SOME recent accounts in the daily Press referring to the separation of uranium (235) would suggest developments arising from a letter in the Physical Review (57, 546), by Dr. A. O. Nier. Nier there describes fission experiments conducted with small quantities of 235U and 238U separated by deposition in a mass-spectrograph. The masses of 238U samples were of the order of 10-7 gm. and those of the 235U samples about 10-9 gm. The samples were bombarded with slow neutrons obtained originally from a cyclotron. Fission products were observed in an ionization chamber when the 235U isotope was used, but not with the more abundant 238U. The 234U isotope was not separated from 236U, but its abundance is very small. It seems almost certain that 235U is responsible for the slow neutron fission, as predicted theoretically by Bohr and Wheeler.