December 18, 1903.] 



SCIENCE. 



779 



found here. This is evidently a substance 

 not necessarily radio-active itself, but one 

 that may possess the same or allied prop- 

 erties with the substance found with the 

 zinc minerals. 



4. The siibstance present in caleite, from 

 Franklin, X. J., and from Langban and 

 Pajsberg, Sweden, is probably yet another 

 body, which also does not respond to ra- 

 dium ; although the willemite found with it 

 at Franklin becomes luminous at the ap- 

 proach of radium as if it were a fairy 

 wand. 



5. There probablj' exists in autuuite, and 

 another yellow-brown uranium mineral 

 from Texas, a fluorescent substance which 

 differs from anything that we have noted 

 in the study of the minerals of the collec- 

 tion. 



6. In the hyalite, from San Luis Potosi, 

 a volcanic mineral, there is present some- 

 thing that responds with a beauty of color 

 that strikingly reminds one of nitrate of 

 uranium; this may be still another sub- 

 stance. 



7. The most responsive of all, however, 

 were the diamonds containing that peculiar 

 substance that gives them what is known 

 as the blue-white color — fluorescent like 

 anthracene, and holding the luminosity for 

 a long time— to which one of us (K.) gave 

 the name of Tift'anyite. 



In the examination of more than 15,000 

 diamonds from British Guiana and else- 

 where, 44 were selected. After an exposure 

 of 60 seconds to ultra-violet rays, these 44 

 diamonds phosphoresced brilliantly and 

 continued to glow for a long time after ex- 

 posure. The luminosity was so great that 

 it penetrated one thickness of white velvet 

 and from nine to twelve thicknesses of tis- 

 sue and blue linen paper. But they did 

 not exhibit their light through black vel- 

 vet, nor apparently were they affected by 

 the ultra-violet rays when surrounded by 



black velvet. These diamonds when glow- 

 ing brilliantly showed absolutely no action 

 upon the barium platino-cyanide screen, 

 nor upon screens of phosphorescent zinc 

 sulphide, willemite or calciimi sulphide. 



The most remarkable specimen was a 

 diamond of 14 |i carats. (This was ex- 

 hibited.) This stone possesses the power 

 of absorbing sunlight and emitting it in 

 the dark. An arc lamp will cause it to 

 store up light and to give it out in the 

 dark. Even a small hand-lamp of one 

 candle-power has caused this diamond to 

 phosphoresce. It responds to polonium, to 

 the Roentgen rays and to the utra-violet 

 rays ; to the rays that pass through a violet 

 glass, and to radium, even in a more marked 

 degree than willemite. 



The print shown was made from a nega- 

 tive obtained by exposing a sensitive photo- 

 graphic plate to the blue-white diamond, 

 and a transparent black stone of 16^ 

 carats, thin white paper intervening, after 

 they had been exposed to ultra-violet light 

 for one minute. The print is the result ; ex- 

 cept that the print of the black stone has 

 been colored to show the reddish phosphor- 

 escence given out by it. 



After another exposure of one minute, 

 to our surprise, the black stone glowed red 

 for fifteen minutes, almost surpassing the 

 phosphorescence of the blue-white stone. 

 At the end of fifteen minutes the red glow 

 subsided, while the white stone phos- 

 phoresced five minutes longer; the light 

 being held twenty minutes after exposure. 



As .stated above, from the work of Wiede- 

 mann and Schmidt, Hoffmann, and Trow- 

 bridge, it appears that the phosphorescent 

 and fluorescent effects observed by the ac- 

 tion of ultra-violet light, produced by 

 sparking, with siich metals as iron, is not 

 due to this cause at all, but may be ac- 

 counted for by the accumulation of an 

 electric charge. The diamonds were 



