40 PHOSPHORESCENCE 
charge had been passed through the tubes and 
gases. Hydrogen, sulphuretted hydrogen, chlo- 
rine, protoxide of nitrogen, showed a feeble light 
for a few seconds after being submitted to an 
electric discharge or a current of induction. With 
oxygen a similar effect is observed. Rarefied oxy- 
gen, enclosed in a serpentine apparatus composed 
of a series of glass globes united by bent tubes 
(fig. 4), in which are soldered platinum wires to 
conduct the discharge, is submitted to the action 
of a powerful induction machine or common elec- 
tric battery. When the current is suddenly cut 
off, the entire tube shines with a yellowish light, 
which persists for some seconds and then gradu- 
ally disappears. The experiment must of course 
be made in a dark room. 
Sulphurous acid gas sometimes shows a similar 
effect. M. Ed. Becquerel has not been able to 
observe phenomena of phosphorescence in any of 
these gases after insolation or after exposing them 
