Linus Pauling Interview, August 20, 1991

THOMAS HAGER: Telephone interview with Linus Pauling, August 20.

LINUS PAULING: Hello?

TH: Hello, Linus.

LP: Yes.

TH: This is Tom Hager.

LP: Yes, Tom.

TH: Hi. Listen, are you settled in? Is now a good time?

LP: Surely.

TH: Good, good. Well, that's great. I've got a few questions for you, about five pages worth, but I don't suppose we'll get through them all today. I wanted to check with you a little bit about the period around-

LP: Just a moment. Someone's... [inaudible]. All right, go ahead.

TH: Okay. I wanted to talk with you about the period when you returned from Europe after your fellowship and came back to Caltech and make sure that I have the right chronology of events there in the late twenties and earlies thirties. You came back from your fellowship, from your Guggenheim in nineteen twenty... let's see what I got down... 1928?

LP: No, 1927.

TH: Nineteen twenty-seven, okay. And then when you came back, were you assured of a position at Caltech upon your return? How was it arranged for your-

LP: Well, in perhaps around June, I'm not sure when, I had a letter from 00:02:00California Institute of Technology. I think A. A. Noyes offering me an appointment as Assistant Professor of Physical Chemistry and Theoretical, or I guess Mathematical Physics. Physical Chemistry and Mathematical Physics. I don't remember the salary. Possibly $3,000, but I don't know. I'm not sure. Maybe less. And so, I wrote accepting the offer, so I did have a job.

TH: And this was while you were in Europe?

LP: Well, yes. That was in Munich. So, I'm pretty sure I remember that we were in Munich, and since we left Munich... in April, it may have been that early. 00:03:00But I'm not sure. But sometime, spring or summer, I had that offer of that job.

TH: And that, as far as you were concerned at that point in time, were there any other options open to you that you were considering?

LP: No. No, I think I just assumed that I'd be going back to Caltech. You see, they had given me $1,500 I think it was, $1,000 or $1,500 when we left in February of 1926 because I didn't have a Guggenheim Fellowship yet [laughs]. And 00:04:00you know, it's well-known apparently, now been published several times, that this was a device that A. A. Noyes resorted to, to keep me from going to Berkeley.

TH: From the clutches of G. N. Lewis.

LP: Yes.

TH: [Laughs].

LP: I had put down- as a National Research Council Fellow, I was supposed to move, and I had put down that I would go to Berkeley. But Noyes, well I think you know the story.

TH: Yeah, yeah.

LP: Noyes told me that I'd better stay long enough to finish up the work I had done for publication, and then he told me that he thought - and this was along about December - he thought it would be better for me not to move because I 00:05:00could go to Europe on my Guggenheim Fellowship and that he was sure that I would get it. In fact, I think the Guggenheim Foundation probably told him that there was no doubt that I would get the Fellowship. Just a moment. Well, that's all right. There. No doubt that I'd get the Fellowship.

TH: Uh-huh. And that was awarded after you had already arrived in Europe, though. You had the money [inaudible].

LP: Yes, and the word came about the end of April.

TH: Yeah. So, when you came back to Caltech, you were set up with your own laboratory space then, and you said that the first title was Physical Chemistry and Mathematical Physics, but it didn't turn out that way, did it?

LP: [Laughs] no. No, and I don't remember how I learned that I wasn't to have 00:06:00that title. And I think that Noyes probably overruled Millikan and just said that I was to be Assistant Professor of Physical Chemistry. And later, two or three years later, I said I didn't want to be called Assistant or Associate Professor of Physical Chemistry, but rather of Chemistry, because I thought what I was doing was not just Physical Chemistry. I called it Structural Chemistry, but I was applying it- well, you know that book, From Ostwald to Pauling.

TH: Yes, Yes.

LP: He tells, or states, that I was trying to unify the whole science of 00:07:00chemistry, or was succeeding, whether I was trying or not.

TH: Uh-huh. Now, in terms of the research interest that you had-

LP: Well no, I haven't answered your question about the laboratory.

TH: Yeah.

LP: Dickinson had gone to Europe. That was I think 1925, before I left for Europe myself, and he decided, I judge, that he would give up X-ray crystallography and turn it over to me. Well, Noyes probably made the decision. 00:08:00So, I was, when I got back in 1927, I was in charge of the X-ray laboratory. So, I had laboratory space and office space that I hadn't had before, and that Dickinson had had. And I guess the annex, the central section of the Gates Laboratory had been built by that time, so there was some extra laboratory office space. It was a rather small section where the library, chemistry library used to be in. So, I had laboratory space and I had graduate students, or at least one immediately. I had had one or two even before my Guggenheim Fellowship.

