic. Then you had another in mechanics, another in optics and so on down the line. These were the written exams. Then you stood for the oral after that. The written exams were just on your major. Your minor had no written exams then.
Weiner:You mentioned earlier that you had two minors, a major in physics --
Evans:Yes, I majored in physics, minored in math and 13th century history. Three-Button-Benny Monroe was my examiner in 13th century history. That was a ball. We had a lot of fun.
Weiner:Then Millikan would be the chief examiner in physics.
Evans:Yes, Millikan, Epstein, Eric Temple Bell in mathematics -- I talked to him later, because it was the habit in those days for the graduate student to go around before the oral examination, which was a rather long exam, as I remember, some three or four hours, and in a pretty tight tense situation, it was the accepted habit to go around to your examining committee and ask each man what he was going to ask you and what he wanted you to know. So we all did that, and of course the graduate students had a channel, had in fact a bound book in which they recorded what the questions were supposed to be, for the benefit of the rest of the graduate students. This book would go around. Then after the exam, you would put in the book what was actually asked. This kind of thing. I remember asking Eric Temple Bell where we would start -- at what level could I assume that such and such was taken for granted and then go on beyond that? I asked him, for example, if I could take Greenís theorem as accepted and just go from it on any advanced mathematics he might want, and he said, ďSureĒ. So we came to the exam, and his first question was, ďDerive Greenís theorem in three dimensionsĒ. He sat there with a smile on his face. So I did it for him, and some 20 years later I saw him at a cocktail party and said, ďYou rascal, what did you do that for?Ē He said, ďOh, I just wanted to see what youíd doĒ.
Weiner:Well, during your own research you were apparently relatively isolated -- not only from Millikan whom you saw occasionally, because by that time your problem was sort of independent -- but also from other students and other faculty. Did you get involved or become aware of other peopleís research, either faculty or students?
Evans:Oh yes, very much. There were a small enough number of graduate students so that we knew quite a lot about hat each other was doing, and we visited each other in the lab and in the halls and there was a good interchange, so that one could feel that he knew all of the doctoral researches that were going on, and had a very comfortable feeling of understanding everything that was going on in the whole Bridge laboratory,
Weiner:I would like to take a break now for a second and then talk about all those things in detail -- for example, Andersonís work which we talked about, that you had some involvement in, and to ask you if you had any knowledge of Charlie Lauritsenís work.
Evans:Yes. At this moment Iím not perfectly clear whether it was Sorensen himself who put up the 250 kilovolt transformers on their successive decks. As I remember it there were three of them, or maybe there were four. And Charlie Lauritsen came and hooked the high voltage end of it to a vacuum tube and started doing some physics with it. Sorensen had gathered the money to do it from the power company, who wanted to know how to make better insulators for their high voltage transmission lines, which was true of most of us. In those days there was a six day week, six and a half day week, day and night affair. There wasnít any of this jazz about not being at the lab on Saturday or anything of that sort in those days. So I was aware, you know, of what Charlie was doing, particularly when he was down in the shop, developing the Lauritsen electroscope, for one thing, and then a young boy came in, began to come at nights and be in the shop -- that was Tommy Lauritsen. He would hang around the lab as a youth. He got very capable in the machine shop and elsewhere. A very fine lad.
Weiner:Well, letís start off by saying that today is the 3rd of May and weĎre resuming our conversation after less than a 24-hour interruption. The last thin --
Evans:-- and no further thinking on my part about it.
Weiner:We did a lot of further work on the documents anyway, so that will be helpful. The last point I was pursuing had to do with the experiences at Cal Tech, and your awareness of other peopleís research. You mentioned that you knew what Charlie Lauritsen was doing with the Lauritsen electroscope, and that young Tommy would come in. I think I planned next; to ask you about Carl Andersonís work, what you knew of it, how you became aware of it, and in one sense, you had something to do with some of the details.
Evans:Yes. Well, Carl was doing his doctorate on cloud chamber measurements, and Iíd have to dredge my memory to make sure, but as I recall, the sequence was cloud chamber work by Ernest Watson, and then Don Lockridge, and then Carl Anderson originally looking for the angular distribution of photoelectrons produced by gamma rays or possibly by X-ray sources. And Carlís cloud chamber techniques were clean and absolutely superb. He did wonderful work. After he got his doctorate, Millikan asked him to stay on and, with funds presumably from the cosmic ray grants that Milliken had, do cosmic ray studies with the cloud chamber. This meant of course putting the chamber in so that its axis was horizontal instead of vertical, and a few things of this sort, and applying the magnetic field to it and looking at the curvature of the tracks. Carl wasnít in this, very far before he began to find that the rigidity of the cosmic ray particles was considerably greater than he had expected and Millikan had expected, and that the energies were in a range which immediately had a bearing on the controversy that was going on then about the origin of cosmic rays. As I recall it, it was mainly between Jeans and Millikan. Do you recall this?
Weiner:Arthur Compton was involved.
