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Oral History Transcript — Dr. John C. Slater

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Interview with Dr. John C. Slater
By Charles Weiner
In Gainesville, Florida
February 23, 1970

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John Slater; February 23, 1970

ABSTRACT: Slater leaves Harvard University for Massachusetts Institute of Technology in 1930 (Karl Compton) to build up Physics Department there; work on quantum electrodynamics. Growth of MIT Physics Department in the 1930s and 1940s, relations between experimentalists and theorists; discussion of works and publications during the 1930s. Changes in U.S. physics; overview of post-World War II physics to 1951, and reasons for establishing own research group; establishment of the Radiation Lab, 1940; magnetron work; Bell Labs visits, 1941-1942 and 1943-1945. Planning of postwar development in MIT Physics Department; transition from Radiation Lab to Research Lab of Electronics; formation of laboratories of nuclear science, acoustics, and spectroscopy; the Lincoln Laboratory, the Instrumental Lab; growth of nuclear branch of Physics Department; physics activity in general in postwar years, Solid State and Molecular Theory Group; the Compton Lab.; Materials Science Center established ca. 1958; interdepartmental and interdisciplinary work; visits to Brookhaven National Laboratory; Slater and Per Olov Lowdinís Florida Group. Also prominently mentioned are: John Bardeen, W. Buechner, Arthur Holly Compton, Edward Uhler Condon, Jens Dahl, Robley Dunglison Evans, James Brown Fisk, George Harrison, Douglas Rayner Hartree, Raymond George Herb, Milton Stanley Livingston, Millard Manning, Jacob Millman, Wayne B. Nottingham, Isidor Isaac Rabi, Schafer, William Shockley, R. A. Smith, Julius Stratton, Robert Jamison Van de Graaff, John Hasbrouck Van Vleck, Eugene Paul Wigner; American Physical Society, California Institute of Technology, Florida State University, Lawrence Radiation Laboratory, Princeton University, University of Bristol, University of California at Berkeley, and University of Chicago.

Transcript

Session I | Session II

Weiner:

Itís February 23, 1970, and weíre sitting in the study of Professor John C. Slater in Gainesville, Florida. Mrs. Slater is here. Weíll start off by talking about the decision to go to MIT in 1930. This was after a very rich period of your own graduate work, two trips to Europe, some fundamental contributions in physics in a period when your reputation had taken hold among people who knew your work. Iím curious to know how this switch to MIT came about; whether you were actively looking for a position in terms of breaking away from Harvard and whether, in addition to that, they were actively looking for someone with your qualifications. Iíd like to explore this whole question in terms of their expectations and needs and your own.

Slater:

Well, I was not actively looking for anything. I was very happy at Harvard. But Karl Compton had been actively looking for me for several years. He had made two strong offers for me to go down to Princeton about a couple of years before the 1930 period. I had gone down there and visited, He was very anxious to have me come in the physics department at Princeton. And I decided that I would not be happy at Princeton, I felt that the small college town was not as much to my liking as a place of the size of Boston. They had a very good department; I was very pleased with it. But I turned him down each time, so that when he decided to come to MIT, itís not surprising that he had me in his mind. In other words, the place that they wanted me to fill at Princeton, if Iím not mistaken, was the one that Eugene Wigner eventually did fill; but they wanted to get me in there before Wigner had come to this country. I knew the history more or less of how I happened to be invited to MIT. I have all the letters of Karl Compton and so on, some of them explaining how this came about. When Compton decided to come to MIT, they felt that one of the first things to do was to strengthen physics. This had been agitated by the young physicists at MIT very much, Manuel Vallarta and a number of others, and also Henry Phillips in the mathematics department and Vannevar Bush. A number of people who were leaders in the Institute very much felt that physics needed strengthening.

They had a list of about four people whom they would try to get as head of the department. They tried the other three before they tried me, but I was just looking last night at Karl Comptonís letter relating to these things. He said that I was the first choice, but they thought that it might be regarded as an unfriendly gesture to steal me from Harvard so they leaned over backwards to try to get somebody else. The first one they tried was Lawrence Bragg. Bragg had had sort of a standing invitation to come to MIT for several years, He had lectured there a number of years before, and everybody liked him, and he liked the place. So they offered the job to Lawrence Bragg, and he said that he still liked the place, but it was too far from home. He preferred to stay in England. Then they offered it to George Thomson with the same answer. Then they offered it to Bill Houston, who was happy at Cal-tech.

So I was the fourth on the list. And, as I say, Comptonís letter said that really they were happier with me than with the others; as he had had me in his mind for a couple of years on account of this desire to get me to come to Princeton. Well, felt it was really quite an opportunity. At Harvard I did have a little feeling that was the bright little boy in the department who didnít really get consulted about things very much. I already had many ideas about how 1 thought the Harvard department could be improved, and Lyman and Saunders were very polite about this, but they didnít do very much about it. For instance, was thinking that they needed a bigger building. I like to draw plans of buildings. had plans drawn up for something which turned out to be very much like the McKay laboratory, which now adjoins the Cruft and joins a number of buildings, but they wouldnít pay any attention to that at all, because they were going ahead with their methods of building a new laboratory.

Weiner:

You were only 29 years old.

Slater:

I was only 29 years old, and naturally didnít get very much attention when it came to problems of that kind. But that was enough to convince me that was interested in building up a department as well as in going on doing my research and doing my teaching. So it seemed to me that it was a possibility worth thinking about. I did not know the MIT department very well. Iíd gone to a few colloquiums and lectures and so on there. But there was almost nobody in the department, aside from Vallarta, that I really did know very much. But Compton argued at great length as to how important he thought it was to build up the place. My principal worry was about possible rivalry with Harvard if the Harvard people felt that he was being unfair in stealing me away. notice in this old correspondence that the first thing that I wanted to be sure of was to have him meet with the Harvard physics department and assure them that we were going to cooperate and not compete. But that was my main worry. And I just felt that it was a job I could do that really interested me very much.

Weiner:

Did Compton have in mind any particular areas to specialize in?

Slater:

No. He and I both felt that we wanted to have a broad department. So we tried purposely to make appointments in a number of different fields. We already had a fairly broad department in that there was a certain amount of work in theoretical physics. Iíve mentioned Vallarta. N. H. Frank was there, W. B. Allis, people in other departments. Julius Stratton was in electrical engineering at the time, but he was around. So those people all gave quite a lot of strength in theoretical physics. Then they had X-rays. B. E. Warren had got his start when Bragg was around several years before. He traveled in Europe, and he was getting X-ray work going very nicely. There was work in the solid-state area. Former department head Norton was an applied physicist but interested in solid-state things. We had, for example, D. C. Stockbarger, who was a practical man in crystals and that kind of thing; and he was the one who actually worked out the techniques that are still used for growing big commercial crystals. And there was Hans Mueller in dielectrics and things of that sort, who had been brought over by Debye. You see, MIT had had a number of visiting lecturers during the l920s. These people on the scene had tried to build up the department by bringing in visitors.

Weiner:

Were there more, would you say, than Harvard had had during the period? Or when they came to the Cambridge area, were they shared?

Slater:

Almost more than Harvard had had, although Harvard had a number. Between the two places, there were many; but Bragg, Debye, Scherrer, Born—those four at least remember—and I think there were one or two others that had been there; and Debye brought Mueller along with him as an assistant, and Mueller stayed on. He liked it and was a very popular member of the department. And so on. So there were quite a number of people in the department at the time. But Compton and I both felt that we wanted to broaden things. The first appointment we made was George Harrison. We felt that spectroscopy was going very strong; that we really should get going on spectroscopy. I had known George Harrison earlier when he was a National Research Fellow at Harvard. I had taught summer school out at Stanford one summer, where he was. So we brought him in and decided that we would have a real spectroscopic effort going on.

Then, of course, Comptonís main interest was electronics, and we wanted to keep that going; so we brought in Wayne Nottingham, who had been one of the students of Compton. We also brought in Lamar, who was working directly with Compton. Compton had some experimental work going on afterwards. In the spectroscopic area, Compton had had interests in the far ultraviolet. Joe Boyce had worked with him. We brought in Joe Boyce. But we wanted to strengthen nuclear things. There had been almost no nuclear physics or anything of that sort. Another of Comptonís moves was to bring in Van de Graaff, who had gotten his start at Princeton; but we felt that his generator was a fine idea, and that that would get us into the machine business, Of course, this was before cyclotrons or anything else.

Weiner:

But that implies money and the need for research support, which is a question I wanted to relate to all of these points that youíre making about strengthening the field. You imply that the strengthening was because Compton was working in electronics, letís get more work in electronics. I have two questions on that. First, was this based on an overall assessment on which direction physics was heading?

Slater:

I think so. We werenít very consciously making a list of the directions we thought physics was heading in, but we were pretty conscious of what was going on. There are one or two more I was going to mention before I go into the question of finances. We felt that radioactivity and those things were very important, and we appointed Robley Evans at Millikanís suggestion, who was in radioactivity and applied radioactivity. And then when the cyclotrons began to be really practical, we decided we had to have one; and it turned out we could get Stanley Livingston, so we had himÖ

Weiner:

Letís see: Evans came in Ď34, and Livingston in Ď38.

Slater:

Thatís right. Iím now stretching out through the whole period of the Ď30s. But during that period we tried to keep a pretty good balance. We were very anxious when Van de Graaffís machines began to operate to see to it that these were used for real nuclear experimentation as well as just practical things; and Bill Buechner, who was one of the students, was the one who turned into the user of this for that kind of work. But I think we were getting a pretty good balance. And, of course, coining back to the theoretical physics area, we added Phil Morse. That was planned when Compton came. So that here we had a fairly representative group of people. Now how do we finance all these people? In the first place, there was and is a great element of strength in the MIT physics situation in that a great many undergraduates have to take physics—essentially all the undergraduates in the institution. I had the principle right from the beginning that the undergraduate teaching was going to be taught by the best people in the department.

We would have senior people doing this— of course, junior people also running recitation sections and laboratory sections. But this meant that we could justify a large number of professors, on account of the large teaching load that we had. So these people were brought in essentially as faculty members and paid by the University. But one needs money for research, and we started right away trying to get grants. And Compton managed to get from the Rockefeller Foundation a six-year grant. Iíve forgotten how much it was. Iíve got the records, but I donít remember. This was for starting research all through the Instituteóó1930 to 1936. That more than anything else is what got us started. The University support for research in each department was small and still is small. But nevertheless we had on the regular University budget, I think it was $10,000 a year for research in physics. And in those days, parceling it out, when somebody could go quite a way on $1100 or something, we were able to buy apparatus. We also needed quite a good many teaching fellows to help with these elementary laboratories and so on, that allowed us to get people in who would also be assistants and graduate students, etc.

Weiner:

The Institute would pay for that, too.

Slater:

The Institute would pay for that, too. And then we managed to get a few grants from special foundations for some of these larger machines. We had a grant from a foundation—I forget which one—for the cyclotron.

