Some additional experiments have been made in France, it appears, to determine the specific action of a considerable lowering of temperature upon the brilliancy of certain bodies which shine in the dark after having been exposed to sunlight. Tubes of glass filled with the powdered sulphides of calcium, barium, strontium, etc., all substances possessing the property of phosphorescence in a high degree, were exposed to the solar rays and afterward proved to be luminous in the dark, this being done in such a way as to fix upon the memory the mean value of the progressive diminution of the emitted light, and the time also was noted during which the light was strong, less strong and weak, respectively. The tubes were next placed in bright sunlight for one minute and then suddenly introduced into a double-walled glass cylinder, the interspace of which was filled with nitrous oxide at 140 degrees C. In about five or six minutes the temperature of the tubes was some 100 degrees. They were then withdrawn, and, when observed in a perfectly dark chamber, no luminosity whatever was perceptible. As the tubes recovered their normal temperature, however, the phosphorescence returned without the exciting agency of the sun’s rays or of diffused light. These results were proved to be general for all phosphorescent substances employed. The experiments showed, too, that the production of the phosphorescent light requires a certain movement of the constituent molecules of bodies.
It is likely that the experimenter was Antoine Henri Becquerel, who discovered natural radioactivity in 1896, and shared the 1903 Nobel Prize for physics with the Curies.