114 FEAGMENTS OF SCIENCE. 



are so large in comparison with the waves of ether, as 

 to reflect them all indifferently. A broad cliff reflects 

 an Atlantic roller as easily as a ripple produced by a 

 sea-bird's wing; and in the presence of large reflecting 

 surfaces, the existing differences of magnitude among 

 the waves of ether may disappear. But supposing the 

 reflecting 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 

 without reflection. Scatter, then, a handful of such 

 minute foreign particles in our atmosphere, and set 

 imagination 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 ex- 

 treme red to the extreme violet, being thus acted upon. 

 Kemembering 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 larger 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- 



