INFLUENCE OF RED AND INFRA-RED RAYS UPON SIDOT BLENDE. 79 



For the curve shown in Figs. 70 and 71 the exciting light was the violet 

 of the carbon arc spectrum. For the curves of Figs. 72 to 75 a spark between 

 cadmium terminals was used in excitation. The intensity of phospho- 

 rescence has been plotted in all of these curves instead of the reciprocal 

 square root, although in some cases the latter value has been plotted also. 



100r 

 I 



Fig. 70. 



Influence of exposure to infra- 

 red on form of decay curve. 



Curve /. Ordinary decay curve 



for X =0.497 tx. 

 Curve /'. Screen exposed to 



infra-red immediately after 



end of excitation. 



6 Sec? 



Fig. 71. 



Curve /. Ordinary decay curve for X =0.497 M- 

 Curve /'. Screen exposed to infra-red after decay 

 had proceeded to A. 



O, Sec. S 



Fig. 72. 



Decay curves with and with- 

 out infra-red. X =0.5460. 



