114 FRAGMENTS OF SCIENCE. 



faces, the existing differences of magnitude among the 

 waves of ether may disappear. But supposing the re- 

 flecting particles, instead of being very large, to be very 

 small in comparison with the size of the waves. In 

 this case, instead of the whole wave being fronted and 

 thrown back, a small portion only is shivered off. The 

 great mass of the wave passes over such a particle with- 

 out reflection. Scatter, then, a handful of such minute 

 foreign particles in our atmosphere, and set imagina- 

 tion to watch their action upon the solar waves. Waves 

 of all sizes impinge upon the particles, and you see at 

 every collision a portion of the impinging wave struck 

 off; all the waves of the spectrum, from the extreme 

 red to the extreme violet, being thus acted upon. 



Remembering that the red waves stand to the blue 

 much in the relation of billows to ripples, we have to 

 consider whether those extremely small particles are 

 competent to scatter all the waves in the same pro- 

 portion. If they be not and a little reflection will 

 make it clear that they are not the production of 

 colour must be an incident of the scattering. Large- 

 ness is a thing of relation ; and the smaller the wave, 

 the greater is the relative size of any particle on which 

 the wave impinges, and the greater also the ratio of the 

 portion scattered to the total wave. A pebble, placed 

 in the way of the ring-ripples produced by heavy rain- 

 drops on a tranquil pond, will scatter a large fraction 

 of each ripple, while the fractional part of a larger 

 wave thrown back by the same pebble might be infini- 

 tesimal. Now we have already made it clear to our 

 minds that to preserve the solar light white, its consti- 

 tuent proportions must not be altered ; but in the act 

 of division performed by these very small particles the 

 proportions are altered; an undue fraction of the 

 smaller waves is scattered by the particles, and, as a 