TH: Who was your first graduate student when you returned?

LP: Sturdivant. Sturdivant was my first. He was the first person to take a Ph.D. in which all of his work was done with me. Or, Sterling Hendricks had started with Dickinson and then continued with me when Dickinson went to Europe. So, sometimes I say Sterling Hendricks. Sterling Hendricks was my first graduate student, but Sturdivant was the one that I took on in 1927, fresh from Texas, and supervised until he got his Ph.D.

TH: Where was your first office? When you came back, I assume that you were assigned your first professorial office.

LP: Well... it was in the corner of the X-ray lab in the basement of Gates. It wasn't a separate room. It was just my desk in the corner. And X-ray apparatus. This was a big room, 30 feet square or something like that, and later it became the student shop for the Chemistry Department after I moved to the Astrophysics 00:11:00building, moved my laboratory space to the Astrophysics building.

TH: And what year was that? That was in the early thirties, right?

LP: Yes. It was '31, perhaps. I think I may have had a room in the basement of Gates as my office for a while. Perhaps from 1929 on, for a couple of years, instead of being just in the corner of the X-ray lab.

TH: Fairly modest circumstances, though.

LP: Well, yes. Well, the research was modest in those days. Not a- no billion-dollar activity.

TH: Yeah. Where did you and Ava Helen live when you returned from your Fellowship?

LP: We rented a house at 320 South Wilson. And it's still there. That's only a 00:12:00couple blocks north of the campus, or was then, and it's just adjacent, the next block from, say, the Beckman Laboratory, along there. Yeah, 320 South Wilson.

TH: So, it was you and Ava Helen and Linus Jr.

LP: Yes. We lived there until 1930 when we went to Europe the second time.

TH: Tell me, during this interim period between your two European trips, how you divided your, or how you coordinated your theoretical interests, the chemical bond work on a theoretical level, and your experimental work on crystallography, 00:13:00and pinning down crystal structures. How interdependent were those two lines of research?

LP: Well, they were pretty independent, I think. In my theoretical work, which was mainly on molecular structure and crystal structure, I made use of values of interatomic distances that had been determined by X-ray crystallography. Not just my own; other peoples'. And in the laboratory, the X-ray laboratory, I and my students were studying minerals and inorganic substances that seemed 00:14:00interesting to me; that seemed- well, not the ones where I was sure that I knew what the structures were even before starting, but substances that puzzled me a bit. And of course, you know I've always- I was in the habit quite early of reading all of the X-ray literature and asking myself whether I believed what the authors said. Or if the authors didn't finish the job, whether I could finish the job. So, a number of my earlier papers were on structures where I didn't need to gather any data. Sometimes it was- but used the X-ray data that 00:15:00other people had published.

TH: I see.

LP: But if it was possible for me to get crystals without too much difficulty, often I got the crystals and repeated the experiments, or extended them, that other people had published. Have you seen the paper that was published about a year ago by me in The Clay Minerals Society magazine?

TH: No, I haven't. In which magazine was this?

LP: Well, the... the publication which is... a sort of newsletter of the Clay Minerals Society.

TH: Oh, okay.

LP: And Mrs. Munro can send a copy to you. She's on vacation this week.

TH: That's fine. I'll ask her.

LP: Next week she can send you a copy. They asked me if I would publish, would write an account of the discovery of the structures of the clay minerals.

TH: I see.

LP: I did that job 1929, 1930, published two papers in 1930. One of them with the title mica, "Structure of Mica," and the other was the structure of the chlorides. But mica and the chlorides are closely related to the clay minerals.

TH: Yes.

LP: Mica can be hydrated and produce clay minerals, or deionized in a sense. So, in these papers, I also discussed the structure of kaolin, kaolinite, and talc [?], and apophyllite and other clay minerals, montmorillonite, and so on. I 00:17:00didn't include them in the title, but I did discuss these structures. So, I'm going to say I was looking for things to do. Reading the literature, I came across a paper by Mauguin, I think, M-A-U-G-U-I-N, in Paris who had made X-ray photographs of mica and gave the dimensions of the unit that he found. And I thought well, I ought to be able to determine the structure of mica. So, I got a nice crystal in one form of mica float and made my own x-ray photographs of it and worked out the structure and published it. And then I went onto the 00:18:00chlorites - somewhat more complicated - and did the same thing the same year I finished the chloride work. I guess I read the proof while I was in Manchester, the spring of 1930.