Weiner:

That was from the Markle Foundation.

Slater:

Thatís right-óthe Markle for the cyclotron. We also were getting grants for the Van de Graaff development. That for a while was out in the country in a place called Round Hill. The Institute owned some land, a curious place; or rather it had permission to use space on the estate of Colonel E.H.R. Green, the son of Hettie Green, who liked science. We had that out there for several years before we moved it back to Cambridge.

Weiner:

How far from Cambridge was it? Was this at Dartmouth, near New Bedford?

Slater:

Near New Bedford. So it was far enough away that you couldnít get much joint work between that and MT, but we accomplished quite a good deal down there.

Weiner:

Was Van de Graaff there?

Slater:

Van de Graaff was there.

Weiner:

Until about Ď37 or Ď38. Salter: Thatís right.

Weiner:

During that time what was his affiliation with MIT?

Slater:

He was a research associate for most of that time.

Weiner:

But was strictly separate.

Slater:

Strictly separate.

Weiner:

Thatís what started to ask you—my question about the finances. I wonder: can you invite a Van de Graaff, who comes with a generator or has the need to develop a larger one, without having a good promise of funds to support him?

Slater:

Well, we had a little support through Colonel Green, think that started out almost from the beginning at Round Hill. He was willing to put up a few thousand dollars. These things didnít cost too much in those days. This was the Depression. One could get people to do things very much more cheaply than one can at present. So the first large generator—2.8 million volts or something like that, one that was not a vacuum generator but just out in the open—was actually put together by the people who were working there (Van de Graaff and then the two Van Atta brothers were connected with it); and by using commercial materials that werenít very expensive; and, as say, Compton was good at raising a few thousand dollars, which is what it took.

Weiner:

Did he ever indicate that some promise from the Rockefeller Foundation prior to his coming there might have influenced him to come? I know that he had received large grants from the Rockefeller Foundation in the 1920ís to develop Princeton.

Slater:

I know that he had some confidence that he was going to get some funds. I donít remember exactly what he said, but Iíve got these letters that could look up and find out what he wrote—just how sure he was of getting finances—because I know that one of the questions I asked him when he was negotiating with me to come to MIT was: could I really believe his promises about being able to finance the development of the department? And he said he had good reason to think that he could. But Iíd have to look at his letter to see just how much promise he already had from Rockefeller. But this total Rockefeller grant was not large. It wasnít more than a few thousand dollars a year for the whole institution.

Weiner:

Iím thinking in terms of a million-dollar grant.

Slater:

It was nothing like that. The whole thing was in the order of less than a hundred thousand dollars.

Weiner:

Because they gave many millions in the l920s for developing certain institutions.

Slater:

Yes. Well, we had nothing like that. It was not one of the big grants.

Weiner:

And there was some support from the Research Corporation.

Slater:

That was probably for the Van de Graaff, think. Iíd forgotten the Research Corporation, but that was one of the places where support came.

Weiner:

There were three places that were listed for support. One was the Research Corporation. The other was the Carnegie Corporation. And the other was the Hyams trust.

Slater:

Yes, I think these were all tied in with that projectóóthat project and perhaps Evansís radioactivity. Those were the two things that were well supported.

Weiner:

Were you involved in raising funds?

Slater:

I was not involved in raising funds. Compton was good at that, was interested in it, and he took that over.

Weiner:

That explains a lot.

Slater:

That explains a lot. Oh, no, the thing started because Compton was behind it.

Weiner:

So when a decision was made to get a man in nuclear physics or to get a Van de Graaff or someone else, it was based on the physics of the situation; because you had the expectation of funds or a promise from the president that he would obtain the funds.

Slater:

Thatís right. During those first few years we had a situation that could never be duplicated again. There were no deans. Deans hadnít been invented. At least they hadnít been invented there. The result was that when wanted to settle something, I went directly to Karl Comptonís office and we talked things over; and we talked them over as if the two of us were trying to develop physics at MIT. Thatís all there was to it. Then when we came to a conclusion, we carried it out. He was an authority and able to do it. So that it was ideal. Then deans began to come in, and intermediate grades of deans and so on. Things have been getting more and more complicated ever since.

Weiner:

I want to get back to the decision to go to MIT. Had you considered other alternatives? You said you werenít seeking a new position. But when an offer comes up, it seems to me that then your mind does open up to the possibility of moving. Did you consider other places that would be likely for you, that would be desirable either in terms of the career prospects—long-range—, the opportunity to do things you wanted to do, not only in developing the department but to pursue the kinds of research you were interested in? Had you given some thought to that?

Slater:

Not to anything except Princeton. The Princeton offer was the only serious one had during the period that was at Harvard. I had had other offers just after finished my graduate work. For example, G. W. Stewart at the University of Iowa was very interested to get me to go out there, had had slight overtures from Stanford, but none of these things developed in a way that they were competing with my interest in staying at Harvard. So that would have been perfectly happy to have stayed at Harvard permanently. I liked the local area and so on. And I donít think I would have considered seriously anything that had come along.

Weiner:

There was no other place then thatÖ

Slater:

There was no other place that would have preferred. No, had no feeling that there was any place that would be as good as where I was. And I felt that there were some aspects at MIT that interested me more than Harvard in that I always was interested in the interrelation between the pure science and the engineering and the applied things and so on, which thought could be done there better than at Harvard.

Weiner:

Do you think this influenced Compton in his selection of you? The only indication youíve given me of his desire to have you is your desire to build up a department. But, of course, he knew your work.

Slater:

He knew my work.

Weiner:

But was he interested in this particular aspect of applied theory?

Slater:

I donít think he thought about that at all. No, think he simply felt that was standing out as one of the younger physicists and thought Iíd be a good one to get.

Weiner:

So you could have been doing something in a completely different field.

Slater:

I wouldnít know. He did not go into the sort of recommendations that heíd had for me. He said at the time theyíd been considering inviting me to Princeton, he got views about what could do from many different people; and that had convinced them that I was the one they wanted to get at Princeton. I guess he just used the same information when it came to MIT. He must have had many letters, which I never saw, about what people thought I could so.

Weiner:

What did you think you could do at this period? In other words, in terms of an approach to physics, what particular approach had you developed by this time? Youíd developed your sense of taste and certainly a personal style—the taste being an ability to recognize important problems and to see what approaches might be fruitful. In looking over the whole scene of physics at the time and taking a look at who you were and what you would be doing then, can you recallÖI know itís very difficult in retrospectÖthings now seem to be very logical. But do you recall any thoughts at that time of ďwhere am I Where am I going? Whatís physics like, and how am I going to contribute?Ē The time period Iím talking about is 1930, in that transition.

Slater:

Well, I think I had very definite ideas as to what wanted and where I wanted to go, and think itís what Iíve done since. In other words, had already very clearly decided that quantum theory could be applied to all kinds of problems, both theoretical and practical, in the study of atoms and molecules and solids. And was interested in the whole range between the purely theoretical side and applying it to all kinds of practical applications. So that felt could work in all those areas, and the more I could do, the better it would suit me.

Weiner:

Did you see a particular group of problems as presenting a major challenge at that time, not necessarily for your own work but something that one could consider the hot field in physics—or the hot cluster of problems?

Slater:

I would say no. I would say that was interested in the whole range of what goes on outside the nucleus. I was never tempted to go into nuclear physics. I felt equally interested in straight physical problems, in chemical problems, in metallurgical problems and so on. And thought this was a wide enough area to keep me going the rest of my life, which it certainly has done. And I was never particularly interested in choosing the things that people thought were hot problems rather than things that people didnít think were hot problems. This never appealed to me at all. I just wanted to be able to work on all these things. Whenever a subject looked to me as if one could make progress in it, worked on it. If it looked too hard, I waited and decided come back when it would appear easier. But I wasnít at all affected by the trends going on in physics. And never have been.

Weiner:

For example, at that time, did you feel that the development of quantum electrodynamics as it stood then was something you would want to work in, or that perhaps if you didnít want to do it personally, that you would want to encourage others to work in it?

Slater:

I felt it was something that very much wanted to work in. In fact, I worked a good deal in quantum electrodynamics and never published any of it, because never was satisfied with what got, and Iíve never been satisfied with what anybody else has gotten. I think the people who have worked in quantum electrodynamics have never touched the real problems, which are the interaction between the radiation field and the atoms; and think you read the fanciest books on it and get the least information. So think thereís a great deal still to be done. But I never was quite able to get the combination, and I donít think anybody else has.

Weiner:

Now weíre talking about style, preferences. You feel you want to tackle it, but if you donít feel youíre getting anywhere on it, if you canít reduce it to a simpler problem that you can understand—then you sort of put it on the shelf. Has that been your approach?

Slater:

Sometimes. When felt there was something couldnít do then.

Weiner:

And the whole quantum electrodynamics work you would say is in that category. When did you start to do work that you just put on the shelf?

Slater:

Oh, I was playing with it before went to Copenhagen. If you read the material that Id been thinking about in Cambridge before I went to Copenhagen, this was quantum electrodynamics essentially.

Weiner:

And so how many times have you returned to it in a way which didnít see publication?

Slater:

Three or four times. I had quite a long thing in progress at the beginning of the war which never got published. Some of that got incorporated into my theory of microwaves. The magnetron theory and so on is set up on a basis that essentially is quantum electrodynamics. People donít always realize that. Ed Condon had done similar things. Ed Condon wrote a very nice Reviews of Modern Physics article early in the war on electronics of vacuum tubes and things of that sort which used the same kinds of ideas that fitted in with what my interests were. But there you were just using practical applications of it. But the fundamental thing that think is that no one has thought through a definition of an electromagnetic field. And think itís rather closely tied in with some of the things that Iíve been concerned with for a great many years-ó namely, self consistent fields and so on.

These are approximations, and I think itís only to an approximation that one can think about electromagnetic fields at all. I think that the people who have written on the subject just completely fail to realize this. So I wouldnít guarantee that I may not come back to it again. In other words, think that there are things to be done. But also feel that there is a very important point in the matter of what one works on. And that is whether anybody is going to listen to what you write. I donít think thereís much point in doing something where you cannot expect anybody to read your papers. And if theyíre sufficiently unpopular and different from the current trend, that doesnít mean that Iíd follow the trend, but might just not try to work in the field because I knew the peopleÖ[interruption] There have been times when I just have stayed away from a field because I thought that the whole trend was so much in another direction which I didnít care for that just didnít think anybody would pay attention to what I was going to do.

Weiner:

There have been cases (which you discussed before in the Kuhn interviews) in which you felt that something you had done was sufficiently important and wasnít being noticed, so you called it to the attention of others in a letter to the Physical Review.

