strong, showing that most rays passed through, while the glass was practically opaque. By this means imitation diamonds can readily be distinguished from true gems.
Action of Radium on Diamond
The /3-rays from radium having like properties to the stream of negative electrons in a radiant matter tube, it was of interest to ascertain if they would exert a like difference on diamond. The diamond glows under the influence of the ^-radiations, and crushed diamond cemented to a piece of card or metal makes an excellent screen in a spinthariscope almost as good as zinc sulphide. Some colourless crystals of diamond were imbedded in radium bromide and kept undisturbed for more than twelve months. At the end of that time they were examined. The radium had caused them to assume a bluish-green colour, and their value as " fancy stones " had been increased.
This colour is persistent and penetrates 108
