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. THE POPULAR SCIENCE MONTHLY 



Fig. 8. Block Diagram to show the Formation of the Travertine Natural 

 Bridge at Pine, Arizona. This bridge was formed by the deposits of travertine 

 derived from the springs on the east. (In the diagram the height of the bridge is 

 exaggerated.) 



country of this sort, the brilliant green of the irrigated valley of which 

 the natural bridge is a part seems remarkably beautiful and is a sight 

 not soon forgotten. Not only is the bridge composed of this limestone 



Fig. 9. Two Views of the Natural Bridge across Swift's Camp Creek, 

 near Campton, Kentucky. (See Fig. 10.) 



