. Annual report. 1st-12th, 1867-1878. Geology. 78 GEOLOGICAL SURVEY OF THE TERRITORIES. flows seem to be so modern that it is doubtful if any important changes have taken place in the surface since they occurred. The river flows over its narrow rocky bed with great velocity. The East Fork enters the Yellowstone on the east side through a narrow granite caiion, and is a stream of considerable magnitude. In the spring season the quantity of water must be great, for the area drained by it is at least forty by twenty miles, where the snow falls in large quantities and remains a large portion of th
. Annual report. 1st-12th, 1867-1878. Geology. 78 GEOLOGICAL SURVEY OF THE TERRITORIES. flows seem to be so modern that it is doubtful if any important changes have taken place in the surface since they occurred. The river flows over its narrow rocky bed with great velocity. The East Fork enters the Yellowstone on the east side through a narrow granite caiion, and is a stream of considerable magnitude. In the spring season the quantity of water must be great, for the area drained by it is at least forty by twenty miles, where the snow falls in large quantities and remains a large portion of the year. About four miles above, Tower Creek enters the Yellowstone. On the west side, just at the lower end of the Grand Canon, within a few yards, is the mouth of Hot Spring Creek. Along the shores, the hot water is oozing and boiling up through the soft mud, covering the surface with its peculiar deposits; one of the springs has a temperature of 127^. A strong smell of sulphuretted hydrogen per- vaded the atmosphere. The banks of the Yellowstone, on both sides, for thirty to fifty feet up from the water's edge, have a most peculiar white- ness, with yellow portions, due to the deposits of old hot springs, which were very abundant here at some period. The few springs that remain are full of sulphuretted and carbonated hydrogeu, forming a black car- bonaceous matter on the surface at times. There is also free sulphur, carbonate of lime, carbonate of iron, &c. It seems quite possible that the Carboniferous limestones do not exist beueath the basalts in this Fig. devil's den, tower creek. region, from the fact that there is not any great amount of cal- careous sediment. High up on the mountaios, on the east side of the Yellowstone, 9,500 feet, there is a bluff wall of limestone like that near Warm Spriug River, evidently the same white compact rock formed from deposits of hot springs probably during or near the close of the Pliocene period. Tower Creek rises in the high
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