Giuseppe Occhialini - Session V

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ORAL HISTORIES
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Interviewed by
Charles Weiner
Interview date
Location
Professor Occhialini's apartment
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This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.

Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event. Disclaimer: This transcript was scanned from a typescript, introducing occasional spelling errors. The original typescript is available.

In footnotes or endnotes please cite AIP interviews like this:

Interview of Giuseppe Occhialini by Charles Weiner on 1971 November 18, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/31789-5

For multiple citations, "AIP" is the preferred abbreviation for the location.

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.

Transcript

Weiner:

Today is the 18th of November 1971 and this is Charles Weiner talking with Professor Occhialini one more time in his apartment.

Occhialini:

Listening to Professor Occhialini — trying to listen to Professor Occhialini.

Weiner:

Last time, which was May I think, we had taken the story up to Brazil. What I would like to do now is to ask you to briefly summarize the trend of your research in Brazil and to evaluate, apart from the personal circumstances, whether that work played much of a significance in your total research orientation — a very general question.

Occhialini:

Well, I am not very proud of the trend of my research in Brazil at all. There, a streak — it was much more than a streak — of weakness in my character was illustrated to me. What I did was not important but I got prepared to do better. The line of research which I had when I went away was to work on weak showers using the type of Wilson chamber which had certain characteristics and had been edited each year without precedents. Four Wilson chambers, as a matter of fact, were corrected. I found in the first Wilson chamber which was built and which was working like a dream, an error, with tremendous ease. When I could see it working, the war between Brazil and Italy started.

Weiner:

What year was that when the war started?

Occhialini:

Let’s see, there was Pearl Harbor in December ‘41. In February ‘42 there was the Conference of the Chancellors and on this Aranya decided to break relations with the Axis powers. The reply of Italy was to withdraw not only the Ambassador but any national in any capacity who had come with the kind of arranged contract with the Italian government. I was one of these people, and I had either to say that I did not want to come back to Italy or to remain there.

Well, it is very characteristic of my general destiny to choose neither. I did not refuse to go to Italy. The English in a kind of way which I am not yet clear completely — and I am not too clear for the fact that I did not want to investigate why. There was no action from my side. I refused the (???). So all my colleagues went away. I did not. I remained there. To refuse to go back would have meant to expose my family, and my father who was a university professor, to vengeance. To take a strong open attitude would have been equivalent to the same. So that having left Italy, not only for a political attitude but also to be free of this kind of tyranny in my family. When I was there I was tied again, so much that when, for example, the Ambassador told me, “Look here, you don’t move from Rio, for the moment for I shall get you out of here.” They were in a bit of despair for I was a rather hot potato and they asked me to declare that I did not want to go, for this would have been completely in order, and I refused this. They found me cagey. And then they asked me to specify on what grounds did the British withdraw my navicert(?).

Weiner:

Withdraw your what?

Occhialini:

Withdraw my navicert(?) — for a man traveling on diplomatic immunity or authorities from Brazil to Italy used to have to pass through Gibraltar. The English had to give permission. They did not give it to me. So they asked me why they didn’t it, “Can you explain to us why?” Then I replied, “Let me tell you at this moment that I am not a fool. If you suggest that there was any kind of action from my side — if you have such ideas, withdraw it, I didn’t do it.” Which of course did not exclude what even now I suspect that people around possibly did some action.

Weiner:

People in Brazil?

Occhialini:

People in Brazil possibly did some action. But I must say that up to now no one came, as it is, to cash. People who might have done were sharks — this professor of biology, Sean, called the shargus(?) of the scientist, the shargus sickness, which maybe you heard about. It was a famous case of typhoid…

Then I came back to Sao Paolo. Three months afterwards war started for good and the situation presented — they would have kept me at the university, but they didn’t. I should have to make an official declaration and eventually to go on the radio to say it. I said that I was not interested. So they said, “Then you will have to withdraw.” I said, “Don’t worry. Now that you said this I will never put foot again in the laboratory,” and I went out. Out of this I said a few times to friends — I had also the idea that if I had to fight against the Germans in some way, it was absolutely stupid to fight it from Brazil. If I had gone on the radio, my father explained to me, this would have been equivalent, one year and a half afterwards, to condemn him to death. So from this point of view, I am rather satisfied.

From the other side, there was always, in my idea — I tried to eliminate this component — there was always kind of a Prince Dmitri attitude (War and Peace).

Weiner:

Yes, I know.

Occhialini:

War and Peace. Prince Dmitri twice in his life dreams that it takes a certain attitude and he turns the tide of a battle — the second time, having dreamt all his life, in the moment in which he tries it, he dies. There was the attitude that I could maybe do a thing of this type and that in the moment in which Italy would have gone out of the war there were some hundreds, thousands of hundreds, some ten thousands, thirty millions of people who would have liked to change sides and who could have hailed one person who had not exactly submitted — this is the kind of situation of the Gomulka — Stafford Cripps situation.

As it was, when Italy went out of the war, I discovered that like in the Dmitri case, that however I would shout at people that I was one of them after all, I had suffered — lack of comfort — I had lost my job, I had lost all money which I had — since I had not been part of a police action which had been taken against them, I was in condition to ask them if they wanted now to fight against Germany… So I was the only Italian who left Brazil to go and fight in Europe. I arrived in Europe — to make it short — I discovered that there was already some evidence of spying from the side of Europeans in the British scientific service.

Weiner:

Do you mean by some of the emigrés from Germany?

Occhialini:

They were looking for Fuchs, end as you know very well, the looking for Fuchs involved poor Bernard Peters in the States, and they had evidence — the first evidence they had — about Nunn-May. As Blackett told me three months afterwards, “I couldn’t do anything. I have seen your dossier and there is written on top of it ‘No’ in blue. It comes from such a height that I cannot do anything. So we must find now some way of taking care of you. I cannot take you in Manchester. It would be of no use.” “Could I go to Ellis,” says Occhialini. Blackett replies, “Well, if you want to go to Ellis, but he is a bit — you can go in deceit.” All right, I skipped Ellis, and I went with a phone presentation from Blackett to see, in Cambridge, Bragg. I really tried to inspire confidence in Bragg. Bragg was extremely kind. I told him that my expedition was eventually to clean the floors in the Cavendish and since I was prevented from fighting I wanted to do something, but for some reason nothing very much did materialize. When I met him again, he came to me very nicely and he apologized. He said, “I’ve been a fool.”

In the meantime, I was pestered by two sons-of-a-bitch, one called Hoff and the other one called C. P. Snow, who were on the gang which was recruiting people from war effort. They were telling me that I was a romantic, that I was a Johnny-come-lately. Hoff was going around saying that I was a Johnny-come-lately and Snow was trying to convince me that it was my duty to go and work in a laboratory… Then there was this interlude of my getting into the General Electric Co.

Weiner:

Through whose good offices?

Occhialini:

I think Blackett. Then I was there on trial for six days.

Weiner:

It was war work of some kind.

Occhialini:

Yes, it was war work. They told me on this occasion, “Look here, you are — but please don’t say this thing to anyone — you are in TR.” Then I went home and said, “Yes, it was all right.” Mrs. Blackett was very curious. She had discovered that — this mania of secrecy that there was — yes, yes, I was saying. “Are you satisfied?” “Yes, I am satisfied.” But to Blackett I said, “They told me that I am in the kind of thing which they call TR.”

Weiner:

Telecommunications Research ,yes.

Occhialini:

“They asked me not to say to any living being these two kinds of things but they assured me that I could tell it to you. To you I could tell everything.” In the morning when gloriously for the first time in my life I came in the place and then put my paper in the bell —

Weiner:

The punch-card, you mean, the time-card.

Occhialini:

Yes, in the evening at four o’clock they called me. They said, “Look here, some people have made a mistake. You don’t have anything. We will rely on you being a gentleman for we told you several things which we should not have told you. Please forget about then.” Then I took out the pencil which belonged to them and laid it on the table and went away.

Weiner:

You told me earlier that you had letters vouching for you from Chadwick, Appleton.

Occhialini:

No, I didn’t have any letters. I never produced any letter, but they told me there, “We don’t understand what happened. Here we have Appleton, Blackett, Cockcroft, all certifying about you. We take you with the idea that it is all right.” “Am I fine?” They said, “No.”