Evans:Yes, Arthur was involved, and very much so, but these were more details, as I recall, later, and these centered too about religious issues and science, werenít there some lectures in a little book.
Weiner:Yes, but there were specific scientific controversies that flared up at the time of the Atlantic City meeting of the AAAS, probably 1931-32, which made the newspapers. There was a very bitter debate between Compton and Millikan that had to do with the actual description of what cosmic rays were.
Evans:Yes, Ď31, Ď32. Well, if I had a quiet time to think about it and reconstruct the details, you might be able to needle me next time to do some dredging about that. But the broad brush things that stand out are Carl in the lecture hall, projecting some of his cloud chamber negatives, and of Carl and Robert Millikan with meter stick, standing up on stools, measuring on the projection screen in the lecture hail, and Carl convincing him that these tracks did have curvatures which were unexpected. And my first recollection about it is that it relates to a controversy on the energy of cosmic rays, and whether they were related to the mass defect minimum in the domain of iron, or whether they were the result of nuclear interactions among the light elements. Carl continued with these studies and he put a magnet up on the top floor of the aeronautics building where Clark, Millikan and Pinkie Klein and that group were using their wind tunnel. The large DC generator which was available for that wind tunnel was then made available to Carl Anderson, and Seth Neddermeyer was beginning to work with him to energize the magnet, and as I recall, these measurements would begin about supper time and continue while Carl and those graduate students just came around to chew the rag (we used to lag pennies, as a matter of fact, while we stood and waited for the cloud chamber to fire). My recollection at this moment is that these were the early days when he had a periodic expansion of the chamber, not triggered by anything, and of course almost all of the films were blanks because there was nothing going on during the sensitive moment of the cloud chamber. Then in one of these pictures, he got a track which was bending the wrong way, for a negatively charged particle, because he thought he was looking at electrons, and this would be a positively charged particle but of smaller track density. Its ionization density looked like an electron, but it was bent the wrong way and had too long a range, too long a path length to possibly be the only positive particle we knew about, the proton. I remember seeing Carl in the morning coming dashing out of the darkroom, and I guess I was the first one he ran into in the hall, and he said, ďMy God, Bob, look at this. This thing is going the wrong way. And I checked the film in my camera. I didnít have the emulsion facing the wrong way; I had it the right way. Everything looks all right here, and I canít imagine what possibly is wrong, but maybe that damn Pinky Klein,Ē who was a practical joker with a well-established reputation in practical jokes on the campus, and whose responsibility it was at the end of the day, when the wind tunnel stopped running and the magnet current was plugged in, to go down to the switchboard and pull out the plugs, connectors, and plug them in for Carlís cloud chamber on the top floor. So Carl suggested that maybe Pinky had reversed the magnetic field on him just to play a joke, and he asked Pinky, and Pinky swore up and down that he hadnít. Then Carl put in a strip of lead across the cloud chamber, so that he could tell from loss of energy which way the particle was going, up or down, and was very careful about knowing which direction the magnetic field was at all times, and I think at just about that time, whether it was just before or just after the lead strip, he added a coincidence counter trigger, so that the cloud chamber waited for its expansion until there was something to take a picture of. And out of this came a particle which certainly had to be identified as an electron with a positive charge. Millikan took ahold of this observation immediately, and it was my first exposure to the question of priority of publication, where shall we send this, to Science or Nature? Where will we get immediate publication? Nobody thought of the New York Times in those days, but this was a rush for early publication, which as I recall just beat the observation of others, wasnít it Blackett, by a matter of days or weeks.
Weiner:No, the first publication was without a picture, in Science. Blackett and Occhialini, considerably later, came up with a confirming observation and the best pictures of the same phenomenon, which were convincing, in a sense more so than the original discovery. This is the interpretation.
Evans:Iíd have to go back and check it through.
Weiner:Iíd like to date, if you can separate the account youíve just given to the beginning, this first observation before youíre talking about the lead screen. I have a feeling there might have been considerable time period in between. You seem to have a good memory of when he came out and told you that this was what he had. Do you remember when that was? Because he did write to Millikan who was in England and France at the time in about October, Ď31, with 12 photographs, some of them positively charged. Let me read from the letter which happens to be in my Physics Today article. That was October. Then the final confirming thing wasnít until August of Ď32. I was just curious if that incident you were describing was the very first or perhaps a later one. Here we are -- Boyce describes in January -- letís go back earlier -- it was November Ď31 Anderson sent him (Millikan) copies of photographs, and he described the puzzling tracks and said, ďPerhaps itís a positive particle moving downward, or an electron moving upwardĒ. Anyway that was November Ď31.
Evans:That could have been it. Do you know whether thereís a lead strip across that chamber? There was the ambiguity of which way the particle was going. And you say the date on that is November Ď31?
