428 FRAGMENTS OF SCIENCE. 



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 analyzed, all the colors of 

 the spectrum are found, and they are found in the pro- 

 portions indicated by our conclusion. Blue is not the sole, 

 but it is the predominant color. 



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 anticipated. 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 scattering particles. They abstract in 

 succession the violet, the indigo, the blue, and even disturb 

 the proportions of green. The transmitted light under 

 such circumstances must pass from yellow through orange 

 to red. This also is exactly what we find in nature. 

 Thus, while the reflected light gives us at noon the deep 

 azure of the Alpine skies, the transmitted light ives us at 

 sunset the warm crimson of the Alpine snows. The 

 phenomena certainly occur as if our atmosphere were a 

 medium rendered slightly turbid by the mechanical sus- 

 pension of exceedingly small foreign particles. 



Here, as before, we encounter our skeptical " as if." 

 It is one of the parasites of science, ever at hand, and ready 

 to plant itself and sprout, if it can, on the weak points of 

 our philosophy. But a strong constitution defies the 

 parasite, and in our case, as we question the phenomena, 

 probability grows like growing health, until in the end the 

 malady of doubt is completely extirpated. The first 

 question that naturally arises is this: Can small particles 

 be really proved to act in the manner indicated? No 

 doubt of it. Each one of you can submit the question to 

 an experimental test. Water will not dissolve resin, but 

 spirit will dissolve it; and when spirit holding resin in 

 solution is dropped into water, the resin immediately 

 separates in solid particles, which render the water milky. 

 The coarseness of this precipitate depends on the quantity 

 of the dissolved resin. You can cause it to separate either 



