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"I wrote an article about the squash court experiment too--if I can find the goddam thing. I write lots of articles. Course, nobody ever reads 'em." After a minute, he comes up with "Early Recollections of the Manhattan Project," an address to the Society of Nuclear Medicine meeting in Chicago in June 1977. In the article he describes how Fermi and his assistants kept building up the nuclear pile to achieve a critical mass, the smallest amount of material needed to begin a chain reaction. They calculated that on the night between Dec. 1 and Dec. 2, 1942, the 57th layer of graphite would make the pile critical. To prevent the neutrons from multiplying and starting a reaction, the scientists used cadmium strips, which absorb neutrons. When all but one of the cadmium strips were removed, it became clear the calculations were correct. "It was a great temptation for me to partially withdraw the final cadmium strip and to be the first to make a pile chain-react. But Fermi had anticipated this possibility. He had made me promise that I would make the measurement, record the result, insert all cadmium rods, lock them all in place, go to bed, and nothing more.
"What people don't understand is that we were really running frightened of the Germans. The main thing was to get a self-sustaining chain reaction before the Germans did. All the people who were involved--Leo Szilard, John Von Neumann--the whole gaggle of 'em had just got off the boat. Fermi's wife was Jewish. The rest of the guys were Jewish. That's why they left. But all the other Huns, their colleagues, were back home, probably working on a chain reaction. So there was a lot of pressure.
"Well, anyway, we put the stuff together the next morning, and it looked as if the thing was going to go critical. Then Fermi says, 'Let's go have lunch.' You'd think he'd want to stay around and finish the damn thing. The criticality kept going up. The counters kept clicking faster and faster. You don't see anything when this happens. The counter just keeps accelerating, like in your car. Course, in a bomb it goes so fast, it blows the thing apart. But then Fermi shuts everything off and says, 'Let's have lunch.' So we started it all up again in the afternoon, and it went critical, and that was that.
"Let me tell you, even at this point I still didn't know what the hell this was all about. Everything was very secret. Besides the Hiroshima films and the strike orders, I got a very interesting tape by Fermi talking about secrecy. He points out that things were classified first by the scientists, not by the military. You hear things now about how the damn Government classified science; not so. I have the tape. He even hired a guy from Yale to draw up the rules for classification. An absolute paranoid. Excellent choice."