Weiner:November Ď31. Boyce was there a little earlier. In January he describes that. He says that ďMillikan and Anderson are working a Wilson Chamber between the poles of a very large magnet, and are obtaining cosmic ray recoil and disintegration tracks whose curvatures can be measured. Everyone seems most enthusiastic about the results. Some of the photographs show simultaneous ejection of plus and minus particles of high speed, as if both a proton and an electron were knocked out from a nucleus by the cosmic rayĒ. That was the description of the thing which had occurred.
Evans:And Joe Boyce wrote this in January of which year?
Weiner:In Ď32, but Anderson had described the same work in November of Ď31 to Millikan who was away. Iím just trying to date it for your own --
Evans:Well, November of Ď31 is a perfectly possible date for this, because I left Norman Bridge Lab for Berkeley in the summer of Ď32. My recollection is that Millikan was definitely on campus at the time that article, without the photographs, for Science, was sent in, and participated in its composition and in the statement of all of the many options.
Weiner:The point about the Anderson work, do you recall any discussions then after that, any colloquia, where this was discussed and speculated on?
Evans:As to whether it was positive electron?
Weiner:Yes. In fact, I think that would have occurred, the final thing would have occurred just when you were leaving or --
Evans:-- I think so, yes, I think thatís true, my next personal recollection about it is from Berkeley, shortly after -- I hadnít been in Berkeley very long. Ralph Fowler was there visiting, and from other data this would probably help give you the months that were involved. We always went down to the swimming pool and played water polo for our lunch hour, and Ralph was a pretty good water polo player too, and he told me during one of these water polo games that heíd just had a letter from Rutherford -- he was of course Rutherfordís son-in-law -- saying that they had produced positive electrons in the laboratory with a neutron source, and this is my first recollection of anybody stating that they had produced them in the laboratory rather than simply observing them in cosmic rays. In those days, we didnít use, the telephone for quick messages, only the telegraph if it was of vital importance, otherwise we wrote a letter. And I wrote a letter right away that night to Carl and said, ďGee, Ralph Fowler says theyíve produced positive electrons in the Cavendish with neutrons,Ē and Carl wrote right back and said, ďWell, yeah, but weíve also produced them in the laboratory with this thorium source that is around the lab, and we donít have any neutron source, as so it isnít the neutrons and we think we know whatís doing it -- itís the high energy gamma raysĒ. So this was the positron-electron pair, and the pair production interaction of high energy gamma rays with nuclei.
Weiner:I can date Fowlerís visit, and I also think thatís early Ď33 by the time Blackett and Occhialini published, and it may have been the fall of Ď32, early Ď33. You would have been at Berkeley then.
Evans:Yes. Then of course, Neddermeyer found -- I wasnít at the Bridge Lab so this was a letter and other channels of communication, and visits -- that the total energy of the positive and negative electron pair was the energy of the photo diminished by 1.02 or 1 anyhow, MeV, and that therefore this might, Oppie guessed, be the other solution, in the Dirac Equation, for the negative energy state of the electron. Then Oppie gave a physics colloquium at Cal Tech which I heard, so I must have been on a visit at that time, in which he made, in his very gentle voice -- which would only be heard about in the first and second row, and nobody else in the room could hear him -- the well-known suggestion of the interpretation. Does that give you anything?
Weiner:Well, I talked with Furry about it when he was visiting Copenhagen this year. I think I have that story, that part of it, because then he and Carlson got involved also in following up that same work, about Ď34. Letís get back to Ď32 while you were still at Cal Tech and ask about a couple of other things that happened -- not your subsequent recollections of it -- but if you recall whether or not you heard about it at the time. One was the deuterium identification which Urey announced in January of Ď32. I donít know if there was any impact there. Urey certainly wasnít there. Secondly, the neutron, which was published in the latter part of February, Ď32, and third of course the Cockcroft-Walton which came out in April, Ď32
Weiner:Yes. Their paper in Nature was end of April, beginning of May.
Evans:On disintegrations? Well, I was at Berkeley when that paper came out and I remember that vividly. Now, so far as Cal Tech is concerned and the personal impact on me of the discovery of deuterium, it was very minor. I have no vivid recollection of it. Deuterium began to be important and a thing that I knew about on a day-to-day basis after I got to Berkeley. I donít remember in which month in general in the summer of Ď32 I went from Cal Tech to Berkeley. I would be glad to try to plow through any old records I have that might show what date we moved, but I was at Cal Tech when Chadwickís neutron paper came out, and remember vividly discussing that among us as graduate students and some faculty members, in that little library room here in Bridge Lab, and I remember my surprise at finding that Millikan didnít believe it. He was not convinced. At least this was the first go-round, and as a young student I was quite impressed that here is a thing that I believed, and my great leader whom I adored, Robert Millikan, said he didnít believe it. Naturally he came around later.
Weiner:Did he offer any reasons?
