of the Yellowstone and Firehole Rivers. 167 
From the large group of springs on the Kast Fork, we passed, 
between the isolated butes, to the valley of the Firehole, where 
the principal springs and geysers are located. The entire feet 4 
averaging about three miles in width, is covered with the sili- 
Hor SPRING Basin. 
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ceous crust as white as snow. Among the dense # ier in the 
foot hills, and even quite high on the mountain side, a column 
of steam, rising above the tops of the trees, reveals the location 
of a spring or a steam vent. As ame out into the level 
open plain of the Firehole valley, the elevated mounds and 
