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 



Fig. 4. 



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 



