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Interview of Giuseppe Occhialini by Charles Weiner on 1971 April 5, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/31789-1
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Topics discussed include: Bruno Rossi, Gilberto Bernardini, Ettore Majorana, radioactivity, Antonio Lo Surdo, Antonio Garbasso, Lise Meitner, Ernest Rutherford, C. T. R. Wilson, John Cockcroft, P. M. S. Blackett, Gleb Wataghin, Gian Carlo Wick, Franco Rasetti, Enrico Persico, Dirac's theory, nuclear physics, Emilio Segre, cosmic rays, James Chadwick, Cambridge University, Shimizu, George Gamow, Frederic Joliot, Cavendish laboratory, P. L. Kapitsa, Hans Geiger, Maurice Goldhaber, Victor Weisskopf, David Frisch, Ehrenburg, Carl Anderson, Guglielmo Marconi, Louis de Broglie, P. A. M. Dirac, fellowship from National Council of Research, Arthur Holly Compton, Surgio de Benedetti, Giulio Racah, Sergei Vavilov, University at Sao Paolo, William Bragg, Cecil Powell, sigma star, and pi-meson decay.
We are in Professor Occlialini’s office about to talk, on April 5, 1971.
I’ll say hello, I’ll be talking a lot. Where do you want me to start from? The field is wide. I have a tendency to go off on tangents, but you don’t compress 25 years of your life in a few phrases, you see, So you can choose what you want me to talk about. I told you yesterday about Bruno Rossi, about the attitude of Bruno Rossi, I told you how his genius was proved fundamentally from the way he started, by the choice of the argument as adopted to a very poor country, and this was the original attitude. He did understand that the tube counter of Geiger-Müller was the great equalizer that would allow a very poor lad to work without possibility of great apparatus or of buying material, most of all without radioactive sources.
Let me ask about this radioactive sources business. What you’re implying is that there was a conscious choice that was made, as to the area of specialty of that particular physics group. One of the things that was a major factor was the resources you had on hand, which means not only the money for apparatus but the fact that even if you had the money, the sources would be very difficult to obtain.
The passage from cosmic rays to radioactivity, for Bruno Rossi and Gilberto Bernardini, was very very quick. We had seminars in Arcetri radioactivity. Bernardini wanted to work in radioactivity and nuclear physics, and Bruno Rossi went on his fellowship in the laboratory of Bothe, which he did I think in ’30. He came back in October, and I remember that he told me, “Look here, [suppose we] are going to work on spectroscopy, sparks and so on. Now, let’s assume that we discover the mechanism of spark. All right. Is it this important? I think that the lab should go to radioactivity.”
This was a decision which has been taken by Bernardini and by Rossi together. And then he says, “All right, what shall we do? We must do something in which we must for the moment employ tube counters. What will we get for radioactive sources?” And I said, “We will employ potassium and ribidium. They are the only sources which a lab like ours can afford.”
So I was the first pupil of Bruno Rossi in this, and I produced the first counter for the spectrum of rubidium. This is called the magnetic spectrum and this was poverty, you see. The idea was of Bruno Rossi. He refused to sign it. I made a mess of it, for I was supposed to go to England and I had to finish it. I remember I spent a lot of nights in the lab. The magnetron was getting warm, switching on and off. Still the method proved its validity. The method — it is the magnetron. The method is the magnetron, with a cathode which is outside. It is very simple. This is the counter, this here. Here is the source around it. It is a very big solid angle, and so the radioactivity is more or less on, you see. It has been there — I think it was a nice thing — it has been afterwards copied by Libby and nowadays is called the spectograph of Libbys.
But theoretically, of course, it is Rossi. For the game, you see, it was well. But this showed that you could not do real radioactivity without having a — radioactive material at your disposal.
It shows this. So, where to go, with cosmic rays? This I did first, to do work and to get new techniques, to come out of this condemnation of the Geiger tube. Oh, it was very good for cosmic rays. And then there was the question of going for the most important thing. The most mysterious, the most fascinating thing was the Wilson chamber.
I was sent to England, to work with Blackett on the Wilson chamber, and the choice of the place was done by Rossi, with Metti, Blackett — and he sympathized, Blackett, very very much. Part of the decision has been due to the fact that the wife of Blackett, one of the most intelligent beings ever existed, was Italian and was speaking Italian. So for a young man who did not have any, a good knowledge of English, it was a good introduction.
This is something I want to explore in detail, but let’s go back a minute. I’ll do this off and on. You were talking about the decision taken between Rossi and Bernardini about radioactivity being an important field. A couple of questions about that. When did they do this? Was it while you were still a student? Was it ‘29, ‘30 or was it just when he came back from his year with —
They’d been working together on slow electrons. They were disappointed by their work on slow electrons, you see. So Rossi gradually dropped out of it and started playing with cosmic rays. Bernardini started studying the disintegrations and used as a tool, the kind of Arcetri seminar, where they started with the Arcetri seminar, and there I do remember that Bernardini brought the disintegrations, the subject of Rutherford disintegration, and wrote after this in Nuovo Cimento a descriptive article called “The Atomic Nucleus.”
I remember this. There was this preoccupation of young men there to produce, so one of the ways to produce was to study an argument, to give a seminar and then to make it, and so I do remember. I remember the insistence of Bernardini, “I looked” — he was telling me, “I have looked at the thing. It is not as difficult as that. It’s not very — it is not fabulous and so on. To work in other things, it is more difficult, to work like Stern and Germer experiments of other type, it requires more complications.”
It is all so simple, you can do it practically in the air, you don’t need and so on — you can start it. I really do remember that when I went in England, then to the same conclusion had come the people in Rome. They said, “You should go into radioactivity. You should go into radioactivity.” This was — and there, well, you see, once or twice the name of Corbino, all right. There is a bit of a father-son relationship between the people of Rome and Corbino. Corbino was what we would call today, what I would call today, an operator — a man intelligent as a physicist, and his great merit was to realize that Fermi was a good thing and to put Fermi in.
Well, everyone knew that Fermi was a good thing, but men, the men who were living in Rome, where all the switches of power in Italy were and in Rome was Corbino. Corbino could make or unmake university professors. So he decided that Fermi was a genius, but this everyone in Scuole Normale, Pisa, from wherever, Fermi and Rasetti school companions came — Fermi was before in Florence. He left Florence and he went to Rome. Rasetti was with him, followed him. They went together. They came. People like Segrè, people like Amaldi. This was the group. And this is the group. They started playing with radioactivity.
The first thing they did — on this you check for, on this I don’t have — is they thought that they could work on very exact spectroscopy of gamma rays. They did a rather nice thing in which the source was in the center, and there were three slits going in, four slits going in four different – sort of like, I do remember, a cross, you see, and the source was here.
This covers kind of a big period. Now I am already talking to you about Rome in 1932-34. Then they took a very important decision. They, and here we come to the business of sources, you see — now, if you you wanted to work in radioactivity you had to have sources. If you wanted to work on hand pure gamma rays, you should have a source of Thorium C two dashes. You cannot do it on radium mixes. Thorium C two dashes. It has been a thing first found out by Chadwick. At least this is what he told me. He told me — I was asking, how did it come, the story of Thorium C two dashes? “Well, you know, Rutherford, you know this kind of things which he asks. He asks, give me a monochromatic gamma ray source, give me a monochromatic gamma ray source.”
And I said, “It is very easy. You must only separate the Thorium C and then you get a lot more energy and you get a line, 2.6 — 2.62, 2.7, million volts.”
I was a fool for I said it and Chadwick was always very secretive. Very very secretive. Very secretive. He was cagy. He didn’t tell everything, you see.
And then I said, it was in public, and then from this moment on everyone started playing with the source, you see. I could have kept it for this laboratory. But I give it in [England].
Then, Rasetti has qualities, is really a modern Faraday, one of the greatest personalities which have ever existed in physics. Rasetti is the man who is supposed to have broken the false pomp and to have sold, and to have it put in order, to have saved Italia again all by himself.
Rasetti when to Charlottenburg to work with…(interruption…)
Balazu is retired, they produced for him two secret books of people who sent papers which had been done in some way under the influence of Bruno Rossi. Secret books, only one copy, you see. So they wrote me and I sent him the paper on rubidium, which had been the first paper I did, and
This is the letter, you see, I’m pretty fond of it because of the sealing-wax atmosphere. The figure was made was made by wrapping a foil around the pencil.
The figure was drawn in the Café Pascosci.
Where was that?
It was in Florence, in the big plaza of Florence. This is the paper. And you see —
— for beta ray emission from —
— radioactivity —
— yes, weak radioactive substances.
This was done by using a pin pen here. This was the pen, and I posted it. I was supposed to post it for an Academy, for Professor Garbasso was supposed to present it, and it had to catch the 11 o’clock train, you see, and this had been sketched.
This was Obacimente?
No, this was Lincei. This was Lincei.
You mentioned by the way that Professor Garbasso —
— yes, Professor Garbasso was the pre-Corbino. He was a man of tremendous knowledge of physics. And he is practically the discoverer of the so-called Lo Surdo effect. He was also a brilliant theoretician and very cultured, so when Lo Surdo playing with a tube, and it was passing a discharge, discovered by looking on a point where there was a restriction, that the lines got split, he says — this I understand, this is the electric field which does it. From this moment on, Lo Surdo(?) to the end of his life published a paper by calling it not the Stark effect, but the analogous of the Zeeman effect in an electric field. The fact that he was feeling he had been robbed of something — when Garbasso said, “What is this? That’s a wonderful Stark effect. What do you mean by Stark effect?”
