NO. 3 



SMITHSONIAN EXPLORATIONS, I915 



17 



Fig. 25. — Great Needle in Yellowstone Cannon, a half mile below Tower 

 Falls, shown by Fig. 24. Picture taken by hanging camera in limb of a tree 

 about 300 feet above top of Needle. Needle probably 400 to 600 feet in height. 

 Photograph by Walcott. 



Fig. 26. — Obsidian Cliff, Norris Geyser Basin, showing columnar structure 

 in obsidian and massive-bedded rhyolite above. This cliff is one of the 

 interesting geological phenomena of the Park. Photograph by Walcott. 

 2 



