ABSTRACT
Dr. Chadwick and Rutherfold have shown that the protons are emitted in all directions relative to the bombarding particles, but with greater velocity in the forward direction. The most direct method of studying the results of these collisions is to obtain actual photographs of the tracks of the particles by the well-known cloud method. Unfortunately, on account of the small number of particles, it is difficult to determine accurately the velocity of the proton in different directions. He concluded that the α- particle is captured by the nitrogen nucleus under these conditions, and that in consequence the mass of the recoiling nucleus should be 17 and its charge 8-namely, an isotope of oxygen. The proton is expelled in the backward direction, and two other tracks ascribed to the escaping α - particle and recoiling nucleus are clearly visible. The author's attention has recently been directed to another interesting photograph in air by a similar method, α- ecorded by M. Akiyama.