It’s something produced by the electric, by the constriction which produces a very strong gradient in the electric field, that is to say, rather to do it by two place as Stark had done it, it was internal. It was due to (???) pinch. This is what we call nowadays a pinch, you see, and in the pinch there were the conditions conducing to this. This was Garbasso you see. He was the protector of all of us.
Surdo was in Rome and Garbasso was —
— No, and Lo Surdo was in Florence before, assistant of Garbasso. Was assistant of Garbasso, and he chanced to find this effect, and then he went to Rome. As far as I am, I think — the first and last thing he did was to accept the suggestion of Garbasso that what he was looking at was Stark effect. So it became, in Italian we call it the Stark-Lo Surdo effect, the Lo Surdo-Stark effect, but if you look at the literature, it was the Stark effect, and this was a brilliant new way to obtain a Stark effect, broadening, electrical broadening of the lines and in certain definite geometrical conditions, splitting.
Garbasso (Lo Surdo?) in a way always had strong father complex towards Garbasso. Garbasso pushed us very very much. He wanted us to — since he was a member of Accademia Linceii, he wanted every session at Accademia Linceii that he could come, presenting something of his pupils. So this explains why I had by night in the Cafe Petrosci to draw. A tremendous, in a way a tremendous man. He died in — while I was in England. He died by leukemia, and it was a big tragedy for all of us, for the — for this lab, for the work. Rossi had been daily into the group of Garbasso, and had gone up like this. Then after his death, the lab was finished. Rossi went to Padua to get a chair, and —
When was that?
When I came back in ‘34, Bruno Rossi was not there anymore. Had left.
Garbasso was the professor that was his title as compared to titles of all —
Experimental — he was the director of the lab, and he was professor of experimental physics. He was a man who knew all of Dante by heart. He was the representative of a type of physicist which nowadays is disappearing. He was, like you say, the d’Andrade type, you know — very much a cultured man. He had a strong philosophical tendency, materialistic as far as science was concerned, you see. He was fundamentally an anti-Hegelian. I do remember some one of his things which was against the Croce and Gentile. Fundamentally that is to say he was a person, he was completely against the idealistic strain, you see, and for the other side, he was a man who in good faith was a Fascist. But some one of the people around him —
I remember that he was, he became, he stopped at the moment doing physics. He became the lord senator. He became the lord mayor of Florence, and then the podesta? The podesta is what substituted for the lord mayor in Florence when Fascism grew in power. The lord mayor elected. The podesta is an old Spanish title. It is like the viceroy. Podesta was the man that in Milan was the administrator for the King of Spain. This was the man who was imposed by the central government, the civil power imposed by the central government. He became the Podesta. He had the theory — it’s explained to me — for —
When he was ill and was in bed, he used to call me. He wanted to talk to me. Apparently my brand of dialectics was appealing to him. And we were talking politics. I never had such a tolerant I remember he was saying that he was Fascist because, you know, the wealthy, the Ghibbelini — you never heard about the battle in Florence between the wealthy and the —?
That’s the Ghibbelini. Well, he was explaining that the first days of Fascism were the reincarnation of the wealth. The Ghibbhelini, of which Dante was one, they wanted the power in Germany (Genoa?), the central power in Germany, by the wealthy. There were other people who wanted local rule not coming from, not based on the German influence. And he was wrong. He was wrong in his — it was an intelligent interpretation of the moment which facts proved, he was proved wrong.
— What was his manner toward the dissenting views of people in the laboratory or where they expressed other than your conversations, which I assume were frank arguments?
He was a man who could talk, very wonderful. He was the man who gave the best lecture on the Divina Commedia which I ever read. It was called “Science in Dante,” in which he extracted from every part of Dante the things which were scientific, you see.
For example, to give you an idea, he gave the sense of color of Dante, Dante’s phrases sounded wonderful in poetry. “When the green lizard, under the sun, crosses the road, it is like a flash.” …
Did he relate this to the green flash?
This was green passing over white, so the result was red. And so on, you see. Then reported the calculation of the size of Hell. What were the calculations of the size of Hell — by some reference that Dante gives, it is true that Dante has given it. And there were all the scientific intuitions were contained in this. He was a man of very very tremendous intelligence. He was an aristocrat.
We were talking about Corbini and Garbasso, as far as relationships go.
Friendly. Friendly. Friendly, but not — both of them, they had stopped making physics at the moment. Corbini was seeing the justification of his life in the existence of Fermi. Fermi had taken over. Garbasso was seeing it in Gilberto Bernardini, in Bruno Rossi, the justification, the alibi for the fact of having gone into politics and so on, you see. From the other side, Corbino was much more let’s say of a political manager. Garbasso was — he was thinking and so on like Corbino was a bit in political scientific life. He was giving addresses. There are two famous addresses which he gave. In one of them, he was saying that physics was finished, there was nothing more, it was an empty field and so on, apart maybe from nuclear physics. Everything was all right, everything was already known. In the other one, he was saying that physics was full of tempests and things which could not be understood and so on. This was evident to me the result of the conversations that you would hear around by scatterbrains like Fermi and Rasetti, you see — to hear them, you see, physics was finished and so on. You can make a horse, you can make a war horse, if you are a good politician, out of one phrase — like you make a symphony out of one note, yes? And so on. This was to say — it was this, and it was in this period that, having decided that physics was finished, the only thing to do was to do maybe in radioactivity and the nuclear physics, which was the ultima thule, that Rasetti went to learn how to separate polonium from tubes of radioactive radiations.
He went with Lise Meitner.
He went with Lise Meitner to learn how to do it — why polonium? Why polonium? Bothe and Becker had discovered that by bombarding with alpha particles, something finally was happening, a rather penetrating radiation. I remember Rossi telling me that he had met Fermi, and Fermi in Rome had told him, “Here there is something big. There’s something big on this.”
When was that?
I don’t remember the date, for the fact that I was told afterwards. I was told after I’d left.
But polonium was, could be plentiful and cheap, for the radium E tubes of desanita of hospitals, if they are treated in a certain way, they must be dissolved in a certain acid, they must be thrown around, put in a certain acid, then you must put in an electrode, or if you do it with two electrodes one of them must have a certain shape to it, there must be a certain ratio and so on. Well, all right, once you know how to do this, you can accumulate, if you’ve got radium E. The tubes, they used for the treating of, to get the source of polonium. If you’ve got a source of polonium, then you’ve got fire power.
Since a neutron, as we know now, is emitted for every ten to the nine, ten million particles, all right, to have one neutron you must have ten to the nine. To see a neutron you must throw ten to the nine particles, so you must have a big strong source. There was built as I was trying to tell you at the first, you should have had the sources on hand. Now, what are the sources in?
It is evident that they were in Rome for there was the Hospital of Sanita and in the Curie Laboratories.
The Sanita Publica.
Yes. And they had it in the Curie Laboratory. They had all the practice, they had all the possible sources of it. This was the father lab of radioactivity. Anyhow, I think that the Romans succeeded in having a source that was maybe once or twice, three times, the one that they had in the hospital. When you had this, then you understand, if you had a source, provided you have a source of polonium, and provided you have beryllium, if the source of polonium is big enough, you’re bound to discover the neutron.
Of course you must have the right operators. What would have been the ideal operators for discovering the neutron, there’s no doubt, was the photographic plate. If the photographic plate had been used, at the moment in which I think, but I’m not sure, that the first — the first experiments were done in Rutherford’s lab, but I don’t know. I don’t know if I’m right, you see. You know very well the neutron was suggested by Rutherford but there was something funny to me in the experiment, the so-called experiment of Slater.
Well when that photographic plate was developed — you should have seen the neutron recoil.
In the year 1931, you need either gamma rays or polonium, but polonium — soon afterwards, you need a source of protons. How do you get the source of protons? Very simple, my dear chap. From alpha particles, you bombard hydrogen. This is the source of protons. Well, could you do it by machine? Yes. We can do it by machine. And what kind of energy do you need? All right. If you talk — for a man like Gamow, who tells you that the energy does not need to be very very high, then you be like Cockcroft and Walton and they would say, Rutherford. You build a machine which should produce 600,000 volts, thinking it is enough. If you are not convinced of this, then you will lose the race, for you will build a cyclotron which should be able to give three or four. It would never be the first time in science, in which out of setting — there are several mistakes — out of setting your aim too far, — you ignore the threshold. You go so much over the threshold that the difficulties for producing your apparatus become very very big. Out of this, is one of the few quotations which I can give you about Blackett.
‘Tis well I say, I think maybe I’m nothing, but I think I know exactly when to stop increasing the size or perfecting an apparatus to start the —
He was talking like the Marine officer, he was. He knew very well it is absolutely no use to build the most wonderful ship if you’re not making it ready for the war, you see. So when they went — and this explains the end. If you are a man like Rutherford — to a sensational you see, well, you understand it, where there is a school. As you hear people talk about at Copenhagen, Geist, all right, there was a lot of Geist, What it was? It was what is called the English way to look at phenomena. The English with all his plan is essentially a bad mathematician that he will always try to build something which is geometrically simple. The German would build a rather complicated apparatus, and then he would start correcting, correcting, correcting, correcting. These are the two different approaches. Rutherford was the first type although the physics of Rutherford was really secondary physics. He had beyond the (frontier?) but he was a man who — well, the atom of Rutherford is something which nowadays every good man, every good young man can calculate. Once you give them the details they arrive at the theory Rutherford did. He was not an authority, but he knew enough theory, and the important thing in this experiment again is the Napoleonic correlation between the Bigness of the apparatus, and the results.