Evans:I donít recall any reasons that he offered. His reason may have been that he hadnít read the paper yet, because itís a very convincing paper. I regard it as a beautiful paper, just beautiful. So that occurred just before I went from Cal Tech to Berkeley. The deuterium began to be important at Berkeley, after the cyclotrons stated running with protons and then with deuterium, which G.N. Lewis provided for them from the chemistry department. He did that because he had got rather teeíd off at the large expensive equipment that graduate students in chemistry wanted, and he was going to show them that they could do good research for pennies if they used their head. So his technical assistant whose name was Mac something -- do you remember this? -- he sent Mac down to the salvage junkyard in Berkeley or Oakland and bought a bathtub, I think for 15 cents, and brought that back and put electrodes in it and began electrolyzing water in order to recover deuterium from it, as a residue, deuterium oxide, heavy water, and the device which Gilbert, Lewis and Mac had developed was a micropycnometer, simply a piece of glasswork capable of measuring specific gravity with great accuracy and precision up to many decimal places. And he hadnít found any use for this device, but with deuterium coming along, great, he gust electrolyzed water in this bathtub for a long time and kept measuring the density, and when the density got as high as it was going to get and was constant, he said, ďHere is a sample of pur deuterium oxideĒ. Of course it didnít have that name then. Letís see, there were the deuton and the diplon Ė-
Weiner:Diplogen, the material was called.
Evans:Yes, it had various names in various places, and it was Karl Darrow who finally straightened this out by getting agreement between the Berkeley people and the Cavendish and others, to change the name. Until then, it was --
Weiner:Deuton and diplon, I think they were holding out for.
Evans:Yes. There was still another one.
Weiner:Heavy water itself was called, Iím thinking of diplogen maybe that was the word for heavy hydrogen?
Evans:Yes. I wish I could remember the other one. There was another one which was never used in polite society, Ureyne, because it came in units of the Peagram. What was that one? It may come back.
Weiner:There are a lot of stories about new particles with funny names that were never public. Did you have contact with Lewisís people at Berkeley, jumping ahead a little bit?
Evans:Oh yes, we knew each other. There was some radioactivity work going on in the chemistry department, with a graduate student called Willard Libby who was using, not a lead-shielded but an iron-shielded counter, and looking for natural radioactivity in all chemical elements. He found some that were true and some that werenít true, and we were in very close touch. I guess he and I were the only people on the campus who were doing anything having to do with radioactivity. Now the Cockcroft-Walton story, and this will bear on the date, the month when I went to Berkeley, as I recall that vividly, on arriving, within a very short time after I arrived at Berkeley, there appeared on the bulletin board a copy of a telegram, I think from Ernest Lawrence, to several members of the laboratory group who were up in the mountains skiing, up in the Sierras. It said, ďCockcroft and Walton have just disintegrated light elements with accelerated particles,Ē or maybe it said protons, I donít remember the exact wording of the thing, ďcome right back, letís get with itĒ. So they did, and in just a matter of days the little tiny cyclotron that Stan Livingston had upstairs in that laboratory, that he had done for his doctorís thesis, they put a source in it, protons, and duplicated Cockcroft and Waltonís excitation function, on one or more of the light elements, lithium, boron, have to look up to see which they were, and extended the voltage range by nearly a factor of two and said, yes, itís true. It never occurred to us to put in a target and actually test this thing. We were all ready to go. A lot of other people were all ready to go too. Charlie Lauritsen and his team were all ready to go, and wasnít Merle Tuve pretty nearly ready?
Weiner:Yes, he certainly was.
Evans:And nobody did it. So Ernie Lawrence reported this to the physics colloquium, and it had been the feeling around there that you had to have five million electron volts before there was any point in trying to disintegrate anything with protons, in spite of the fact that Oppie was around and available, and that Gamowís papers had been published and showed very clearly that there was barrier penetration for alpha particles coming out, and therefore for others going in, and for charged particles going into a nucleus. So they just never tried it, because the conviction among all the experimentalists was, you had to first get these cyclotrons bigger and better until you had them up to five MeV and then theyíd try. Ernie said in the colloquium, ďThis was the genius of Rutherford, he told Cockcroft to try the bombardment, at the low energyĒ. When John Cockcroft came later to Berkeley on a visit, he and I sat out on the porch at the Faculty Club and chewed the rag about what had been going on in various places, and I told him that. He said, ďAbsolutely notĒ. Rutherford had, quite the contrary, encouraged him to accelerate charged particles, multiply charged mercury or whatever he could get, looking for lots and lots of MeVís, and not realizing the importance for nuclear barrier penetration of having a low charge and a high velocity. And that he, Cockcroft, had held out against Rutherford, and insisted on doing it the other way, since he knew and believed in Gamowís model.
Weiner:Thereís a memo from Cockcroft to Rutherford in Ď28 or Ď29 giving Gamowís ideas. Cockcroft went to work on it. Then they (Cockcroft and Walton) tried to reconstruct the story in 1931, between them. There is some documentation of this. The letter in the notebook which records the results. In that page of the notebook thereís a letter from Walton to Cockcroft in Ď31, the note for this in Ď32, and it gives this story, which you heard in June of Ď33 when Cockcroft was at Berkeley. I think, by the way, as far as the timing goes, the Cockcroft-Walton work supposedly was published in April or May of Ď32. I know that. Rutherford writes here, on the 21st of April, Ď32, he says, ďNext week a short account should appear in NatureĒ. I donít have the date here but I know that means May at the latest.
