ABSTRACT
IT is well known that the primary β radiation emitted by the great majority of radioactive substances contains a number of groups of rays expelled with definite velocities. When the β rays are analysed by their passage through a magnetic field, and received on a photographic plate, they give a veritable spectrum, consisting of a number of well-marked bands. It is also well known that the γ rays of radium B and C in passing through matter give rise to high-speed β rays. The penetrating power of these rays has been examined by the electrical method, and has been shown to correspond approximately with that of the primary β rays from the same radioactive substance. The values of the velocities of the excited β rays were determined by direct comparison of the positions of the groups with those of the stronger lines due to the primary rays from radium B.
