The Manhattan Project: Making the Atomic Bomb

One Last Look: The Lewis Committee

On November 18, Groves appointed Warren K. Lewis of the Massachusetts Institute of Technology to head a final review committee, comprised of himself and three DuPont representatives. During the next two weeks, the committee traveled from New York to Chicago to Berkeley and back again through Chicago. It endorsed the work on gaseous diffusion at Columbia, though it made some organizational recommendations; in fact, the Lewis committee elevated gaseous diffusion to first priority and expressed reservations about the electromagnetic program despite an impassioned presentation by Lawrence in Berkeley. Upon returning to Chicago, Crawford H. Greenewalt, a member of the Lewis committee, was present at Stagg Field when, at 3:20 p.m. on December 2, 1942, Fermi's massive lattice pile of 400 tons of graphite, six tons of uranium metal, and fifty tons of uranium oxide achieved the first self-sustaining chain reaction, operating initially at a power level of one-half watt (increased to 200 watts ten days later). ²⁵ As Compton reported to Conant, "the Italian navigator has just landed in the new world." To Conant's question, "Were the natives friendly?" Compton answered, "Everyone landed safe and happy."²⁶ Significant as this moment was in the history of physics, it came after the Lewis committee had endorsed moving to the pilot stage and one day after Groves had instructed DuPont to move into design and construction on December 1. ²⁷

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