114 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



tions as the one just described. A spring on a level with the river has 

 an enormous square basin, 30 feet across, of unknown depth. We called 

 this the Bath Spring. A little below is another singular form of won- 

 derful beauty. The water issues from beneath the crust near the mar- 

 gin of the river from several apertures. The basin itself is 15 by 20 

 feet and 20 feet deep. It seemed to me that nothing could exceed the 

 transparent clearness of the water. The slightest object was reflected 

 in its clear depths, and the bright blue tints were indescribable. We 

 called this the Cavern. The mud springs are also numerous and im- 

 portant in this group. As usual, they are of all sizes, from an inch or 

 two to 20 or 30 feet in diameter, with contents varying from mere turbid 

 water to stiff mud. They seldom have any visible outlet, but are in a 

 constant state of agitation, with a sound which varies with the consist- 

 ency of the contents. There are several of the mud-pots which give 

 off a suppressed thud as the gases burst their way through the stiff 

 mortar. Sometimes the mortar is as white as snow, or brown, or tinged 

 with a variety of vivid colors. One mud-spring, located in the woods 

 near a small lake on the east side of the Fire-Hole, has a basin 30 by 40 

 feet, with sides 15 feet high, in constant action, frequently hurling the 

 mud outside of the rim. All around it are a number of little vents, 

 which keep up a simmering noise, some of which have bailt up little 

 cones 4 to 12 inches high, which have in many cases closed themselves 

 up at the top and ceased. On removing the cone, we found the inner 

 sides lined with the delicate crystals of sulphur. The last stage of these 

 springs, in many cases, seems to be a steam-vent, at which time the 

 sulphur is deposited. On the west side of the Fire-Hole, and along the 

 little branch that flows into it from the west, are numbers of springs of 

 all grades, and the broad bottom is covered with a snow-white siliceous 

 crust. Near the base of the mountains, there is a massive, first-class 

 boiling spring, in a constant state of violent agitation, sending forth 

 great columns of steam, with a singular toad-stool rim. There are some 

 springs around which the siliceous deposits have assumed a form like 

 the toad-stool fungus. It flows out from beneath a hill 150 feet high, 

 composed of a kind of stratified cement, which was certainly deposited 

 in the lake when these hot springs were in active operation. It is 

 undoubtedly formed of volcanic ejectamenta mingled with the deposits 

 from the hot springs ; 196°. There are some that might be called spas- 

 modic springs. There is one massive spring, with a most beautifully 

 scalloped rim 15 by 20 feet, which is always agitated, but occasionally 

 shoots up several feet with great violence ; 196°. About three miles up 

 the Fire-Hole we meet with a small but quite interesting group of springs 

 on both sides of the stream. There is a vast accumulation of silica, form- 

 ing a hill 50 feet along the level of the river; upon the summit is one of 

 the largest springs yet seen, nearly circular, 150 feet in diameter, boils up 

 in the center, but overflows with such uniformity on all sides as to admit 

 of the formation of no real rim, but forming a succession of little orna- 

 mental steps, from one to three inches in height, just as water would 

 congeal from cold in flowing down a gentle declivity. There was the 

 same transparent clearness, the same brilliancy of coloiting to the waters, 

 but the hot steam and the thinness of the rim prevented me from ap- 

 proaching it near enough to ascertain its temperature or observe its 

 depth, except at one edge, where it was 180°. It is certainly one of the 

 grandest hot springs ever seen by human eye. (Fig. 46.) ,But the most for- 

 midable one of all is near the margin of the river. It seems to have broken 

 out close by the river, and to have continually enlarged its orifice by the 

 breaking down of its sides. It evidently commenced on the east side, 



