Two British scientists join Los Alamos, NM, and prove to have important impacts on the implosion program. Geoffrey Taylor (arrived May 24) points out implosion instability problems (especially the Rayleigh-Taylor instability), which ultimately leads to a very conservative design to minimize possible instability. James Tuck brings the idea of explosives lenses for detonation wave shaping (2-D lenses for plane wave generation originally proposed by M. J. Poole in England, 1942), but suggests developing 3-D lenses to create a spherical implosion.