774 



SCIENCE. 



[N. S. Vol. XVIII. No. 4G8. 



mauu and G. C. Schmidt, in an article on 

 luminescence, reached the conclusion that 

 the violet light alone of the electrical dis- 

 charge does not cause phosphorescence, 

 which is 'due to peculiar discharge rays 

 analogous to cathode rays.' M. W. Hoff- 

 man confirmed the above. J. Trowbridge 

 reported, 'The action of the X-rays on this 

 mineral (fluorite) was exactly similar to 

 that of electrification,' and concluded that 

 'by them (X-rays) an electrical charge is 

 communicated to fluorescent and phosphor- 

 escent substances.' 



While there may be no question as to 

 the above statements for the particular 

 materials examined— and they are doubtless 

 true for many other substances— yet in our 

 observations there are some which do not 

 admit of the sweeping conclusion that all 

 fluorescent and phosphorescent phenomena 

 observed in minerals subjected to rays 

 coming from the sparking of high voltage 

 currents with iron terminals are due to 

 electrification. 



The ultra-violet light was produced by 

 a triple spark through quadruple iron ter- 

 minals (we may so designate them) with a 

 high voltage current. The direct current 

 was taken from a 110-volt circuit passed 

 through a Ruhmkorff coil with a 12-inch 

 spark and stepped up by two Ley den jars 

 in series. The sparker was provided with 

 a quartz window surrounded by vulcanite 

 and otherwise insulated to permit comfort- 

 able handling. As the number of observa- 

 tions to be made was very great, it was 

 impracticable to remove each individual 

 specimen from the exhibition cases and 

 storage cupboards to the dark room, al- 

 though this was done in many experiments. 

 Flexible cables 200 feet long were joined 

 to the apparatus. This was placed upon 

 rollers and could be moved easily to the 

 various aisles between the cases. The Pif- 

 fard lamp was joined up with the appa- 

 ratus by insulated wires, further protected 



by rubber tubing, 36 feet long. About 

 13,000 mine];als were thus examined by 

 night. 



A large mass of original material has 

 been gathered, of which only a few general 

 observations and tentative conclusions are 

 here presented. 



The three most responsive minerals to all 

 three forms of activity were found to be 

 willemite, kunzite and certain diamonds. 



In a subsequent investigation with the 

 still more rare and novel element actinium, 

 the particulars of which will be given at the 

 end of this paper, these same three min- 

 erals were found to respond markedly to 

 that substance, though with some special 

 features. 



1. It was found that Avillemite from 

 Franklin, N. J., is both fluorescent and 

 phosphorescent with the Roentgen rays, 

 ultra-violet rays and when exposed to 

 radium emanations. These properties 

 were retained, although in some instances 

 the specimens were considerably altered 

 by decomposition. Foreign specimens of 

 the same species were not aft'ected at all. 

 The willemite retained its luminescence for 

 more than twenty-four hours after it had 

 been exposed to radium; the latter not 

 being then within 100 feet of it. Willemite 

 and diamond also responded to polonium 

 that formed a coating on a bismuth rod. 



Willemite has also been noted as tri- 

 boluminescent, i. e., emitting light upon 

 attrition or percussion, even when it merely 

 strikes the side of a glass in which it is sus- 

 pended in water. 



2. The ealcite from Franklin, N. J., 

 showed a distinct red glow with the ultra- 

 violet rays. This mineral, as well as the 

 associated willemite, showed very marked 

 peculiarities of color, the willemite green 

 and j^ellow-green, the ealcite a red glow. 

 These effects were so characteristic that it 

 required but a moment to identify the 



