82 



THE DESERT 



Colored air. 



Different 

 hues. 



Producing 



color. 



the coloring of it that makes it so apparent ? 

 Probably. Even the clearest atmosphere has 

 some coloring about it. Usually it is an inde- 

 finable blue. Air-blue means the most delicate 

 of all colors something not of surface depth 

 but of transparency, builded up by superim- 

 posed strata of air many miles perhaps in 

 thickness. This air-blue is seen at its best in 

 the gorges of the Alps, and in the mountain 

 distances of Scotland ; but it is not so apparent 

 on the desert. The coloring of the atmosphere 

 on the Colorado and the Mojave is oftener 

 pink, yellow, lilac, rose-color, sometimes fire- 

 red. And to understand that we must take up 

 the ground-glass globe again. 



It has been said that our atmosphere breaks, 

 checks, and diffuses the falling sunlight like 

 the globe of a lamp. It does something more. 

 It acts as a prism and breaks the beam of sun- 

 light into the colors of the spectrum. Some of 

 these colors it deals with more harshly than 

 others because of their shortness and their 

 weakness. The blue rays, for instance, are the 

 greatest in number ; but they are the shortest 

 in length, the weakest in travelling power of 

 any of them. Because of their weakness, and 

 because of their affinity (as regards size) with 



