INOS 3) SMITHSONIAN EXPLORATIONS, IQI5 IW, 
Fic. 25——Great Needle in Yellowstone Canyon, 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. 
mA | 
Fic. 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. 
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