of thie, Yellowstanaaed Winataie Medes 165 
the lake. The summit of this deposit rises about 600 feet above 
the lake; it is the remains of one of the most interesting group 
of springs in the vicinity; there are now many steam vents 
lined with a brilliant coating of sulphur. The deposit is from 
50 to 150 feet in thickness, and when not mingled with sulphur, 
is as white as snow. Silica predominates over all other mate- 
rials; but it is much variegated by oxide of iron, sulphur, &e. 
At the foot of the mountain, near the margin of Pelican Creek, 
a few springs issue from beneath the crust with a temperature 
from 150° to 180°, but this great group may now be regarded 
as extinct. 
We will now leave the Yellowstone Basin, and, pursuing 
a westerly course, make our way over the high range, or divide, 
into the great Geyser Basin of the Firehole river, a branch of 
the Madison Fork. The mountains that surround the Yellow- 
stone Basin are of the same character as those which, extend 
down the branches of the Madison and Gallatin Forks for thirty 
miles; and not until then do the sedimentary or granitic rocks 
appear to any extent. Immense quantities of obsidian also are 
found on both sides of the range. Little lakes, varying in size 
from the diameter of a few hundred yards to four or five miles, 
are scattered all about the sources of the Missouri, Yellowstone 
and Columbia. Some of them are situated on the very sum- 
mits of the mountains, ten thousand and eleven thousand feet 
above the sea. 
Traveling in this region is attended with great difficulties, 
on account of the fallen timber. The uplands, as well as the 
lowlands, are covered with a dense growth of pines, the majority 
of which have a trunk not over six to twelve inches in diameter, 
In crossing the main divide between the drainage of the 
Yellowstone and the Madison, we first strike the sources of the 
hundreds of vents. There was one locality, covering several 
acres, that presented one of the most beautiful of scenes. The 
