A little bit about the administrative side. In the meantime progress was done. The calculations that I did not undertake led to results which later proved to be good enough, but we did not trust them sufficiently so that at the end a greatly simplified model was actually used. In the meantime also, the various separation methods, the methods of making material, made progress, improved. There were three different ways to get the material. One was separating the really useful active low abundance uranium 235 for the bulk of U238 by using a gaseous molecule containing uranium, uranium hexafluoride, and using the fact that the lighter isotope diffused faster. It worked. It worked much too slowly. Urey at Columbia University worked- was working on it. He worked out the method that proved very useful in separating other isotopes used in other parts of physical chemistry, but for the war effort; no.