ABSTRACT
The account was given of recent experiments of Sir Ernest Rutherford and Dr. Andrade to determine the wave length of the very penetrating gamma rays which are emitted from radium. The spectrum of the gamma rays was obtained by a photographic method by reflecting the rays from a thin slip of rock salt. The radioactive source consisted of a fine glass tube containing a large quantity of radium emanation. An account was also given of the methods for determining the magnetic spectrum of the beta rays. For this purpose, the rays from a fine source, passing normally in a strong magnetic field, describe a circular path and fall on a photographic plate. It is supposed that the breaking up of an atom is accompanied by the expulsion of a swift beta particle from the nucleus. This beta particle in escaping from the atom sets the external electrons in rapid vibration, and gives rise to the gamma rays observed.
