ABSTRACT
One of the most interesting properties of the radioactive substances, thorium and radium, is their power of communicating temporary radioactivity to all bodies. The emanation from thoria loses half its radiating power in about one minute, but the emanation from radium continues radiating strongly for several weeks. On the contrary, the excited radioactivity due to thoria falls to half its value in eleven hours, while that from radium decays much more rapidly. The rate of decay of the excited radiation from radium is not regular and depends largely on the purity of the radioactive material employed. The characteristic property of excited radioactivity is that it can be confined to the kathode in a strong electric field. It is probable, therefore, that the radioactivity is due to the transport, in the electric field, of positively charged carriers of some kind.