Slater:

This I have continued to do. There are a lot of things that I did before the war that nobody reads any longer. So I just go ahead and put them in later papers and put them in books and so on, hoping that they will get noticed. For instance, there was a long review article in Reviews of Modern Physics that I wrote in 1934 on the electronic structure of metals. There are many things in that that people still havenít noticed and that are just the kind of thing that Iím pushing at present.

Weiner:

When you say ďhavenít noticed,Ē I guess thereís a double feeling involved. One is the recognition that this is a contribution that you madeÖ

Slater:

I donít mean that. I mean that they havenít absorbed it and started to use some of these things.

Weiner:

But psychologically Iím sure that there is some satisfaction when someone does recognize a piece of work. Iím not saying that thatís the motivation. The motivation is that here people are doing something in the same literature which they should be sharing. Thereís another way or another approach which would save them much trouble and take them out into new fields. And in a sense youíre inviting them to look at it in a different way, and youíre recalling to them what they could have seen if theyíd looked in the first place.

Slater:

Thatís the feeling that Iíve had. I donít care whether they pay any attention to whether I did it or not. But the fact that it exists and that I think itís the right way to go about it-óI think that is important to let people know.

Weiner:

Now weíve been discussing personal style. I wonder whether thereís any problem, as chairman of a department of one of the largest science institutions in the country and in the world, in following out that personal policy. Because you have a larger responsibility in terms of training people who will be going into fields which are either fashionable or where thereís a need for more well-educated people. You may choose fields which are likely to get support at a particular time, rather than other fields which are not so highly supported. So I think that the kinds of decisions that you would have had to make as chairman would have been a little different than in your personal work.

Slater:

Thatís right. Oh, I encouraged many things in the physics department that I didnít want to work on personally. And I tried to be just as broad as I could so as to represent all these various fields. In other words, I think we had a better overall representation in the fields of physics than almost any other physics department that I know of. And I continued to use this principle after the war in building up things. I thought we were weak on nuclear and high-energy things, and we made a very big effort to develop that area at the Institute and so on.

Weiner:

But during the pre-war period there was a great deal of diversity, and you didnít feel the department should specialize.

Slater:

No, I didnít. I felt it was much wiser to be broad, to be able to train people in all kinds of areas. And I also felt that in a place like MIT, where we could keep close relations with many of the engineering departments, that we wanted to be doing good work in the fundamental science on which those engineering departments were based.

Weiner:

I detect in reading through your history of MIT a policy of diversity but yet with great individual freedom for someone who wants to specialize. You have a man in acoustics; let him build the department and program of acoustics. And although you are not the specialist and the department is not specializing in it, you have, in fact, a small acoustics department and a small radioactivity department. Perhaps it was because you were a big enough department to do this. In fact, you were a federation of departments.

Slater:

Thatís right.

Weiner:

It is quite different than most places I know of.

Slater:

We really were from the beginning, and I really felt this was the right way to do it.

Mrs. Slater:

ft was a pretty stable department too, wasnít it? Because many people spent a whole lifetime there.

Slater:

Thatís right.

Mrs. Slater:

Which isnít the case so much anymore.

Slater:

No, people didnít go away and leave.

Weiner:

IĎm sure if added up the number in your history, I would have an idea of the total staff or the average number in the l930s. Whatís your estimate now?

Slater:

On the order of magnitude of thirty faculty members and probably 30 or 40 junior staff-óthat kind of thing. It was large. I know right after the war, when we were building up our department again, it appeared to me that we were the biggest department perhaps except for Berkeley. I tried to make comparisons, and know that in that period just after the war, when Lawrence Bragg was the Cavendish professor, compared with him on what they had at Cambridge. We were just about the same size.

Weiner:

I think I have some figures on the number of PhDís that were coming out of MIT during the Ď30s. I donít know if itís very large. Well, itís not a bad number—between 1932 and 1942 there were 85 PhDs. It seems that Ď36, Ď37 and Ď38 were the peak yearsóó14 physics PhDís in Ď36, 12 the next year, then 12 in Ď38.

Slater:

Thatís about what I would have thought.

Weiner:

And you would say this was pretty evenly divided among the various fields.

Slater:

think they were pretty evenly divided.

Weiner:

I had a breakdown for nuclear physics PhDís using a rough approximation of what is nuclear physics and what isnít, because it was during a period when the field was changing. There were about 14 in nuclear physics out of the total of 85, for that 10-year period. I donít know whether there was any other group that was as large as that.

Slater:

Well, of course, in that 10-year period we were definitely building up, so that think there were probably a number of other departments that were bigger than we were. When went to the Institute, it was a very small department.

Weiner:

Were there large-scale increases in enrollment during the 1930s?

Slater:

Very much so.

Weiner:

Undergraduate?

Slater:

Undergraduates as well as graduates. I remember writing somewhere that at the time that I went to the Institute, we were the 13th department in MIT in size or something of that sort; and by the time that the war came on or just before or just after, we had grown to be the second or third biggest department in the Institute.

Weiner:

There were 18 graduate students in 1930-31, and there were 61 in Ď39-í40.

Slater:

Yes, and of course there were 150 or something like that right after the war. But the number of undergraduates grew in proportion or even more so. I think that MT was and guess still is quite a leading producer of bachelors in physics, including some very well-known people.

Weiner:

Was the policy then to encourage people who received their bachelors to seek admission to graduate schools elsewhere?

Slater:

I never took that policy very strongly. If they wanted to stay, they stayed; and if they wanted to go, they went. I felt that it was their business, and I didnít care. We found in many cases that the best-prepared graduate students were the ones who had gone through our undergraduate training; and felt that it was rather a foolish policy to make people go somewhere else if they didnít want to.

Weiner:

But did you have a limited number, though, that you could accommodate every year?

Slater:

We had a limited number, but it was big enough so that it never seriously troubled us. We could use it to screen out applicants that didnít seem very good, but we never had any trouble to take on all the ones that seemed promising.

Weiner:

Was there any policy of assigning people on the basis of specialties? In other words, if you had only 20 graduate students or 30 that could be admitted that year, regardless of their undergraduate source, was there a feeling that they had to maintain the diversity in the department? Was there a conscious policy of admitting three people in solidóstate and four in nuclear physics? Of course, Iím saying this in an extreme form.

Slater:

Yes. There was a little but not very much. If somebody came along who was applying for an assistantship or something, and we very much needed an assistant in that particular area and he looked pretty good, weíd take him even though there might be an equally good person in another area that didnít need somebody so much. So there was a little conscious choice like that, but it never got to the point where it made us turn down a really good man in one area in preference to a really good man in another.

Weiner:

Well, one thing that would affect it would have been whether the funds were specifically allocated to certain areas, and you implied in a sense that they were; that the radioactivity operation brought in its own support.

Slater:

Yes, but this was mostly for apparatus construction and postdoctoral people and so on.

Weiner:

I see. There was no question of once you have a machine you need people to run it?

Slater:

No, we never got into that situation.

Weiner:

Not pre-war.

Slater:

Not pre-war. Not post-war either very much—at least not while I was running the place.

Weiner:

On the number of students in the Ď30s, it seems to me that the Depression would affect the total situation of the department in terms of faculty, in terms of available jobs for graduates at all levels, in terms of sources of financial support either for fellowships, whether through the Institute funds (Iím sure they were depleted) or through grants made from corporations or foundations which themselves were affected by the Depression. Is there some way that you can analyze the effects of the Depression on these various aspects of the department?

Slater:

I donít think that I really can, because, after all, we started this particular operation in 1930 and the Depression started at just about the same time, so that I had not known any previous situation to compare it with. We just took what we got and made out as well as we could.

Weiner:

Were there any specific budget cuts that you were faced with? The Depression did take a tollÖ

Slater:

There were budget cuts, but they didnít particularly affect us very much For example, there were one or two years when MIT held backóI think it was 10% or something like tható-out of faculty salaries till the end of the year to be sure they had enough money to pay us. We always got it back at the end of the year. But the budget was already small enough, even in the beginning, so that there were no further cuts, as I remember.

Weiner:

I see. So there was a 10% withholding.

Slater:

Thatís right. No, think there were no actual salary cuts. Obviously, we couldnít make as many new appointments as we would if we had more money, but obviously we did make a good many new appointments anyway. I suppose we were in a favored position since Compton was a physicist, but he didnít press this at all.

Weiner:

What about the number of students who came in during the period? Was this affected very much by the Depression in terms of their ability to pay the tuition?

Slater:

Well, almost all of them had to get assistance of some kind—teaching fellowships, research assistantships and so on, which we were able to give them. They had very small tuition that they had to pay along with this, so that we found that students could come. I donít doubt that many more students would have come if the money had been more available.

Weiner:

How about jobs, for example, for people who majored in physics at the bachelorís level but ordinarily would not continue at the graduate school? What kinds of jobs did they usually get and how did their opportunities change throughout the 30s?

Slater:

Well, Iíd say on the whole they got pretty good jobs. We didnít have any serious employment problems. We had several people on the staff who had very good industrial connections and things. For example, Arthur Hardy, who was in optics, had very good connections with the optical companies; and other people with other kinds of industrial companies—Nottingham with the electrical industry and so on. So that even right through the Depression we had no real problems of people who couldnít get placed.

Weiner:

Where would the undergraduates go—in other words, the people with bachelors in physics—primarily industry?

Slater:

They would mostly go into industry. There were many other places in placing our students. We had many very good ones who had no problem whatever getting placed, and a few who were problems. I remember one man for whom we had to write on toward a hundred letters of recommendation. We began to use the same letter over and over again. But these people all got jobs and all got respectable jobs. Itís surprising how many of the students who were graduate students in those days are turning up in very good positions now.

Weiner:

Well, I meant, of course, to ask about graduate students, too, but I was thinking first about the undergraduates.

Slater:

But the undergraduates, too.

Weiner:

They would go primarily into industry.

Slater:

Primarily into industry. They were oriented more in that direction than people from many physics departments, and there are a lot of very good industrialists at present who were MIT undergraduates in physics in the l930s.

Weiner:

Is there any record that you know of, either in your files or at MIT, which would provide some statistics of the breakdown of employment of the people who left with a bachelors?

Slater:

I donít have that, I have the feeling that this is in the MIT files. At least all the time I was there we kept a card file on each graduate and tried to keep it somewhat up to date. So I would suggest going to the MIT physics department and seeing if these still exist, I just donít know. They may have thrown them all out.

Weiner:

It would reflect trends in employment in terms of which industries were beginning to employ physicists and in what capacity, whether this has changed over the years, and whether the change corresponded to the development of the concepts of physics itself. It would be interesting. We often assume things about this, but I think we have to pin them down.

Slater:

No, I have never had that material arranged statistically.

Weiner:

I want to jump now to the graduate students. It seems to me that if universities were affected by the Depression, at least in one way-ó that is, not by expanding as rapidly as they wanted to, not hiring as many new faculty, especially at the lower level, as they would want to-óthat the employment opportunities would be somewhat restricted for those who had university careers in mind. Do you have any feelings for this? For example, one symptom would be that you had some good students who just hung around for an extra year, because they didnít find the job that they wanted.

