NOTES SMITHSONIAN EXPLORATIONS, I9Q15 WIE 
Fic. 15—Sidney and Stuart Walcott cutting out specimen near the Growler, 
Norris Geyser Basin. They were driven back many times before the hot rock 
was finally secured. Photograph by Walcott. 
Fic. 16.—Algal growth in cool pond where there was no mineral matter in 
solution to be deposited. Photograph by Walcott. 
