182 GEOLOGICAL SUEVEY OF THE TEREITOEIES, 



oxidized, unites with the iron and alumina found in the clay and forms 

 the sulphate of alumina and iron. There were, also, in this group a 

 number of springs that were extinct. Between the active springs, in 

 which the mud was very thin, and those which were extinct, nothing 

 remaining save the hardened clay, there were springs of every grade as 

 considered in reference to the consistency of their contents. The water, 

 in the lapse of time, becomes less and less, either b}" finding new chan- 

 nels, or more likely by evaporation ; the mud becomes thicker and thicker 

 until finally all the water disappears, leaving merely vents through which 

 steam escapes; and after a while even these become extinct, and the 

 orifices become clogged up with detritus. All hot springs and salses are 

 the evidence of languishing volcanic action. 



We reached Yellowstone Lake on the 28th of July, and on the 31st a 

 small party of ns left the lake to visit the geyser region of the Fire-Hole 

 Eiver, the head-water of the Madison. The remainder of the party 

 were to move camp some twenty-eight miles farther to the south, where 

 we would join them in about a week. After a hard day's travel of 

 thirty-one miles through heavy timber we reached the head-waters of 

 the east fork of the Madison, or Fire-Hole Eiver. The mountain range 

 over which we passed was igneous, and in man^^ T)laces masses of pure 

 obsidian were observed. We passed by a number of fumeroles, from 

 which steam and gas were escaping, while all about them was the 

 white siliceous deposit, mingled with sulphur and iron, indicating the 

 past existence of hot springs. The water in the stream on whose bank 

 we were encamped was quite warm, although in the morning the mer- 

 cury in the open air was down almost to the freezing-point. x\bout a 

 mile and a half from our camp were some hot springs, covering an area 

 of about 200 square yards. Their temperature varied from 128^ F. to 

 199^ F. The deposit of some of the springs was calcareous. 



Leaving here we proceeded dovrn stream, passing a number of hot 

 springs, some of which were noticeable from the iron deposited in their 

 basins. Their temperatures were from 142° F. to 192° F. The iron was.de- 

 postied on an organic material, which was abundant in springs of low 

 temperature. Just before going into camp we piissed four hot springs 

 of considerable size. They were each situated in the center of a slightly 

 elevated mound, which sloped gradually from the edge of the spring 

 until lost in the general level. The first was 4 feet in diameter, having 

 a temperature of 102o F. The second was 2 feet in diameter, its tem- 

 perature being 170^ F. The third was only about a foot in width and 

 reached 174o F. The fourth and largest was somewhat irregular in 

 shape, being about 15 feet in length and 5 feet in width, the thermom- 

 eter here recording 150^ F. A short distance from these springs was 

 a small mud-spring about a foot in diameter. At the bottom of it, ^.bout 

 a foot from the suriace, was an agitated mass of thick, bluish mud, hav- 

 ing a temperature of 190° F. 



Our camp, on the evening of August 1, was on the right bank of the 

 east fork of the Madison or Fire-Hole River, in the lower geyser basin 

 of the Fire-Hole. We divide the springs and geysers of this basin into 

 seven principal groups for the puri)ose of description. Immediately 

 opposite our camp rflong the river, occupying a space about a quarter 

 of a mile wide and nearly two miles long, was the first groui>. Here 

 we recorded the temperatures of sixty-seven springs. The lowest w^as 

 10G° F., the highest 198° F., and the average 159° F., more than one- 

 half being above 100° F. The temperature of the air was about 50° F. 

 Some of these were geysers, vvith small tubular orifices, i^rojectiug the 

 water from 2 to 5 feet. There were also some large tranquil springs or 