Then I go back home. It was Easter 1945 for the story. Blackett was on holiday and he came in the evening. A few years ago I met Blackett and I told him I gave it up, for I was talking to him about this and I said, “I really had to make an effort,” for I said, “This was the worst day that I had ever lived and the temptation of killing myself in your house was very real.” Blackett said, “What did you say? I don’t understand. Why should you have killed yourself in my house?” He had forgotten. I said, “Please Blackett, forget, forget.”

Then Blackett said, “Don’t worry, boy, I shall take you out of here,” and so on. After three or four days he said to me, “Look here, you do understand now what happened?” I said, “No, I don’t understand, and all of this is like the Castle of Kafka.” Then, “all right,” he said, “some time I shall explain to you.” Then afterwards he told me that the first intention was that I should go to Canada and Los Alamos — this was the idea — from the moment which they sought the invitation and the invasion which had been in the middle, the fact that for some reason there had been a snafu by which I went by boat and not by airplane.

Weiner:

From Brazil?

Occhialini:

Yes, I paid for my own ticket.

Weiner:

You mentioned one time that some people had helped out.

Occhialini:

Are you suggesting that I am contradicting myself? [Laughter]

Weiner:

No, I am taking the opportunity to corroborate your testimony. Didn’t you mention that some people or some foundation or group of people in Brazil gave you some money to finance the trip to England, or did I misunderstand?

Occhialini:

There was not a foundation. There was one man who is one of the big Italian financiers who gave me a letter in which he was introducing me to a firm in London. I received this letter — “This will introduce our friend Occhialini” and so on — and there was a friend of mine who was one of the greatest lawyers in Italy, Ascorelli, cousin of Pontecorvo, the most intelligent man I ever met, and he was a friend of these people. I showed him — we had dinner with them — at the end of the dinner when we went home I said, “This is what they gave me.” He said, “What is it?” I said, “This is an introduction. What shall I do with it?” He said, “This offers you a trip, but it is not written.”

Then I met again the person and he said to me, “Look here. I want you to know that we think that going away to England you do a very very silly thing. The war at the moment is ending. They will betray you anyhow — the English. We feel that you are making a mistake. Anyhow we want to give you a chance. Certainly you shall be betrayed. When you find that you have been betrayed, please don’t get in an inconvenience. Here we have a guarantee that you can pay your ticket.”

Weiner:

To come back to Brazil. [Interruption]

Occhialini:

This gentleman in London inquired very quietly about me. In the conversation there was not an inkling that he had been told to put money at my disposal. But that’s it. Anyhow, I’m too vain to come back with the tail between my legs.

Weiner:

Yes, well, we got on this because you had mentioned about coming over by ship on which you paid your own way instead of by plane, and you were about to make the point that it would have been different if you had come by plane. I don’t understand exactly.

Occhialini:

If I had come by plane I would have traveled in one day. Coming by ship I had to travel up to Sierra Leone and there wait for a convoy. It was a very hard trip. It was a French ship. I discovered afterwards that they had given me the worst cabin on the ship. There was a tube as big as this — the steam which was passing over me. Before I made some mild question, then I went to sleep on the bridge… I had a hammock. I swung it up on the bridge. After we arrived in Sierra Leone they told me that the ship should be left free, for in case of submarine they didn’t want to have my hammock stopping. Not only, but in one or two days passes an airplane — on a ship of this type it was called – Grua(?), Charger de Grua. In an airplane I could have gone in ten minutes, but as it was, I had to wait. I was impatient. They said we cannot move now for there is the invasion. We cannot go now… So that I was extremely worried for I was afraid that the war would have been finished before I should come as the conquering hero.

Then Blackett came to me one morning and said, “Look here, I think that the thing is finished. You have a Brazilian friend in Bristol. You have been showing interest in this emulsion technique.”

Weiner:

When did your interest in the emulsion business start?

Occhialini:

My interest in the emulsion started in Brazil before I left. Shargus received me in his laboratory and there was a brilliant biologist called Le Blond. Now I think he is in Canada, who was working with sections on emulsion, and he was working in thyroid with iodine, Sulphur and so on. There I got interested and I started dreaming about the possibility of treating the emulsion in a special way. I had a full collection of crazy ideas when I arrived in England, for my interest had been, in 1934, since in Florence there was not very much to do, I had asked Blackett to send me boxes of the Hereford(?), which was the first Ilford emulsion for producing tracks. I remember they were yellow boxes with wonderful blue labels. I treasurized them so much that I never got to do anything with them. This was my treasure, I was dreaming, and asking people if I could get alpha particles because I wanted to start looking at the alpha particle, but I never could really get the alpha particle. From the other side, the political situation was such in Italy that — I had a rather long eclipse which started in ‘34 and went also in Brazil. Fundamentally, I do remember the invasion of Austria, the invasion of Czechoslovakia, the bombing of London — they were coming all the time — it was very difficult.

Then Blackett did a wonderful thing. He said, “Look here, you get out please. You go to —” He had a special fund from the Royal Society and he went and collected the money from the bank in Holborn, I remember, and he put the money in my hand.

Weiner:

He was working in London at this time, wasn’t he?

Occhialini:

Yes, at this moment, he was living in London. He was living in Midevale(?) and he was in Admiralty work in operational research. So he was in London.

Weiner:

When you first came, he was in Manchester?

Occhialini:

When I first came when?

Weiner:

To England, in order to participate in the war.

Occhialini:

He was in London. When I arrived, I met him — two hours after I arrived he phoned me that the S.U.S. which was jointly created by Jimmy Crowther and Esther Simpson. He called me and I arrived in the Admiralty in Whitehall, very eager to talk and so on, to be received by a very busy Blackett who talked to me five minutes and said, “We shall meet — come tonight to live in my house — and we talk tonight. Now please, I I’m busy.”

And then I went to Bristol and I met Powell there, whom I’d never met before — whom I had met — what did you say?

Weiner:

You said he got the money from the Royal Society fund. Was that money for transportation?

Occhialini:

It was money so that I could go — so that I could transport myself — he gave me this money as a kind of order/mission. He said, “Look here, you are going to investigate now for me what are the possibilities of the technique in Bristol. You are sent by me with this money.” I went there. I got interested, and then discovered that — well, there was work on result of nuclear emulsions, but there was no work on nuclear emulsions. People there had simply a group of emulsions which was exposed to the Liverpool cyclotrons and it was the joint work in which there was Powell, the brother of Heitler, Hans Heitler, Pickavance, Nunn-May, Chadwick, and another one whose name I have forgotten. They were working on butterflies.

Weiner:

Of this bunch, Chadwick was the only one at Liverpool, right?

Occhialini:

Chadwick was at Liverpool.

Weiner:

And the rest were at Bristol?

Occhialini:

Pickavance was not in Bristol. There were only at this moment two people in Bristol. Nunn-May was on his way to Canada. Powell was in Bristol and Hans Heitler, the small brother of Heitler, was in Bristol too. There was another chap — a name like Guggenheim — never mind.

Weiner:

On the time scale, from the time of your arrival in England until the time you arrived in Bristol, how much time had elapsed?

Occhialini:

I went to Bristol practically soon after Easter. I went to Bristol before V-D Day, let’s say, I went to Bristol in four months.

Weiner:

So if you arrived around Easter, then you got there in the summer?

Occhialini:

No, I arrived, I think — when I arrived there was in full swing the Ardenne offensive — but I don’t remember where I was in Christmas. This is one of the holes — tremendous holes — in my memory. I don’t remember where I passed Easter. I don’t remember if I passed it with Blackett. I know that I passed another Easter with Powell, and sometimes I have a tendency to confuse the period. Let’s say December, so three or four months.

Weiner:

When you arrived there, was there any prior understanding with Powell?

Occhialini:

No, no prior understanding at all. I arrived there as a visitor and I found that Rosenblum was there too.

Weiner:

Had he come over with the Paris bunch, or what?

Occhialini:

He had come out with the Paris bunch and the Rapkine Mission.

Weiner:

Blackett had arranged with Powell, of course. Had he known you were coming?

Occhialini:

No arrangement with Powell. I suppose — I had gone to Bristol on Easter Day. When I went to the General Electric Co., after the two or three days that I passed there, there was an interim of holidays, due to Easter. Blackett went away. I went to Bristol to pay a visit to a young man who was a friend of mine who had gone to work in the Borden(?) Neurological Institute on a British Council fellowship.

