Shortly before the Second World War time, Nishina reported on a series of prominent nuclear physical and radiochemical studies in collaboration with Kimura. They artificially produced ²³¹Th, a member of the natural actinium series of nuclides, by bombarding thorium with fast neutrons. This resulted in the discovery of ²³⁷U, a new isotope of uranium, by bombarding uranium with fast neutrons, and confirmed that ²³⁷U disintegrates into element 93 with a mass number of 237. They also identified the isotopes of several middle-weighted elements produced by the symmetric fission of uranium. In this review article, the highlights of their work are briefly summarized along with some explanatory commentaries.

(Communicated by Toshimitsu YAMAZAKI, M.J.A.)