SCIENTIFIC USE OF THE IMAGINATION. H5 



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 

 consequence in the scattered light, blue will be the 

 predominant colour. The other colours of the spec- 

 trum must, to some extent, be associated with the blue. 

 They are not absent, but deficient. We ought, in fact, 

 to have them all, but in diminishing proportions, from 

 the violet to the red. 



We have here presented a case to the imagination, 

 and, assuming the undulatory theory to be a reality, we 

 have, I think, fairly reasoned our way to the conclu- 

 sion, that were particles, small in comparison to the 

 sizes of the ether waves, sown in our atmosphere, the 

 light scattered by those particles would be exactly such 

 as we observe in our azure skies. When this light is 

 analysed, all the colours of the spectrum are found, 

 and they are found in the proportions indicated by our 

 conclusion. Blue is not the sole, but it is the pre- 

 dominant colour. 



Let us now turn our attention to the light which 

 passes unscattered among the particles. How must it 

 be finally affected? By its successive collisions with 

 the particles the white light is more and more robbed 

 of its shorter waves; it therefore loses more and more 

 of its due proportion of blue. The result may be anti- 

 cipated. The transmitted light, where short distances 

 are involved, will appear yellowish. But as the sun 

 sinks toward the horizon the atmospheric distances 

 increase, and consequently the number of the scatter- 

 ing particles. They abstract in succession the violet, 

 the indigo, the blue, and even disturb the proportions 

 of green. The transmitted light under such circum- 

 stances must pass from yellow through orange to red. 