Weiner:

This was not Lattes.

Occhialini:

No, this was not Lattes. This was a biologist. This was Fernandez. When I came, I found that Powell was not there, so I could not have a chance to see anything at all. But when I came back to London I found that I was fired by the General Electric Co. Then I came back again and I was there. When I was there they gave me a microscope and I started making measurements and so on. I made a group of measurements. I worked very hard and I did a series distribution of range and so on. I remember that it was the understanding that I would not know what it was all about. Every half hour I would ask Powell to displace the plate, to put another plate. Powell was very excited for the fact that my distribution was showing a spread which was much better than the one done by the professionals. This was evident. Then I remembered that there was this kind of dosen(?) curves. I said, “Look here,” — they had a paper which was coming out — “would you mind if I substitute, they gave the same results for they really show that the method is much more powerful than we thought.”

Weiner:

How do you account for the difference in what you were getting and what they had gotten?

Occhialini:

Method. For the first time which I was doing this type of measurement I know very well, I went shuffling the things, I found the difference between — but overall my work was never continuous. From the moment in which I was starting to discover anguish… I remember it was a wonderful thing. This was an example of the thing, I started to worry for the fact that there are too many… stopping, started to worry for the fact that the spread is growing too big and stopping, starting to worry for the fact that odd numbers seem to be prevalent and stopping — so I was eliminating the anxiety about knowing what was happening by stopping. In any moment in which I was aware that I was starting to take more than a fatherly interest in the measurement I would stop — and this I think is simply this — I believe that when a person does this type of measurement there is one moment in which he becomes partial to something. He plots the maximum, he plots the thing eventually. He decides that the maximum is at sixty — if he starts finding particles at sixty-five or seventy, at this moment he starts to get worried for it spoils his statistics. He sees that there is building another peak, which is not supposed to be there. He does two things. Either he starts reacting against it, insisting on it, or he starts to pull back the thing. This is one place — one of the kinds of things which is between God and the man who is in darkness looking at something.

Then, after this, Powell had me called by Tyndall and Tyndall said, “Here you are for a present period of one month.” He asked if I wanted to join — I came back when they proposed me, and the same evening — [Interruption]

— to the train where I could talk to Blackett. Blackett said it was all right for me. He wrote a letter for me, which I copied, in which I was writing to Appleton who was supposed to finance from the DSIR, — I don’t know how the connection I had come to Appleton but Appleton had received me when I came to London and sent me people who picked me up from the boat in a tremendous hurry, so I thought that I was going to be parachuted two days afterwards in Italy — and I remember the letter of Blackett. He was saying — it happens this, this and this — I remember the phrase: “While I insist that I still want to do the job for which I was called for” — I remember this thing here, provisionally and so on, but I said that I am still in disposal for this. With this, I went to Bristol. At this moment I started working in Bristol.

Weiner:

There was a specific grant made to whom — to you or to Powell?

Occhialini:

There was a specific grant made to me, that is to say, they had a grant there in Bristol. They had a series of grants and they passed this grant to me. It was 25 pounds a month which Connie says was plenty of money corresponding to what she was getting. It was what it was. Connie was not there then. So this is the first part in Bristol.

The second part in Bristol is the coming of the Ilford people and the discussion about the production of more emulsions which had the characteristic of being much more (???).

Weiner:

With a specific research line in mind, or just generally?

Occhialini:

It was generally. Everyone who had been working with this kind of thing — I must insist — a man who has been working in the Wilson chamber knows very well as a feeling, that if you want to increase the density of the track you increase the pressure. It was very very difficult to understand why this image was so poor. We were developing, of course, they were very very primitive. Before my time, never anyone had gone in any actual passion of research on the way of developing.

Then we got there a person called Chilton from Ilford, and then I do remember that maybe at this meeting Rosenblum was present and it was put forward a plea for increasing the concentration of silver. Don’t ask me please how this condition was formulated for I am not in the condition to say who did it. Certainly they had gone on very very happily with this. I do remember that I was very excited for Chilton, I had met — he had been a student while I was in Cambridge and he left very very hopeful. But Powell was rather skeptical for he said that on many occasions we have asked them to deliver the goods but they did not. Fundamentally, at this moment, they had this group of plates exposed… and they did not see any reason to go out on this routine work.

So they left, and at this moment having received from a girlfriend of mine a book on photography, as a present, on which I was completely ignorant. The book on photography was called The Scientific Photographer, by A. S, C, Lawrence. It was a green book which now is out of print. There was the fundamental suggestion that the reason that you must use temperature of 18° centigrade, 65° fahrenheit, is so that you can give definite power to the balance of chemicals which are there. Otherwise, if you go under this temperature the developer becomes insensitive.

Then I asked for a group of emulsions and I put on them thorium stars and the day afterwards I developed them — the first development which I did. It was terribly simple — there was nothing — I used a developer which was called x-ray developer. A very alkaline developer, which I discovered afterwards but I did not know then what alkaline meant. I discovered one night with Connie what pH meant. This is a story from a few months afterwards. Then I developed them, I dried them, and I discovered that in this (???) emulsions, this way of developing was giving tremendous increase in the number of readings. What did I do? All right, I took a plate, I put thorium inside, you leave the thorium during two or three days or even a few hours, but two or three days is better for you get then all of a certain definite age — very few done when the thing is wet — you put in the solution, you put a drop, then you dry, and then you wait, and then they develop this thing and they write their own — do you know what I am talking about?

Weiner:

Yes.

Occhialini:

Then you develop, you dry, you put them under the microscope. When I had them under the microscope I noticed that these were different from the stars, which in my first phase — sorry, I interrupted myself. I put them in a cold developer. Then you fill them with cold developer. Then you raise the temperature, you explode speedily the plate and then you stop it in cold water. This is a kind of cookery thing that with some dish is done, you fore-warm and then you stop. You do it with spaghetti — you put them in cold water — you cook spaghetti the same. There is a moment in which you freeze them by washing them in cold water. I remember Powell gasped when I said that. He said, “How did you do it?” I said, “It is what I told you.” He said, “What did you tell me. Ah yes, it is true, it is true, you are right,” and so on. I remember he said, “How did you do it?” “Well,” I said, “I put the plate in, I put in the cold, I had ice, and I put the ice” — I did not want to dilute so much so I had this block of ice and I had a bunch of French lettuce and I put in the French lettuce.” “In French lettuce you put them — now I understand.” “What do you understand?” “Yes, I went into the darkroom. There was this French lettuce laying around” — I remember this phrase — “I thought someone had been rush.” It is the first time that I heard this word “rush,” I don’t know if it is apt.

Weiner:

Practical joke, or —

Occhialini:

“I thought someone had been rush.” But practically in the same day, believe it or not, at a distance of a few hours, maybe in the same evening, did arrive a group of plates from Ilford… this had been shown to me and they were put in a drawer. I went on with my measurement of the thing and so on, and then after two days I went to Powell and said, “Look here, you received plates from Ilford.” “Yes,” he said, “so many times they have been promising the delivery of goods.” I said, “All right. Since now I have developed this other plate. Now I have become practically an expert. I have developed two plates, and before I did not know from where to start. Can I try it?” “Please help yourself.” This happened at six o’clock in the evening. At seven o’clock I had done in the solution, alpha particles. The morning afterwards I was after all developing them, drying them, I threw them in a lired lamp…

Weiner:

According to your technique –

Occhialini:

No, no, this was absolutely regular. Then I put them in the microscope. Well, I can tell you, the thing from outside under the microscope, I said, “Powell, come please, I think that the son-of-a-bitch of Chilton has done it.” He comes and says, “Hell, I have never seen anything of this type.” I said, “Look here, little boy, this kind of thing we must tell to these people of Ilford. After all, it has been passing for a possible four days… for I said that this kind of interval which it had been laid in the drawer and the time for laying in the drawer. “Well,” he said, “Let’s look at the letter again.” We looked at the letter and it said we send this letter to you and also to Mr. Livesey(?) in Cambridge — I was a bit bitter at this moment.