TH: Yeah, yeah.

LP: So, in this case, Mauguin was not able to determine the structure. He published his observations on- published the X-ray pattern, and I was able because of my having made use of the stochastic method, or of the coordination theory of silicates and so on. But I did, I published quite a number of papers that had been suggested on substances, inorganic compounds, as a result of my 00:19:00reading what somebody else had done. Sometimes making mistakes, sometimes not able to finish the thought.

TH: Now, when you-

LP: By the way, there's a book coming out edited in Yugoslavia, with quite a number of articles in it, one by me on the chemical bond, a festschrift. Another 90th birthday festschrift. And Verner Schomaker and Dick Marsh- well no, I think it was your author, or Dick Marsh, I guess - wrote an article, about 30 typewritten pages, on my early crystallographic work.

TH: Oh, okay. That's good to know.

LP: It's, I thought, pretty interesting analysis. I didn't find anything wrong with it. They read all of these early X-ray papers that I wrote and discuss and comment on them.

TH: So, this was Schomaker and Marsh?

LP: Yes.

TH: Yeah, okay.

LP: I suppose maybe a couple months or more before that book is available.

TH: Yeah. I might be able to talk them out of a manuscript if I'm nice.

LP: They sent me a copy, but I don't know where it is. I-

TH: Um- no, I'm sorry, go ahead.

LP: Well, so as I say, their comments on the significance of my early crystallographic work I found pretty interesting. I sure do find them, these 00:21:00comments, interesting.

TH: Yeah, yeah. No, I'll get in touch. You were still performing experimental work yourself. You didn't delegate all of this crystallographic work to your graduate students or postdoctoral fellows.

LP: Well, when are- what period is-

TH: Well, let's talk again about the period between your European trips.

LP: Well, I got an assistant along about '29 or '30, Weinbaum.

TH: Oh, yes. Yes, yes.

LP: Sidney. Sidney Weinbaum. And he was more interested in music, piano playing, and chess - Southern California champion - than in science. He didn't have the sort of curiosity and devotion to science that I had. And when he graduated, I 00:22:00suppose got his bachelor's degree, he didn't have a job, and I gave him a job. The institute put up the money. So, much of the work, X-ray work that I did then, I got some crystals and minerals and got him to make the X-ray photographs and to measure them and give me the data, and then I would analyze the data.

TH: Oh, okay.

LP: Then, of course, Sturdivant was doing the same thing for me from 1927 on. Well, about that time when I got back in 1927, I can remember my taking X-ray pictures of topaz. I got a big crystal of topaz from Tiffany's in New York.

TH: [Laughs].

LP: After a while, they wrote asking me to send it back, but I took the X-ray pictures and measured them just the way I had from 1922 to 1926, measured them myself, and made the calculations myself. And of course, Ava Helen helped me until Linus was born. So, from 1927 on, occasionally I operated the X-ray procedures myself and measured the photographs myself, but pretty soon it just wasn't sensible for me to put in time doing that, and I would rely on Sidney Weinbaum or on one of my graduate students to do the work in the laboratory.

TH: Yes, yes.

LP: And of course, that continued up until my vitamin C days when I began making experiments myself, measuring vitamin C in my own urine when I didn't have a laboratory. It's when I was at Santa Barbara. But from the time I was about 30 years old on, it was rather [unintelligible] for me to do experiments. Well, during my immunology period we kept the rabbits at our house, our home up on Fairpoint. The breeding rabbits and the immunized rabbits. I injected the immunizing antigens into the rabbits myself, but other people came up and drew blood from the rabbits. I didn't draw the blood myself.

TH: I see. And I assume you didn't do the precipitation reactions or any of that yourself either, then.

LP: I didn't hear.

TH: I assume that you didn't do any of the serological reaction work, any of the precipitation reactions, or anything like that.

LP: No, no. Mainly Pressman, but many other people. There were about 20 people involved altogether in that work. Graduate students, visiting professors, and postdoctoral people [laughs], a whole lot of them.

TH: Now, in 1928 you published your earliest sort of quantum theoretical work on the nature of the chemical bond, a sort of a preliminary paper. And then it was 00:26:001931 when you started publishing the series, correct?

LP: Yes.

TH: Yeah, and during that interim period, you had said previously that you were working out the mathematics more precisely, or more fully, to support your ideas.