Rutherford was very impatient with his young people. For example, I’ve been told that he was very disappointed with Blackett. There’s a famous phrase of him, I don’t know if Blackett knows. You know, in corridors you hear more than the people — and what Blackett — the Wilson Chamber had been invented. Wilson was a perfectionist. There’s a well-known anecdote, maybe you’ve heard it, it’s printed somewhere. When Professor Rutherford passed one day in Cambridge, he found C. T. R. Wilson was cleaning the top of the Wilson chamber to make it very very clean so that he could take good photos. He was coming from Manchester — when he arrived, in Cambridge, he found Wilson was still cleaning it. Well, here my memory fails, for this — but I know, I would like to tell you that I was present, but here my memory…
That’s all right, this story which Rutherford was telling was really a satire on Wilson. A satire on Wilson’s. He smiled and said, “But it was not the same Wilson chamber top. It was a different one.”
A difference in approaches.
This is the difference in the approaches, but it shows you — it shows why Rutherford, being a go-getter, was a very impatient man. He did not like the perfectionism of C. T. R. Wilson, the perfectionalism of Dee, but he liked Cockcroft, because Cockcroft was one of the most efficient personalities that ever existed. First of all, Cockcroft took from Walton. Walton had not made the wrong design. I told you he wanted to make an apparatus, but they thought it was wrong. It was not wrong; it was the first betatron, and Cockcroft decided that the best thing was to build a common, what is called a Marx generator, which is the type of Marx generator. You can do it quickly, sealing wax, the old way, sealing wax and so on. He did not like Blackett in the first time. Blackett wanted the people to build a something chamber which would go like this, like this, like this. Blackett was working there. The months were passing and nothing was happening. He was shouting. …
Now we’re resuming after lunch. There were a couple of things that you said. You mentioned the Corbino speech, the two speeches. Do you recall hearing those speeches at the time they were delivered? Let me refresh your memory. In 1929 at the Italian Association for the Advancement of Science in Florence, Corbino delivered the speech where he talked about nuclear physics being the only live field for the future, and I wondered, when you were telling me about the speech, whether it was from reading it later, from hearing it at the time, or from reading it many years later?
Even then, even then, I am not so sociable as to go to any speech, passing the time in society, so I was not there when he said it. In ‘29, I remember Florence. I am not so sure that it was there. I read it. Then in one of the speeches, he said, “Gentlemen, a few years ago, I was the sun. Now I remember, it all seems to be clear, and everything is full of tempestuous weather.” I don’t remember. I can find it.
I have the speech. I have it in translation.
There are two speeches.
Yes, I’ve seen the other one.
He had two speeches, you see. Speaking about it — it’s very nice, you see, in Rome they have a father image of Corbino, you see. And in Florence, they have a father image of Garbasso. Everybody cried when he died, you see. For me, when he died, it was to me a big crisis, also for the fact that I was feeling responsible.
Responsible in what way?
There was some misunderstanding. I was in England, and while I was in England, I lost my job, and I did not keep in Florence very well informed the people on what was happening in Cambridge. I was bloody right for I was in a place without all the ballyhoo of press and so on, Anderson would have been left ear(?) to see if this photo was a positive electron or not.
While as it was, from 18 February ‘33 to ‘28 February, ‘33 in ten days, he succeeded in squeezing the paper into the PHYSICAL REVIEW which was showing the photo.
It had not been published till then?
It had not been published.
The discovery was the preceding summer of ‘32.
The announcement was in the preceding summer. It was done in the newspaper called Science that no physicist would read. Then came out another letter, in which he was describing bursts which he had seen in the chamber. He was saying that in this burst, a certain number of particles seemed to be positive, and certain particles seemed to be negative, you see.
You were talking about Anderson in his first observations. Let’s get to that in sequence. It’s relevant later. But the point that we got off on was your reaction, you know, when Garbasso died.
My reaction was, my quilt complex, out of my silence, you see. So that my Professor Garbasso knew that the positive electron had been confirmed from reading(?). He did not know from me at this moment when he was ill. Still in time I sent him a long letter explaining, and apparently the letter was formulated in such a way that he forgave me, so I was accepted again in Florence.
But by the time you came back, he’d already died.
Well, he died. He died in ‘33, you see. He died one month afterwards, more or less. You see, practically the last letter which Garbasso received was from me. Apparently, it was the last joy of Garbasso that one of his pupils had made good.
Let’s get to another point.
Yes. You understand, please — do you understand why, to recall the past is not always fun.
It’s very painful.
Because of the fact that sometimes, …
It came out in what you said about the day-to-day working of the lab and your relationship to Garbasso as far as the leadership goes, it’s quite clear. Let me ask you a question, because this relates to something. I have a list of the people who were at the 1931 Rome Congress on Nuclear Physics. Now, I’m especially interested in a lot of the Italians, and I know of no better way to get at it than just to read the name of the man and see if you can tell me something about the person, Now, this is not as dull as it sounds, because it may give a pretty good picture of the distribution of physics in Italy which will enable us to see beyond the Rome group and even beyond the Florence group that we’re talking about now. Are you willing to try, if I just mention.
I remember the photo. I was not there and I know why I was not there.
Let me go through the names, and then I’d like to talk to you about the meeting. Because I’ve attached my own views, some special significance to the meeting.
I remember the photo very well, I remember —
Well, this is taken from the photo. All right, let me start with first, Marconi. Was he at the University of Rome?
No, Marconi was the president of the General Council of Research. See, he was the man who was the source of money power.
Based on his reputation, his prestige?
Based on his — yes, based on his reputation, his prestige. …the Institute of Physics is called Marconi.
But not then, was it — his name now, Marconi, but — I don’t know, did it have that name then?
I only know that he was the thing, and two days afterwards, the first report of the Blackett and mine work which came out, came out on a bulletin of C & R2 for the fact that Marconi sent me a telegram — I did not know him — sent me a telegram saying please send report. Then I say to Blackett, these people kept, they keep me starving and they want a report. He said, all right, send the report, maybe then you will stop worrying me about your starvation.
And I sent the report in which I sent these two photos.
— was that ahead of your publication?
The publication had already come out in the Royal Society. It came out in the Royal Society, but I provided the two photos. I say to Marconi, I had these two photos and so on. The Marconi took out the research and he published the thing, you see, on the complexity. I remember the letter — it was not bad, very funny, you see — I do remember it was not a bad letter, and I remember the phrases of it. But in the same way in which I cannot stand my photos, I cannot stand my handwriting, my writing. I know they were saying, well, such a complexity, such a complexity was not expected, and so on, and then they said, and so, and the last phrase was, and so we’ve been led apart from any theoretical implications or suggestions to propose the existence of a positive electron, confirming the Anderson suggestion in SCIENCE of so and so.
So this was Marconi. Go on.
An interesting point. Rossi we know about. I want to get back to something about him. He was at the meeting. Who else from Italy? Wataghin from Turin. You mentioned in conversation that he was born in Russia. When did he come to Italy?
Well, he might have come to Italy in 1918, ‘19.
As a young man,
As a young man, he went to the university here. He was a Turin man. If you want, you might see him and ask him.
Some time I might say a hello to him.
I know him rather well. He was in a way a kind of Black Duck — White Duck, you see.
No, not a Black Sheep. Remember that Fermi did not dislike him, but he was too vague for the Cartesian, the iconoclast(?) Fermi, you see. Then he left. He went to Brazil. He went to Brazil and he sent a letter to me saying that he would have liked me to move to Brazil. The second page was filled with the economical conditions there. I took out the second page, for I was very much afraid if anyone found it, they didn’t pay me enough, and if they decided I should go without this — so this is my knowledge of Wataghin. I was with Wataghin in Brazil, in Sao Paulo. Then the war started. Well, when Brazil declared war to Italy. They couldn’t leave, both of us at Sao Paulo. They arranged it so that Wataghin could — born in Russia, could declare his fidelity to the United Nations, and as for me I could declare that what I felt had been always known, and that I could not now renew in writing, accept the declaration simply to keep the job. So was thankfully declining and resigning. This was part of the story for I knew very well that had it been in Italy known, that I had said publicly in Brazil that I was fighting against Italy, my father would have been among the three hundred in the Massacre.
He was in Italy, your father? What did you bring up about —
Professors in general.
I misunderstood something you just said. OK.
My family was in Italy. Wataghin was in Brazil. I was in Brazil. So, Brazil was fighting on the side of the Allies. I was an enemy alien.
You were talking about the difficulties of keeping your university position in Brazil. We jumped ahead, but you finish the story.
Yes, and it was my acquaintance with Wataghin.
Well, then let’s get back to Wataghin. Where did he take his degree?
And he stayed there as a professor?
He stayed there as a research worker. Then he went to Brazil. While he was in Brazil, he won a professorship in Italy. It is done by Concorso.
Well, you’ve got to learn a few things in this life.
This is the most important world in Italy, Italian university.
Well, I know. So he entered the competition while he was away? And won? What university?
I don’t remember. I know that my father was one of the five who judged him. I remember, I got a telegram from my father, tell Wataghin he was judged the first.
On the Concorso, I’ve come across one thing I’m not sure about. Was it known publicly beforehand who the judges were going to be for the particular competition?
No. They were nominated by secret ballton, afterwards, when all the material is in.
Corbino in his speech — I don’t want to get off on this either, but in 1929, in a public speech he says, “I was responsible for having the first chair of theoretical physics created in Italy in 1926, and was successful in getting it for Fermi.”
Now, the point is, there was an examination, but what he’s saying is that there is a possibility — he was claiming credit for his influence.
