Between the lake and this group of mountains--the three highest of which bear the names of Langford, Doane, and Stephenson--is Brimstone Basin. For several miles the ground is impregnated with sulphur, and the air is tainted with sulphurous exhalations. Streams of warm sulphur-water course the hillsides and unite to form a considerable rivulet called Alum Creek, whose channel is coated with a creamy-white mixture of silica and sulphur. Old pine logs, once lofty trees, lie prostrate in every direction over the basin, which covers an area some three miles in extent. From all appearances this basin must have been the scene of thermal activity within a comparatively recent period; but now not a spring can be found with a temperature above that of ordinary spring-water. Similar brimstone basins are numerous around the lake, on the lower slopes of the mountains, at the foot of bluffs, or more frequently in level districts. The latter are always wet, and generally impassable, the thin crust covering an abundance of scalding mud, especially dangerous to horses. The Upper Yellowstone rises in the high volcanic range which shuts off the Yellowstone Basin from the Wind River drainage, forming what is known as the great water-shed of the continent. This range of mountains has a marvellous history. As it is the loftiest, so it is the most remarkable lateral ridge of the Rocky Range. The Indians regard it as the "crest of the world," and among the Blackfeet there is a fable that he who attains its summit catches a view of the land of souls, and beholds the happy hunting-grounds spread out below him, brightening with the abodes of free and generous spirits. In the expedition sent across the continent by Mr. Astor, in 1811, under command of Captain Wilson P. Hunt, that gentleman met with the first serious obstacle to his progress at the base of this range. After numerous efforts to scale it, he turned away and followed the valley of the Snake, encountering the most discouraging disasters until he arrived at Astoria. Later, in 1833, the indomitable Captain Bonneville was lost in this mountain labyrinth, and, after devising various modes of escape, finally determined to ascend the range, which tremendous task he succeeded in accomplishing, in company with one of his men. It was this same line of snow-clad, craggy peaks that turned back Captain Raynolds in 1859. [Illustration: BREAKING THROUGH.]