Ten miles northwest of Heart Lake is Madison Lake, the source of Madison River, the country between being a somewhat rugged range of mountains, of which Red Mountain is the most conspicuous. To the eastward from Heart Lake is Mount Sheridan, from the summit of which a magnificent view of the Yellowstone Basin can be obtained. Nearer the great lake is Flat Mountain, whose altitude falls a little short of 10,000 feet. Between Flat Mountain and the Yellowstone Range the divide is very low, some of the branches of Snake River extending up to within two miles of the lake, where the elevation is not more than 400 feet above the lake level. It is doubtless this singular interlacing of the headwaters of the Yellowstone and Snake River that gave rise to Bridger's story of the "Two Ocean River." At sunrise on the morning of August 10th, at the west base of Flat Mountain, the thermometer stood at 15½° Fah., and water froze in Dr. Hayden's tent that night a quarter of an inch thick. It was in this neighborhood that Mr. Everts was lost from the first expedition. The country between Flat Mountain and the hot springs at the southwestern extremity of the lake is a level plateau with alternating spaces of grassy glade and dense thickets of pine around and between a perfect network of small, lily-covered lakes. The hot springs on the lake shore are numerous and of great variety and interest. There are no true geysers, however, though some of the springs are pulsating springs, the water rising and falling in their orifices with great regularity. Higher up the bank are a large number of mud-springs, two or three hundred in all, of variable temperatures, the most of them not differing materially from those already described. Some, however, have a character strikingly unique. The area covered by the springs is about three miles long and half a mile wide, a portion of it reaching out into the lake. Some of the submerged springs have built up funnel-shaped craters of silicious deposit, from five to twenty feet in height, rising from the bottom to the surface of the water. Extending a pole over the deep water, members of Dr. Hayden's party caught trout and cooked them in these boiling springs out in the lake without removing them from the hook.