Well, it was quite a credit for influence or if you want, foresight — you know very well that you started — well, this is Russian. It’s an addition of my own. You started with philosopher, natural philosopher, physicist, automatically physicist. Then theoretical physicist came afterwards, and physicist is theoretical. Then the Russians says come the diplomat physicist. That is the physicist which keeps the relations good going between East and West, see. Now being space, research would like to add another type of physicist — the physicist company agent. That’s the man who builds the satellite, so acts to distribute the money to Elliot Brothers, to Amaya(?) and so on.
Wataghin himself was a theorist?
I feel that he was a theorist, mainly a theorist.
I’m interested in him for another reason too, because he shows up in Copenhagen at some of these annual meetings, and is one of the very few people from Italy who comes to Copenhagen during the early l930s, and I was curious how that happened, what his link might have been. Perhaps I should ask him.
Well, he had very much imagination; he had too much. He’s typically Russian. To understand what the Russian is, you see, the Russian will take the most — well, the man that they worship the most in Russia is
Plotzi. (Slotsky? Kolaski?) There are people the same will discuss, will, invent secret radiation in one page, and then in the next page, will speculate on the possibility of Delos and Forbus — being artificial. You see. You know Delos and Forbus — they are the two Mars satellites. They say they may be artificial satellites that have been built and so on. Well, I think that his influence was very good. He was the master of Giancarlo Wick. Giancarlo Wick was his first pupil. He has been extremely important. He went to Brazil and you could say he was the best European ambassador to Brazil. You could define him as the father of Brazilian physics.
He turned down the chair when he was elected to it in Italy?
No. He asked for a leave, and then he was in Brazil, and then he asked for a holiday, a long sabbatical stay, you see. He went to the states in ’60, you see. What men in Italy do, people out at CERN, for example, they don’t turn down their chair. He was there occupying a cultural position. He was still — the same that happened to Viki Weisskopf when he went to direct CERN. He — he didn’t lose his job at MIT did he?
The next one is Trabacchi in Rome, who was at the Sanita Publica.
Trabacchi was very important for the fact that he was the man who produced the polonium afterwards. A very intelligent man. He produced the polonium.
He supplied it.
He supplied it.
The tubes and so forth.
It’s in the papers —
His name is on them along with D’Agostino and the whole bunch.
That’s right. So the thing — and also I think that he had some part…
Trabacchi we talked about in terms of his important role in supplying the polonium, supplying the tubes. Another man is Cantone from Napoli.
Cantone, yes, he was one of the local barons.
Baron, is what the students call (???) nowadays. Baron is a man who by cartism(?) or by strength of arms conquers position. A university professor is called a baron in Italy nowadays by the students. So I am a baron, and Cantone in this epoch was, called rightly, a baron. This was a man who had a lot of power, which means that he could elect a professor whom he wanted. Also let’s say, Corbino was a prince, Garbasso was a prince, — but not a very cruel prince. Cantone was a duke, and if I do remember, I remember my infancy — a rather cruel one.
Did his influence extend beyond his own university in Naples?
Oh yes, it extended all over Italy, for the people in this period. They were making night and day. You must realize that Italy has changed quite a lot, but then it was as feudal as —
Even now, professors, don’t speak about “assistant to my chair,” they speak, “My assistant.” It’s a matter of the arrangement, and a man will try to push his assistants to become —
Then the situation changed, and nowadays it is much better.
But the way one would express influence of this kind would be primarily through the Concorso, through the boards of examiners? Or was there some other way? How does one make decisions which affect all of physics in Italy if not through controlling the appointments?
Well, they control appointments.
How about the funds?
And also the funds. If you are a big shark, then you can control the funds much better than if you are a little fish.
OK, going down the list, now, we were talking about Cantone.
A big fish, fat. Forget about him.
Now, just one final question about him. Was there any specific field of physics that is identifiable? For instance, was he an experimentalist, Cantone?
He was an experimentalist.
I don’t remember. It doesn’t matter.
Ah hah, Parravano was the greatest of all the barons in chemistry. In chemistry there were much more baronies. There was — Not now. My friends are all dead. I tell you of before, you see. See, it’s very hard to speak about dead people — to speak against dead people.
You can’t speak against them by definition.
I cannot speak against them, so what can I say about them? Parravano was an example of (???), a leader, a king of kings amongst chemists. Parravano was the man who was making good weather and bad weather all the time. He was recognized as the lord. I met him only once, at a speech — I remember, the lunch, it was free, it was good — the speech, even better. He said he was faced with a fundamental truth in life, that the only way of living one’s life is to be loved. If you succeed in being loved, then you are great. That is the only quotation which I got from him.
He had a chair of chemistry at the University of Roma?
Of Roma. It was always the place — with the (inaudible) popes, you see.
So that was Parravano. Rasetti we talked about. I know about him for the moment. Fermi was there. All right, now Persico, you talked about him —
— ah, yes, yes.
He was Fermi’s childhood friend.
Fermi was a real prince. Persico was the man whom the people of Rome were calling the Cardinal in particus fidelium. He was in Florence where, it was not Florence but a certain surroundings. Persico was a theoretical physicist. There is a moment in which — as a man of low pressure. I can go no for days, you see. There I sonly a moment in which I collapse, but don’t be afraid.
OK, I won’t bury you, you won't bury me.
Philistine must have originally meant, in the minds of those who invented the nickname, a strong, dogged — the life and the point of the chosen people, of the children of the light.
Philistinism — we have not the expression in English, perhaps, we have not the word because we have so much of the thing.
Then there are more, you see.
OK. Now, to completely change the subject — we were talking about Persico —
Well, Persico, I don’t want to drop Persico.
You haven’t said anything about him yet. I just mentioned his name so we can start from scratch.
Persico was a theoretical physicist. He was a professor in theoretical physics. He elected Bernardini his assistant, so that Bernardini could have a chance for a place in the Institute and the university. He called us one day in his studio, explained to us that Dirac, what was the theory of Dirac, about holes and so on. And this again was of tremendous importance, for having been introduced in this way I was one of the few people in the world who knew that there was such a Dirac theory. In every text book by now, you’ll read that it was absolutely evident that the Dirac theory was the positron. I know it better. Only I still got in my eyes, in front of my eyes, a postcard, which has been destroyed since, in which it is written even if the positive electron should exist — no, even if it does exist, I still do not believe in Dirac’s theory. Signed, Niels Bohr. That’s right!
That’s fascinating. This was sent to —?
This was sent to Blackett.
Let me check in the Bohr papers to see if something of that exists.
Well, I don’t know — remember when.
I mean, that particular — there may be a letter too.
I think it was a very short thing, but you can check and so on. On this, I know very well — even when I came in Florence, very chastised, for this reason, that this professor had died, that people, they are feeling that I treated him as an old man. You see, I had not treated him as an old man, but it was simply feeling that I didn’t have any more job and — I know, I know I had no bitterness. But I could not go on, advertising to people that we were confirming that — for another reason. We knew that the gamma rays absorption was due to the(?) positive electron. That’s all right. Before publishing anything, — when you tell to people that such a certain thing exists, anyone can jump to a conclusion. It was in Cambridge, they could not. And there was a feeling that there was a party — my feeling, not to give any information to anyone even about my ideas. Even my ideas were derived from the surroundings.
Persico read us this. See. Persico kept us, in this isolation in Florence, completely in knowledge of whatever was happening in the scientific world.
So you see, sometimes, there is a moment in your life that makes you dream, you know, of building a chart, you see — in which your chart, you put images of sayings and so on. All right. Should I do a thing of this type, Persico is one on it.
Did he discuss the objections to the Dirac theory?
Yes. Yes. He explained to us that — well, he discussed it in a rather humorous way. The implications were evident, you see, he was one of the few people that knew of the existence of monopoles. You see. But you remember the Copenhagen, Faust — the Donkey-electrons should wander quite aimless through space, just wander, only with hole-like particles, they could have said to have found the feather.
This is, you know, the text of the Faustus.
These zwei monopoles that Dirac (massutif?). Well, this is Persico.
That’s Persico. When did he leave Florence?
He left Florence when I came back. Persico went to Milano.
When you came back. ‘33.
Yes. So we were very much in the hole, you know, without Bruno Rossi, without Persico. We were very very much in the hole.
These were senior men in age as well. You were all pretty young, the ones who were left.
Persico, Fermi and Rasetti — Persico had been a campanion in school of Fermi, was in the place which is the most important nobility place in Italy, it’s called Scuole Normale of Pisa. Does it mean anything to you?
Yes. I’ve been there to study the letters of Fermi kept there.
This is a place where people get a fellowship and where they — it is a college. It is one of the two or three colleges that are in Italy. The aristocracy of, the Italian School of Mathematics came out from there. Levi-Civita, Ricci de Bastro and so on.
Now the director of the school is my friend.
I didn’t understand that that was his position, in Pisa.
In Pisa he’s the director of the Scuole Normale. See, he is the director there. There is nothing, there is no situation in Italy so noble as the Scuole, being in charge of the future — the best young brains of Italy. You know him?
No. You mentioned Levi-Civita.
He was one of the great men of mathematics.
Yes, I don’t know if he was at this meeting. I am not so sure, I do not commit.
He was at the Rome meeting anyway.
He was at the Rome meeting, yes,
And he was on the mathematics faculty of Rome, is that correct? His position at the time, he was from Rome at the time?
Now, getting back to the list a gain, Gian Franceschi — from the Vatican?
I don’t know him. This was, what year was it? ‘31?
That would be — I got my degree in ‘39.
Well, he may not have been at all involved. He may have just been in the picture as one of the staff people, I don’t know. Then Vallauri from Turino.
Vallauri is a professor of electrotechnics. One of the big people in the Polytechnic.
And Giordani from Napoli.
