Trowbridge and Burbank — Phosphorescence, etc. 55 



Art. VIII. — Phosphorescence produced by Electrification / 

 by John Trowbridge and John E. Burbank. 



Various investigators have stated that the X-rays can com- 

 municate an electrical charge to bodies. We were interested 

 to discover whether this statement could be verified by means 

 of the phenomena of phosphorescence. When flnorite, in the 

 state of a comparatively coarse powder, is heated to a low red 

 heat for about an hour, it loses completely its power of phos- 

 phorescing under the effect of a low red heat ; if it is then 

 electrified by means of the brush discharge of an electrical 

 machine, and then submitted to a low red heat, it suddenly 

 phosphoresces. In this connection it is interesting to note a 

 statement of E. Becquerel upon the effect of electric sparks 

 on phosphorescent bodies. In his work entitled "Lalumiere 

 ses Causes et ses Effects,"* he says, "In order to submit the 

 substances to the action of electric discharges they were placed 

 directly upon an insulated stand, if they were in fragments — 

 or in tubes if they were in the state of powder — in such a 

 manner that the discharge terminals were two or three centi- 

 meters apart. One or many electrical discharges are then 

 passed from Ley den jars between the terminals. We then 

 find that not only the bodies in question become phosphores- 

 cent after the passage of the discharge; but also, as is seen 

 later, they are made phosphorescent by these electrical dis- 

 charges when subjected to heat, even if before having been 

 submitted to the action of the discharges, they had been cal- 

 cined so long as to be entirely deprived of the power of phos- 

 phorescence by elevation of temperature. The electric light 

 acts, therefore, like sunlight, but with greater energy by reason 

 of its greater intensity on account of the position of the 

 bodies; and it is capable of making bodies acquire phosphores- 

 cence which did not previously possess it. There is no neces- 

 sity of submitting fluorspar or the diamond to heat imme- 

 diately after having been exposed to the discharges. The 

 elevation of temperature can take place even after the lapse of 

 some months?" 



Becquerel evidently attributed the effects observed to the 

 light of the discharge, for he says further, p. 55 id., " The 

 electric spark acts only by its light, but its action is more ener- 

 getic than that of sunlight by reason of its great intensity and 

 the proximity of the source." 



In an article on luminescence by E. Wiedemann and Gr. C. 

 Schmidt the conclusion is reached that the violet light alone of 



*Pans, 1897, p. 55. 



