yellows back of rim. A gray, clear deposit outside of this. 
Stream and gray bottomed white a* A d yellow borders with beauti- 
ful white darker centered ros islands. Arms of spring 
long; one is partly bridged across. 
Mount Sheridan. August 23, 
As we ascend, the broad, dark plain spreads itself out 
before us and lake after lake breaks upon the view. Heart 
Lake, half hidden in the fog 'and polished most perfectly 
reflects the cloud-filled sky that one seems to look 
down through the somber forest into a world below. Following 
this comes the many armed Yellowstone Lake with its satellites. 
Then Shoshone and Lewis Lake to the west. There also were the 
Beula Lake far southwest. 
On leaving camp, August 23, I spent a few minutes taking 
notes about Columbia spring and the geysers, then rode to 
the left up an open way that leads up to Mt. Sheridan, 
400 or 500 feet above camp. I came upon an outcrop of 
whitish and yellowish rock with feruginous weathering that 
proved to be porphyry --a creamy white macro cryst aline 
trachyte. Of this I obtained two specimens 
(10, 11). There is a large thickness of this rock, indeed 
it with similar varieties extends almost to the summit of 
the peaks. There ore occasionally outcropt however, of 
masses of darker rock which at a distance might be taken 
