﻿Characteristic Curve of a Photographic Emulsion. 367 



of inflexion has moved so near the origin that the part of the 

 curve to the left of this point does not show on the scale to 

 which the curves are plotted. On the other hand, the 

 theoretical curves in fig. 12 are characterized by the fact 



Fig. 12. 



that the ratio of the ordinates for different sizes of grain is 

 independent of the intensity, and the value of I at the points 

 of inflexion, 1; and the average sensitivity do not change as 

 the grain size is varied. Thus we cannot explain the effect 

 of a variation of grain size on Svedberg's assumption. 



Xow let us assume that the sensitivity of a nucleus depends 

 on the size of the grain in which it is contained, and that if 



Fig-. 13. 



it is in a large grain it is more sensitive than it would have 

 been in a small one. The effect of this on the distribution 

 curve for the larger grain in fig. 11 is to shift it bodily 

 nearer the zero, thus decreasing the value of I; and increasing 

 the average sensitivity, as in fig. 13. The N I curves 