I was feeling partly elated, partly dejected. I felt that here was a mission that I could do. I felt that without my intervention we would not have at this moment — I did not want to push any more the situation. I got up and said, “Look here, it is seven o’clock. I must go away.” I left a bit of the thing — a bit of paper, written in pence, as big as this — “Dear Dr. Chilton, Ilford, Ltd., Dear Chilton, It works.” Signed, C. F. Powell and G. Occhialini. I left the paper and this. The morning after they said that I arrived just in time for these other people spent some time in exposing the thing to neutrons, while we did the right thing, exposed them to alpha particles, and they were discussing it. At this moment this thing started.

The evening afterwards for showing the alpha particles I took some cellophane and banging the alpha particles, I had some collodium(?) and made a kind of bubble to put the thing in. In darkness I exposed the alpha particles there and then they were developed, maybe at seven o’clock. They were ready to come under the microscope at 11 o’clock. Then at 11 o’clock there were the protons — beautiful. At this moment you are in condition to compare the end of the protons with the thing, and so on.

Three days afterwards they sent us another group of plates — this was called the Ilford (???) — and I remember they were a flop. Chilton brought it. I was in despair. Being rather temperamental, I was practically crying. He said, “Can you find again the thing?” “Yes.” At this moment, Chilton did not come alone. He was accompanied by a gentleman who at the moment I did distrust… I had the idea that Chilton had done the work and here he was accompanied by this superior executive, very well-dressed, beautifully. He was an Englishman, very neat-looking. He was called Dr. Waller. I don’t take very much to people who are well-dressed and to people who are good-looking. He had the Mountbatten head. Then when they were there, I said, “Can you do it?” Waller was saying, “Yes, we can build it again equally.”

Weiner:

A Dr. Waller came along and said, yes, he could do it.

Occhialini:

Yes, to make this thing short, my impression of Dr. Waller was that he was too well-dressed so that he was a highly-paid executive, while Chilton was the man who was doing the work. This impression remained for a month out of the fact that in a deliberate way I refused to have contact with the Ilford people. I felt that being a guest this kind of thing was to be taken by the authorities in place. It was involving also the possibility of spending money.

They they went away and at this moment Christmas was approaching. I said, “Well, look here, we should do something about it.” It was absolutely imperative to me that we should publish something for a very simple reason. I had come to England. It was one year since I had left. It was a question of vanity. Men and women — women too — whom I had dropped(?) in Brazil, and people who were in Italy, they should know that I had been taking a decision and that the decision was for some reason justified. It was my vanity. It was the vindication of my judgment since I could not have proved that I was going to fight — this was the thing.

Then we say we must. “All right,” says Powell at this moment. I present you at this moment with a different Powell from the Powell as he became afterwards. This is one other thing that — in a way, when I met Blackett, he made something different out of me. With Powell it was different. Without any hesitation I can say that I was his Pygmalion, but I don’t know how —

Weiner:

You were saying you were his Pygmalion in a way.

Occhialini:

I think in a way yes for I remember his saying, “All right, we say that we got these things with the emulsion, we publish it, all right, so what?” I said, “Wait a minute, here, don’t forget that I’ve been” — [Interruption]

—At this moment I’d been playing with this emulsion a tremendous amount. I found that here we had a tremendous instrument, but we should put it in writing. Then I intimated what could be done. I said, “Look here. You give me the separation between thorium C and thorium C”, long alpha particle, on the old emulsion. I’ve done it for the first thing. Now I’m doing it again on this. We found out that my spread was quite good; now we’ll see what kind of spread we will get with this.” I was feeling my way for I did not know, but I was using all what I had. Then I said, “Maybe we can do it for thin tracks we can intensify them.” What was important at this moment was that I had brought to Bristol a new tool. Don’t laugh please. Microphotography — please don’t laugh. I went one day at 12 o’clock to London, I went to Cambridge to see my intimate friend Letice(?) Ramsey. She had bought for me a Leica attachment for taking microphotography, which was impossible — don’t forget, the war finished — I got it. I came back. I arrived at half past nine, I went in a pub, I got a person I met who had a Leica, we went together to the Lab. I didn’t even know how to use a Leica for I never had a Leica in my hand, screwed it and then we took the photos of these things. This man was an amateur. He taught me also how to print. I didn’t have much practice — everything you must start. So at this moment we had a collection of prints. We had put photos and we had shown and so on. For this we must have a very very long proton. And I said, “All right,” since up to this moment even I knew that the longest proton you can get from the 13 MeV proton which originated in the bombardment of boron — called boron protons — 13(?) million volts, which were in the old emulsion 1300 microns. In this they were becoming 750 microns. There was all kind of thing.

It was Christmas. I went on fighting in order to get the best possible photos. We made this kind of modest thing — we wanted to send it to Nature. Nature said no, that it was not too good so we sent it to the Review of Scientific Instruments. Then at this moment the Atomic Commission started saying “No.” At this moment I learned that this was a thing which had war-potential interest.

Here I drop some other particulars for I must drop, I must eliminate one or two names. I really did discover with a lot of work that what Mr. Chilton had done for us — it had been done with possibly a thousand pounds spent by a Dutch contributor in Canada, by a man called Demers. Then they were saying, “Demers has been prevented from publishing it through security reasons. You should not publish it.” “Well,” I said, “Look here, this is too much. You prevented me from going to fight. I get in touch. I come in this place.”

There also was something more, that Powell was not in order of sanctity.

Weiner:

He was not what?

Occhialini:

He was a leftist. He had not taken part in the war effort. People were feeling it tick that the poor bastards who had been working in Los Alamos could not publish absolutely anything while he had been all of the war sitting in a kind of comfortable way. Now he would get this. Maybe there was a suspicion that this work had come out from the left’s work. There could be a possibility for Nunn-May, after all, was in this direction. He was a good friend.

Now, if you don’t mind, I come back. So there was a kind of faint suspicion in the air that this Johnny-come-lately had given an order to Ilford, Ltd., on the basis of this information, as one of the Atomic Commission also claimed afterwards that he had done. The astonishment of Powell when I had produced, when I had shown him — the gasp he gave was not very well imitated. The fact of being suspect of not having had the initiative when there was this kind of epoch-making breakthrough, and having put them in a drawer when it was something that did show — certainly he did not drive me with visible fingers, telling me, “Look here, you might develop them. Please develop them. It might be important.” What he said was, “In the past already they tried to do things for us, they may do it lots of time(?) — All right, develop them.” My argument proved two things. One of them is that this kind of work, as far as I am concerned, was independent of the work of Demers. It proves also that as far as Powell was concerned, he was independent too, for otherwise he would have been more eager. I know that afterwards it came out that everyone knew that this was a wonderful achievement.

Then, also, in order to parry this situation and also to reply to the Army, I said that it seems to me only right that we put the name of Mr. Chilton in it. So we put the name of Mr. Chilton. Then the paper was written by Powell and myself. The photos were provided by Powell and me; one photo was provided by Livesy (or possibly Gibson, I have forgotten now the name). Chilton arranged the names in a kind of mysterious way. It was Powell, Occhialini, Livesy and Chilton, which was a kind of anti-alphabetical order in which the name of Powell, mine was coming after, which was crucial but was OK by me. Then at the same moment — as I think I had told you once I had begun first of all to realize that this kind of thing was a bit like the typewriters of (???), monkeys at typewriters. Here you had something. You had a breakthrough and we did not have the people for there was one old lady and Heitler, making two microscopes that we had. This was all of Bristol when —

Weiner:

Well, it was all of Bristol with Powell but there was more to Bristol —

Occhialini:

What?

Weiner:

There was more going on in the Laboratory, but this was all in Powell’s group, you mean.

Occhialini:

This was the nuclear emulsion work. This was the thing. At this moment all the fourth floor was occupied by Signal Dept., or the Navy, and so on.

Weiner:

I am confused. You say there was an attempt to prevent you from publishing the paper and then you got on to the story about the name order and so forth.

Occhialini:

Yes, there was an attempt to do this. This had given us, at least me, a kind of anguish. It went on at a certain time. I took the train and I went to London where I found out I brought the photos to London to Blackett. Then Blackett told me that he had heard about this Demers development. I recited for him the same rigmarole which has convinced everyone who has heard it. It was more or less this. “All right, really, you kick me out from the thing. You cannot prevent. Now, you send me to Bristol and I produce a certain work while I am there. But look here, really, it is a bit too thick.” Blackett was not completely swayed by this argument. He had been during too many years making war not to understand that, after all, the interests of a son-of-a-bitch don’t matter very much. He told me practically — not in these terms — that I might become one of the casualties of the war.