Slater:

Oh, I think this happened, but I think this always happens, and very often this is a fine thing. Some of our best work has been done by students who have stayed around an extra year after their doctorís degree because they didnít find a good job right away. But donít think we had any who were hanging around very long waiting for a good job. No, we felt then, as I still feel, that people in the first couple of years after their doctorís degree can be extremely valuable if theyíre kept on where they are or go to another laboratory as post doctorals. And, of course, one thing that helped a great deal on that was the existence of the National Research Council Fellowships that were operating much as the National Science Foundation Fellowships are operating now. Youíre undoubtedly familiar with these. But many people held such fellowships.

Weiner:

What did they do when they came? They had no teaching responsibilities, and generally when they applied, they would indicate at what institution they would like to work and would give some indication of why, in terms of a person there who was doing the work or some research facility there. But one thing Iím not clear on in the process is whether the receiving institution—MIT in this case—would be consulted beforehand by either the applicant for the NRC fellowship or his sponsor or adviser.

Slater:

Yes.

Weiner:

Did you, for example, communicate in some informal way saying that ďyour man, So and So, would be welcome here if he is able to bring an NRC fellowship with himĒ?

Slater:

I donít think it usually happened in that order. Someone would be applying for an NRC fellowship and would ask us if we would take him if he were granted such a fellowship; and we would say yes or no, as the case may be. I think this was more often done by the applicant himself than by his professor. But in any case, we would look at the situation and let them know.

Weiner:

And your decision as to whether to take him would be based on the qualifications of the man and how well you thought he wouldÖ

Slater:

How well he would work on the problems, yes.

Weiner:

I do have some figures on the number of NRC fellows who came during the Ď30s. For example, in 1930 you had one; and in Ď31 you had two. These may not be accurate, but theyíre about right. In Ď32 there were three, and in 1933 there were five. Do you recall that there were so many around that year, and do you recall anything about theÖ?

Slater:

Oh, Iíd have to remind myself who they were.

Weiner:

I do have that but not with me unfortunately.

Slater:

I know that we built up and built up to aÖ

Weiner:

Van Atta, for example, wasÖ

Slater:

Van Atta came as one, as I remember it.

Weiner:

For a two-year period.

Slater:

Yes. In a good many cases, some of these people came as National Research Council fellows and then we kept them on as research associates or something of that sort. Iíd have to look at the records to know just what kind of appointment they were on each year. But these fellowships were invaluable and also the existence of our research associates were invaluable in keeping a good staff in the laboratories.

Weiner:

Now, I know about the role of research associates in the post-war period because youíve described that in the histories.

Slater:

Weíd had some before the war, not nearly so many as after the war; but the same general idea.

Weiner:

These were post-docs.

Slater:

Post-docs. They were paid by MIT.

Weiner:

see. How were they used generally?

Slater:

In the laboratory.

Weiner:

In other words, would it be very rare that a theoretician, say, would be a research associate?

Slater:

I just donít remember how it actually worked out, I remember that we had a number of post-doctoral theoreticians around, but think in almost every case they were NRC fellows or some similar thing.

Weiner:

Rather than research associates.

Slater:

I believe so.

Weiner:

While weíre talking about people in the department who were not permanently attached, I should ask about the visiting lecturers. Youíve mentioned that there were a number of foreign visitors in the Ď20s. How often, do you think, did you have outside lecturers? Youíve showed me the documents; you put it down day by day. But how many outsiders do you think you would have, letís say, in the normal course of a semester or a quarter?

Slater:

You mean people who would just come in for one lecture, that kind of thing?

Weiner:

Yes, there were two categories. One was visiting lecturers and the other, people who stayed for a month or a quarter or whatever.

Slater:

Yes. Well, of course, one thing connected with that is that some were at MIT and some were at Harvard so that the number of people who would appear on the scene was quite considerable. Now, letís just look through some of these calendars, because the thing that struck me (I went through them last night) was how many there were in the course of a year, and I wonít start at 1930—Iíll go along—letís take Ď33. Here is January Ď33. Well, Jack Kirkwood and Joe Boyce were both talking, and the following week George David Birkhoff and G. W. Pierce-óH.W.B. Skinner. Skinner was the Skinner with OíBryan, an Englishman, who was around for a year working on soft x-ray spectroscopy. He was talking. The following week A.S. Coolidge on chemistry and T. E. Sterne on astronomy and Vallarta and David Langmuir and Cecilia Payne.

Weiner:

These were all local people.

Slater:

These are all local people. So Iím just looking to see how far I have to go before I come to the first visitor. Oldenberg in Ď33, but I guess he was local by then. So Iím coming to a lot of local people. Well, here on March 21st is the first one that I see: Mr. Auguste Piccard of the University of Brussels on ďOur Free Balloon in the Stratosphere.Ē But he was not at MIT; he was at Harvard. Farnsworth from Brown on electron diffraction. First colloquium given by William Shockley in 1933 on conversion of light into heat in crystals. He was already doing that as a graduate student. Then letís see: The following week-óMarch 27th to April 1st—Robert Mullikan was talking; Bill Hansen, the microwave man. Then the following week, Joos, the semi-conductor man. Skinner again. There were also quite a number of visitors in mathematics.

Weiner:

These are joint MIT-Harvard?

Slater:

Attended jointly by the people from both places.

Weiner:

Listed as physics, though.

Slater:

Listed as physics—physics and astrophysics we labeled it then. Robert Brode in May. Later in May, Ivar Waller was around giving lectures. He was around for several weeks.

Weiner:

There were no special summer schools.

Slater:

Well, I wouldnít say that. There was a mathematician from Paris a week after that, and he talked for several weeks. Karl Darrow was around a bit later. We had summer sessions on spectroscopy, and had them on some other topics.

Weiner:

Oh, yes, spectroscopyÖand applied spectroscopy.

Slater:

Thatís right. We had radioactivity things in the summer and so on. These were fairly short sessions. I didnít hit a particular year that had as many as sometimes, because there were some periods when there were several different lecturers for considerable periods.

Weiner:

Iím glad you did this, because I gather from it that you had a tremendous stockpile to draw on just in the local area.

Slater:

In the local area. Thatís right.

Weiner:

And because of the diversity within MIT itself, it seems to me that by using someone, say, from your radioactivity group, it would be of general interest to the larger group, but those people perhaps were not in regular contact.

Slater:

Thatís right.

Weiner:

Thereís a question Iíd like to explore. If your department was, if youíll permit me, something of a federation of various departments, how did these various specialized groups, some of which by their size were quite substantial, communicate? Did the people in radioactivity regularly come in contact with the people in high voltage or in acoustics or in spectroscopy, or was it only on a basis of shared interests on a particular problem?

Slater:

Well, they pretty much went to all the various kinds of colloquia. That was one of the reasons we had as many of these colloquia and seminars as we did. I think people werenít as selective then as they are now about just going to ones in their own field. And then, of course, these different people were all engaged in elementary teaching and that kind of thing, so they got to know each other in quite different ways from just through their particular field of research. So it was not big enough to break into cliques very much. I think there was a good deal better interrelation between the different parts of the department than there is in most departments now.

Weiner:

Was there any journal club type ofÖ?

Slater:

Well, some of these colloquia were journal club types of things. There are a good many that are reports on other peopleís work or reports on whatís going on in the laboratories, things of that kind.

Weiner:

And were students involved in that?

Slater:

Oh, yes. I remember read the first appearance of Bill Shockley, who was still a graduate student then.

Weiner:

I can understand a student being on the program as a speaker if he was that good. What about the graduate students themselves participating as auditors?

Slater:

Oh, they would all come. This was essentially for graduate students. All these things read were for graduate students.

Weiner:

So this was the one occasion where the entire department would at least be invited, not necessarily be present.

Slater:

Yes.

Weiner:

Do you have any estimate of the size of these meetings, how many people you would get? I know a long period of time has elapsed since.

Slater:

Well, the room that we had them in holds about 190 people, and that room was generally at least half full.

Weiner:

How many would come from Harvard? About half of that number?

Slater:

No, not that many, simply because they had similar ones at Harvard, and there again they were about the same size room and about the same number of people and relatively few people would go back and forth. But people would go back and forth when they had topics that particularly interested them.

Weiner:

So these were MIT physics colloquia to which any area person would be invited.

Slater:

Yes. See, this calendar that I was reading you things from was something that I organized but which contained notices of Harvard meetings as well as MIT meetings. I simply operated as a sort of a clearing house to have these notices all sent to me, and weíd put them down in one place so that people would know what they could get at the various institutions. This includes not merely Harvard physics but Harvard astronomy and mathematics, medical school, etc.—similar to different departments at MIT. Whenever I thought something would be of interest to physicists, it appeared in there.

Weiner:

Were there any specifically organized joint sessions in the 3Os?

Slater:

Once in a while but not very often. Of course, we felt that this gave us enough flexibility. It was easier just to do it this way. And when some visiting speaker came in that was particularly interesting, or when some topic was particularly timely, then a lot of people would go back and forth from one place to the other. They had the notices, and it was easier just for each of us to organize his own things, but to let the other place know as to what was going on.

Weiner:

Iím asking now a number of questions that are not necessarily connected, but before we get onto something else, they are things that I recall that I left out or that you left out and Iíd like to focus on. One relates to the teaching load of the faculty. We discussed before their research interests as if well, they were free to pursue it, but, of course, when they were hired, they were judged on their ability as teachers.

Slater:

Thatís right. Of course. Very much so.

Weiner:

And Iím curious to know what the teaching load was, whether it differed at various levels of faculty rank, and whether this was a source of continuing conflict in terms of balancing the needs for teaching against the desire to do research.

Slater:

No, I think people were more used to teaching then than they are now. I donít remember any particular conflict. About on the average, there were two courses that a person would be teaching at a time—sometimes a little extra, sometimes heed be giving one graduate course and giving some lectures in an elementary course and doing some recitations in an elementary course or something of that kind. There was no great difference between different levels in the department. They had about the same sized teaching load. My recollection is that they all took it very peaceably without any complaints at all. When somebody had a particularly big job of building up some apparatus or something or other that needed special time, well, Iíd give him a lighter teaching load for a term or something of that kind. But in general there was agreement that teaching was a very essential thing and everybody was glad to do it.

Weiner:

Did there develop during this period any competition or rivalry with Harvard? You mentioned that this was a problem, at least in your mind and Comptonís in terms of your originalÖ

Slater:

It worried me at the beginning. It worried me perhaps because when I first told Bridgman that I was going to MIT, he was a little bit worried; but it never developed into anything. No, I think that we were very peaceful.

Weiner:

Within the department you had various groups, and one way to divide it is in terms of their special interestsóóacoustics or spectroscopy—but another way to divide it is between theory and experiment, between theoreticians and experimentalists. I know that you referred in your history of the department to the theoretical group. Did they work as a group, or were they in fact attached to whatever particular laboratory was most appropriate?