Evans:Maybe they didnít see the Nature article. Maybe this was the Proceedings of the Royal Society.
Weiner:The next thing I found was a letter from Lawrence to Cockcroft, where he thanks him for the reprints of their epic-making work. He used that term. That was written the 20th of August, Ď32.
Evans:This could be it, you see. But as to my not knowing when I went to Berkeley, it was sometime between May and August, thatí sure. Itís in that time window, and there was this fascinating telegram. I always admired the complete publication which Cockcroft and Walton had made in 1930 in the Royal Society, when as Cockcroft reminded me, when we were talking about it in this visit in the Faculty Club porch, they had published full details of their expectation of successful disintegrations at these low energies, with their reasons, based on the Gamow theory, and Cockcroft told me they weíre all ready to do their experiments -- they had some preliminary stuff going, as I remember it with perhaps Geiger point counters as detectors, in 1930, when the buildings and grounds people came around and said, ďWe are now tearing down your building beginning tomorrow, kindly vacate.Ē So instead of sitting on all these ideas, they openly, freely and completely published the whole blooming business in 1930 in the Proceedings of the Royal Society -- and nobody took it up, left it all alone for two years, while they got a new building, rebuilt their equipment and went ahead and did their job.
Weiner:Well, everyone had other approaches. They were pursuing different things.
Evans:One of the many things where the Berkeley group missed the boat-- they missed the boat on that one, as did many other people. They could have marched straight ahead. They missed the boat on the positron. They missed the boat on artificial radioactivity.
Weiner:And fission? Evans; Yes, the fission story is very interesting, because we almost had that here (at MIT) too. Close but no cigar, you know. Everything was done right by Jack Irvine in his doctorís thesis, and he could only find in all that large number of products of bombardment of uranium with neutrons, which had been ascribed to trans-uranic elements by Fermi and others -- Jack Irvine did his doctorís thesis with me, and Jack Irvine chemistry said, no, thatís not true. The only one I get that can be in that group of uranium or above is the 23 minute isotope. And this was true. His source strengths were not great enough to get neptunium, which would only have given about 2 percent of the activity that he was observing, because the neptunium half period is longer, so he didnít catch the neptunium. And we had only this 110 milligrams of radium and beryllium as our neutron source at that time, and we had sent out some time prior to that, some vials of uranium oxide, to be left near the Berkeley cyclotron to catch neutrons, all clearly labeled and packaged and with my return address on it and all of the postage on it. These never came back from Berkeley, and on inquiry they concluded out there that they had been lost. So Jack Irvineís thesis went ahead only on our little neutron source. He turned his thesis in and had his doctorís oral two days after the announcement of fission, and everything heíd done was right, except he didnít find fission. Berkeley of course missed artificial radioactivity. They missed production of Nitrogen-l3 which was going on gaily. Any target bombarded with deuterons in the cyclotron would, because the target became contaminated with pump oil containing carbon, any bombardment of Carbon-12 with deuterons produces Nitrogen-13, the first of the artificially radioactive nuclides. And it was there just zooming away. What it was doing was producing an enormous counting rate in the detectors which were being used, which were either Geiger point counters or Geiger-Mueller counters, and Ernie said, ďThese counters are no good in the magnetic field. Thatís whatís doing it. Take them out and put in linear amplifiers, the Wynn-Williams type of thing and letís use that for detectionĒ. What was actually going on, if they had taken a little more time to notice that there was a buildup of activity, which went like 1 minus e to the minus Lambria-T -- but after theyíd turned the beam off, the counter would slow down, with a half period of something like ten or twelve minutes -- then they would have discovered a whole lot of things, because it was artificial radioactivity producing this effect and not the magnetic field on the detectors. The positrons were being captured and producing a half-MeV radiation. They could have done a little bit of lead absorption experiment to see what the energy of this delayed radiation was, and found to their astonishment that it was smacko half-MeV -- a whole lot of things could have been done. We discussed briefly on the staircase the cream-skimming procedure which was characteristic of that era at Berkeley. They discovered a lot of things and did a lot of good stuff, but a lot of things went by because of lack of thoroughness.
Weiner:They were also very much concerned with development of instruments, and you have to wear a different hat for doing that and for doing the work with the instruments. Letís talk about the transition from Cal Tech to Berkeley. Were you thinking, when you were about to complete your degree, about a possible permanent position somewhere, either at Cal Tech or elsewhere?
Evans:Yes, I think by then I was committed to the academic life. Iíd decided it wasnít music and it wasnít industry, it would be the academic life, so I would be thinking in the long pull of an academic position somewhere. And I thought very fondly of course of Cal Tech, of returning there. That would have pleased me very much. That was the beginning or pretty close to the depths of the Depression, in the midst of 1932, and a good many of the graduate students who were getting their degrees then were naturally very anxious about getting a job. And many did not get any. I remember that some of them like Jack Workman who was there urged several of us to join together to go to the state of Washington and grow apples, and we fresh new PhDís in physics were to become apple farmers. It was that bad. This was a very serious suggestion which we all considered very seriously. I made application for a National Research Council fellowship, and was fortunate enough to get it. So I went to Berkeley.