Anyhow I visited Blackett some times and I said, “Now, you sent me. I have been working very very hard just for the fact that you have been so generous about it. I went to get out of this inferiority complex. It is absolutely evident that we cannot do it if we don’t get some help. We must get some help, Blackett.” Then Blackett, being socially concerned, put his weight behind it and established a panel. In the house of Blackett, in Maidevaile(?), we decided that the state should intervene. Ten thousand pounds, or five thousand pounds, should be given to Ilford Ltd. for a contract to help them. Not very very much, but this already was showing a kind of trend, a kind of pressure.

They issued a contract for producing microscopes and for buying microscopes for this technique — Cook — and they established a panel. This panel was Powell, Rotblat, and a few others, who I don’t know very much about.

Weiner:

Who was the panel connected with — DSIR?

Occhialini:

I don’t remember now.

Weiner:

Atomic Energy?

Occhialini:

I don’t remember for it was Blackett who sponsored it, so I don’t know. It was really Blackett who induced the government, which was the Labor Government at this moment, but I don’t know through what — maybe it was the DSIR. At this moment I was making a lot of hay out of the fact that Powell might not have been fighting during the war but it was completely unfair to have one person who volunteered to come and who had abandoned everything as I had abandoned at this moment — for the war was finished — and then they should treat me as a son-of-a-bitch, as a foreigner.

While Blackett was never committal, I feel that something came out. We got the permission to sign the paper. So the paper came out, also the name of Chilton, which was equivalent to say that Ilford had done something. It was, in my opinion, an act of justice, and it was also giving, following my idea of the right dimension —

Weiner:

When did the paper appear?

Occhialini:

It appeared in January or February of 1946.

Weiner:

There wasn’t much of a delay.

Occhialini:

The plate, I suppose, was developed in September and if they had followed my advice — I never worked so quick. In the end what I was reduced to was to take back the photos in such a way just to convince everyone of this.

Here I used more the Rutherford technique than the C. T. R. technique. I don’t say “one,” I speak about myself. I think I am correct. I had in this period a tremendous charge. I had this nationality humiliation. I had this kind of rage against the people who had prevented me from being dropped as a parachutist in Italy so that it frustrated me. I had this kind of debt of gratitude towards Blackett. Also I had another source of thing and it is that I was feeling that life — I had a great admiration for Powell — and I was feeling that life had been unkind to him for he had not received enough credit. As a matter of fact, the first time I went to Blackett I asked him a very simple question. I said to him, “Will you explain to me why Powell is not an FRS?” So there were these kinds of components and when a man has two or three reasons which are not contradictory and so on.

So this in a way justifies the big “I” which is in this story. I claim, as Oliphant might certify if he remembers a certain thing, that they said it was my report and it is very dull. Then I said, “Look here, this is something which needs power. It is absolutely evident that this is a kind of new dimension.” “This,” I said, “is the realization.” I remember that I was quoting, at this moment, Dr. Arrowsmith. This is the realization of Dr. Arrowsmith’s dream. “And we are here at a kind of turning-point in the breakthrough.” Dr. Arrowsmith in the film — I don’t remember the book — goes out bangs out of the lab with a microscope, saying, “I am going to do research, anywhere, anywhere.” When this happened, at the cinema, in the door, a group of Cavendish young men whom I knew — I don’t remember who they were (they might have been Shire, Lewis, Wynn-Williams, and so on) — they said, “Think about the man going into the world to do research with a 41” microscope.”

At this moment it was true. One or two months afterwards it was not true anymore. You needed more than one microscope. You didn’t need a gun, you needed a full battery of guns. You need an Army. At this moment I said, “We need people, good people.” I said, “Look here, I left two young men who are a bit frustrated in Brazil. They are sons of refugees — both of them Jewish or half-Jewish. One is called Lattes; the other is called Camerini.” They said, “Look here, what you advocate?” “I advocate that you should call them.” “Well,” I said, “We got the money from the DSIR. We can do it. We have one place for one of them, but one of them is rich — that was Camerini.” All right, first of all we call Lattes, and then they said if Lattes finds it is good, we will phone to Camerini. I had left Lattes my Wilson chamber fully mounted. I had spent — still I do regret — before leaving Brazil I had spent the last ten days and practically all the ten nights in mounting again this Wilson chamber which had been packed up at the moment which I had been obliged to leave the lab. So that when I went away the Wilson chamber was working — practically at 11 o’clock in the night it was working and at 7 o’clock I was leaving to take the airplane to Rio and then to (???).

“Is he good?” “I think he is good but I cannot tell you much… but I will tell you that here there is very little to be done. If we must have something done at this moment we must have in this place a Foreign Legion. We must have people coming as much as possible from every part for if you wait for people to come down from the Army, if you wait for these people to be reconditioned again, we lose everything which you have — and people who have not been so much involved in the war, like the French, at the moment at which they can lay their hands on this emulsion —.

So a letter was sent to Lattes. I sent a letter to Lattes with one of the photos and asked him. And then Camerini — Lattes called Camerini.

Weiner:

Lattes and Camerini were available from the same?

Occhialini:

From DSIR, yes. Camerini decided he was coming on his own steam and Lattes took the involvement on himself to invite Camerini who was his school companion and his best friend.

Weiner:

Where was Lattes from originally?

Occhialini:

He was from Italy. His family was from Italy but he was born in Brazil, and then they had come back to Italy. He had parents here. Camerini was born in Italy and they had been immigrated… He was born in (???) so he was not an exile.

So this covers the kind of story of how the emulsion came — how the cook — how the funds to buy more microscopes, to give the microscopes to Imperial College, to Cambridge, and to Bristol, became a part of the state, of the government, sponsored by Blackett —

Weiner:

— through the panel.

Occhialini:

— the panel. Third, how the Foreign Legion of Cambridge that started with me was tripled in number by the addition of the two pupils of mine, Lattes and Camerini. This is the story.

Now to this I might add that you might in the future get a different story from the one which I gave. You might even in the future be presented with some written evidence of some kind which might tend to prove — I don’t know — that things had not gone as I put them. Should this happen, hearing the story, you will be interested in the story, and you might eventually decide that every document which you cannot date… might portend to prove anything at all. This is just in case.

As a finishing touch, I would like to put the thing in order. Then when the paper came out, it was only after a month that Powell explained to me that he had learned that Chilton who had signed this paper was practically a representant deluxe — what do you call it? He was an import agent. I had always treated him, since he had brought the emulsion and I did not want to know how the thing was done, so I was not indiscreet — I knew only that they had put more silver now. This is a problem. You know very well that there is a moment in which when you are in an emulsion or in anything, once you add something more, it will precipitate. How they succeeded in adding, merging, putting ten times more emulsion inside — avoiding it to make a block and to leave it in — this is a thing which I learned only years afterwards. At this moment I did not know. Powell did not know. And not only, but we made assurance each to the other that we did not want to know, because otherwise we might have been tempted to be smart, to be wise and so on, and then we might have deprived Ilford Ltd. of this kind of little boom which had been theirs.

Chilton, as I said, was only a representant deluxe. Do you know now what a representant deluxe is?

Weiner:

No, I’m not sure I do.

Occhialini:

He was an agent. He was the person who takes orders — liaison officer. He had not produced the actual emulsion. Who had had the idea which prevented the agglomeration? Who was doing the work at home? Mr. Waller, the man so nicely dressed that I always had decided and so on. I had time, years afterwards, to apologize for this. [Interval]

It has passed nearly twenty years but he is still good-looking. You don’t imagine a man who works in chemistry dressed in this kind of polished way, so neat.

Weiner:

Hadn’t you consulted with Chilton before you added his name to the paper?