Slater:

I donít think there were any rules about it. A number of the theorists did work pretty closely with experimentalists. Others didnít. Some people worked with experimentalists in other places. For example, Vallarta was interested in cosmic rays; we werenít doing much of any cosmic ray work experimentally, but he would work with people in other places—Arthur Compton and Millikan and so on, who were working in cosmic rays, trying to work up a theory connected with their observations. So that think that almost all of the theorists were in a sense interested in experiments in the related field, and sometimes these experiments were going on there, and sometimes they were going on other places. But there was no effort to regiment them or anything of that kind.

Weiner:

What was the primary strength of the theoretical group as you saw it, in terms of the types of abilities that they had?

Slater:

Well, I think they were unusually good in classical mathematical physics. Of course, the Morse and Feshbach book was one of the outcomes of that; and Strattonsís work on electromagnetic theory. And of course we also had a lot going on in quantum theory, and then other related things—a lot of optics, a lot of relativity (there were quite a number of people interested in relativity—special, general and so on), thermodynamics; quite a range of things.

Weiner:

On balance, if you had an ideal department and an ideal group of theoreticians as a measure, what would you say were the weaknesses of this group? What would you have added or what other emphasis would you have liked to have seen?

Slater:

I donít know, I was pretty well pleased with what we had. Of course, theoretical physics has changed since then. We havenít got the same things now. But I felt—and I still feelóóthat that general kind of breadth is very good, not to have people all in one quite narrow field.

Weiner:

Was there anyone in particular you would have liked to have gotten in the period who you were unable to get? Someone you really sought but who just wouldnít or couldnít come?

Slater:

There wasnít anybody we really made a strong effort to get that we didnít have, because we were pretty well fixed up as it was. I remember we did make a bid for Ed Condon in the early days. And although we were very friendly with Ed and so on, he felt that we already had enough going on in spectrum theory and why should he add onto what was going on at the time. So he didnít come.

Weiner:

Where was he at this time?

Slater:

I think he was still at Princeton. But I donít think there were any others that we made an effort to get.

Weiner:

How about the European physicists? Were there any either in the early Ď30s or later when war came who became available?

Slater:

I donít recall that I made any effort to get any European physicists at all in the department while I was there. This is not strictly true. We did have some European physicists, but they were brought in by other people. For example, Nottingham brought in Eric Rudberg from Sweden. But he was very specially interested in what Nottingham was doing. As far as the theorists were concerned, I didnít feel in that period that they had very much to give that we didnít already have.

Weiner:

I thought of this because you said that of the four people being considered for the department chairmanship originally, it turned out that two were Europeans—Bragg and Thomson.

Slater:

Yes. There had been quite a tendency towards cultivating the European physicists in the l920s, before I went into the department. This was partly because a number of the people who were in the department had studied In Europe and they knew the European physicists, and I think in the Ď20s European physicists were a good deal more essential than they were in the Ď30s. I think we didnít have as much in this country. But you notice that the two Europeans that were thought about were both experimentalists—namely, Bragg and Thomson.

Weiner:

This was for a department chairman. So there were other factors involved, too—particularly the prestige attached to the name of either one of them. Iíd like to explore in a minute the relations with European centers of physics in the Ď30s. But before that, I want to get back to your theoretical group and to ask about Morse and his students. When you look at it, you see that there are a number of very good papers coming out and a number of Ph.D. students that he had during that period. Now, their work primarily was on nuclear physics, and it seemed to have reached a peak in 1936 or Ď37. At least they were publishing heavily—relatively heavily in it—and producing doctorates in the field. What was your opinion at the time of their work? This was a developing field.

Slater:

Well, I certainly thought it was a developing field. But Morse, of course, was interested in that, but also interested in a number of other things. He was beginning to develop his acoustical interests then. So I didnít feel that we were really doing awfully well on nuclear theory. I felt that this was a somewhat weak point in what we were doing actually. Which was one of the things in my mind after the war in building that up more heavily. But, of course, there wasnít a great deal of nuclear theory going on at that period.

Weiner:

Well, but Ď36-Ď37 you had Betheís review with Bacher and Livingston which some people felt was a nice way of pulling things together and in a sense made it apparent to others that the field had come of age. But do you recall your reaction to those articles? You werenít working in the field.

Slater:

I wasnít working in the field, but of course I was conscious of what was going on, and I was more or less relying on Livingston and Evans plus Morse to keep us informed as to how things were developing, and they were doing this pretty well. We were having a course on nuclear theory, which Robley Evans was teaching in those days—long before many other places were doing it—and we were training people in the nuclear area even though we didnít have any Bethe in the department.

Weiner:

Evansí courses developed in a book later.

Slater:

Thatís right.

Weiner:

What about Van de Graaff? When he came he was isolated physically—geographically—and then he physically was reunited with the department about Ď37, I guess. What was connected with this change and this transition?

Slater:

He just stayed isolated. He was just that type. He never mingled very much with the department.

Weiner:

Did he have many students? Did many students work with him?ó- people who were taking their degrees?

Slater:

Well, a few. The two who continued in that line were John Trump in electrical engineering, who went on with the practical use of electrostatic generators in therapy and that kind of thing, and Bill Buechner, who spent his career at MIT. But then he also had quite a number of others who were working with him. Various people—Jim Fisk and various others—spent periods, even though they didnít take their degrees with him, working in the laboratory there. They were just sort of all pitching in in building the machine and trying to get it going. But Van de Graaff never did much in teaching courses or trying to attract students. It was just mostly a question of getting apparatus built. Van de Graaff never personally cared much about doing a thing with this machine. He just wanted to build it.

Weiner:

You would say he was interested in the engineering end of physics rather than in physics itself?

Slater:

I would say so, yes.

Weiner:

More engineering than physics?

Slater:

No, I think he wanted to get a machine that could be used for all kinds of purposes. But he showed very little interest in actually making use of it.

Weiner:

Well, would you take a look at the subsequent developments then? First of all, he came back to the campus.

Slater:

He came back to the campus because the Round Hill proposition sort of evaporated. Colonel Green died, as I remember it, and it didnít seem particularly worthwhile to try to continue working out there. And in the meantime, the vacuum-insulated generator had been developed, and you didnít need the enormous space that we needed for the one that we had at Round Hill. So when money was got for building (and this money came from Rockefeller, as I remember it) a vacuum-insulated generator, everybody decided that had better be done right on the campus. And naturally Van de Graaff came back along with that.

Slater:

I wasnít involved in getting that. No, Van de Graaff and Compton between them got that.

Weiner:

Did things change when he came back to the campus?

Slater:

I wouldnít say so.

Weiner:

You said he was pretty much isolated.

Slater:

He was pretty much isolated.

Weiner:

When did the decision to build the cyclotron come about, and was that regarded in a sense as a way of being more up to dateÖ?

Slater:

That was done essentially at Robley Evansís suggestion. Evans felt that we really needed to have a source of radioactive isotopes and so on and of the things that one would do with a cyclotron. So he started agitating for that a year or two before we managed to get Livingston to come and to get the funds for building the cyclotron.

Weiner:

Do you recall the circumstances of it—of how he initiated this and with whom the idea of the need for the cyclotron was discussed, the arguments he might have used for it, and how people in the department, including yourself, reacted at first?

Slater:

Well, his work was largely with radioactive tracers and that kind of thing. And he just made a persuasive argument for feeling that we had to be able to produce these things, and the cyclotron was the most practical way to do it. I agreed completely with him, and I think everybody else did. It seemed like very good sense.

Weiner:

It seems to me the most ominous thing about it would be the need for support and the fact that this is a larger scale of physics than had previously been employed, even at MIT.

Slater:

Yes, but a cyclotron that size didnít have a very big requirement for support or a very big staff.

Weiner:

It was the 42 inch that was decided onÖ

Slater:

That was the second one, wasnít it? Wasnít the first one smaller? No, I guess that was the one that he built first. No, this took support. Here again I didnít have to do the money raising myself; it was between Compton and Evans. They managed to get the support they needed for it.

Weiner:

You feel that this was astir about a year before Livingston came. In other words, the project had been defined and approved.

Slater:

The project had been defined; we knew what we wanted; we knew that we needed a man; we needed enough money to build the thing. And we needed to be able to operate it. So this was a development out of Evansís ďradioactivity center,Ē as he called it. And there again Compton backed us up and helped out with the fundraising.

Weiner:

Had anyone else been working on radioactivity prior to Evansís coming in 1934?

Slater:

No, not as far as I remember.

Weiner:

You hired him.

Slater:

We hired him.

Weiner:

Do you recall why? Why did you want him?

Slater:

Well, we thought this was a coming field, that we couldnít afford not to be interested in nuclear structure and things related to it. And we did a considerable amount of writing around the country to find who the promising people were, and remember a very laudatory letter from Robert Millikan about Evans, and that appealed to me and to Compton more than the letters we heard about other people. So we hired him.

Weiner:

I see. Now, what were your expectations of what nuclear physics or radioactivity research at MIT would be? The reason Iím asking this is because their work, Evansís work, was rather specialized.

Slater:

Very specialized.

Weiner:

It was certainly applied, and it seems to me in looking through the papers of the period that there was relatively little concern with nuclear theory and with the structure of the nucleus in terms of some of the more fundamental work.

Slater:

Thatís right. This is true. Well, I think that our point of view was that here was a good man and weíd let him develop in the direction he wanted to develop in. I think when we got Livingston in as well as Evans, we felt that broadened out the basis, because Livingston was somewhat more interested in the fundamentals as well as interested in cyclotron construction. So between the two, plus other younger people that we had in there, we felt that we were representing the different aspects of it well enough. I suppose that the fact that I never was personally terribly interested in nuclear theory was one thing that kept us from looking for a straightforward nuclear theorist. I donít think Compton was very much interested in it either. I think we both felt pretty much along the same lines on that—that these were fascinating problems, but we were stronger in the other areas; okay, letís be stronger in the other areas. And also always I had a certain feeling that we wanted to tie our physics interests in with the various engineering aspects at MIT.

See, we havenít said anything about one question that you raised earlier, and that is: what are the interrelations with the other departments and with the developments in different branches of engineering, and so on? [pause in recording] I was starting to say something about the relation of physics to other departments at MIT. There was a long history of the physics originating other branches of applied physics or engineering at MIT. Way back in the l880s, the electrical engineering department grew out of the physics department, and this is one of the earliest electrical engineering departments in the country. There was a group in physics which got interested in these things, and they started giving courses and granting degrees in electrical engineering, and finally they broke off into a separate department. Then in about 1920 the aeronautical engineering sort of developed from physics. E. B. Wilson, who was the head of the physics department then, was of course a mathematician, but he was very much interested in aeronautics and felt that that field ought to be developed, and he started giving some courses in that, and people broke off and made a department. To a large extent the more practical radioactivity work came from physics. We started under Evans and Clark Goodman and Livingston in the l93Os work in applied radioactivity and that kind of thing, which got things going for the present nuclear engineering, nuclear science and so on department—the nuclear engineering department and the nuclear science work.

