INTRODUCTORY 5 



a companion volume on the ocean the title of "The 

 Opal Sea." A better term than "opal " could scarcely 

 be found for describing in a word the color of the 

 desert itself. The marvellous air, wholly free from 

 the vapors and impurities of coast and valley places, 

 while it sharpens detail and reduces difference of 

 plane, at the same time throws over every object 

 in far or middle distance a veil of lilac atmosphere 

 wonderfully thin and transparent. Owing, perhaps, 

 to the high power of these color-waves, the eye is 

 hardly interfered with in penetrating shadows. As a 

 result, one receives the full effect of every tone of 

 color, whether in light or shade: while all come to 

 the eye softened but enriched, and with that inde- 

 finable opaline quality that gives magic and fascina- 

 tion to the most poetic of gems. 



The geological simplicity of sand and rock does 

 not result, as might be expected, in poverty of color. 

 Sand, particularly, might seem to be capable of 

 little change of hue. But, on the contrary, its re- 

 flecting power gives it special value as a color agent, 

 a means of taking on varying effects from the ever- 

 changing sky. In the northwestern arm of the Colo- 

 rado Desert are two great masses of sand. Flattened 

 domes in shape, the higher one rises, I should guess, 

 to five hundred feet above the surrounding levels. 

 The sand probably overlies a rocky abutment of the 

 adjacent foothills, and has been heaped there by 

 that scarifying wind, the terror of railway employes 

 whose lines are cast in the division which includes 

 the San Gorgonio Pass. For months these sand-hills 

 were in my daily view, and to describe the shades of 