Occhialini:

Yes, we did consult. We said that we might add the name of Chilton to the paper and Waller gave the approval to this. So we did not know. I know for I talked about this to Waller. I said, “This has been one of the gross injustices” that we had done, but this shows l. a. our ignorance —

Weiner:

— of the process itself

Occhialini:

It shows our ignorance since we were only strategists. Whoever would tell that there was in Bristol a kind of buoyant(?) doctrine and so on — well, look here, the person who developed the plate, never had developed a plate before. What happened with the temperature development? I dropped it at this moment for I put it all on these emulsions. I decided that this should be dropped. It was only one year afterwards, when one night Bøggild of Copenhagen was at the lab at 11 o’clock having tea and Bøggild said, “Certainly, it is a pity, this thing is 50 microns — very small — if only we could find a way of developing an emulsion, say, of 200-300 microns.” I said, “I think I can do it.” There was a young man called Paine. Connie was around, Connie [Constance Dilworth] was in the picture at this moment. I said, “Look here, go please to the icebox and take some ice.” He went and took the ice. We put the new plate in frozen developer; we put another plate in common developer. After ten minutes we looked at it. The one put in the frozen developer was white; the other one was black. Then we fixed. One of them was completely without grain; the other one had a considerable background and — [Interruption] — where the source, and we put, I think. We had plates which had been exposed to the cyclotron, which was there, like this —

Weiner:

Not in Bristol.

Occhialini:

Not in Bristol, in Cambridge, and it was evident that in one of them, in the cold there was nothing; the other one was showing tracks so that we got the effect. Then we came out with a Nature paper and the boy called Paine who provided the ice signed, and Connie too.

Weiner:

Whose names were on it altogether?

Occhialini:

Dilworth, Occhialini, and Paine.

Weiner:

Bøggild was not on it.

Occhialini:

No, this was what happened between 11 o’clock and 1 o’clock in one evening, and then we showed the effect to B&oshlash;ggild and said you asked for something for this — it is possible. Then all this work started again. Connie took a part in it, and we discovered, again from the book of Lawrence, that you should use avidol (of-it-all?) — we didn’t understand what was happening when we were using boron plates, the things to develop in whatever temperature — and then Connie finally started adding together all the work which we had done and said, “Look here, I just discovered that everything went all right.” But from the moment in which not having any more plates to use, we started using the boron-loaded plates, we didn’t have any peace. On this, I accompanied Connie home, and I started going around in Cambridge. At 6 o’clock in the morning I was back in the lab to investigate what had happened with a group of plates which were boron-loaded which had been left to dry. They were all filled with caves.

Then from 6 o’clock to 8 o’clock I had understood that the plates were badly alkaline. They were so alkaline that whatever you should do, the developer would — and this was explaining a lot of things which no one knew. Photographers knew, but no one knew a damn about what it was. Why you should wash one thing and so on? People like Rotblat were investigating why the alpha particles had a certain length. They write a letter and say, here, there is a very funny fact which Rotblat says are alpha particles which are all a length but with a length then it is easy to discover that — all right, I said, “Powell, tomorrow morning we shall show those alpha particles. Then we put, we bang(?) the emulsion, we dry the emulsion, we put a lot of glycerine in the emulsion so that we absolutely bang the effect of these particles which are going in, you dilute the emulsion by adding a bit of water and then you plate it and then you get a lot of particles — what one used to call prehistoric tracks. This is the part of the thing.

Then, as you can imagine, there was a kind of revival inside the lab. Here had come another young man called Cuère — now he is a professor at Strasbourg. Then back from the Army comes a brilliant young man who was the nephew of Lord Rutherford, called Peter Fowler. All these people together, on exposure of a plate, again with the cyclotron – they were going to study deuteron induced radiation an dother things. This was a moment in which I was a loner. Everyone of these people had gone in a certain field and I was at this moment simply studying with Powell n-p scattering, putting neutrons in an emulsion and then studying the distribution from this. There were a lot of physicists. I didn’t enjoy it.

In the meantime these young men had wonderful distribution, had ranges of tables, there were ranges of particle groups which were coming out. This went up to May, June, July, August.

Weiner:

We are still in what year?

Occhialini:

1946. In August I went out to explore caves in France. I had been practically a professional in cave-exploring in France in the Pyrenees. I went with a friend of mine called Cousins(?), who had been the assistant of Professor Piccard. He had made one of the first atmospheric flights in a gondola in an epoch-making flight in 1934. He had this interest. I met him years before in 1932. He had come to visit Blackett and we discussed and discovered we had a common attraction. During the war he was taken prisoner by the Nazis. He was in a concentration camp. He was in intelligence… And then he went to Bristol. We found ourselves, and we decided that we were going to explore in this kind of old problem which we had left, which we had been talking years before.

He was in Brussels. I met him there and we got climbing finally. I brought the plates to the top of the Midi and then went down. Then we visited Lattes after they were — I did not succeed — first of all, I didn’t have any money for I went on my own steam there. I had difficulties in leaving England. For some stupid reason at the moment I was leaving they tried to stop me — I don’t know — it was the security act… Then I succeeded in getting out.

Weiner:

With the plates?

Occhialini:

With the plates. The plates were exposed and they came out.

Weiner:

When you wanted to take the plates up there, was it with a specific purpose in mind looking for a certain kind of particle?

Occhialini:

Cosmic rays.

Weiner:

But no specific problem — just expose them to cosmic rays at a very good altitude.

Occhialini:

No, I knew very well that cosmic rays were a tool which were much more powerful. I’d been interested already in cosmic rays. I felt that this thing should be done. I was interested in stars. I had prepared myself for this, and I knew at this moment about things which had not interested people. I knew about mesons — I was the only one practically at this moment. No, I was not the only one for Lattes also.

Weiner:

A man was awarded the Nobel Prize for the discovery of it in the thirties.

Occhialini:

I beg your pardon.

Weiner:

You said you knew about mesons. Well, there were people who won the Nobel prize for it. Anderson — no, I’m sorry not Anderson, but anyway, Anderson discovering the mesotron in 1937, the so-called meson — so it was common knowledge in physics, wasn’t it, that these existed?

Occhialini:

First of all, it was common knowledge of the existence of mesons. This is correct. What I claim is that I knew something about mesons, in particular, I knew that mesons if captured should give rise to a star of some kind. This was not common knowledge yet. It was coming out from the Japanese work and the Rasetti paper. It had been very very difficult to see mesons during the ten years. There were existing at this moment three or four meson tracks in a Wilson chamber. That was all that was happening since the mesotrons. I was looking for mesotrons. I was interested.

Now it must be clear that if you have one particle which ionizes not very much, you cannot see it. So it has never really been seen in emulsion. This was giving the chance of observing them. This was the idea.

In September I started to get restive. Lattes told me that he had discovered that there was a recession which I called — I enjoy giving names to things — competing(?) the emulsion. So that whatever we were I was having this emulsion of mine, there was a moment in which the image would go down, there was a chance even that maybe it would disappear completely and everything was (???). So I succeeded in getting the emulsion back. They arrived back. They had maybe been exposed too warm. We didn’t know very much about them.

The first night I did the first. They arrived. I developed them, as I could, and then there was a moment at half past eleven at night, or twelve, that I had them under the microscope. The first that came out — when you are busy a realist(?) example the rays(?) “come out”, it is called. It is lithium which disintegrates from the electron and then produces beryllium 8 which bangs, goes into alpha particles, so you can see the tracks, blind like this. You don’t see the electron in this place, bang, but the hammer.

I remember that when I saw it I phoned to Powell. Powell was not there. Then I went out and I went to Mott’s house. I said, “Look here, Mott, please come.” He said, “I want to sleep and I will see you tomorrow.” “All right.” The morning afterwards the microscope had become the kind of thing which you see in laboratories when there is a visit. Everyone around was coming to inspect the thing. Then I went to Powell and said, “Look here. Here I am in the same situation in which we were a few months ago. Here we got something which is important. I think the deuteron disintegration can wait. Of course you will tell me that I am an adventurer — I don’t care. I will say that I have at this moment something in my hand — I can exploit it for I am a loner. “All right we will do this. We will leave these boys to the microscope to look at this, and from this moment every bloody other microscope which you have will be put on this.” The same evening I got a track which was getting one or two or three particles were coming out. I called Lattes and I said, “What do you think this is?” Lattes looks at it and says, “This is a meson entering in one nucleus…”

All right, the morning afterwards at twelve o’clock —

Weiner:

Where had these plates been exposed?

Occhialini:

Pic du Midi.

Weiner:

These were the ones.

Occhialini:

These were the pi-mu plates. However, I was in great despair for a lot of these plates were black, black like night. You couldn’t see anything. This had been the problem of many generations of people… I went to look in a photographic book and I found out that if you have some time silver, use metholated spirit on top of the thing, then put a drop of metholated spirit, I passed over it with chamois leather — it gives transparent again. So here I had six new plates to add to the two which were transparent themselves.

