122 FRAGMENTS OF SCIENCE 



By the scientific use of the imagination we may hope 

 to penetrate this mystery. The cloud takes no note of 

 size on the part of the waves of ether, but reflects them 

 all alike. It exercises no selective action. Now the cause 

 of this may be that the cloud particles 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 seabird's wing; and in 

 the presence of large reflecting surfaces, the existing dif- 

 ferences 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 hand- 

 ful 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 

 extreme 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 com- 

 petent to scatter all the waves in the same proportion. If 

 they be not and a little reflection will make it clear that 

 they are not the production of color must be an incident 

 of the scattering. Largeness 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. 



