ABSTRACT
The radiations from radium are very complex in character and comprise three kinds of rays. The greater part of the rays emitted bear no resemblance to ordinary light waves, but consist of flights of material particles projected with enormous velocity. The characteristic radiations from radium are invisible to the eye, but are in part, transformed into light when they fall on certain fluorescent substances. An ordinary X-ray screen of barium platino-cyanide is rendered luminous in a dark room when the rays from radium fall upon it. The emanation, mixed with the air, is conveyed into the electroscope, and the radiation from it ionises the gas and causes the collapse of the leaves. If the current of air is stopped, the rate of discharge rapidly decreases with the time, falling to half value in an interval of one minute. The emanations of thorium and radium have been the subject of a large amount of investigation.
