GEOLOGICAL SURVEY OF THE TERRITORIES. 127 



ing the river we found that a. short distance above the bridge it emerges 

 from a deep canon. At tlie lower end of this caQon there are a number 

 of hot springs on the edge of the river. We could distinguish at least 

 four. They were surrounded by a considerable deposit of sulphur and 

 iron. They give off sulphuretted hydrogen abundantly. We were some 

 500 feet above them, and yet the surrounding air was strongly impreg- 

 nated with it. It was impossible to reach the springs to take their 

 temperatures. The canon is about a mile in length, extending from the 

 mouth of Tower Creek, opposite Tower Falls. It is one of the finest 

 caiions I have ever seen. The walls are perpendicular and the river 

 flowing below is a perfect torrent, of an emerald-green tint, caiDped 

 with white foam. The fall of the river for 2i miles is 229 feet. On the 

 western side of the canon the rocks have been weathered into towers, 

 with sharp pinnacles, giving it a most picturesque appearance. 



The height of the eastern wall is 34:6 feet above the level of the river 

 opposite Tower Falls. At the lower end the height probably reaches 

 500 feet. This wall, from top to bottom, is composed as follows : 



• 1. Soft, gray sandstone. 1 



2. Columnar basalt. j 



3. Conglomerate. U46 feet. 



4. Columnar basalt. j 



5. Trachyte. | 



6. Limestone (?). 3 



The layers of basalt mentioned above, Nos. 2 and 4, extend the length 

 of the canon and present the most regular hexagonal columns that I 

 have ever seen anywhere in the West. It was impossible to obtain the 

 exact measurements, but I should estimate those in layer No. 2 to be 

 15 feet in height, while those of No. 4 were i^robably between 20 and 

 30 feet. The conglomerate No. 3 was probably about 100 feet in thick- 

 ness, and composed of large fragments of all kinds of rocks, the vol- 

 canic predominating. It was so infiltrated with sulphur that the whole 

 bed had a bright yellow color, especially noticeable at the upper end of 

 the canon. The sandstones on the top were very soft, and had weath- 

 ered so as to give a rounded top to the wall. The general color of the 

 trachyte was a violet, and it rested, I am inclined to think, on lime- 

 stones, although on this i)oint I am not quite certain. Above the caiion 

 the Yellowstone Eiver flows through quite a Avide valley, which on one 

 side is comparatively open and on the other side bounded by high hills, 

 which slope to within a short distance of the river's edge. Just above 

 this valley is the lower end of the Grand Canon. Both sides of the 

 river above Tower Creek have once been the seat of hot-simngs, whose 

 most active period has been long passed. There are at present only a 

 few springs remaining on the western bank, while on the east there are 

 extensive deposits containing sulphur, selenite, and alum. We spent 

 four days in camp No. 9, while Dr. Hay den and a small party made a 

 side trip to Clarke's Fork of the Yellowstone. Daring this time, in 

 addition to some trips to Tower Falls and the vicinity, I also made two 

 trips up the East Fork of the Yellowstone to a locality where one of the 

 members of the expedition discovered some very fine crystals of ame- 

 thyst. This locality is some ten miles from the main Yellowstone. 

 The specimens are found on a hill on the left side of the river. It is 

 about 1,000 feet in height and the summit entirely destitute of timber, 

 the rock covering it being basaltic. Over the basaltic floor, quartz, 

 agate, jasper, and silicified wood are found in quantity. There seems 

 once to have been a forest standing here which the lava has inclosed 



