NORTH AMERICAN NATURAL BRIDGES 



423 



Fig. 7. The Lava Natdkal Bridge across Bridge Creek, 

 Yellowstone National Park. 



Simply that portion of the rock of the former fall between two pot-holes. 



village of Pine about 90 miles south of Flagstaff in Arizona, and can be 

 reached by a horseback iournev of three davs from that city. As one 

 travels south from Flagstaff through the forest reservation he passes for 

 miles over a lava plateau which, were it not for the pines and cedars, 

 would be called a desert. The forest does not fulfill the usual concep- 

 tion of a wooded region since the trees, though gigantic, are far apart 

 and underbrush is entirely absent. After many hours of travel over a 