Acoustics started in physics and spread out from there. There were developments in physics in the practical study of heat and so on which were taken over by mechanical engineering. So that I think we had a very strong feeling that when a part of physics grew to a point where it ought to be developed into engineering, MIT was a good place to do it. I was always on the lookout for places where one could get interrelations between physics and electrical engineering. And, of course, this developed much more after the war than before. These various interdepartmental laboratories were an effort to have joint—what we would now call interdisciplinary laboratories—laboratories between science and engineering. So I felt that this applied radioactivity was an area that we very well could develop at MIT, and it was not being developed very much in other places. Thatís perhaps why we pushed that a little more than the straight nuclear theory.

Weiner:

But the original choice was to get somebody in nuclear physicsÖ

Slater:

To get somebody who seemed like a good man.

Weiner:

The fact that it turned out that he was interested in the applied aspect of itÖ

Slater:

That was his interest rather than our choice.

Weiner:

Right. And that fitted in, as youíve just explained, to a long tradition. So you didnít in a sense feel disappointed, because that, too, was appropriate. With your own theoretical interests, did you have some expectations that the work they were doing would ultimately relate in a very direct way to the development of nuclear theory, which Iím sure you recognized as important?

Slater:

I would have been glad to have seen that happen. They didnít carry this very far. I would say on the whole that in the post-war time, the thing that actually did relate more to nuclear theory was Buechnerís work on nuclear energy levels and so on, because his work, along with the work of Herb at Wisconsin and various other people, really started that field in nuclear spectroscopy—the study of the details of nuclear energy levels. Of course, after the war Weisskopf was around, and Feshbach and the others were interested in the theory of those things so that I felt that this was a real contribution toward nuclear theory. I would have been glad to have seen this happen earlier. I felt that we were really dragging our feet on the application of the Van de Graaff machine on account of Van de Graaffís lack of interest in it. And was anxious all along to see that getting to the point where one would be getting real nuclear spectroscopy going, but it took really practically until the end of the war before we could make much progress in it. But that was the direction that I thought was a good one to travel in. And think it turned out to be a good one. In other words, all this study of nuclear multiplets and that kind of thing, which in turn led to all the study of parity and the quantum numbers that come into the nucleus, etc., were very similar applied to nuclear theory to what Iíd done years before applied to multiplet theory in atomic spectra. So naturally was interested in seeing these things develop. But felt that the first step had to be getting the experimental work in shape. And thatís one reason why I always was anxious to push the use of the Van de Graaff machine, which seemed to be a good device for measuring nuclear energy levels. So it was mostly a question of timing and not of lack of interest in such problems.

Weiner:

Well, then the war came.

Slater:

The war came in, and of course we couldnít do a thing for 10 years then.

Weiner:

Letís get back for a minute to solid state. In your own work itís very interesting to see the trends, where you worked, say, in atomic physics from 1929 and earlier—in other words, the application of quantum theory to the atom, letís say, and you were doing this from 1929 to Ď31 approximately. It sort of spans this transition to MIT. And then in 1933 you turn to solid state-in Ď33-í34 were the review papers, which you hadnít, at least visibly, from what I can see, done much on since 1929 since your work on metals.

Slater:

Well, there was a paper in 1930 on what I called ďCohesion in Monovalent Metals,Ē I think it was.

Weiner:

Thatís what meant. It was work that was done perhaps around that time.

Slater:

Thatís right.

Weiner:

Iím curious about this transition from the application of quantum theory to atoms and then deciding, as you indicated, think, in this interview with Kuhn, to colonize the field of molecules—the quantum theory of molecules—and then getting off from that into the solid state from about l934 on.

Slater:

Well, of course, Iíd been interested in the solid state before I was interested in the atoms and molecules. I did my thesis with Bridgman in solids and was very anxious to get back into that as soon as thought one could in a practical way. But when it came to applying wave mechanics to the problem, I felt we couldnít get anywhere until we could really solve essentially a self-consistent field for a crystal. And the self-consistent field for atoms developed with Hartreeís work and so on, which I was following very closely. The thing that really opened up the field of the solids was the Wigner-Seitz paper in 1933. That gave a really new idea and new direction for working in the theory of solids, and I immediately jumped in there, because I saw that one could do things that I had not been able to do before. So thatís what turned me back in that direction. In other words, I saw a way of making real progress, which had not been possible before that paper.

Weiner:

Had you been in touch with them on a personal basis?

Slater:

Oh, very much so.

Weiner:

All along? Because Wigner came in 1930. Seitz was a graduate student shortly after that.

Slater:

Yes. You see (I think mentioned this in the Kuhn interview), we really had very close relations with the physics department at Princeton for quite a number of years after 1930. Compton had been trying to get me to go there in Ď28 and 29, I got to know them then. And we decided, when Compton came to MIT and I came to MIT, that we were going to try to keep good relations not merely with Harvard, because Iíd been at Harvard, but also with Princeton because Compton had been there. So we had little annual visits of the students and faculty from MIT to go down to Princeton. They would come up to MIT and so on. We really knew them very well. So that not only Wigner and Seitz but Condon and Shortley, and the other people who were around in Princeton in those days, we were very close to. They came to MIT very frequently. Some of them had spent periods with us at MIT. Bardeen, for example, had been at Harvard as a post-doctoral for a while, and then he went to Princeton, etc.

Weiner:

Did you correspond much?

Slater:

Oh, we corresponded a good deal.

Weiner:

Is that included in your files?

Slater:

I donít know how much was actually correspondence and how much talking when we made these visits. But I knew about Wigner and Seitzís stuff before it came out, and I know that I had correspondence with Seitz while he was still a graduate student about details of potentials to use in his problems and things of that kind.

Weiner:

Then their paper and the work leading up to it convinced you that the opportunity was at hand to get back to something that you felt was of deep interest to you.

Slater:

Yes, I felt that we really needed to have some real energy band calculations, which nobody had seen his way to do before that. The work that Bloch and the others, who had been working on energy bands, had done was very oversimplified and artificial; and I didnít think that was going to get us anywhere. Wigner and Seitzís paper also didnít go very far, but I saw in it the machinery for getting the real energy band calculation, which they didnít dig out of their method as rapidly as I did. But I saw how we immediately could start in, and I wrote a paper on energy bands in sodium very promptly after that just to show what one could so.

Weiner:

We should get the timing on that.

Slater:

That paper was 1933, so that it came very Soon after the Wigner-Seitz paper.

Weiner:

You have the ďElectron Theory of Metallic ConductionĒ in Ď33, and then the virial paper comes up in October of Ď33.

Slater:

Thatís a different thing. Thatís not the one Iím talking about, Let me look it up.

Weiner:

There was a June Ď34 paper prior to your review article.

Slater:

I guess thatís the one.

Weiner:

ďElectronic Energy Bands in Metals.Ē This was a Physical Review paper. Thatís the one. The Wigner-Seitz paper wasÖ

Slater:

Yes, thatís the one. ďElectronic Energy Bands in MetalsĒ in Ď34 is what Iím thinking about. It was actually done in Ď33, but it didnít get published until Ď34. And that I got going on before the Wigner-Seitz paper was out, but when Iíd had preprints and that kind of thing. They knew I was doing it. I wasnít trying to get ahead of them. But that gave a real start to things, and from that point on we were able to have a number of graduate students working with me on it and got results that still have a great deal of sense in them.

Weiner:

How did it happen that you did the review article for Review of Modern Physics?

Slater:

They asked me to.

Weiner:

Who was editor then?

Slater:

John Tate.

Weiner:

Thatís right. He had just started in 1929, He asked you toÖ

Slater:

Yes, he asked me to prepare such an article.

Weiner:

What did you have to do to do that? It seems to me that it was a fantastic review of what was going on.

Slater:

I had to do a lot of work. That was the first time Iíd really set up a bibliography, for example. But was already pretty familiar with it. In other words, it did not lead me into things which I wasnít working on. But it allowed me to bring together a lot of things that I felt needed to be brought together.

Weiner:

Did you learn something from it?

Slater:

I would say so, yes. I always do whenever I write a paper. I know a good deal more when I get through than I did when I started.

Weiner:

Well, I was thinking that it was a very fortuitous circumstance. Here is your renewed interest in the subject. Well, your interest had been there, but the opportunity to do something about the interest was revived, and then the invitation came to write a paper shortly after that. Why do you think he selected you to do it?

Slater:

Well, guess that he knew that Iíd been working in the field.

Weiner:

Was it a consequence, do you think, of the paper that you had published earlier?

Slater:

I think probably.

Weiner:

I guess the timing is important here.

Slater:

I donít know.

Weiner:

JuneÖ

Slater:

No, the paper that I had published had not reached him at the time that he asked me to write that thing, Iím sure.

Weiner:

Well, the Reviews of Modern Physics paper was October of Ď34, and then Phys. Rev. paper was June.

Slater:

Yes.

Weiner:

When did you work on the review article?

Slater:

worked on that during that summer, the summer of Ď34-late spring and summer, And already had talked at Physical Society meetings and so on about some of this work; so thatís probably where he knew that was working on it. And I donít know whom he asked for advice. He may well have asked the Princeton people or something like that, and they suggested that was set up to do it. Of course, it was a help to be asked to do that, but I donít think it made a tremendous difference. I think that probably I had decided about then that it was a good idea to write such a review article anyway, and I accepted because it fitted in with what I was interested in doing.

Weiner:

Did you perceive any very important major qualitative change in the field of solid state—other than the particular subject that you were interested in? You saw the opportunity in your own work to get back to it. But did you see this as a larger development that would in fact open up what people would term a new field or a renewed field?

Slater:

Iím inclined to think I did. I had been wanting to get back to this ever since quantum mechanics came in. This was the area that wanted to work in, because I thought that there were tremendous numbers of things to be done in it. So the reason why I was doing atoms and molecules was not so much I wasnít interested in the solids, but felt that one had to solve some of the problems in these simpler systems before one could hope to do them in something as complicated as a crystal, so the atomic molecular papers were largely preparation for getting back into the solid state area. And by Ď34 I felt that the time had come when I could so this. You see, the whole theory of semi-conductors and so on was in pretty good shape by then. That was Ď30, Ď31, Ď32, A. H. Wilson and various other people, R. H. Fowler and so on, were writing papers on this; and I felt that the point had been reached where one could put things down in a fairly consecutive kind of way. Also, I was working then already on getting ready this series of books that Iím still working on. In other words, the first one, Introduction to Theoretical Physics, had already come out. I had done some work on quantum theory, including a little bit on solids, in there; and I had every intention of going on and doing that in a more elaborate way as time went on. So I have always used review articles as a way of trying out ideas that I would later incorporate into books. And this review article was, I guess, the first of those that I wrote.

