178 EEPOKT UNITED STATES GEOLOGICAL SUEYEY. 



into the water, which has a temperature of 201° F. This temperature is 

 3° more than that obtained by Professor Bradley in 1872, due, perhaps, to 

 an increased activity in the spring at the time of my observ^ation. The 

 water flows from the spring through a beautiful white-lined channel. 

 The two vents have temperatures of 194° F. and 195° F. 



]Sro. 9. Bed Terrace Spring. — This is a lake-like pool 60 feet long by 20 

 to 25 feet wide. It is on the south side of the valley, back from the 

 creek, and is conspicuous on account of the brilliant color disi)layed on 

 its terraces. These terraces are like those of Gardiner's Eiver on a 

 very small scale, and are at the north end, where the pool is very shallow. 

 The water from the pool spreads out over them and deposits ferric oxide 

 on cooling. The active part of the spring is at the south end, where the 

 water is of a handsome blue tint and is bordered with a gray and yel- 

 low rim of coral and mushroom-like forms of geyserite. Dense clouds 

 of steam are given off from this part of the spring, and the water bulged 

 constantly during the time our observations were made. The temper- 

 ature was 190° F. Professor Bradley, in 1872, recorded 187° for the 

 pool. About 2 feet from the south end of the pool is a small geyser- 

 like cone 6 inches high. 



]^o. 10 is a green-lined pool with two basins separated by a constric- 

 tion. The total length is about 40 feet and the diameters respectively 

 of the two basins, 18 feet and 25 feet. The temperature in the smaller, 

 >&, is 140°, and in the larger, a, 132°. There is a slight bubbling on 

 the surface, and the outlet is by l^o. 8. This pool is in the timber, and 

 there are others in the vicinity that were not noted. 



Iron Pot. — This is a deep, crater-like hole, with smooth, dark sides. It 

 is about 6 feet in diameter, and was named by Professor Bradley. The 

 water is 6 feet below the surface, although seen to fill the basin by 

 Professor Bradley on one occasion in 1872. The deposit is reddish 

 brown in color and mainly siliceous, the color being due to the iron 

 contained in it. This spring is near the foot of the spur south of the 

 .Sheep Cone. 



Nos. 11 to 16 form a small group or cluster on a flat mound south of 

 the Sheep Cone, between it and the Iron Pot. 



Ko. 13, which is really two springs in one basin, being separated only 

 by a band of beaded silica, and is the principal spring in the cluster, 

 having the highest temperature, and being in active ebullition con- 

 stantly. The deposits about the spring are very handsome beaded, 

 pearly masses. 



No. 11 is the largest spring and '^o. 14 the smallest, being merely a 

 fissure-like hole. The temperatures obtained in this group in 1872 were 

 :from 191° F. to 193° F. 



The mounds which are so conspicuous in the valley of Sentinel 

 ' Creek are, I think, the craters of old geysers whicli have become ex- 

 tinct as geysers by the closing up of the orifice, so that now we have 

 only the small springs on the summit, which are secondary in their 

 formation. I do not believe that at the present time any of them are 

 -veritable geysers. 



HALF-WAT GROUP OE, EGERIA SPEING-S. 



.This group of springs was designated the Half-way Group in 1871 

 because it was some distance up the river (about two miles above the 

 open portion of the valley). It is, however, within the limits of the 

 Lower Basin, the canon which separates the latter from the Upper Basin 

 beginning just above the Egeria Springs. Since 1871, also, the extent of 



