22 PHOSPHORESCENCE 
dozen electric discharges passed through non- 
phosphorescent bodies such as marble, certain 
varieties of apatite, etc., will give them the pro- 
perty of becoming luminous by heat. On twenty- 
one days of eaposure to light, these substances 
rendered artificially phosphorescent lost that pro- 
perty again. But if kept im a dark room, they 
retamed it. ‘The term ‘‘non-phosphorescent 
bodies,”” used by Pearsall, is rather exclusive ; as 
phenomena of phosphorescence are so universally 
spread, that scarcely any substance, if properly 
experimented with, will prove to be non-phospho- 
rescent in the strict sense of the word. His ob- 
servation is, however, exceedingly remarkable. 
Some years ago M. Schénbem showed that 
metallic arsenic becomes phosphorescent when its 
temperature is raised to a certain degree.* I 
imagined that antimony might present the same 
phenomenon, but found it was not the case. 
Stibine, or native sulphuret of antimony, I found, 
however, to be very phosphorescent when heated 
ina crucible to a dull-red heat. The light pro- 
duced is white, with a sight tinge of yellow. I 
have lately observed that copper, native sulphuret 
of copper, gold and silver are notably phosphores- 
cent when melted on charcoal before the blow- 
* The metallic arsenic is placed in a small glass globe, and 
heated with a spirit-lamp. The light is emitted at the same time 
that the characteristic garlic odour is developed. 