LP: Yes. I was trying to find some way of making the calculations more straightforward and understandable. I asked Sturdivant, who had a master's degree in mathematics, if he would attack the problem of the tetrahedral carbon atom, the quantum mechanical problem, and see if he could find some way of making progress that I had overlooked. But he never got anywhere.

TH: I see. Okay.

LP: So finally, in 1930 I thought of the answer, the way to handle it.

TH: And tell me how that came about. Tell me a little bit about how you found that answer.

LP: The... Well, I don't... know. I no longer remember, or perhaps never have clearly in mind, just how my own thinking was developing during the period, 1927, '28 to 1930, the end of 1930. One thing I suggested to Sturdivant, that we should try solving the Schrödinger wave equation using a set of tetrahedral 00:28:00coordinates. That is, could we find a set of coordinates in which the- such that the wave equation could be separated into three differential equations and partial differentials rather than being a combination of all three coordinates. And actually, something of that sort was done by a famous theoretical physicist, Hans Bethe, who discussed the tetrahedral quantization, but perhaps even later than my 1931 paper, I don't remember. At any rate, what- his discussion wasn't 00:29:00very... I'm not sure that I knew about it, but it wasn't closely enough pertinent to be valuable.

One thing I remember is that Slater pointed out that the 2p wave functions in their real form, rather than the complex form with imaginary numbers, could be described as pointing in the three- in directions, the directions of the three Cartesian coordinates, 90 degrees from one another. And I'm not sure that I knew that. I made use of the Z function, but in my earlier work I was trying to 00:30:00hybridize, I guess I would say now, the complex functions in the XY plane. And it hadn't been clear to me that it was only for certain special applications that these complex functions were the important ones, and that the real functions are just as good, or even better for other purposes.

TH: Ah.

LP: So, I think the fact that Slater had published a paper or given a lecture in which he made use of these three equivalent, real functions - not imaginary, or 00:31:00not complex - stimulated me to go back to the calculations I had made and referred to in my 1928 paper, which I had made using the complex functions. The fact that I was using the complex functions and also taking into consideration the fact that the radial functions, before the 2s orbital and the 2p orbitals, are different... was responsible for the difficulties that I had during the period of 1928 to the end of 1930.

So, at some time during 1930, I decided that even though the mathematicians are always happy when the equations involve the square root of minus one [both laugh] when they're dealing with imaginary or complex numbers - they're just hip on that, you know...

TH: [Laughs].

LP: The fact that it wasn't necessary to use these imaginary or complex functions, but that one could handle, deal with just real functions for the wave functions impressed me. And gradually, during 1930, as I recall, I continued trying to attack the problem by making use of the real functions, which I can 00:33:00understand better, visualize better. And then, of course, there was the great idea I had in December 1930, I think - possibly January '31 - the great idea that I could assume that the radial function, or the s orbital and the p, 3p orbitals was the same, as an approximation. And that I then had to deal only with the angular functions. The so-called surface harmonics, or zonal harmonics. Well, surface harmonics that I knew all about, knew how to handle. And that was when great progress was made in just one day.

TH: So what you did was essentially one level of complexity fell away at that point.

LP: That's right. From being and requiring very complex mathematical calculations involving complex function, or involving real function - they were still very complex - the problem became quite a simple one, from a mathematical point of view. So simple that- well, just very simple. And I knew enough mathematics, of course, to be able to handle the problem with ease.

TH: Now, tell me again the great idea in your own words, again, was to assume that the equivalents of - or for practical purposes, for approximate purposes - the equivalents of the s orbital?

LP: Well, to assume that the dependents on the radius, the distance of the electron from the nucleus, was closely enough the same for the 2s orbital of carbon and the 2p orbital that I could take it as the same, as an approximation. And of course, it's turned out to be a very good approximation. So, that was the main point. The main idea that I had in late 1930. That of taking those functions as equal to one another. Of course, it would have been possible to go 00:36:00ahead and apply perturbation theory, in which you introduce a difference between the s and p radial functions as a perturbation. But I never got around to doing that, and just wasn't worthwhile [laughs].

So, this was quite a good approximation. And it applies not only to the carbon atom, the s and p functions, but to the 3s and 3p and 3d functions in the heavier transition metals and so on. That is, this wasn't an assumption made specifically to discuss the tetrahedral carbon atom. It was a general assumption that I could make that simplified the quantum mechanical considerations for 00:37:00essentially all atoms in all compounds. And my 1931 paper contains the most important applications.