Giordani’s a chemist, and he was a very intelligent man. He was young then. I didn’t know that he was there. When they were finished, he found himself in a position of great responsibility. He was actually the president of the atomic energy in Italy. And he organized the organization of the ENFN, what is it? Nuclear physics, and Frascati, and the sections on (???) all came out from this. Then he became the president of the CNR. There he had a stroke and he died. During the war, he has been the — during the war, he was one of the men responsible for this thing called IRI. It’s a very distinctive Italian initiative university in which the state intervenes with a certain percentage, the majority of shares. There are lots of industries in Italy which are IRI. See, they are partly state-owned, state-controlled. It is a form of the state capitalism. A good man and a chemist, yes.
A chemist. Borino?
From Bologna, yes. And Majorana?
Well, it doesn’t say here, but the one I know of course is the one who worked with Fermi, but Bologna.
No, this was the master of Bruno Rossi, this was a man endowed with a lot of experimental capacity. He worked practically in everything. There was in a way a continuous fight between him and Corbino, to decide who was most top dog.
I’d say there’s a great deal of politics.
There was. He spent a lot of his life in working in photographing spectra. It was an old tradition. All in all, in his last few years, he dedicated his life, if I am correct, (you can check it) to shielding and gravitation.
He was of the same generation as Corbino? Of the same chronological age?
Yes, he was also on the same level.
Most of these people who you refer to were barons, would you put them in that same category? For example, who did we talk about before? — from — Cantone, for example, and Bonino, Corbino, Garbasso — were they all the same age?
Yes, I would put them in the same category. I would say this, that among these barons of which I heard, Corbino and Garbasso were in the state of gods. But they were not cruel gods. They were good. They were progressive forces. They fostered their people and they helped their people. I cannot, I will not risk to give the same type of testimonial to honor anyone else of those names. Don’t forget that. I did not say that. I will be heard speaking about them in an equal condition from now on, they are “dead” to say the word. Nowadays, the baron, you see, — in the lab is holy saint Professor Occhialini, you see, santo, big glamor, Professor Occhialini —
This is written. If you travel in the corridor, you will find that there are a lot of writings. I don’t go there. I don’t thrill them for what it’s like — avanti?
We were talking about what I will call the other Majorana —
— the big Majorana.
And we agreed that he was in the category of baron. About the same age as Corbino and Garbasso and Cantone, but with important differences.
And his work was in photoelectric effects.
Yes, he did a lot of work, you see. He was supposed to be a kind of prince of experimenters. All right. He did exist. I remember when I came back from England — one of my friends were, Rosani, who was professor at Padua who got the chair which Rossi left when he had to leave for excellent reasons. There was — as I say, there was something changed.
Yes, in this moment we fight, I fight for the defense of Padua against Rome, against Naples and so on. The situation is different. While if I look behind, I find out that we are not so bad. We’re not cruel. These people, they are really wicked. He was announcing me that I will find in Italy the risks of talking were not so bad. As I say, there have been people that talk too much, and then they say, the Concorso, and so on you see. Now, it is a battleground. You don’t respect very much by telling what you think about a person nowadays. More right, just one more right, you see.
But you’re saying that perhaps this change took place after —
— after the war. After the war, and the elimination of the fight — yes?
You were just making the point about the change that had taken place, in the postwar period, regarding the kinds of political fighting that would take place at the universities, in terms of the ability to speak out, and not have it held against you and so forth, and you were making the point — I was just belaboring it now — But there’s one more name on my list, and that was Carrelli. That’s the final name.
Carrelli is a professor in Naples. He was a professor in Namples, he was a spectroscopist, and he has been during a long time — responsible for “tibu” and the radio, direction of radio, — he was one of the promising young people of the Segrè epoch. While Segrè was working in quadrupoles, I remember Carrelli, was working in spectroscopy and so on. This was the thing which was there. There were two people. The two prominent uncommon people were Carrelli and Bonino, Secarista(?) and so on. He’s a very intelligent man. Very intelligent. And he called Majorana in Naples, where he was professor in Naples.
This is Ettore Majorana we’re talking about.
Yes, Ettore Majorana in Naples. He was there the last time. The first and last time I met Majorana was in Naples.
Carrelli is listed here as of Catania at the time in 1931.
I would not be surprised. When I met him, it was in ‘37, coming back from Brazil, — I landed in Naples, and I met him there. Carrelli in Naples, and for the first time Majorana, and Majorana disappeared 15 days afterwards.
Well, that was a long tedious task, but anyway it was helpful to me, because these are just names, and now fit together and make some sense.
But I didn’t give you in a complete who’s who, but you realize it.
Oh no. I just wanted —
— don’t ask me what Majorana did. When I was a young man, Majorana to me was a very powerful professor of physics and so on. I did not know what he was working on — I was too ignorant, you see, to understand what he was doing. Carrelli and Segrè I do remember, for we had some occasional meetings, and two weeks I was assisting — then I do remember what they are working in, what they are working about. You forgot a very funny fellow. What you had, you had Italians down there. I remember — yes, yes, yes all right.
I gave you the names because the list of the others is pretty clear, where they’re from and so forth. My purpose in this was to give me a head start on who’s who. It saves me many steps. Also in the process, you said a lot of other things in terms of relationships, different places, and it’s precisely that point I’d like to get back to and then get you into Cambridge. You mentioned the decision that was taken by Rossi and Bernardini, in terms of radioactivity, and the difficulty of following through because of the sources, and then you very nicely showed how Rasetti’s work solved one of these problems, which made it possible for the Rome group…
The Rasetti specialization — Rasetti had been up to then a spectroscopist, decided he was going to become a radioactive chemist. He was going to spend a few months to learn separation, so that people could enter in this field, really an unknown field, you see, of this extraction. There’d been always some idea of magic about the idea of the source, of the cleanliness of the source, of the contamination of the source –- of the oxidation of the source, of the way you should mix it and so on. And then, there was this question of the polonium production, optimization, the beryllium and so on.
Well, you explained that, and the fortunate position of the Rome group, because of their supply through Trabacchi of the polonium.
Yes. Let me substitute for this word position, the fortunate initiative of the Rome group, and the wise initiative of the Rome group.
But suppose that same initiative existed in Florence, it would not have been possible to get as good results in terms of the supply of radioactive materials, because there was no corresponding institution in Florence.
Well, being in Italy, you see, being in Italy, it was really a question of sharing and — I don’t know. I don’t know. Certainly since the Bureau of Sanita was at a distance of one mile, from the new place where the Institute of Physics was going to be, the fact of having this kind of centralized thing was certainly fortunate — it was a very very happy iniative — it was the right moment for – what mattered was polonium. Why polonium? Something which would give alpha particle with very very little gamma radiation.
The alpha particle of polonium are not very energetic. But there is on the other things(?) a radiation of 0.7, which you cannot solve very easily, while what you get from radium, plutonium, and all the other things is 2.1, 1.8, 1.7, and so on. And very very dense(?). While polonium, it approaches the pure alpha particles.
Now, since what we are going to investigate was, to bombard elements and to see gamma rays coming out, it was evident that the best thing to use was something that did not have its own gamma rays for this, which would introduce a problem of background to report. As a matter of fact, the polonium - beryllium was not dangerous to carry around. Even in the emission there was no neutron — at this moment, I don’t know, but I only knew then that Rasetti had charged himself with all this.
The problem is not clear to me in Florence because you implied that because of the difficulty of getting radioactive sources, the decision was to go into cosmic. First the decision was taken to go —
— no. No, no, no, no, sorry.
Then I misunderstood.
It was, when you write history —
— could you close the window, because there’s a loud hum coming now.
When you write history, you must look at what happened afterwards, you see. In cosmic rays there was a problem of radioactivity which was tied with a lack of existence of the possibility of penetrating power, to lack of the existence of a new gadget — rather easy to use, requiring very very little difficulty to go in the study of high energy radiation. It is well known that it is easier to study high-energy radiation rather than small energy radiation. In that case you must have windows. You must have solved the problem of contamination.
So that, the first decision of Bruno Rossi was to go into cosmic rays. Then, Bruno Rossi, they hit on the idea…
Anyway, Bruno Rossi never thought seriously that he might go into radioactivity, but he was very very much absorbed in cosmic rays, he was feeling that this was the direction in which we might go. And this became a policy when he came back from Bothe, and he suggested that we might try doing it. And he suggested that the only way to do it was by using things(?) which are plentiful and cheap, and we should be working on something which had such a small effect, which would not be absorbed. This was the beta radiation from potassium — and rubidium. And so we started on rubidium, why? — just for the fact that the gamma radiation of rubidium is very very small, and rubidium has a rather small energy, potassium has a higher energy — and also, as it has been shown by Colosta when they went to find the cosmic rays in a mine of potassium, they found the operator was getting practically swamped with gamma rays. Like this they discovered that the potassium was gamma, was gamma radioactive, that is to say, but they only circled from a mountain of potassium. They did discover that they better stay out of there, rather than to go inside the earth to study the source of cosmic rays.
When was that?
This I think was in — I think it was in the paper of Bothe and Colosta was in ‘29. I would say that it was between ‘29 and ‘30.
We were talking about the beta ray studies of potassium and rubidium, and the gamma rays.