Weiner:

Do you think that others (that you recall) felt the same way about this time, in Ď33 and Ď34—that in fact this was the opening up of a new field?

Slater:

I think so.

Weiner:

Whom would you cite? Wigner and Seitz obviously, butÖ

Slater:

Well, Iíve already quoted to you Bill Shockley, who was giving a colloquium in 1933 and did his degree in Ď35 or Ď36, He certainly felt this very strongly.

Weiner:

Were there any institutions where you felt that this took root pretty strongly right at that time? Certainly at MIT, and you can attribute it to your own interests, and the fact that there were students willing to go along with you.

Slater:

Well, I would say the other one was Princeton, with Wigner and Condon and I guess Bardeen was around then. If he wasnít there at that moment, he had been. I think he was there.

Weiner:

And Herring was also.

Slater:

And Herring was there. But the time I had spent several months at Princeton in Ď37, they were very much interested in these things. But I would say that those two places and Harvard, too, were very much interested. You see, Van Vleck had come back to Harvard by then. He was interested in the magnetic things but also interested in the more general solid-state work. At Harvard Bardeen had been earlier, and Harvey Brooks was getting his degree at Harvard in the late l930ís—a number of other people were around, Malcolm Hebb and so on.

Weiner:

I was concerned mostly with this period around Ď33-Ď34, when there was a recognition that something new has opened up. Let me ask this: was there any sense of excitement about it?

Slater:

Well, there certainly was as far as I was concerned. In other words, I was trying to get all the students I could working on this, because I felt here is a fine new field which is bound to develop into all kinds of results. I didnít have very many students, but the few that I could get together I gave a certain sense of excitement to.

Weiner:

Thatís an interesting point about new graduate students coming into the department at MIT. Do you recall the particular interests? Did you see it change? In other words, if you had a group of, say, 10 coming in in a particular year, was there a tendency for them at a certain period to be very excited about solid state or nuclear physics?

Slater:

I donít think that they came in with any very definite ideas as to what they were excited about. I think they mostly decided whom they wanted to work with. I think that was true with most graduate students in those days. Donít you think so?

Mrs. Slater:

I think it still is.

Weiner:

I donít know about the highóenergy fields. I wonder sometimes if thereís not an idea of ďI want to work in particle physics.Ē

Slater:

I think that does go on now.

Mrs. Slater:

Yes, but lots of times without much backup. Thereís not much back of it. Theyíve just accepted something.

Slater:

No, I think theyíre mostly affected by fads. But of course we had a lot of interest in the solid-state things through Nottingham in his electronic work. That was affecting the interests of the graduate students quite a good deal. Nottingham had very many good students. They were interested in electronics of crystals and things of that kind. In fact, people would shift back and forth. Shockley did his thesis with me, but he also did some work with Nottingham while he was around. And I think this tended to give an interaction between the theory and practical things that was quite useful.

Weiner:

That depended pretty much, though, on the willingness of the student to make the link. In other words, the people were there, the faculty was there, but it was up to the student to link these fields.

Slater:

Well, I think we had more adventurous students in those days than one has at present. They werenít governed by fads or anything like that the way students are now.

Weiner:

Well, the department was smaller, too, so people were visible, and there was easier access, Iím sure.

Slater:

Thatís true.

Weiner:

I think that before I get onto more detailed discussion of what you did once the field was reopened for you, Iíd just like to touch on one subject; and that is this transition that you describe as being symbolized in 1933 at the Chicago APS meeting in terms of American physics showing its strength. You made the statement in your published article on this that the program itself was distinguished not only because of the many important European physicists who were there, but because it showed the number of American physicists on the program who were doing first-rate work.

Slater:

Thatís right.

Weiner:

A couple of questions associated with that: Do you feel that there was a particular turning point that you can identify, where it was quite visible that, as Van Vleck has put it, American physics came of age? And do you distinguish between the different fields? Well, certainly experimental and theoretical is one distinction. [pause in recording] Just to remind you: we were talking about this transition, and I asked you when you thought it had occurred, whether it can be identified in that sense; and whether you can analyze the general statement in more specific categories—theories, experiments or various fields-óevaluating the relative strengths and weaknesses from your perception at that time.

Slater:

Well, it was obvious in the first place that there were great advances, going on in the nuclear physics area. The apparatus, the Van de Graaff machine, the cyclotron and so on, were making new possibilities in experimental things—the discovery of the positron, the discovery of the neutron; all these things were showing that there was a great deal more going on in the nucleus than some people had supposed. And there was obviously a lot of progress being made in the theory as well. So that I think that the trend was already clear there then that nuclear and high-energy physics was going to develop into a much more important branch of physics than it had been before. But at the same time, all these applications of quantum mechanics to solids and to chemistry and so on made it clear that there was a great field developing there, too; that latter one perhaps more in the theoretical direction than in the practical direction simply because the experimental work on all the semiconductors and so on had not developed very far then. They had to wait until after the war before that really came through in an experimental way. But I felt very definitely that here were two sides of physics which were becoming differentiated from each other more than they had before, and that both were in for very exciting developments. I think I realized that very thoroughly then. Thatís one of the reasons why we wanted to bring in nuclear people to MIT as well as the more practical and more solid-state ones which we had had before.

Weiner:

Do you feel that the relative position of American Institutions in the field was essentially different than European institutions in regard to those questions you just discussed—in terms of those fields?

Slater:

Well, yes, I would say so. The development of the high-energy experimental techniques—the accelerators and so on—was entirely an American development. The development of the application of quantum mechanics to molecules and solids was almost entirely an American development; so that it seemed to me that the future was on this side of the ocean and not the other side. And donít forget that Hitler had come in, and it was clear that a lot of the European physicists were going to desert and come in this direction. This was just at the beginning of the Hitler situation; the Mussolini situation was already developing; so that it certainly looked like a general breakdown of continental European science and a corresponding buildup for American science.

Weiner:

Where would you say, in terms of the world scene, that the major centers of activity were? I donít mean as they were in the Ď20s, but I mean as they were in, say (if you could take Hitler out of the situation), prior to 1933? Where were the major places? If you wanted, for example, to instruct a graduate student at that time to dip into the places where the action was, whether in the U. S. or abroad, and if you had to compile a list—and Iím not asking you to—but in terms of the places that one should be sure to visit for so and so reasons? How would you characterize them?

Slater:

Well, letís go down the various countries. Iíll take the foreign ones first. In England, certainly Cambridge, but Bristol was building up very well; Manchester was doing good work; Oxford was beginning to get back into its position. So those were all places that were quite active. Then London too. Then in Germany, certainly Gottingen, Munich, Leipzig, Berlin at least were all very active. France was not developing, as much as they have since then. People would go to Paris but it was not very exciting. I think that they were lagging behind. And, of course, the Dutch universities have always been very good; the Swiss universities have always been very good; the Scandinavian ones—Copenhagen, Stockholm, Uppsala, etc. Rome had a good deal going on. So there one has quite a selection of places in Europe, but this is strictly before Hitler. Then in this country, aside from the Cambridge area and Princeton, certainly Chicago, certainly Berkeley, certainly Cornell, of course Michigan. I would say those were probably the strongest ones. But a lot of places were very rapidly developing.

Weiner:

How about in the area of theory? Would it be a fair distinction to make—I mean is it a realistic question for me to ask? Would you have answered differently if I said to send someone in search of institutions where they could prepare themselves very well for work in theoretical physics?

Slater:

This wouldnít change very much. Of course, I forgot to mention Caltech. Certainly Berkeley and Caltech between them were doing remarkable things in the days when Oppenheimer was oscillating back and forth between the two and so on. No, I would say that they were the same ones.

Weiner:

The change that you felt had taken place in U. S. physics by 1933ó-you identified some symptoms of it: what do you feel the weaknesses were of U. S. physics? What could have been developed further at that time—I mean, it was developing rapidly; there was a large institutional base, there was first-class work done by a large number of people, but also there was a certain tradition, and perhaps there were weaknesses in work in this country that you felt.

Slater:

I think there was somewhat too much feeling in many places that the only good physics is experimental physics. It took a fairly long time for people to accept theory as well as they do now.

Weiner:

Even in the 3Os?

Slater:

Even in the 3Os I would say there was some feeling of that kind. Donít you think so?

Mrs. Slater:

I think so very definitely.

Weiner:

When you say people, do you mean people making decisions on hiring of faculty?

Slater:

I think so.

Mrs. Slater:

Who were setting up Ph.D. requirements and that sort of thing.

Slater:

Many of the old-line faculty members were definitely experimentalists who had very little use for theory, and there were fairly few institutions that were pushing theory at full speed as Harvard and MIT and Chicago and Berkeley and Pasadena and Ann Arbor were doing. But even at Chicago you found that there was quite a good deal of preference for experimental physics rather than theoretical physics.

Mrs. Slater:

Yes, but then, of course, they were following in the footsteps of Michelson and Millikan. They were the traditional people then, and there was not too much theory going, and graduate students werenít required to take a lot, compared to what was done, say, just after the war when these things were revised at Chicago, for instance, and a great deal more theory was put in as a requirement for the doctorate.

Slater:

I think that at Chicago, Arthur Compton was the moving spirit in putting more emphasis on theory. Donít you think so?

Mrs. Slater:

Yes.

Weiner:

get the feeling that those, on the other hand, who were trained as theorists in the U. S. got a great deal more experimental work than people in Europe.

Slater:

Oh, they did.

Mrs. Slater:

They were physicists, not mathematicians.

Slater:

In Europe theory was always regarded as something quite different from experiment, and a theoretical physicist was not trained very much in experimental physics. This was never the case in this country.

Weiner:

Did you get to Europe again in the Ď30s?

Slater:

Several times.

Weiner:

Under what circumstances?

Slater:

This was not to stay for any period, but I went to several scientific meetings. I was there in Ď32. I was there in Ď34. I was at one of the early meetings of the Union of Physics in 1934.

Weiner:

The London meeting where there was a joint program on nuclear physics and on solidóstate physics?

Slater:

Thatís right. I was at that meeting. That was the one where dislocations first came on the scene. There were a lot of interesting things then. As I remember it, there was some other conference that was sort of in connection with that. Iíd have to look up the records to remind myself of just where went. But those two times I was in Europe. I guess those were the last times before the war.

Weiner:

In Ď34 when you went (which was just at the time when weíve discussed the field of solid-state physics taking root once again) did you detect a change in the approach and the atmosphere and the attitude toward solid state?

Slater:

Oh, yes, very much so.

Weiner:

The meeting itself, I guess, was a symptom of it.

Slater:

The meeting was a symptom of it. But at that same time I visited some laboratories, went to Bristol, for example, and visited. Mott was just getting going then. In fact, I believe it was at that same time that Mott ran a conference at Bristol. Anyway went to a Bristol meeting. And surely the whole emphasis thereóand that university was just getting built upówas on solid state. The general atmosphere was very strongly headed in that direction.