Weiner:Did you discuss this first with Millikan?
Evans:Oh yes, he was my strong sponsor for it. Probably heís the one who suggested it, I donít recall that. He must have been, though because he was a true friend and supporter.
Weiner:He was aware of the fellowships because he was on the fellowship board of the NRC, and helped to set them up in the first place. Do you recall what it is you said you would do? Your fellowship application usually indicates the research you would like to pursue, and the second part of that is, why Berkeley?
Evans:It was radioactivity. I expected to continue my work in radioactivity, and particularly then you see it was geophysical radioactivity. The thesis had involved improved methods for measuring the radioactivity of rocks. That was all clear. We knew how to measure the uranium-radium series with good accuracy in ordinary rocks and soil samples. And this would lead you toward the possibility of geological dating of basaltic flows and granitic rocks and things of this type, provided you could learn how to measure the thorium series also, and could learn how either to measure the accumulated lead with isotopic separation, or the accumulated helium. So then one would be able to make geological dating of igneous rocks, and make enormous strides forward in the field of geology. So that was what I was really heading for, and began collaboration with the geologists at Berkeley, Williams and others.
Weiner:Had you started that collaboration while you were still at Cal Tech?
Evans:No. That was after arrival.
Weiner:Why did you select Berkeley for pursuing that particular subject?
Evans:At this moment, I donít remember why. Certainly somebody advised me. It could be that Millikan advised me, but it was Leonard Loeb I went to, as the guy under whom I would work.
Weiner:Was there anything that attracted you to him, or was this Millikanís suggestion? Did you specify him as someone youíd like to work with?
Evans:In my application? I probably did. At this date I donít recall why. He had a book on kinetic theory with which I was familiar. Thatís all I recall knowing about Leonard Loeb before I got there. Then I learned a great deal about him, a very interesting character.
Weiner:We have a 300 page autobiography that he wrote specially for our archives.
Weiner:Yes. We requested this from people of his age at a certain time in the early part of the program, and he was one of the people who responded, just wrote it, not for publication, but for our archives.
Weiner:A whole well-organized story.
Evans:He was a terrific writer, as you know, and wrote many books, and when I arrived, he had the beginnings of a book which he was writing. I was always amazed at the way he wrote, because he wrote longhand and I had the impression always, when visiting his office and seeing what he was writing on, that he never went back and made any corrections. He just wrote it straight out and that was it. My own writings, I rewrite, and I always have three steps, of done, finished and polished. Done mean itís nearly OK now; polished means itís ready to send out and let somebody else see. But not Leonard. First draft, boom that was it. He turned over all of his graduate students to me and said, ďYou take them and direct them and have funĒ. So we did.
Weiner:And you put them to work on your problems.
Weiner:So it means that even though you were an NRC fellow, whatís called a National Research Fellow that you took over a faculty function there. Did you direct any of their theses? Evans Oh, I did, sure I directed their theses, sure, Finney and so on -- doctorís theses, yes, they did all of that under my direction and I set up a graduate course in radioactivity, which I taught at Berkeley.
Weiner:There was nothing else like that before.
Evans:No. There wasnít any field of nuclear physics yet, and nuclear physics was exclusively the field of radioactivity, just as in the titles of Gamowís books. Thatís all there was. Nuclear physics as a subject began, so far as Iím aware, here at MIT in the fall of 1934 when I began my graduate course in this topic, and chose not to call it radioactivity but to call it nuclear physics, a broader view.
Weiner:When was the radioactivity course set up at Berkeley? You arrived in the summer of Ď32 -- was it that fall or the following?
Evans:Iíd have to look it up. I may still have the course notes for it.
Evans:Physics. I can put that on my list of goodies to look for, in Arizona, and see if I still have those notes. I must just still have them, in a binder chucked back with my lecture notes from the nuclear physics course here.
Weiner:What was the relation of the work in the department per se to the work that was beginning to develop quite actively under Lawrence who was still part of the department -- from your point of view, in terms of how you perceived attitudes and what your relationships were?