Yes. I was explaining logically how a group was working in cosmic rays, would, following a certain strategy, and I didn’t tell you that the strategy was mine — it was Bruno Rossi — would study again natural gamma rays, for what you get from such a material as potassium — something that you can maybe study in the same way. Since the cosmic ray, radioactivity, is very very small, then you can make the next step by using the apparatus which you use for this rather small radioactivity, to detect small radioactivity. This was the idea, you see, and in order you have potassium and you have rubidium which is relatively small, and at this moment people didn’t even know if — all general ignorance — they are like this. And then Bruno Rossi hit on this rather simple way of doing it. He was demanding a Geiger counter and magnet, and we had in the lab a magnet which had been used for the Zeeman effect, which had enough… So all the apparatus was more or less like this. There was this here, there was the rubidium salt, put on this. There was this counter, with the exact size, about the size of a rolled cigarette aluminum paper, aluminum foil around it, and then there was the caraton(?). In short, it was going into radioactivity by using the resources which were at our disposal. There was the idea of getting more, and it was for this, that I went to Blackett with a very ambitious project: (a) to learn how to have this miraculous, unbelievable, complicated, devilish Wilson chamber to work, and also to learn a bit, all that I could learn, about radioactivity and so on. And here I want to be absolutely clear. When I came there, I went there with a fellowship for three months. July, August, September. I stood there three years. There was no plan from outside that I should do any work there. There was on the contrary, there was the idea that I should come as soon as possible, so that I could help the lab.
I see. Who paid for the fellowship?
CNR. The National Council of Research. But who was supposed to have the fellowship was not me but my senior and superior, the person who had more age and experience, Bernardini, and Garbasso arranged another fellowship for three months, and the fellowship was for Bernardini. Bernardini went into the military service, so he could not use it. Then, not by merit, by only for the fact that there was next on the list, the fellowship went to me. Then it was decided that I would go, for a certain term.
Go to England, why? When people tell you that I knew a lot of English at this point, it didn’t prove very much, I know it very badly…
You were saying… why England? Why go to Cambridge? And you were saying, it was believed one reason was that you could speak English somewhat. (!) And I didn’t know if you were going to tell me a more substantial reason.
Because that’s the reason, well, this was my first idea, and the thing which was nearer, was Germany. But when Rossi went, I don’t remember where, and he met Blackett and his wife, he came back with such a glowing report that I decided this was the place, you see.
Think about this, you see. I was telling my daughter day before yesterday, after all, it was in 1952 that I went for the first — no — I lied to her. It was in 1942 that I went for the first time in my life in a sleeping car.
I used to go from here to Cambridge third class, two nights you see. There was this Wilson anniversary and not anything was granted. So I had again the same thing as here you see. I started whenever I started, from Paris, and landed and then, I arrived at 6 o’clock in Edinburgh — it was like, really like, the old time again, you see, when to pass all the night in train, you see, and to come and ride unwashed, unshaven, in the…
OK, the point was, about why Cambridge and the other places — and you said how Rossi’s meeting Blackett and his wife, you told me earlier, with her knowledge of Italian, the fact that she was Italian—
She was Italian. Blackett was considered to be at this moment… Blackett, I must say, in this epoch, was known for his work. But in the general epoch, around Cambridge, he was just very successful photographer, a very ingenious mechanical person, he was that, you see. On the other side of this idea was going to the place where Rutherford was going, you see. I remember that I went to see, two days before leaving, I went to say hello to Bernardini, he was a soldier, you see. He went the year afterwards. And he chose Dahlem.
I remember the letter in this moment which he sent me. I remember how he was ending the letter — he said, “Look here, shall I tell you that I wish you good luck, for this three months, which you are going to pass near Rutherford, — believe me that it is a bit like to wish you happiness for all the rest of your life.” Says Bernardini. It was actually prophetic for me, saying that to look at my life, you see, whatever happiness…
Then I had this extravagant experience, to arrive in the house, and Blackett, when I did, to be offered first thing in English, the packet, the cigarette, and so on. Then the first English he did ask me, he said, “All right, how is the political situation in Italy?”
“Well,” I said, “I’m not very much — I’m not very much interested in that.”
Then Mrs. Blackett said, “Look here, we know all about it, and what your attitude is and so on. Here you are in the house of friends, and we are feeling certainly the same way you do. Please relax.”
And this clinched it, I was an anti-Fascist, but I understood that in England, that you don’t get into political activity simply by poetry. You must give some time — political education is a hard job. Even if you are to do it in an amateurish way — it is a very hard job.
Today, this morning I left the story of Rutherford and Blackett a little.
Yes, and before we get to that, let me ask you one other question. You said the possibility was to go to Germany, and you said why the emphasis changed to Cambridge, just what you got through saying. Two things I want to know. Where in Germany, and secondly, since you told me that one of the reasons you went to Cambridge was because of the cloud chamber, and it wouldn’t have been possible really to consider any other place, I don’t understand the fact that there was even another choice. You did say that there was one, the possibility was to go to Germany.
Well, please, do consider that I was — that I had to choose where to go, as a second —
— next in line?
Next in line. What was frightening me was the idea that I might have gone there to learn radioactive chemistry. This it seemed to me was one other thing that I might have been required to do. For this it might have been either the Curie Laboratory, either Dahlem. As a matter of fact when I went away, I had an ambitious project — it was to do the Wilson Chamber thing (a) — (b) it was to try to learn something about how people work with radioactive substances. The first thing on the first days Blackett taught me was how to make polonium source… (end tape) Before in Germany.
At Lise Meitner’s laboratory.
I don’t remember where.
He was in Berlin in 1930.
This is one of the funny things in life, you see. He was living in a laboratory where there were people who knew radioactivity, but he too when he had learned some little tricks of radioactivity, right away a source of gamma rays and so on, he had found it at the time when he had gone abroad. So he has done again what I did — the same thing — I learned how to cut leaves for the electroscope and he taught me how to make polonium two ways, on a rotating road(?) and on electronics. I showed such enthusiasm that he stopped me and said, “Look here, this is all my supply. You are depleting practically all of it.”
There was the lab which he was directing which was the radioactivity part of the Cavendish Laboratory, just for students, so they were measuring decrease of time and activity; they were measuring ranges of alpha particles — all this was a part of the practical education. Since he was directing this laboratory, he had no difficulty at all in telling me, “If you want to start learning this so that you can go home with some art, but if you want to work to learn this Wilson chamber, I am afraid that three months will not be enough.” And sometimes people have gotten the kind of funny idea that maybe I went there in order to learn how to control the Wilson chamber with counter — to learn how to do it — and then come back. Not so. I came there, sent to learn the fundamental of this technique, and I did not even dream for a moment that I would be associated with any work in the Cavendish Laboratory when I went there. I went there as a subsidiary — I was feeling that I was like a technical man who went there to learn something. I was very very conscious of the fact that I was occupying the place of my best friend Bernardini, so that when Blackett told me that he had come to the conclusion that we might do something together, I momentarily was in a hole. I was very very remorseful.
As a matter of fact, one I sent to Bruno Rossi a pupil of mine, who is a big man now. He was a brilliant young man, and I sent him for one year. After one year he wrote a very shy letter saying, “I would like to stay more with Professor Bruno Rossi.” And I said, “Tell Professor Bruno Rossi my name and that I don’t forget that he sent me for three months and I remained three years, and that this has taken away every right of mine to deny the same right to anyone.”
Was it toward the end of the three months that you were faced with this decision?
No, it was fifteen days after I came there. Blackett went on a holiday in August and by August we had already discussed the thing, so much that he gave me the key of his house so that I could build in the shack of the garden an apparatus to build counters so that it would be more clean than the known level of radioactivity of the Cavendish Laboratory. Because if you start building a counter it is one of the most vulnerable things to radioactivity. You seal it and if in any way it is not clean it gets mad and then you don’t know…
I will say this: out of the experience that I got with Bruno Rossi I knew how to use Geiger-Muller counters. And in England there was no activity done with Geiger and Muller counters apart from the activity done by a brilliant physicist, Hugh Webster, who was working with Chadwick. Webster was working with Chadwick on polonium and beryllium radiation. And he was the one who very nearly discovered the neutron. I must say he was very unlucky. When some time I shall write my real history, my secret history of physics, I shall explain why — what is the necessity for discovering a new particle and the different situation in which it might have been discovered then. But, of course, you are not interested in discovery.
Webster, in my opinion, was unlucky on two or three counts. First of all, the source which he had at his disposal was very very small. You cannot work with something which — when you have a ground of cosmic rays and you work in a laboratory which is contaminated and you get particles in your things, and when all of what you get is one or two impulse — it is very very difficult. There is really no substitute for intensity.
I want to get back to conditions of work at the lab. First, you had said that he was the only one who had done anything with the Geiger-Muller counter there, and then you said that you had come with that experience.
The Cavendish had tremendous experience in the Wilson chamber. There were then two Wilson chambers of Blackett’s (automatic), one Wilson chamber of Feather’s, one Wilson chamber of Alexander’s with a magnetic field… (Interruption) Now then, what was I saying?
You were talking about the very early decision to stay, to extend the three months into a longer period before the three months had really started very much, and you were about to explain something along those lines by telling me the story about the experience you had with Geiger-Muller counters.
I was saying that here I was in a place which was the first big laboratory I ever met in which they had experience in the Wilson chamber, they had experience in the ionization chamber, they had a school which had developed the automa(?) method Wynn-Williams, Duncanson, Muller had brought it to a high state. They were measuring actually individual alpha particles; they were measuring individual protons; they were measuring things with big rays(?) gratings. They had come out of the crystal stage and they were counted. Day and night the counting would go on due to the fact that electronics had arrived in the Cavendish Laboratory, and they had concentrated in these two directions. The tube counter had been invented in Germany and they simply did not have enough people. There was only one person who had been — yes, they tried to put someone — will you switch this thing out? If he has not died, he did occupy a very high place in the organization of science in the States.
