U. S. GEOLOGICAL SURVEY 
BULLETIN NO. 217 PL. X 
A. CRACKED SURFACE OP VOLCANIC BOMB, CINDER BUTTES ; IDAHO. 
Four-tenths natural size. 
tf ; JJg?*& 
B. FRAGMENT FROM A CINDER CONE, SHOWING DENSE PORTION DUE TO HARDEN- 
ING OF SPLASHES OF LIQUID LAVA, CINDER BUTTES, IDAHO. 
Four-tenths natural size. 
