428 POPULAR SCIENCE MONTHLY. 



delicate photographs. It is certain that the background of the sky it- 

 self is by no means black. The only question is, whether the light from 

 this background is mostly reflected by our atmosphere from the stars. 

 It may seem questionable whether such is the case, because the fraction 

 reflected in a clear atmosphere is not supposed to exceed one-tenth the 

 total amount of light of the stars themselves. On the other hand, the 

 seemingly blue color of the sky might seem to militate against this view, 

 since the average color of all the stars is white rather than blue. The 

 subject is an extremely interesting one and requires further investiga- 

 tion before a definitive conclusion can be reached. 



