Mr. M. A. Henry (_Scientific American_, April 2, 1921) points out that the problem of the chemist “is to produce a phophorescent substance which will stand up longest under the terrific bombardment of the radium rays and which, at the same time, will give off the most light. Such progress is being made in this direction that today [1921] only about one-twentieth the amount of radium used four years ago [1917] is needed in the making of luminous material. And the chemist insists that he has only scratched the surface of possibilities in this direction and that even better results can be attained. At present the life of the zinc crystals is from 15 to 20 years, although the radium lasts for centuries. “This life will be much longer if the instrument to which it is applied is kept away from the light most of the time. The crystals, already stressed by the radium rays, have an additional strain imposed by the light and this hastens the process of disintegration. Strong sunlight, especially at the seashore where the presence of much ozone in the air intensifies the ultra-violet rays, has a very destructive effect on luminous material. For this reason the manufacturers of this delicate substance usually guarantee it for about half its normal life, or ten years.” A radium-lighted fish-bait is now on the market, and fishermen say that this bait is very successful in attracting fish which haunt deep water. RADIUM MAKES GEMS BLUSH D. Berthelot, F. Bordes, C. Doelter, and others observed that the rays from radium induced important changes in the colors of minerals. Dr. T. Squance, of Sunderland, England, succeeded in transforming a sapphire of faint pink hue into a gorgeous ruby color, and a faint green sapphire into an oriental emerald hue. It was already known that a diamond exposed to the rays of radium glows with a beautiful green light. In experiments carried out at the United States Bureau of Mines (1921), in Reno, Nevada, a colorless Colorado topaz was tinted yellow by exposure to penetrating radiation. If a method can be devised to make the color permanent, the discovery will greatly increase the value of the gem-stone material found in the west. If we submit yellow phosphorous to the action of radioactive substances, it becomes changed into the red “alotropic” variety. Certain of the rays decompose ammonia, and water under their influence is subjected to electrolysis, yielding oxygen and hydrogen. A RADIUM CLOCK