The point is this: when I came there, they wanted me to — Rutherford said to me: “Look here, you get some tips from Wynn-Williams. Why don’t you build a high-tension generator?” Immediately, I must put their condensers and so on. That was too difficult for me. How were we going to get tension? The same way as Rossi did. How? We had a group of dry batteries. It is true — it takes more current, after all.
While I was arriving, Webster, who might have been the person, left and went to work in Bristol. Now, he’s in Australia. (I met him two years ago. I never met a person with such joy, with such an effusion.)
And then I inherited a group of the things which there was. Of course, I couldn’t do very much about the material when I needed something which was different.
When you came, it was clear that you were to work with Blackett primarily, even at the stage when you were coming just to learn techniques? But at the same time you were encouraged to dip in to other things — with Wynn-Williams.
No, this was later.
I thought maybe it was. Let me then take it back to this period and bring you up to a later point. First of all, you came in July.
I think I came in July. I don’t remember exactly when. I might find out only by looking at certain newspapers. I came a few days after the war in Spain started — a few weeks afterwards. No, sorry, I was thinking about another departure to Brazil. I went in July 1931. I remember my friend Racah and I were exploring a cave at this moment. I had to give up this cave in order to go to England. It was very very sad. Racah brought me there to this tremendous hole — they made at first 120 metres — I started the exploration there. Then I came out, still all dirty, went down and changed and started for England. I remember the day when we arrived on the mountain, they asked us, “Who has won the tours de France?” They didn’t have any newspaper — the people who arrived two or 3 days before, and so we told them.
Just a question about Racah — where did you know him from?
When I was a student in Florence. He was not my school companion; he was one year after me. He was younger by one year than me.
Just one other simple question on Florence — you said when you got your examination for the degree that you were told to report to the laboratory the next morning and that that was a position without any pay. You were there two years. What happened during that time? Did it change to a paid position?
In Florence first I was like a voluntary assistant, the first year. Then I became assistant, not a regular assistant. For this, you were supposed to give a concorso.
I went back from Cambridge when the concorso was given and I had my concorso. And this was in February 1932. Six or seven months afterwards they wanted me back so that I could have a status, and then I was in the administration. But for this I was not paid. I had my fellowship. My fellowship, which I had been given for three months, was very very ample. It was 10,000 lire. I remember… I had done my calculation… I had the dream which every young man has at a certain age: I wanted a motor bike. And then I calculated that if I had gone there and worked and lived a very modest life, I might have come back with some of this money and might have contributed to buying a motor bike. But the motor bike idea was ruined. Then they gave me two other but life was bloody expensive in Cambridge. Whatever you did was very expensive. I had difficulty making ends meet and in the year 1932 I arrived, I think, with not one penny(?). I survived because I got a prize of 50 pounds from the Cavendish. There was a tradition that from what was left from certain laboratory fees, 50 pounds was pooled and was given as kind of a reward to some young man who had done well, so as to say, this is my life and this may be the prize number one I got.
Then the photo had been sold to the Illustrated London News.
The photo of the pair production?
Yes. The Illustrated London News paid 100 pounds. It was given to Blackett and Blackett gave me 50 pounds. Then, one day, Mrs. Blackett who was on radio giving Italian lectures, lost her partner with a bad throat. By telephone they rushed me to London to BBC to substitute with her. I substituted for the other partner and this gave 50 more pounds.
When you got the Cavendish prize from this pool…
It was not a Cavendish prize; it was something by which they told me, “Look here, you have been awarded this kind of pool.” Then I went to Blackett and I said to him, “I want to thank you.” He told me not to thank him, but if I wanted to thank someone to thank Cockcroft. No one wanted to have the responsibility of this thing.
This brings me to the question — in the first month of your stay you had apparently come to the decision with Blackett that you were going to stay longer with the full knowledge that your own fellowship was going to run out in three months. Was there any promise, any idea you had of a fellowship or some kind of funds coming from some other source? You say no. Was there any prospect of a continuation, an extension of the fellowship?
No, but remember this, that Blackett had an idea that I could get a Rockefeller fellowship, and then came the man of the Rockefeller fellowship and Blackett invited him, and Blackett wanted very badly — you see, at this moment, I really had become friends with Blackett, and he wanted me to stay more.
I think it was during the Clerk Maxwell Celebration, if I do remember, that this man came. To put it very simply, the Rockefeller Foundation gives fellowships; it does not prolong or renew fellowships of other institutions. This is what I learned.
Was the man you saw, Tisdale?
Yes, I remember the name Tisdale. I was introduced to him.
So it wasn’t their policy.
Mrs. Blackett did what she could and invited him to their house but there was nothing to be done.
When you had decided to stay, did you have a time period in mind? Were you thinking, well, I’ll stay an extra year, or was it just open?
It was completely open. The very simple idea was this that Bernardini had made the prophesy and it was true that this was the chance of a lifetime, that after this, nothing would matter anymore. Believe me that when your eyes have seen first something, it is worthwhile. This has been the general(?) line which is never said — you find endless poetry and praise which said this, you see.
It was anticipated of course that it would be a shorter time and it was also anticipated that the thing would behave gone on a certain line while it did not go on a certain line. It was anticipated that this would have been an excellent way to do counting of ions. We didn’t anticipate that we could measure a ray dispersion. On this there is one person whom I would like you to see. He is called P. I. Dee.
Yes, he is in Glasgow now.
Yes, we met in Rome once and we went over the old times.
It was very difficult to build for me in a period in which my interlocutor understood half what I was doing and what I was saying. I was trying to look intelligent, doing what women are supposed to do, standing and admiring everything. The first person who had the idea of controlling the Wilson chamber with some kind of counter was P. I. Dee at the Cavendish. When he came there I really don’t know. What Dee wanted to do was this: he wanted to have a Wilson chamber. He wanted to get the proton in the Rutherford experiment by a Geiger point counter. He wanted to repeat the Compton-Simon experiment. He wanted to do this: here is an alpha particle which scatters in one direction. You have a proton which goes in another direction so you have got a longer range. When the proton arrives in a certain direction, then you fire the alpha particle, you fire the Wilson chamber. And so you choose and you accumulate a good number of Rutherford information.
Now, this would have been a wonderful idea in 1920 or 1921, ‘22 or ‘23. It was not any more a wonderful idea, but it was the idea. So I think that chronologically he was the first (and in fact he told me) and I remember the state and confusion in which I was when I was in the library talking and I heard the name Dee — a funny name — and then Dee came in the room. He said, “Look here, what you and Blackett are trying to do is an experiment similar to something which I proposed.” I was sorry. I did not know how long before he had proposed it. But Dee was a perfectionist. I would not be surprised if he had been leaving this idea during three or four years.
When I came to Cambridge I was dreaming about studying anti-(?). It is now everywhere in the world. The first time it was evident in the world I explained it to Blackett, you see, “Look here, this is what Rutherford does with alpha particles, with three layers of aluminum. I said, Do you want to do it with a counter?” He said, “Yes.” I said, “What is the difference between the Bothe-Geiger experiment and this? Well, in one case you detect a particle by its presence; in the other one, you detect it by its absence.”
The complication about the Wilson chamber was and it is even now that it is a relatively slow apparatus.
Even when automatic?
Even when automatic because it requires a certain time for setting and you must do of clearing experiments of this type. So this was making impossible the dream of Shimizu. Shimizu was a young Japanese who came to see the Wilson Chamber, and he put a handle, and this is still sold as the Shimizu chamber. It was for alpha particles; it is no good for electrons.
I do remember a wonderful story Blackett told me which I could put in my book of papers. Blackett says, “This is worth trying. It’s so and so.” I lost that.
But what Wilson had discovered was that you must go through a rather complicated business in which you take a moment (movement?) like this, then you do it again, then you do it again, smaller, smaller, smaller, then the chamber is clean. To do this you must use a rather complicated system of camps(?). Blackett was the first who invented a lot of these camps(?), and in the old tradition of the Cavendish, of the jack-of-all-trades, no one would do it for him, he had to build it with his own hands. During this time, Rutherford was fuming. “What is this perfectionism?”
(???) told me once that he was shouting: “One of these days I will call the carpenter and ask him to do a Wilson chamber in wood and it will work. What is this man Blackett doing?”
If I believe Blackett, Blackett was going on, unruffled, and then one day, Blackett turned two or three switches and then in three months, it took ten or twenty more pictures than had been taken. All these difficulties had made the thing so automatic, it was so rugged, it was so solid, so British-built, that the thing was going on automatically taking things. And what was more important, it was precise.
It was the beginning of the production line technique.
This was the result of the coming of a Navy officer, like Blackett, an engineer, tired of preparing for the next war, to work in physics on a fellowship. This was important that Blackett was always an apprenticed machinist(?), and his attitude was this, you see. And Cockcroft and Walton were people who became physicists, and Lawrence. They became physicists and they have shown the old sealing-wax and string people they could build things wonderfully and they could sometimes clear think about things. The presence of people like Rutherford you would not question. There was only one Rutherford. What was counting while the experiments were difficult to make was the quickness with which we were doing them.
Exactly. And another tendency at the same time and also a man who was full of ideas and who was also a wonderful engineer in a way was Kapitza.
He, of course, was very much still there. His laboratory was being built at about that time, wasn’t it? The Mond.
The crocodile laboratory, yes, was being built at this period, but he didn’t have any time to work in it, you see. It was built and then he went away, possibly a few months after I left.
In the summer of ‘34.
I left in March, April of ‘34.
