86 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



of the old laot-spriiig deposits is silica, origiDally as white as snow, but 

 very much of it is tinged with every possible shade of color, from the 

 most brilliant scarlet to pink or rose color, from bright sulphur to the 

 most delicate cream. There are portions of the day when these colors 

 seem to be more vivid, and the rugged walls of the caiion stand out more 

 in perspective, so that while the falls fill one with delight and admiration, 

 the Grand Oaiion surpasses all the others as the one unique wonder, 

 without a parallel, probably, on our continent. We may conclude, there- 

 fore, from the i)oiut of view presented above, that while the canon has 

 somewhat the appearance of a great cleft or canon, it is simply a chan- 

 nel carved by the river out of predeposited materials, after the 

 drainage of the old lake-basin. The walls themselves, it seems to me, 

 explain the manner in which the connection was formed from the surface 

 with the heated interior, for they are seamed with the irregular fissures 

 or furrows which pass up through the basalt and connect with the old 

 hot-spring deposits. And so it is with the walls of the caiion, all the 

 way to the mouth of Tower Creek ; sometimes we find the irregular ma- 

 son-work of the basalt, then the breccia or the curiously variegated hot- 

 spring formations, the whole covered to a greater or less extent with a 

 later deposit from the waters of the old lake, which now appears in 

 horizontal strata. 



As I have previously stated, the entire Yellowstone Basin is covered 

 more or less with dead and dying springs, but there are centers or 

 groups where the activity is greatest at the present time. Below 

 the falls there is an extensive area covered with the deposits which 

 extend from the south side of Mount Washburn across the Yellow- 

 stone rim, covering an area of ten or fifteen square miles. On the 

 south side of Mount Washburn, there is quite a remarkable group of 

 active springs. They are evidently diminishing in power, but the 

 rims all around reveal the most powerful manifestations far back in 

 the past. Sulphur, cop]ier, alum, and soda cover the surface. There is 

 also precipitated around the borders of some of the mud springs a white 

 efifloresence, probably nitrate of potash. These springs are located on the 

 side of the mountain nearly 1,000 feet above tlie margin of the canon, 

 but extend along into the level portions below. In the immediate chan- 

 nel of the river, at the present time, there are very few springs, and 

 these not important. A few small steam vents can be observed only 

 from the issue of small quantities of steam. One of these springs was 

 bubbling quite briskly, but had a temperature of only 100°. Near it is 

 a turbid spring of 170°. In the valley are a large number of turbid, mud, 

 and boiling springs, with temperatures from 175° to 185°. There are a 

 number of springs that issue from the side of the mountain, and the 

 waters, gathering into one channel, flow into the Yellowstone. The num- 

 ber of frying or simmering springs is great. The ground in many places, 

 for several yards in every direction, is perforated like a sieve, and the 

 water bubbles by with a simmering noise. There is one huge boiling 

 spring which is turbid, with fine black mud all around the sides, 

 where this fine black earth is deposited. The depth of the crater of 

 this spring, its dark, gloomy appearance, and the tremendous force 

 which it manifested in its operations, led us to name it the " Devil's 

 Caldrpn." There are a large number of springs here, but ho true gey- 

 sers. It is plainly the last stages of what was once a most remarkable 

 group. Extending across the canon on the opposite side of the Yellow- 

 stone, interrupted here and there, this group of springs extends for sev- 

 eral miles, forming one of the largest deposits of silica, but only here 

 and there are there signs of life. Many of the dead springs are mere 



