INORGANIC RESPONSE 



159 



record (a), before warming, slight fatigue is observed, 

 in (c), after cooling, the reverse, or staircase effect, 

 appears. 



20 c 



20C 



50C 



FIG. 101. INFLUENCE OF TEMPERATURE ON EESPONSE 



Illumination 20", obscurity 40". 



In (a) is shown a series of responses at 20 C. the record exhibits slight 



fatigue. (6) is the slight irregular response at 50 C. (c) is the record on 



re-cooling ; it exhibits ' staircase ' increase. 



Effect of increasing length of exposure. --If the 



intensity of light be kept constant, the magnitude of 



M f - 

 \" 



l LI. 



2" 



& 



(6) 



t P 



AJUlJ,.. 



10' 



8" 9 



10 



FIG. 102. KESPONSE-CURVES FOR INCREASING DURATION OF ILLUMINATION FROM 



1" TO 10" 



In (a) the source of light was at a distance of 50cm. ; in (6) it was at a distance of 

 25 cm. Note the after -oscillation. 



response of the sensitive cell increases with length of 

 exposure. But this soon reaches a limit, after which 