Evans:There were lots of interchanges of ideas and good knowledge of what everyone was doing. There were not only the regular physics afternoon colloquia, but there was an evening colloquium, a very informal thing. I seem to remember it was Monday nights, perhaps. This was mostly organized by Ernie Lawrence and his people. Stan Livingston of course was prominent in that group at the time I arrived, because heíd just finished his doctorís thesis, been asked to stay on, and build a bigger cyclotron using the Poulsen arc magnet, they got, I guess, from the San Francisco Navy Yard, to make a bigger machine. Leonard Loebís attitude was, snort, snort, this guy is a promoter, he wants things bigger and better, and heíll just continue each time he finishes one he wants to build one thatís bigger and that automatically will have to be better. So this went on, step by step, as you note through the set of machines, and Stan was asked to stay on and get that machine into operation. Then this whole group of young men whom you know well came into the scene. The department seemed, as I recall it, to be small enough so that I felt I knew everybody on the faculty and all of the graduate students, and we all knew each other, both socially and in the laboratory scene. Stan Livingston and his wife Lois and my wife Gwen and I were very close friends, and of course had many discussions about our long-range futures. Those were very tough times. You know, we might be able to time my arrival at Berkeley by the date of the Bank Holiday, because as I recall, my first pay check from the National Research Council had been deposited in the bank by me the day before they closed, and I had to I believe write or possibly I telegraphed to the National Research Council about my predicament, and would they be good enough to send another check, which I would not deposit in a closed bank, but would convert to something that I could use to pay rent and get food. We had just one child then, just one boy, but the general strike came on then too, with Harry Bridges, or came I guess a little later. There was the general strike which was a tremendously traumatic thing to go through. We may have had two by then. Maybe the general strike was the following year. Do you remember when it was? [March 6-9, 1933]
Weiner:No, I canít place it.
Evans:There was a two-year span there, where there was the Bank Holiday and the general strike. Leonard Loeb was the leader of a group of vigilantes who marched the streets at night to see that order was kept, to back up the police, and things of this sort. It was a very traumatic period, and for those who went through it, leaves lifelong scars being very careful about nickels and dimes and things like that. You just donít get over it. The decades donít remove it.
Weiner:In your case the NRC grant would have kept you off of starvation level. It would have been adequate.
Evans:Yes. Oh, we saved money on it. My wife was a great manager. We saved money on it, sure. She ran the house, for -- as I remember it -- $90 a month. Maybe it was even less, which was pretty good, including rent, food, clothing, all the rest -- a dollar a day for food for the whole family, yes.
Weiner:Well, you certainly couldnít buy research materials out of that. Did that come out of the department?
Evans:Yes, Iíd say so.
Weiner:From their research budget -- what did you need? Did you need very much? What about your sources? What did you use for sources?
Evans:My sources were natural materials, you see. These were rocks and things of that sort.
Well, we'll get to that another time. I know that by the time you left, you had a vacuum furnace and a number of things.
Yes. Those were built in the shop there. My first vacuum furnace I built with my own hands at Cal Tech. That was a crummy little thing when you look back to it, but it was the old sealing wax and string business. You got an iron plate and got a piece of a U-bar and welded some end plates on it, and strapped it down with baling wire, and put sealing wax around the edges for a seal. And I got an old transformer from the power companyís scrap yard, tore it apart, took off the secondary and wound my own low voltage higher current secondary out of one inch by 16-inch copper busbar by hand and with wooden spacers, and all that. No, we did it all ourselves. There was very little expense there.
They had a very nice vacuum head electroscope that I designed, and that Julius Pearson built in the Cal Tech machine shops. Millikanís typical way of handling that was, when I wanted that instrument and showed him the designs and my reasons for it, he said, “Come with me,” and we went to the physics shop at Cal Tech where his instrument-maker Julius Pearson was the head of the shop. He introduced me to Julius Pearson and said, “Make anything he wants.” And Millikan turned around and walked away. That was it.
Weiner:Did Pearson come from Chicago with him?
Evans:I think so, yes. Great guy. Yes. So when I got to Berkeley, it must have been Leonard Loeb who arranged with the shop there that I could design a vacuum furnace that would be built by machinists. And that was done.
Weiner:It would be interesting to check whether it came out of his research grant or the departmental. I have both figures.
Evans:That would be great, to find out where that came from.
Weiner:I dug those out of the files last night.
Evans:There werenít any outside purchases or anything. These were all instruments built in the shop. I built a recording camera for reading out an electroscope, so that I wouldnít have to stay up all night with my eyeball on the microscope eye-piece, but could record this. This was a wooden drum about 15 inches in diameter, in which I put a five-inch wide strip of photographic paper, and got 24-hour recordings. This way I got more sleep than I otherwise would.
Weiner:You were always doing automated things like automatic sample changers and so forth. I do have the information I was asking about, I have it right here. When it came time for you to take the equipment with you, they do refer to the sources -- anyway, when it was sold it was credited to the physics department research grant, which was No. 211 and so forth. And it said that the total cost of the apparatus and supplies referred to on the list was $574.75. The items referred to as shop-constructed apparatus consisted originally of an electric furnace, two vacuum chambers, miscellaneous carpenter shop made items, acquired at a total cost of $325. Stock supplies originally cost $185. Apparatus, $65. Since so and so is of no further use, experiments completed -- anyway, it turns out that the actual value was the salvage value of $203 and if MIT wanted to pay $250, fine.
Evans:Iíll be darned.
Weiner:And the big question was whether the fund could be credited to Physics Research Grant 211, and -- this is what I was looking for -- since the purchases were made from research grants, then the proceeds of the sale to MIT should go back to that research grant.
