Page:Popular Science Monthly Volume 78.djvu/433

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PSM V78 D433 Lava natural bridge in yellowstone park.png

Fig. 7. The Lava Natural Bridge across Bridge Creek, Yellowstone National Park.
Simply that portion of the rock of the former full between two pot-holes.

village of Pine about 90 miles south of Flagstaff in Arizona, and can be reached by a horseback journey of three days 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 conception of a wooded region since the trees, though gigantic, are far apart and underbrush is entirely absent. After many hours of travel over a