GEOLOGICAL SUEYEY OF THE TEREITOEIES. 



91 



springs at the present time, the remains of the dead springs cover the 

 greater portion of the surface, and those which are more active present 

 the evidence of far greater power in past times. 



From this point we proceeded to the sulphur and mud springs near 

 the banks of the Yellowstone, about two miles above, in a straight line. 

 In the interval we passed the remains of many old springs, but none 

 above the ordinary temperature ; but the deposit seemed to cover the 

 surface more or less. The old lake deposit is also quite well shown in 

 the rather high, step-like hills which extend back for five miles from 

 the river to the basaltic rim of the great basin. We pitched our camp 

 on the shore of the river, near the Mud Springs, thirteen and a half 

 miles above our camp, on Cascade Creek. The springs are scattered 

 along on both sides of the river, sometimes extending upon the hill-sides 

 50 to 200 feet above the level of the river. The chart will show the lo- 

 cation of the principal ones. (Fig. 26.) Commencing with the lower or 

 southern side of the group, I will attempt to describe a few of them. The 



Fig. 27. 



MUD CALDRON, YELLOWSTONE RIVER. 



first one is a remarkable mud- spring, with a well-defined circular rim, com- 

 posed of fine clay, and raised about 4 feet above the surface around, and 

 about 6 feet above the mud in the basin. The diameter of the basin is 

 about 8 feet. The mud is so fine as to be impalpable, and the whole may 

 be most aptly compared to a caldron of boiling mush. The gas is con- 

 stantly escaping, throwing up the mud from a few^ inches to 6 feet* in 

 height; and there is no doubt that there are times when it is hurled 

 out 10 to 20 feet, accumulating around the rim of the basin. (Fig. 27.) 

 About twenty yards distant from the mud-spring just described, is a sec- 

 ond one, with a basin nearly circular, 40 feet in diameter, the water 6 or 

 8 feet below the margin of the rim. The water is quite turbid, and is 

 boiling moderately. Small springs are flowing into it from the south 

 side, so that the basin forms a sort of reservoir. The temperature, in 

 some portions of the basin, is thus lowered to 98°. Several small hot 

 springs pour their surplus water into it, the temperatures of which are 

 180°, 170°, 184°, and 155°. In the reservoirs, where the water boils up 



