380 



C.P. l^ittingham and P.M. Bishop 



light and the flash is increased until maximum yield is obtained 

 when the two are separated by 8 - 10 sec. With further increase 

 of the dark time, the yield falls off rapidly until there is no 

 further influence of the background light on a flash given after 

 a 20 sec. dark period. 



The results of the converse experiments, with a background light 

 of 700 mp and a flash of 644 mp are shown in the same figure. 

 Maximum yield from the flash is obtained when a dark interval of 

 7-11 sec. intervenes between the background light and the flash. 

 The yield decreases rapidly as the dark period is increased be- 

 yond 12 sec. The size of the increase in yield at its maximum is 

 greatest with this combination of flash and background light. 



The data thus show that a background light which enhances the 

 yield of oxygen from a flash when given simultaneously, can be 

 separated in time from the flash and still produce enhancement. 

 The time course of this effect is very similar whether the back- 

 ground is at 700 rap and the flash is at 644 mp, or the background 

 is at 653 mp and the flash at 69 7 mp. 



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