COMPENSATION METHOD 



29 



inertia, and to my mind the most successful is the 

 method Korn has suggested of keeping the cell 

 always sufficiently illuminated to overcome it. 

 Thus suppose we represent the effect of light on 

 resistance by a curve of the form shown in Fig. 9, 

 the point P gives us the place on the curve after 



Receiving 

 Galvanometer 



-/v 

 FIG. 10. 



which for every increment of light 6L the decrease 

 in resistance in a small time t is dbR. If suffi- 

 cient light OL be allowed always to fall on the cell 

 so that the inertia YP is overcome., the effect of 

 any additional light will be very rapid. The com- 

 pensation method of Korn gives further a much 

 brisker action, and the scheme is seen in Fig. 10. 

 Here the light which has traversed the revolving 

 photograph falls on the selenium cell S^i. This cell 



