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. 23. 



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 

 divide between the valleys of 

 the Missouri and Yellowstone, 

 and flows about ten miles 

 throngh a canon so deep and 

 gloomy that it has very prop- 

 erly earned the appellation of 

 the "Devil's Den." (Fig. 23.) As 

 we gaze from the margin down 

 into the depths below, the little 

 stream, as it rushes foaming 

 over the rocks, seems like a 

 white thread, while on the 

 sides of the gorge the somber 

 pinnacles rise u}) like Gothic 

 spires. About two hundred 

 yards above its entrance into 

 the Yellowstone the stream 

 pours over an abrupt descent 

 of 156 feet, forming one of the 

 most beautiful and picturesque 

 falls to be found in any coun- 

 try. The Tower Falls are about 



il 