Let me tell you what I have in mind to do about Cambridge and then let’s decide when we should do it. What I would like to do is systematically talk about Cambridge itself, about the organization of the laboratory, the little things that you were talking about, about the glass-blower, about the relationship of the experimental physicist to the things he needs in his work, about Rutherford’s attitude, about the relationships between Kapitza and Chadwick, Cockcroft, Walton, the role of Wynn-Williams — all of this. I want to know about the international aspects of the laboratory and the various research students. I think Gamow came on a visit when you were there.
Gamow came on a second visit.
Bethe was there.
I never met him there.
I don’t want to get into it at the moment but these are the kinds of things. It is a full story in itself. Those are general questions about the laboratory. Then I want to do in very logical order the specific work that led up to that. (Interruption)
I said I would like to cover in general your laboratory relationships and so forth. You started to tell me about the kind of limited relationship you had with Rutherford and your attitude toward it. I said I wanted to talk about laboratory organization in general and then to do a very logical step-by-step approach to your specific research. We have talked about certain circumstantial up until that point — how you got there, how you decided to stay. So for the remaining period of time today why don’t we continue with the circumstantial because I’d rather not see us interrupted with the other but do it in a continuous stretch. If it is all right with you I will ask you some questions.
First, about the organization of the laboratory itself. You mentioned that Blackett was in charge of a radioactivity group.
He was a tutor. He was a Professor of Optics, if I do remember well, and he was also in charge of the laboratory work, the exercises.
The practical work, I think they called it.
In German they called it the practical work. And he was a lecturer in optics. More important, he was a Fellow of King’s College. Don’t forget how tight is the organization. John Cockcroft was a Fellow of Trinity College, and everyone of the people around were in some way associated with this sorority, let’s call it, of the colleges. This was the staff. In this picture, all the front line are staff people. They were, for one reason or another, the boss — what they used to call the samurais, meaning they had the boshido law. They were the important people, the people who were bound to have the best tables. They were all tied to the college system. When they were inviting me to lunch, they were inviting me in the college. It is where people like Feather, people like Wynn-Williams, all these people were around, in different seniority. The new generation of physicists were initiating the industrial revolution which I was telling you before, which you so very aptly said that Blackett was one.
That was one standard. The other standard was that of the gentlemanly life in the university — is that what you are saying?
I was not speaking about the two standards but about the two groups, combining together the two classes, if you want to talk in Marxian terms. There were the people who had the tendency to make physics by the use of certain tools and the people who were starting in the use of new technique. The two classes are invented by me for the fact that I was feeling that here, a revolution is happening. I was feeling that the protagonist of this revolution was Wynn-Williams. Wynn-Williams, for people like Rutherford, was an excellent tool. This is the definition of revolution — a person who in the first generation are tools; in the second generation they become diverse because they learn what makes the… Cockcroft was a tool, you see. The system of distribution of the Cavendish — it was very difficult to have things done in the workshop because there were too many people there. The thing was dying, like in Milano and in Paris and in London, was dying because there were too many people. Too many people doubling up the conditions. Then there were the people who were doing their own work. Some of them were very wonderful. Lewis, who later became one of the big bosses in atomic energy, I remember coming on a bicycle where he had a purse, as big as this, completely full of everything that a mechanician would use.
What was the reason for this large increase in the laboratory?
No, the point is that this has always been a laboratory with a lot of people. There were no more people. It was a part of the population. But there were new lights coming out. Rutherford and Chadwick were counting particles or detecting things, which was clean, with a microscope. At the moment when they decided they might do it electrically, it was a completely new then they decided that they must make like Ellis and Rosenblum who discovered the fine structure in alpha particles — all right, this is something in which you have something to say. Rosenblum has got a magnet from Bellevue — all right, we must design our own magnet. Then Cockcroft designs the magnet. It was big like a yo-yo. And then you must have a very great stability, so you must build a contraption with mercury, and so on. And they were counting at this moment — they were not counting by dozens the alpha particles and protons — they were counting by millions. They needed fast counters. And then comes Wynn-Williams.
But all of this — don’t forget that in this organization the Napoleon moment which Chadwick had was possible — why? Just for the fact that he was counting aluminum protons and he had only to take out the source and to put in another one and then he detected the protons. Then he takes away the hydrogen and he puts nitrogen and he gets the kick. Again all the discovery of the neutron is in this. How could he do it? He had an apparatus built for this. He had built the apparatus. There was a group of people who had built the apparatus four or five years before. There was all the experience of Wynn-Williams, and so on, you see.
At the post-prandial speech in the honor of the Cavendish dinners, Feather declared the alphabet of the Cavendish. There is a phrase about me which is completely unfair.
Do you have that? I’d love to see it because he published in an article one paragraph of it — the one starting with “p.”
The thing about me was very very unfair. I remember — I was talking to Chadwick. Chadwick was assuming I was making an ideological mistake. I wasn’t. I remembered it to Feather. Feather still knows it by heart. In these post-prandial speeches, you know, people they fool. Then Feather at the speech in honor of C. T. R. Wilson said, yes, he remembered the old times with C. T. R. Wilson — and he goes on reciting it — and he had forgotten the existence of it, but I told him about it. And then there was one which was rather important: there was a young technical man “N” called Nutt. This was the man who was keeping in order the apparatus of Chadwick and Feather was saying: “Nutt, N is Nutt.” Who is Nutt? He is the discoverer of the neutron. Occhialini was — this is the only one which I remember — “the primitive linguist with his hands in his hat will demonstrate his latest absurdist impossible theory,” and then they say: “I wonder if it will always be so.” This business of the hat, it was correct because when I was standing with Chadwick, I took the hat and this is the Wilson chamber. “Are you talking through your hat?” shouts Chadwick to me, and I say, “I am sorry, I am telling you again, this is the Wilson chamber. I am not talking through my hat.” I was trying to explain to him that I think that gamma rays were produced by us for it was coming after a moment in the Royal Society in which I looked out — I was sore with him for his insistence in wanting the positive electron to be a sub-state of the neutron.
You know, in our paper, we did say that Dirac was right. If you read the paper of Anderson, you discover that Anderson was speaking about positive electrons being due to the breakage of a proton into a neutron and something else. We believed in the Dirac theory. This is a bit unfair to Blackett — the way I am putting it now. I will re-word it in another way.
Blackett spent a lot of time in convincing me that there was sense in this theory, and that it was much better to accept a theory, rather than to accept nothing. Niels Bohr did not believe in it. I’m not sure Rutherford ever believed in it, or Chadwick ever did believe in it. This was one of the elements. Then… negative electrons had been observed by Joliet and Curie going towards the source — the magnetic field — and then we had the fact that there were two groups of experiments: one German, and the other English. And the American Chinese were proving that when you go at a certain energy on gamma rays something funny happens you seem to get a new way of absorption. The absorption, the measurement of scattering of this radiation was living in the German paper by Meitner and Hupfield(?) — to a radiation there is scattered around of the same energy as this radiation incident. The English evidence of Tarrant and Gray was showing that the radiation remitted was between one archimedian(?) and a million volt. The attitude of everyone was to trust Lady Meitner, but these two poor guys, since they were Gray and Tarrant, no. one did believe. Everyone was saying that having built and having worked in an ionization chamber the result is certainly over-corrected, so no one knew what they were meaning. Once you believe — anyway, we came to the conclusion that the absorption of gamma rays, the creation of positive and negative electrons, and the subsecret disappearance of the positive electron by (???) will lead to an anomalous absorption and will lead to irradiation of (???). This to Blackett and myself was absolutely evident. We printed it at the last minute for we were in doubt… I don’t exactly remember the situation. There is a cricket word meaning it goes with a spin in the wrong direction.
In American, we call it “to put English” on something. It is the same term.
So… we really felt the Dirac theory was established… and in this way, we could measure the mass and the positive electron had been detected… At this moment, Chadwick…
That was when?
Which paper was that?
This was two papers. One initial paper after five consecutive nights in the Cavendish laboratory I succeeded in getting the bloody chamber to work. My having the neutron source showed that there are positive electrons coming out, especially through a plate, and so on. The neutron source was so small that I had to take special trouble… I took 250 pictures and sweated blood for it. But Chadwick did not want to believe that this was due to the component of gamma rays. He wanted it to be associated with neutrons. And he was wrong. And then I lost my patience and I asked Blackett if he would get for me a source (???) and then I started counting.
I remember at the Royal Society when I arrived. On the special machine I took — I developed the plate and the plate was dried on the train. It was a very very bad one. I said, “It is still evident that there are tracks carved as positive which come from the gamma ray source.” And Chadwick shouted, “Yes, but they come from every side.” Then I said, “I have here a photo which Professor Chadwick maybe would like to see. I will present it to him tomorrow morning at breakfast.” He asked for it and I showed it to him now but it did not convince him.
You know there was a silly tradition you must remember the vanity tradition at the Cavendish. They had not only to produce good work with the Wilson chamber, but they had to produce bloody good photos. Blackett would not allow, Fowler, and so on. In fact, when some more of the photos were so bad, when the thing came out, he said I should not even sign this paper the photos are too bad. I said, sorry, but I cannot do very much about it. You cannot have good photos when you have a light that shines inside the thing and you need to follow all the tracks of the particles and you want to know that it does not bend, you must illuminate the glass. And you put a patch, if you do not want to have it outside, you put a patch of lead over here — this was the point, when you put a patch of lead here first, then you put paraffin here protos(?), so the gamma ray absorbs and the patch of lead was showing… Did you ever hear a thing called “Fido?” Fido was the artifice of warming with flame the derivation field so as to boil away by radiation the fog. This was employed for the first time, prepared with gasoline and so on, in the Ardenne, at the Christmas offensive. This was the kind of thing…
(explanation far away from microphone)