TH: Yeah, yeah. The-

LP: And then, of course, I went on to make use of various quantum mechanical principles which were new ideas that hadn't been known in the pre-quantum mechanical days to discuss various other aspects of chemical bonding. Partial ionic character, one-electron and three-electron bonds, electronegativity scale, and so on. They all are based on ideas that come from quantum mechanics. All of these applications to chemistry. And people would have had to be pretty smart in 00:38:00the pre-quantum mechanical days to have recognized any of these principles, and nobody did recognize.

TH: [Laughs] right, right. Would you call- the idea that we just talked about, I'm trying to fit that into the idea of stochastic methodology, and it doesn't seem to me to be a good example of stochastic thinking. The principle, the 2s and 2p equivalence, do you read that-

LP: No, I don't think so. In the early days of quantum mechanics, many quantum mechanical calculations were made by nearly everybody working in the field that were approximations. One would say here I can set up the Schrödinger equation 00:39:00with a complete expression for the potential energy and the kinetic energy and so on, and the equation is then too complicated to be solved in the early days. But if I make some simplifying assumption, then I can solve the equation. So, this was general practice, and this was called a zero-order calculation. Then the person could say now what is the difference between the actual Hamiltonian for the system and the one that I've used as a zero-order approximation. I'll 00:40:00take that difference as a perturbation.

So, perturbation theory in quantum mechanics was developed, described in many early books and papers. Of course, also in my book on quantum mechanics with Bright Wilson. But perturbation theory was developed and one could carry out a first-order approximate perturbation treatment that you have the zeroth-order calculation, then you have the first-order perturbation calculation, and then you could go on to the second-order perturbation calculation. And many people did. Sometimes the first-order correction was zero. You had to go to the second-order correction. So, this is quite a standard approach in the early days.

TH: Yeah.

LP: That everyone made. So, what I succeeded in doing was to carry out a zeroth-order perturbation calculation for methane, for the carbon atom, and then for palladium and platinum, and so on, all of the problems that I treated. But this was hardly an example of the stochastic method.

TH: Yeah, yeah.

LP: The question was, in the case of a crystal, you want to determine the location of the atoms that will fit the X-ray data. And the method that I developed, or perhaps refined, was not to try to discuss all possible 00:42:00arrangements of the atoms, but to concentrate on the arrangements for a particular crystal that seemed to me to be the most likely ones on the basis of my knowledge about how atoms interact with one another. And making use of information, for example, such as with the mica. The mica crystal splits into sheets because it has cleavage on only one set of planes.

TH: Right.

LP: And other people too I'm sure recognized, by 1929 or '30, that this mica must have some sort of a layer structure. So, the stochastic method was of great 00:43:00value in crystal structure determination.

TH: Yes, yes.

LP: And in a sense, of course, in my discovery of the alpha-helix I was using the stochastic method and I got a structure that didn't agree with the X-ray data. [Laughs] or seemed not to agree. That's why I held up publication for a year and a half, I think. I felt so strongly that the structure must explain the X-ray data that I didn't want- even though I thought also I'm pretty sure that this alpha-helix is right, I took a chance by waiting a year and a half and then 00:44:00finally published the structure with Corey.

TH: Yes, yes. Let me ask you a quick question about that. What I have heard from talking to Verner and Dick Marsh and some other people about Robert Corey was that he was such a careful experimentalist and so precise, wanting to pin down as much information experimentally as he could that, say take the alpha-helix example where you came up with a theoretical structure a year and a half before you published, did Corey play an important role in convincing you in some way to hold up publication? Or was he a restraining influence in some ways?

LP: No, I don't think so. Here it was March 1948 when I discovered the alpha-helix, and I didn't get back to Pasadena- I didn't let him know, didn't write him about it, didn't get back to Pasadena until September. And I could, of 00:45:00course, have written a paper about the alpha-helix and the gamma helix in Oxford-

TH: Yes.

LP: ...and published it by myself. I felt an obligation to Corey. I would say that he didn't contribute anything to the discovery of the alpha-helix in the pleated sheets, except that I made use of the somewhat more refined estimates of bond lengths and bond angles that he and Verner Schomaker and Dick Marsh, and all of the others who worked on determining the structure of amino acids and simple peptides, had obtained by their careful X-ray studies. And you know, the 00:46:00first structure related- of any substance related to proteins that was published was Corey's structure of dioxopiperazine.

TH: Right.