Evans:Iíll be darned. Youíve really got it. I admire your preparation for this.
Weiner:Well, this is a trivial point --
Evans:I havenít been able to get the time to get out old things and refresh my memory on these things. But youíll needle me next time. [Crosstalk] -- say, ďHere are somethingís, why donít you look up if you can and see what happenedĒ.
Weiner:Why donít I say now that we can call this part of it to a stop, and give just an idea of what we should pick up on next time?
Evans:All right. Can I give you one minute? I know you have to run, but you asked me last night just as we were breaking up about my decision to go to MIT, and we can defer that, if you like. Thatíll hold perfectly all right. But I could give you the broad brush quickie on it if you want.
Weiner:I was going to suggest we get into that transition now, so we know --
Evans:Right, and then we can take it up with more needles. [Crosstalk] That was interesting, because it was still a very difficult time economically, of course, and my recollection is that I most of all wanted to go back to Cal Tech and to hopefully be on their faculty. And Millikan did make an offer of assistant professor at some salary, forgotten what it was, somewhere in the domain of $2400 to $3000, perhaps, that ball park. Then out of a clear blue sky I got a similar offer from Stanford University, and Iíd been down to Stanford several times. Bill Houston was there visiting, and Bill and I and Mildred had been very good friends at Cal Tech. Here came this offer, so I had two of them, and it was tough to decide which one. And I was right in the midst of that when a telegram came, I think from Slater, though it might have been from Karl Compton, but it more likely was Slater, and youíve probably got a copy of that.
Weiner:No, that I donít have.
Evans:I just might possibly have that, and if I do, Iíll -- shall I make a note of that, to look for the MIT, well, Iíll call it just telegram, for quick notes, 1934. So here was a Depression year, and a guy sitting there with three faculty offers. I think I either responded by telegram or letter, and if I by chance have saved the file, Iíll give you the whole thing, because there were some very rough words written by Millikan to Compton accusing him of stealing, through knowledge of individuals which had been gained by the National Research Council competitions for fellowships, and this was --thereís some phrase about the odor of SO2 will be smelled from coast to coast. Itís quite a powerful letter. He really laid it on. So here I was with three offers, all of them quite acceptable. I didnít know which way to turn. I was seeking again advice of minds older and wiser than mine. I asked Leonard Loeb what to do and he didnít want to make a decision, said they were all good places, and couldnít make a mistake -- told me a little about MIT. All Iíd known before about MIT was the scoop we under graduates had of it on the Cal Tech campus, and the fact that Harold Edgerton and his wife, Ester, and Gwen and I had become good friends in 1928, when we were on the Travel Prize in Europe, and it happened that the four of us were on the same boat coming back from Europe in the fall of Ď28, so I had visited the MIT campus. I knew one person here, Harold Edgerton, and that was about it. So I wanted to know a little bit more about MIT. Certainly Gwen and I never even considered weather -- or any of the parameters that this generation considers so carefully as to where theyíll go. Finally, as the guy who might be the most helpful of all to me, I went to Gilbert Lewis, G.N. Lewis, who I knew well from visiting in the Faculty Club at lunch and things like that, and his two and three dimensional chess games and what not. So I went over and told him I wanted his advice, and I showed him the papers, and here I had three faculty offers, and he damn near kicked me out of the office. He said, ďIn a time like this, youíve got three faculty offers, and you come in here with a problem? Get out of here. So I made a few more inquiries, and came to MIT.
Weiner:Thatís very interesting, as a transition. Next time weíll talk about the expectations, because obviously you knew you were going to continue your research, because you arranged to take your apparatus with you.
Evans:Yes. The initial telegram from MIT said, ďWe want to develop strength in radioactivity. Would you come and initiate it?Ē This kind of thing, very specific and perfectly clear. At Stanford they were mainly an X-ray team, of course, at that time, and Cal Tech was mainly cosmic rays. This one was an offer to continue in the line I was in, radioactivity, which was blossoming by then because in January of Ď34 artificial radioactivity had come on the horizon, and I was very much intrigued about that too, and that in retrospect may be the reason I chose MIT, because it was a clear opportunity to continue that line of research.
I think thatís a good point to stop.
 Winners of first prizes are: Robley D. Evans -- Pasadena; George T. Harness -- Glendale; Edwin M. McMillan -- Pasadena Second prizes: Robert J. Coulter -- So. Pasadena; Joe W. Schweinfest -- Anaheim; Charles C. Lash -- Los Angeles; Kenneth A. Solomon -- Eagle Rock Edwin M. McMillan -- Pasadena; Albert E. Lonbard, Jr. -- Pasadena
 Filed Feb. 4, 1931; Issued Oct. 24, 1933. No. 1, 931, 689
 Pun on names of Harold Urey and George Pegram.-ed
 Gwen sat in the laboratory and read mystery stories to R.D.E. while he built the transformer. This was before the birth of Dick, June 17, 1930