SELIG HECHT 



341 



is at once apparent that the relation between the velocity and the 

 intensity is not linear. What the relation is does not appear defi- 

 nitely, but the smoothed curve passing through the points is decidedly 

 logarithmic in appearance. This is substantiated by Fig. 3 in which 

 the logarithm of the intensity is used as abscissa rather than the in- 

 tensity itself. The fact that the curve becomes a straight line shows 

 that the velocity is some logarithmic function of the intensity. 



$J 8.0 



I 

 I 



I 



JO 



6.0 



— ^^ 



o X 



20 2.5 3.0 



loganthm of Intensity 



3.S 



Fig. 3. Relation between the velocity of the latent period and the logarithm 

 of the stimulating intensity. The points are the same as in Figs. 1 and 2. The 

 straight line is drawn passing through the center of coordinates and has a slope 

 of 2.2. 



To find the exact correspondence between the two, a simple mathe- 

 matical treatment is sufficient. The equation of a straight line is 



y = ax + ft (1) 



in which a is the slope of the line, x and y the abscissa and ordinate 

 respectively, and h is the distance above the center of coordinates at 