LP: Which is glycine and hydride. Cyclic glycine and hydride. And the result came out just what I had predicted, in that even the bond lengths and bond- well, the bond lengths are determined by the ring, but the bond angles aren't. The bond lengths were essentially what I had predicted from substances, crystal structures that were really not very closely associated with, connected with proteins. And then, the next one was the structure of glycine done by Corey and 00:47:00one of my graduate students, Gus Albrecht. And then, over the years, the next 10 year-[tape ends]

LP: -some of them, and not at others.

TH: Uh-huh.

LP: And nobody else anywhere in the world had succeeded in determining a single one of these amino acid or simple peptide structures correctly. There had been a dozen papers published perhaps, but all wrong.

TH: Yeah.

LP: So, I thought that Corey really has contributed for-by verifying these interatomic distances and bond angles and hydrogen bond lengths as really 00:48:00applying reliably to amino acids and peptides, and presumably also to proteins.

TH: Yes. That's interesting that between March in '48 and the time you came back in September that you didn't communicate your ideas about the structure. I mean, that sort of indicates the relationship by, it seems to me, in which you were working in terms of the larger overall structure, and he was working in terms of the subunit, smaller scale structure.

LP: Yes. Well, I don't think Corey had... well, I think Corey's nature was not such that he would have been delving into, or striving as I was, to determine 00:49:00the structure, the secondary structures of proteins.

TH: Yeah.

LP: And not many people I think had this nature. Of course, Bragg, Kendrew, and Perutz [laughs] published a paper. There's a book, a sort of festschrift for Bragg published on the 100th anniversary of his birth, Lawrence Bragg. I have a short paper in that book, and... Todd, Lord Todd.

TH: Yes.

LP: Alex Todd has a paper in which he refers to the episode that... in a way somewhat different from what he told me back about 1964 when Bragg, after 00:50:00publication of the paper by Corey and me, Bragg rushed over to Todd's office in the Chemistry building with that paper and said, "I talked with you a year or two ago about this. Why didn't you tell me then that the peptide group is planar?"

TH: Ah [laughs].

LP: And Todd said to me, in 1964, that he answered Bragg by saying, "Well, I thought that I did. I can clearly remember telling you that I had always thought that this carbon-hydrogen bond has some double-bond character." And that didn't mean anything to Bragg [laughs] because he didn't know much chemistry.

TH: Ah-ha.

LP: So, Todd thought that he was telling him that they shouldn't work with a nonplanar nitrogen atom.

TH: Well in fact, in the papers that your group published, wasn't it clear that the peptide bond was planar?

LP: Oh, yes. Well, in the other substances that have a structure somewhat like atoms, amino acids, the planarity showed up.

TH: Yes.

LP: Pap-structures that were published before 1937.

TH: Yeah.

LP: So, in 1937, I was making use of that idea of planarity, and of course, it's discussed in my Nature of the Chemical Bond, published in 1939 [laughs]. So, Bragg, Kendrew, and Perutz I judge didn't read The Nature of the Chemical Bond before publishing their paper in 1949.

TH: Uh-huh. Um-

LP: Well-

TH: Go ahead.

LP: In this book for Lawrence Bragg recently published this year, in this book, Todd tells a story but says that Bragg had told him that a chemist, a physical chemist, had told Bragg, Kendrew, and Pertuz that the three bonds from a nitrogen atom were at smaller angles of around 90 degrees; that you had a pyramidal structure, and that Todd said, "Well, you shouldn't have asked a physical chemist, but an organic chemist." Well, that was new to me.

TH: [Laughs].

LP: But Todd's memory of... well, it may be that Todd didn't tell me the whole story then in 1964.

TH: Yeah, yeah.

LP: So, Bragg, Kendrew [laughs]- Bragg was pretty irritated by having lost out on discovering the alpha-helix, and just as he was irritated with me for my 1929 paper on the silicates.

TH: Yes, I seem to remember that, hearing about that as well. Was it in the silicates paper that you published your set of principles on determining crystal structure that we were just talking about?

LP: Yes, yes. And I start out by mentioning Bragg as having formulated a principle which was that the oxygen atoms are in a close-packed arrangement. And actually that principle is sometimes useful and sometimes not because about half 00:54:00of the silicates, or even less than half, have oxygen atoms in one or another of the close-packed arrangements, but the others don't. So then, my coordination treatment is essentially universally applicable, my other principles based on these ideas, the valence, the bond strength idea, and so on.

TH: Yeah. Speaking of his irritation with that paper, the- when you went over to Manchester in 1930, did you get a sense that- how were you treated by the Braggs on that visit?