Weiner:

Did people begin to identify themselves as specializing in that field; and, if so, did they use the term ďsolid stateĒ?

Slater:

I donít know if they used the term or not, but they certainly were identifying themselves with it.

Weiner:

In other words, this is someone who is saying, ďIím a nuclear physicistÖĒ or ďIím aÖĒ

Slater:

Oh, no, I think there was a distinction then as there is now.

Weiner:

Well, the program of the London meeting was divided into ďaĒ and ďbĒ—solid state and nuclear physics. And there are some letters from Joe Mayer, I guess, who was there or perhaps Spedding. He was writing to G. N. Lewis, and attended both. Of course, as a student of G. N. Lewis, heíd be interested in everything. He attended chemistry meetings and everything else, and he detected that this was a very important period. Letís get back to what I opened up with, and that is your own work in solid state in Ď33-í34. Iíd like to ask first about the review articleówhat you expected it to accomplish and in fact what it did accomplish in terms of reactions of others and its effect on the developing field of solid state.

Slater:

I donít think had any great expectations one way or the other. I was getting a number of students started in this area, and Iíve always felt that one of the advantages of writing an articleóparticularly a review article—was that there was something I could ask the students to read and learn the general trend of things. So that I was more interested in my own students than was in its effect in other places. I donít think it had any tremendous amount of effect in other places. I donít think people paid very much attention to it.

Weiner:

Well, you did indicate that some of the things in it are becoming useful today.

Slater:

Thatís right, was convinced that they would be, but people as a rule are very set in their ways; and if things come along that are not in the lines that they are thinking on, they just donít even bother to read it.

Weiner:

Were the problems that you faced in working on molecules and then in solids analogous to the problems that you were tackling earlier in atoms?

Slater:

Oh, yesóvery closely analogous. I was using practically the same techniques on them.

Weiner:

Did you see your work as an extension of the earlier work?

Slater:

Oh, yes.

Weiner:

In other words, it was sort of a continuum.

Slater:

Absolutely. No, the earlier work I felt was sort of preparation for doing the work on solids. And, as I say, the mathematical techniques I was using were practically identical.

Weiner:

And yet you felt that during that period—letís say prior to l934—your work was not in the mainstream. Youíve explained it before in a sense. ďMainstreamĒ meaning that perhaps not too many people were taking the same approach or were interested in the same problems.

Slater:

Yes. They essentially paid no attention to this.

Weiner:

You did what you wanted to do. I wanted to pursue the next set of papers that you did after 1934. That relates to the Thomas-Fermi paperóďThe Thomas-Fermi Method for MetalsĒ in Ď35. Hereís where you apply the Wigner-Seitz methods.

Slater:

That was one of the places.

Weiner:

Right. Youíd applied it earlier in two papers.

Slater:

Thatís right. And a number of my students were applying it through the whole period of the rest of the Ď30s.

Weiner:

How did Krutter fit into this?

Slater:

He was a graduate student. This was essentially his thesis, which we worked on a good deal together, and he didnít stay with that field, but he did some nice work for his thesis. And then Millard Manning and Jacob Millman were two people who worked in that field. Manning was quite active then. He did a lot of work both on atoms and on crystals. He unfortunately died during the war. That was the end of his career. Millman started in with me, but he turned into an electrical engineer and is a very successful professor of electrical engineering now. A number of my students from that period went into electrical engineering, or into applied physics. Marvin Chodorow, who worked with me just before the war, is now head of applied physics at Stanford, for example.

Weiner:

They had worked with you on solid-state problems.

Slater:

They worked with me on solid-state problems. Dick Feynman did his bachelorís thesis with me on solid state. Of course, he didnít stay in that area.

Weiner:

He, I guess, has returned occasionally to areas where thereís a challenging problem that fits in with his abilities or interests.

Slater:

He occasionally does.

Weiner:

You mentioned in this paper that I started to mention-óthe Fermi Metal paper—that for the first time the theory of ferromagnetism has advanced far enough to make one fairly sure of its correctness But why had there been doubts about the correctness of existing theory?

Slater:

Well, the existing theory was based entirely on Heisenbergís work. This was never able to predict why one material should be ferromagnetic and another one shouldnít. Itís just not the right way to go about ferromagnetism. But Heisenberg and Dirac and Van Vleck had so completely dominated the field that this was the only thing that people were ever taught about magnetism, and to a very considerable extent itís still the case. In other words, Iím still fighting that battle.

Weiner:

At that time was there something which it did predict which could not be verified? It seems to me that there are only two objections to a theory. One is an inability to predict something, to give you an answer thatís needed; and another is to give you an explanation for which there is no way of checking.

Slater:

The Heisenberg theory predicted a great many things, but none of this could be calculated in an a priori way. You had to put in empirical numbers to make the thing work. But it did so much that the people that were interested in it, just werenít interested in going any further. They just closed their eyes to the fact that fundamentally you couldnít start with wave mechanics and come up with the results that they were talking about.

Weiner:

That explains to me, I think, a difference in your style and perhaps those of some other people during the period, that is why you pick up the problem in the first place. Your interest in the metal, for example, was perhaps quite different than the othersí interest in the metal.

Slater:

I think thatís right.

Weiner:

And so you were asking different questions about the sameÖ

Slater:

I was never satisfied with any theory that didnít come out of the fundamental principles of quantum mechanics perfectly straightforwardly, and I still stick to that point of view; whereas a great many people were willing to make what they would call models, put in something that would look plausible, out of which you could get formulas that would describe the facts, but where you could not derive this model from fundamental theory. I felt here we had a fundamental theory as a challenge to be able to explain everything we see around us in terms of that fundamental theory. So Iíve always discarded anything that didnít fit into that.

Weiner:

[Question is lost as tape is turned over]

Slater:

I feel that my personal work during the period from Ď34 to the beginning of the war was almost entirely devoted to trying to work out the theory of solids based on wave mechanics. In other words, how can we apply it to more and more problems? And many of these were problems that other people werenít feeling particularly. They werenít working in the same area. But they were mostly things that have turned out to be a start of a great deal of work since then.

Weiner:

It seems to me that solid state as a field is very difficult to define. I feel that itís an umbrella kind of a thing, rather than the straightforward thing like nuclear physics where thereís a particular thing to focus on. You identified the theme in your own work. What other themes do you think were developing during that period which were dominant themes? What other kinds of pursuits do you think contributed to what we now call solid state that would fit into this period before the war—from about Ď34 to Ď40?

Slater:

Well, of course, one field that was very popular starting with 1934 was the study of the dislocations and other things that keep a crystal from being a perfect crystal. I was feeling all along that that was an important thing but probably not as important as the enthusiasts were thinking at the time. But it meant that one wanted to study a crystal with an irregularity in it of some kind as well as a perfect crystal. Well, by the time you get crystals with irregularities, you can lead to almost anything involving solids. Some of my work—in fact, quite a bit of it thenó-was really using that idea. For instance, the Ď36 and Ď37 work, partly with Shockley and partly my own, on excitons, absorption of light by crystals and so on, and also, some of the magnetic work were using the ideas of irregularities in crystals. The whole theory was built up on that basis. Thereís work that Iíve done since the war, some of which has never been published, and Iím even resurrecting some of that now, along those general lines. But I felt that one had to understand the perfect crystals first before you could get the starting point for doing the crystals with imperfections.

Weiner:

So this was going on in parallel.

Slater:

That was going on in parallel, and, as I say, there was a great deal of interest among physicists in these imperfections, dislocations, how they affected plasticity and many practical problems; so that, for example, Fred Seitz was spending almost all his time on irregularities in crystals—the ďFĒ centers and alkali halides and that kind of thing Mott was spending almost all of his time on it. I felt I didnít want to go into that completely, but there were many problems relating to the perfect crystal that had to be cleared up before one could handle the imperfections properly.

Weiner:

Were there any other approaches that were developing in parallel during this period?

Slater:

Well, I donít quite know how to answer this, because Iíve always regarded the whole field as a unified field in which I wouldnít think about different approaches. Iíve been interested, and other people have been interested, in different kinds of problems, butÖ

Weiner:

Thatís what really mean—clusters of problems that people would tackle because of their special interests. In other words, there are people who would focus on theÖ

Slater:

Well, for example, John Bardeen was very much interested in electrical conductivity, and Shockley worked in that some and so on. Various people did. This is inherently an interesting question, but I never was very much interested in spending too much time myself on the details of electrical conductivity, thermal conductivity, the things one called transport phenomena. I felt that these were not the places where you were going to learn very much new theory; that you were going to apply things in a sort of a practical way. But I preferred to work in areas that brought one closer to places where I thought we didnít understand even the fundamentals. And I felt that magnetism was one of those. Of course, I was interested in superconductivity—everybody was. I still donít think superconductivity is all settled. But that was one of the things that concerned people. But nobody really got to the bottom of it in those days, and maybe not yet.

Weiner:

May I ask a final question, which might serve as a transition for some other talking some time in the future? When the war came your work was interrupted. I donít want to go into that now, because that is a whole separate story. But when the war was over, did you pick up the same theme? That is, when you were able to get backÖ

Slater:

I picked it up but not immediately. I wasnít sure for several years after the war whether to go back into exactly the same things or whether to go into the electronic area that Iíd been working in, because I saw that there were a lot of interesting things that probably would be coming along in the electronic fieldó-also in the low-temperature field, which we were working in. So for a period until about 1951, I worked more in the microwaves and the electronics than I did in solid state. I could have been pushed very easily one way or the other into going on with that field or even going into the accelerator field and so on—I played with that some—or going back into solids. We had quite a nice laboratory going for a number of years at MIT which I was running. I was doing some experimental work then for a while on microwave applications at low temperatures and high frequencies applying to solids. We got many things going.

Weiner:

Thatís another whole story.

Slater:

Thatís another whole story. We had a laboratory there for a few years at which most of the present experts on solid states and microwaves were on hand for a while. So I could have gone in various different directions. And it was actually about 1951 that I decided that Iíd better go back to the same field Iíd been in before. I got interested in it to some extent through seeing what was going on in semiconductor theory and that kind of thing. This was still before Shockley and Bardeen had come up with the transistor. But I then decided that I would organize a research group, picking up where we had left off, but trying to do what I had never been able to do before the war, and that is to have a large enough group so that I would be able to keep continuity in it. With these preówar students—Iíd have to teach each individual one from the beginning. And I felt if I could get a larger group, people would just pick up by association with the other students many of the things that otherwise I would have to teach them individually.

Weiner:

It also had to do with the amount of time you had available.

Slater:

Thatís right. I could hardly have done that while I was still running the physics department. I started that about the time that I stopped running the physics department, although actually I had it going before that, but not very successfully.

Weiner:

I said that was the final question, but I have another final question, and another one, but I had better stop.

Session I | Session II