758 



ENERGY AND VISION 



among women, between and 100 per cent One man showed a 

 marked difference. 



The figures express the energy necessary for continuous impression 

 but by making the same assumption as Langley concerning the 



IZk 



^y^ 



Ct 



Fig. 5. Adjustable window. 



minimum amount of time necessary to perceive distinctly a very 

 faint light, (about ^ second), these figures may be expressed in ergs 

 per ^ second, by dividing them by 2. 



The size of the retinal image was approximately 0.01 sq. mm. 

 ±0.002. 



TABLE III. 



Men. 



* Observer "I" was included in the mean, although he seemed to be quite out 

 of the normal. 