LP: Oh, I was treated fine. Bragg arranged a house for us to live in during the months we were there, and a maid too, a cook to work for us, and got him, got 00:55:00Linus Jr., age five, admitted to a school for that month. And in general, he was very helpful. And I was disappointed - I perhaps have told you - I was disappointed there weren't any seminars. And in particular, Bragg did not ask me to give a talk about my ideas, and nor were there any other seminars. At Caltech, I was used to going to two or three seminars a week. And then, in addition, during this month, there never was a time when Bragg asked me to come to his office or laboratory to talk about scientific questions. So, I had 00:56:00thought perhaps we can- and I have said that I didn't think of myself as a competitor to Bragg. I thought of myself as a member of the next generation, with Bragg as one of the revered leading scientists who had been making great discoveries in the past.

TH: Ah, I see. Well, maybe that's what he didn't like [laughs], what that attitude [laughs].

LP: Yeah, [inaudible]. Well, I also mention, in my article, that unfortunately in 1926 when quantum mechanics came along, Bragg was in a responsible position as head of a physics department, with many duties. There was no possibility for 00:57:00him to learn quantum mechanics. Well, so my feeling is that he felt handicapped all of his later life by the fact that he didn't have a good understanding of quantum mechanics.

TH: Yeah, yeah.

LP: And that perhaps he didn't want to talk to me because of having a feeling of inferiority in this respect that would be revealed if we discussed scientific matters in the sort of thorough way that sometimes a couple of scientists engage in when they are talking together.

TH: Yeah. That's interesting, that that would - of course, it makes sense - that that would mark a dividing point between generations of chemists. And in fact, common sense would say that of course the difference between knowing quantum mechanics and not knowing quantum mechanics at that point in history would have been essential in determining how successful you'd be in future research to a certain- I mean, certainly, you're proof of that.

LP: Well, I think this is something that applies mainly to physicists.

TH: Yeah.

LP: That a physicist, the older generation was just handicapped [laughs]. Some of them, of course, professors of theoretical physics, had such a good background that they could go ahead and master the subject and make contributions. Epstein, for example, at Caltech was a member of the older generation, but he was able to make an important contribution. More than one. 00:59:00One of them by developing the theory of the Stark effect of hydrogen. But Bragg- Epstein didn't have any administrative duties at Caltech. He was teaching theoretical physics and so on, whereas Bragg, probably his time was taken up with all sorts of duties.

TH: Yeah. But, in any case, you never got the impression that he was - I mean on any personal level - that he was irritated with you, other than the fact that he simply didn't sit you down and have a long talk with you? He was-

LP: Well, no. It wasn't until many years later that I realized, or was told by people, that Bragg had resented my having made these discoveries.

TH: Yeah. I see. And you know, I don't have my notes here with me, was Sir Henry still around at that time?

LP: ...Sir William?

TH: Oh, I'm sorry. William Henry, yeah.

LP: Sir William, yes. And I haven't been able to remember whether I met... whether I ever met him. I think I did, but I just don't have a clear memory of him.

TH: Okay. Yeah [inaudible].

LP: I'm pretty sure that I went to - but not absolutely sure - that I went to the Royal Institution in 1930. But whether I met Sir William or not, I just can't remember.

TH: A couple of more quick questions, and then I'll let you go. You've been great today and I don't want to take up too much more of your time, but about this 1930 trip, how was it funded and how did you arrange to get time off to go over for that period of time?

LP: Well, I missed one term by leaving in April of 1930 and got back in time for the fall term. So, it was a sort of sabbatical, six months or three months. The institute didn't have then, and I think doesn't have now, a system of sabbatical leaves like most institutions have, but I was given special treatment.

TH: Yeah.

LP: So, I applied to the Guggenheim Foundation for a Fellowship to last seven months or six months, and it was turned down. And the institute I think gave me a travel grant of $1,000 and continued to pay my salary.

TH: Oh, I see. Okay.

LP: Just as back in 1926, the institute had given me $1,500 and an appointment as Research Associate. I was called Research Associate.

TH: Yeah.

LP: During the period that I was not in residence, '26, '27.

TH: So, you were paid a salary while you were in Europe at that time, the earlier trip.

LP: No.

TH: Oh, I see.

LP: I was given a travel grant of $1,500 which also was to provide our expenses. I didn't get any salary in 1926, '27. But Noyes was eager enough to have me [laughs] off away from Berkeley I guess...

TH: [Laughs].

LP: ...to put up that. And he may have put it up himself, that $1,500. So, that was just given to me in January or February, and it lasted - barely lasted - us until we got the Guggenheim Fellowship.

TH: Yeah, yeah.

