OUR GREATEST NATIONAL MONUMENT 



257 



self, seen under the heavy 

 clouds which usually cover 

 it, is apt to convey an idea of 

 somber coloring. But, when 

 one comes up to the fuma- 

 roles, he is almost over- 

 whelmed by the indescribable 

 riot of color (see page 273). 



The colors of the canyon 

 are almost entirely due to the 

 wonderful atmosphere and 

 the brilliant light which floods 

 its recesses. Under such 

 leaden skies as usually prevail 

 in the valley, even the canyon 

 itself would show to very poor 

 advantage. The reason why 

 the valley fails for the most 

 part to show much color at a 

 distance is due in large meas- 

 ure to the fact that all the 

 colors of the spectrum lie 

 close together, so intermin- 

 gled as to blend into neutral 

 grays or browns when seen 

 from a distance. But, while 

 thus largely losing their ef- 

 fectiveness at a distance, the 

 colors are for this reason all 

 the more striking when seen 

 close up, for then each is 

 heightened by contrast with 

 the other (see page 273). 



The throats of the fuma- 

 roles and the ground around 

 them are most often burned 

 into some of the various 

 shades of red which are fa- 

 miliar in the different tints 

 of brick in common use. 

 Sometimes it will be a light, 

 pinkish tone; again a bright scarlet; or, 

 in still hotter places, rich crimson passing 

 into purple and black in some of the very 

 hottest vents (see page 278). 



With such deep-burned purple patches 

 is frequently associated a bright orange 

 deliquescent incrustation of the greatest 

 richness. These two colors are most 

 often found together in fumaroles bear- 

 ing so high a concentration of acid as to 

 have eaten away all soluble constituents, 

 leaving spots of purest white silica stand- 

 ing in most pleasing contrast with the 

 purple and orange. 



In some places considerable areas are 

 leached out to a gleaming white by the 



Photograph by R. F. Griggs 



THREADING A WAY THROUGH ONE OF THF CANYONS 

 IN THF SAND-FLOW 



The sand-flow fills the Valley of Ten Thousand Smokes 

 (see text, page 241). 



acid fumes. When to this are added 

 faint tinges of pink and yellow, there re- 

 sults a beautiful flesh color of the great- 

 est delicacy. Again, the ground color of 

 red, white, or gray may be overlaid with 

 copious deposits of pure yellow sulphur. 

 Bright colors are by no means limited 

 to the large and vigorous fumaroles. 

 Over many hundreds of acres in the val- 

 ley, where steam is everywhere seeping 

 up from beneath, the ground glows with 

 the most brilliant colors imaginable. 

 Sometimes it is black with the character 

 and consistency of asphalt. This grades 

 through various shades of blue into deli- 

 cate light pearl grays or alternates, as 