Weiner:

This is the end of Tape 1. [Tape 7 using total count] Tape 2 [Tape 8] is defective. We recorded about 3/4s of an hour of it before the tape ceased to move and we will have to do something with the tape before we can transcribe it.

Tape 8 (partially defective)

We were at a very interesting point.

Occhialini:

This is the story about the so-called sigma star. I must say that for my own benefit — the old emulsions, the prehistoric emulsions, had been used — they were called half-tone emulsions and were supposed to be no good. But then one or two years afterwards, just for fun, I wanted to in one of them, remembering my first trial, I wanted to try again this famous development. Then I did discover that we would have discovered the pi-mu meson on those emulsions, even if the concentrated emulsion had not been discovered, for the richness of the track was such that certainly the loss of energy, the grain density, corresponding to the 6 million volts, the meson, the moment — well, the track density corresponding to the energy of the mu-meson when it interrises(?) for the pi-mu, its integration was visible. How do I know? Well, I looked at proton. I had a special exposure to Pic du Midi once again and I enjoyed developing, looking at the emulsion. Of course, I did lose time in trying to find the difficult pi-mu decay, but since I had protons I went on measuring from the end of the proton what was the distance, and I did discover it was very very easy to follow up to a point. This point was enough to decide that this thing which is — the particle which dies here and the other particle which goes out — the last 600 microns of the pi-mu, of a mu meson were visible. So that in a way it would have been much more enjoyable to do it — this was done on (???) plates. I tell you once again, I asked Ilford for I wanted to give to a young man as his subject, now please discover the pi-mu meson, not on this super-duper — then we didn’t have any track practically. It is only through this that — in a product like this, when you have got an artisan thing if you don’t watch the production all the time there is a moment — you need the user control. And Mr. Waller had done this for us day by day. It was our bread. It was our life.

As I told you, a few weeks before when they produced another plate, I thought since it was not giving the same result, I thought the first one was a fluke. I was desperate. Mr. Waller said this was no chance, “Don’t worry, for we know how to reproduce. We are always changing the procedure but we can always come back to it.”

Weiner:

Let’s go back to what you were saying before about the fact that you had two plates and then by this little trick you had four more. That’s where the sequence of the story was interrupted by the phone call. So, you had consulted with Lattes after the first two — you had told him about it after you had seen the tracks and interpreted them as mesons on the first two plates?

Occhialini:

No. It was in the evening that I was going at the microscope when I found this star not extremely (???), it was something which was coming from the emulsion was doing this… Then I decided it was a meson and I was ready to argue on it. I called Lattes. I went out at this moment. I don’t know if it was in the evening that I called him or I called him — I laid it again in position the morning afterwards. “Lattes,” I said, “Look here, can you tell me what is this funny thing?” Lattes looks at it, “Elementary, this is a meson entering,” and so on. I was ready to fight for it and then I really did understand that Lattes was even better than I thought.

Then we went on on this and we produced a paper — at this moment Perkins had produced plates (??) — so I did not know it but I was racing Perkins. Perkins might have detected the pi-mu meson himself without my generous attitude of saying that these were our plates and that we should look at them together but at the moment, of course, I needed Powell. I could not go looking myself. We produced this track and our paper came out one week afterwards.

Weiner:

How come so fast?

Occhialini:

Just for the fact that I was looking during the day, I was taking photos during the night, so I had all the mosaic ready. We sent the paper away as of Friday night. On Saturday morning came out the paper of Perkins. Next Saturday came out our paper. And I managed also, since I had two more photos, to add two more photos. You will find out that in the paper it is written — I insisted — I said if they wanted to add them it was OK by me but I wanted to add that these had been added afterwards. I did not want to destroy — out of something which was not a trick but simply a desire of producing rich information and to put in print something which was beautiful to look at — I did not want to infirm in some way the claim.

Do you understand the Lattes story? This paper was not signed by Lattes.

Weiner:

I understand.

Occhialini:

At this moment Lattes started to get a bit restive and went to Powell and said, “Well, at this moment, we might do something with this.” Powell said to him, “All right, you will dedicate yourself to anything which looks like an induced star.” Lattes came to me and said, “Look here, I made a contract at this moment.”

Weiner:

Which contract?

Occhialini:

With Powell. He said, “What do you think?” I said, “I’ll think about it.” Then Powell comes to me and says… he had made an arrangement with Lattes about this and “Maybe it is the time to consult you to see if this thing is all right. What do you think?” I said, “To me, this is a useless contract.” He said, “Why?” “I don’t see at this moment what else there is in this place. What remains to you in this moment is to give to him something which has to do with small stars produced by something. Well, small stars means that if you got small star one, or two, or three, or four, or five, what is left to us are the very big stars, but the big stars are not of interest at this moment for the muon from what I have seen they are always spectacular but they don’t contain anything. This contract should be changed for this means exactly that you have to look at the big stars.” At this moment it seemed to me a bit unfair for if you started looking — I was right. Then they did a very nice thing. What Powell was saying, “After all, we took out the cream with the meson.” “Well,” I said, “I am very sorry. I remember that when I was with Blackett we never admitted that anyone had taken the cream. Remember too that Perkins had taken the cream, no you are taking the same.” “What can we do with the stars?” “Well,” I said, “We can maybe find the mass of this particle and if we get a lucky disintegration in which everything is charged, in which you got momentum — after all, we might, it would be a pity to lose it.”

Practically, when we were discussing it, I wrote to Lattes and said, “Look here, this arrangement is no good to me. I never interfered when you people were banging statistics and deuteron, groups of particles, direction, angle of scattering and so on. But at this moment it is so nice for you to cooperate, but the contract which I made with Powell is that I can share these plates. I will only share with conditions that are reasonable, but I don’t accept,” and so on. And they said, “Oh yes.” And then they said, “Look at this star.” I said, "Did you tell to Powell?” “Not yet.” “When did you find it?” “Just now.” “Just now,” I said, “Look here, boy, this is a bit” — Camerini was looking out the window — “This is really, I am not stupid, you can’t fool Powell.” I never could prove it. It was a star which had three particles going from outside… one, two and three coming like this and another one going in this direction up. This was really the dream of a man who works, the kind of thing in which possibility you have got momentum. Then the day after this (???) said, “Well, I think that this seems to prove that the mass of the meson is not 207. It is at a minimum 218 or 219.” These two boys had gone very near. This shows tremendous power of the method.

Weiner:

This conversation occurred just over the plate.

Occhialini:

What?

Weiner:

This conversation about the estimate of the mass occurred just after you had looked at the plate.

Occhialini:

This conversation occurred after I had served notice to Powell and Camerini that if Powell, with his well-known generosity, wanted to give up the same sigma capture stars, this meant that he had not suffered as much as I did so he could put all of it away. As far as I was concerned, I had enough vision to understand that if you toss something out of the window it means that it is of no use, but if you are proved wrong — twenty-four hours afterwards came the confirmation of this. So I always remained with the doubt that these two boys scanning had found this, and then had said that the best thing would be to make a contract — this is the usual gold-digging technique. You find a nugget in a place, you go back and say you have been prospecting and you want to buy this bit of land, all right, you take it, there is the gold… I never insisted, I always felt we were a very funny bunch. To be gentlemen was difficult. These two people were very very devoted to me for what I had done. On the other side, both of them were frustrated by Brazil. They had not been fairly treated by the people. Then there was me with my complexes. Then there was Powell also, Powell the leftist, Powell the man who had been left out of any development. We were all out to gain some recognition. I never trust a hungry man, a thirsty man.

Weiner:

Now, the conversation about the possible mess — what was the next step? What did that raise in your mind? The first paper, the discovery that you could detect mesons, that was enough in itself, that was important. But there was no implication at that moment for theory or anything else —

Occhialini:

Yes, that is true, but due to the fact that they had been very late in sending these plates for about a week, this was shared with Perkins.

Weiner:

That was technique — the fact that you could detect the meson on the plate.

Occhialini:

No, excuse me, there is nothing technique. The fact that you can detect — you postulate the capture of mesons and that when mesons are captured and they arrive in the emulsion they produce disintegration, that they are really, maybe when they are negative — at the end they are able to give their mass maybe and to up in energy and to break up and split up an atom — well, this is something for people. The Japanese had been supposing about it. It was evident by the work of Rasetti that they were getting and so on. There was also a little research that was coming out at this moment.

