detonation in a bomb. We were to be given access to technical information on the plutonium project, but not on the U²³⁵ project, nor would we have any information on the design of the bomb. Stressing the importance of our project and the need for absolute security, he told us that we had no knowledge of the status of German physics, but they were known to be working on atomic research. Dr. Compton concluded by saying it took many people of diverse backgrounds to accomplish our objective. He asked for full understanding and cooperation between those with academic backgrounds and those who had come from industry.

Dr. Compton was a handsome man of about fifty with deep-set penetrating eyes. I felt that he was talking directly to me and later I learned that my colleagues had that same impression. We left the room awed by the words we had heard and the intellect and sincerity of the man who had spoken them.

The second secret lecture was by Enrico Fermi. About forty years old. Dr. Fermi was a small, energetic, enthusiastic man. He spoke his fluent English rapidly with a slight Italian accent. This theoretical physicist gave a clear picture of a complex process to a group of engineers whose only background in atomic physics was the few lectures they had recently heard. In about an hour. he described the fission of' U²³⁵ by neutron bombardment to produce free neutrons and several elements near the middle of the periodic table, the conversion of U²³⁸ to plutonium by the capture of neutrons and emission of Beta particles, the slowing of high energy neutrons by graphite, the neutron flux required for a chain reaction, the use of a neutron absorbing material such as boron to control the pile. Finally, he described the pile which had recently been operated in the squash court of the West Stands. We were immensely impressed by the work of this giant among physicists and equally impressed by his ability to communicate with us.

A great mathematician and theorist. Dr. Fermi was also a superb experimentalist. By the time of our arrival in Chicago, the pile had been moved to a safer location at Argonne. Some time later. Bill Overbeck arranged for the nine Du Ponters to visit the Argonne Laboratory. At the time of our visit, Dr. Fermi was seated at the control panel and his assistant. Leona Woods, was on top of the pile. I believe they were measuring the neutron cross-section of various elements. They communicated by walky-talky phones over loud speakers, so we could hear their exchanges. Dr. Fermi was reading instruments and controlling the pile, recording data, doing calculations with a 24" slide rule and plotting results on graph paper. Leona introduced the samples into the pile. At one point we heard the shattering of a glass beaker she apparently had dropped. Without missing a beat in his experiment. Dr. Fermi said, "Leona, what are you doing? Having a tea party?" A remarkable man!

The third secret lecture was given by Dr. Charles Coryell, a member of Glenn Seaborg's group, which was developing the chemical process for the separation of plutonium. The problem was akin to the proverbial finding of a needle in a haystack. Here the challenge was to isolate a few grams of plutonium from a huge mass of uranium contaminated by thirty or so radioactive fission products. As a mechanical engineer, I remember only that he said the process involved the use of lanthanum as a carrier for the plutonium and a succession of oxidation-reduction steps.

Our workdays were busy ones, building instruments in the shop and in the classroom soaking up science and technology completely foreign to our backgrounds.