6o 



Fir.. 45. Spiral Nebula HV 24 Comae Berenices. 



the average) fainter, stars does mean the addition 

 of a greater number; hut toward the outer boun- 

 daries of the known sphere the increase is less rapid 

 than would be anticipated. Kapteyn pointed out 

 that this might be due, at least in part, not to an 

 actual thinning out of the stars near the outer 

 boundary of the sphere, but to scattering of light 

 by minute particles distributed at wide intervals 

 through space. What would be the result? We 

 know that the sun appears red at sunset, or when 

 seen through smoke, because the blue light is 

 intercepted and scattered by the minute floating 