Weiner:

Do you mean the papers of Conversi and Piccioni?

Occhialini:

Yes, but don’t forget, for the love of Mike, that the paper of Conversi and Piccioni was absolutely unknown at this moment. It had not come out in any way. This was the thing, but the fact that you don’t get anything blind — that after so many years of attempts with the Wilson chamber, with counters in the middle and so on, any fool can go, open a book, and look at the kind of thing. This was opening the origin, this was all opening the field, how they die, how they are captured, what is their mass, where they come from, they are created inside the mu. We were thinking at this moment that they were mesotrons, pi-mu, that is to say, not the mu meson we were thinking they were.

Weiner:

The Yukawa.

Occhialini:

Sorry, we were thinking that Yukawa and mu were the same thing, but there was something which was raised by Pancini, Conversi, Piccioni that it was not absolutely clear. People in coming back from the war did not know — it was not emigrate. It was so little emigrated that people who had suggested it before had been the Japanese again. It was one of the black pages of American physics when Bethe — and I don’t remember the name —

Weiner:

Marshak.

Occhialini:

Marshak. They published the paper in which they suggested the hypothesis of a double-meson without quoting the Japanese and giving our experimental evidence which had already come out in photos. Of course, they could have been thinking about it and so on, but not these people. They were in one work, so they were not so innocent. They should have known the Japanese paper which had suggested it.

Weiner:

They didn’t at that time.

Occhialini:

They should have known. It was wonderful, for after the hypothesis of the two mesons came out, then a group of people said that they had thought about it. The first were the Japanese.

Weiner:

There is a chronology on that and the communication problem —

Occhialini:

Look at the chronology and you will discover that the thing was certainly in the stars. Anyone who could read, could think, could take out of the first paper of the Japanese and the paper of Rasetti which was talking about capture, and about the apparent paradox of Pancini, Piccioni, and Conversi, could certainly add two and two together. In one square millimeter — this was the wonderful thing at this moment — was the reply.

Weiner:

On the plate, you mean.

Occhialini:

On the pi-mu — when the pi-mu came.

Weiner:

When the first packet of plates was studied and you described that in your paper, were you aware of the significance that this would have in terms of the whole challenging of the Yukawa mesotron confusion and all of the work that had developed from that? Or was it only later that these qualifications came out of it? From your point of view, it was significant enough to do what you did?

Occhialini:

Will you ask me your question another way, please?

Weiner:

Was it apparent to you when the plate was made showing the pi-mu what the significance was in terms of accepted ideas in physics?

Occhialini:

When the pi-mu came, the significance was absolutely evident, so I reject this question of yours as an insult. (Laughter)

Weiner:

It seems to me that, yes, you know what it is in terms of physics but was it something that you got very excited about? In those weeks following where the division of labor was decided upon by Powell and then readjusted and so on, was there really the feeling that this was very very hot?

Occhialini:

Look here, the first paper which we wrote together… during the night, you ask me if I was excited and I will tell you that I don’t know if we were excited but a person who goes to bed at three o’clock and comes back to work at ten o’clock in the morning, certainly must have something to carry it on. Lunch was done in 40 minutes. I used to visit the pub. When I was entering the pub, people were shouting, “Give us the last, give us the last,” for I was coming at 10 to 10 to have a beer and then go back again.

So the first paper says we give two examples of a star and what can do this little plate and so on. We found a group of things which shall be described, and we feel absolutely sure that in these plates we have a group of phenomena which will change radically our ideas… Powell said look here, he wanted me to put this in good English. That if they ask us, we dare. “Excuse me,” says Powell, “Please finish. Let’s finish, for when we are going to finish it, I am going to look for them.”

So I was really feeling that the technical break-through, not only but there is a lecture of mine in this period in which I was saying that this is only the start. I was explaining what I was feeling in terms of science — this is only the start. I was saying that it seemed to me evident that in the moment in which we should find a way of producing bigger grains, more sensitized grain, we shall have attacked the minimum. We must only wait at this moment.

When I met Waller, he said, “Hell, if I had known that you were sitting on this type, but every one of you people was telling me that it was wonderful. You never told me that this emulsion was very good but that you wanted me to produce something more sensitive. No one told me.” This was in the period that not knowing Mr. Waller was the Mr. Waller and still thinking that he was a clerical worker, very well-dressed, and that he was telling people what they should do, I never cottoned too much to big directors of laboratories.

So that when you ask me, I think the reply is yes. For example, already, this kind of thing looked to me evident that here there was a key. The key was the fact that a particle that would live such a short time, that would decay in flight, could be stopped in such a short time out of the fact that it was passing the (???) material this way… It was crossing the Wilson chamber. It was decaying in flight. As it decays in flight there is a tremendous bang so that you have got something which comes in but a muted bend and the particle goes out with a tremendous kick if it is thrown forward. Once you get the particle, you stop it in a real short time. It is still alive and kicking when it is at zero energy. At this moment, either it captures it — it is captured or it decays. If it decays in flight you don’t have a chance to observe it. You can observe it in a bubble chamber, you can observe it in emulsion, but you cannot observe it in a block of lead for what you get in a block of lead, what you don’t know is this: that there is one particle that comes in, there is another particle which comes out. They are not the same particle. This is the famous story that Lord Rutherford tells, the story of the old lady who throws the ball — I think she throws the ball under the bed in order to know if there is a burglar under the bed or not. If the ball comes out from the other side — I heard it once, it was very nice — if the ball comes out then you know that there is nothing. If it stops then it means there is a burglar. Then the question is this: what would happen if the ball got focused and the focused ball sends out the other ball from the other side. What would Lord Rutherford have done? The reply is… that Lord Rutherford would have lain under the bed to look.

Weiner:

Let me ask about this period, after the first realization which I wanted you to describe and you did, was there any communication at Bristol or anywhere else, with any theorists to discuss the significance of this? Or any communication with anyone elsewhere in terms of private letters or conversations before the paper was published?

Occhialini:

There was no theoretical work done — no. Are you thinking about something? I would be extremely happy if you are thinking about something for then you would give me the cue to give a reply.

Weiner:

No, I’m fishing because I am interested in the general process of communication, but don’t let that inhibit you.

Occhialini:

It won’t inhibit me in the least but from the way you ask you can get a certain type of reply which contains all the truth or another type of reply which is very diplomatic.

Weiner:

I have no specific instance.

Occhialini:

That’s all right. I give you the diplomatic answer.

Weiner:

Too bad.

Occhialini:

All right, sorry, up to now from you I only kept seven things. This is the eighth. [Laughter] He was telling me — Segrè — very interesting, why don’t you give it to me so that I can deposit it in the National Academy of Science…

Now, we had these two mesons. These two mesons were showing — one of them was interrupted, broken, but was consistent. The other one was 600 (???). Both of them were showing this thing — pack, pack(?) — world famous wiggling and this thing coming out. Then we go — Blackett comes to Bristol, and we show him the thing, thorium, and he says, “Look here, out of this — if it is a definite rule in physics then this is the explanation, this is the most light, but there is also a definite rule that before setting it… every possibility should be investigated. Is there any other mechanism which can explain this after all?

I am very lazy — I don’t know if you noticed — terribly lazy. I need to be honest, I don’t have a triggering mechanism… Then Blackett had already criticized me in a postcard for the fact that in the paper notwithstanding that I had looked again and so on, there was left in caution that was saying a meson coming in while the title was the disintegration produced by particle of and so on. …Well, this is not my fault. I had corrected everything… as I explained. Then he said to common friends that — three letters to which I received here, I got — and now he was coming, suggesting that people were jumping to the easiest of the things that this was a phenomenon and so on…

All right, this put me in fire. Then I worked it out [by] three methods. One of them was very simple — the possibility to catch it with silver. If you can catch it with silver then you have a guarant(?) estimated curve in a point where you can only (???). So if you treat it with silver… the two bits will be brought in a region of wide angle, so you can get the thing which is cut in, can be digested (???). This was admitting that you had the two things (???) that were not seen…

Then the day afterwards — I put it down. I put it down and I passed to another one there. It was Froehlich at teatime. I said, “Look here, Froehlich, I pass. Will you explain to me something here.” [Cassette ends suddenly]