NO. 3 



SMITHSONIAN EXPLORATIONS, I915 



13 



Fig. 18. — One of the Three Sisters Springs filled with boiUng hot water, 

 through which bubbles of steam are rising. Photograph by Walcott. 



Fig. 19. — Great Sulfosel Hot Spring, about one mile northeast of Great 

 Fountain Geyser, elevation 7,300 feet. The main opening of the spring has a 

 temperature of 201.2° F. (93° to 94° C). Water cools toward run-off in 

 foreground, to 172.4° F. (78° C). Siliceous deposits al)out this spring extend 

 as cornices out over edges. Algal growth abundant in water at 134.6° F. (57° 

 C). Fine specimens were collected for National Museum. Photograph bv 

 Walcott. 



