RELATIVE STIMULATING EFFICIENCY OF LIGHT 



163 



of the same flash-frequency but of different ratios between the 

 light and dark periods are arranged in order as to relative stimu- 

 lating efficiency. When this is done it is apparent that those 

 lights of flash-frequencies of 30, 20, and 10 per second in which 



FIG. 4. Paths of a typical specimen of Vanessa in a field of light composed of 

 two horizontal beams of equal illumination, 10.5 m.c., crossing at right angles, 

 the light in one beam being continuous and that in the other intermittent. (Re- 

 duced by three-fourths). The intermittent light was produced by a disk with 

 three-fourths, removed. Other explanations of this figure are the same as those 

 given in the description of figure 2. Note here also that the degree of deflection 

 varied with the flash-frequency. 