LP: I saw somewhere a statement, I've forgotten where, that the Guggenheim Fellowship was awarded in January. But it wasn't 'til April that it was awarded. But as I say, I think Noyes knew, had been assured by the Guggenheim people... 01:04:00See, I had had lunch with the director, the president of the Guggenheim Foundation.

TH: Aydelotte?

LP: Aydelotte, in 1925. Or perhaps early nineteen- yes, in 1925. Possibly even, well I can guess it was early 1925. And I think that they considered giving me a Guggenheim Fellowship in 1925, the time when a small number, half a dozen or eight, something like that, of people were given Guggenheim Fellowships without 01:05:00any competition. Without any announcement. The first year in which applications were accepted was 1926.

TH: Right, right.

LP: I think I sent my application in at the end of November of 1925, perhaps.

TH: What was your motivation for going back to Europe? Was there something spec-obviously you wanted to spend time in Manchester, and were there other specific goals for that trip?

LP: Well, I went to Munich too, to make some more quantum mechanical calculations. So, during the summer, and during the next five months, most of my time was spent making quantum mechanical calculations.

TH: Uh-huh. And visiting with old friends, I assume?

LP: Well, to some extent. The... yes. I'm not sure I had many old friends, but [both laugh].

TH: I was just thinking of the people around Sommerfeld's group who you would have known from your earlier trip.

LP: Yes, yes.

TH: Did anything occur during that time? Thinking back to when you got back that winter and made a breakthrough in terms of your mathematical approach, did anything happen during that summer in Munich that you think might have been important in that evolution of thought while you were doing this quantum mechanical calculation?

LP: ...I don't think so. I was striving to solve a number of problems. Just a moment... Thanks. I was striving to solve a number of problems, and didn't- and my memory is that I didn't have very much success.

TH: Yeah.

LP: But I'd have to look over my papers, which are in Corvallis, to see.

TH: And it certainly- your trip to see Hermann Mark was certainly fruitful though, at that time, and picking up the electron diffraction apparatus.

LP: Yes.

TH: Yeah. Now, was that just a happenstance, or had you planned in advance to see him and explore that possibility?

LP: Well, I didn't know about his electron diffraction work.

TH: Ah.

LP: I had met Mark on the earlier trip and I went to see Ewald in Stuttgart because he was a leading X-ray crystallographer, and went to see Mark, sort of to see what was going on, but you know, to talk with Mark about what he had been doing. He had published an analysis of X-ray diffraction patterns of fibers. Cellulose and... other, that's macromolecular carbohydrates as well as proteins. He was working on the structure of rubber. So, already at that time, I judge, I was interested in- well, I know I was interested in the question of the 01:09:00structure of cellulose and did a little work on it. Never published. I wasn't successful at that work. So, he was one of the leading- and he had published a large number of papers on X-ray crystallography.

TH: Ah.

LP: Then, in Munich, I went to see Gossner and Mussgung, who were also publishing papers on X-ray crystallography. So, that trip was, I think, stimulated mainly by my interest in getting better acquainted with some of the X-ray crystallographers.

TH: Yeah, yeah. And the- finally, when you made that- later that winter after you were back and you made that breakthrough in thinking about the mathematical approach to structural questions, I seem to remember reading somewhere in an interview where you said you sort of were so excited by that breakthrough that you worked almost all night doing calculations.

LP: Yes, that's what I've said several times recently.

TH: Yeah.

LP: But I can't remember whether this was a day in December or a day in early January. The paper was published the 6th of April, I think. Sent in the 24th of February, something like that.

TH: Yeah, yeah.

LP: And the... there's no doubt that when I had this idea, I was very excited.

TH: Uh-huh. Would you say that up to that point, in terms of your scientific work, that that was perhaps the most exciting moment to that date?

LP: Yes, I think so.

TH: Yeah, okay. Very good. Listen, Linus, this has been absolutely wonderful. I really appreciate your taking some time and letting me talk with you a little bit more. And what I might try and do is a little bit later on, in another week or two, I'll try and catch you again and ask you a few more questions if that's okay with you.

LP: Okay. Well, this is... I suppose it'll be [inaudible] very mobile, so I-

TH: Oh, so this is a good week for you-

LP: -Yes [laughs].

TH: -to talk. All right, well then let me give you a call tomorrow and we'll see how you're feeling, and if you feel up to it, we may do it more then.

LP: Okay.

TH: Thanks a lot, Linus.

LP: Yes.

TH: Bye-bye.

LP: Bye. [Tape ends]