BULL. GEOL. SOC. AM 



VOL. 21, 1909, PL. 22 



Figure 1. — The Bridge at Natural Bridge Station, Powell County, Kentucky 



Formed by the lieadward cutting of two streams. Photograph used by courtesy of the 

 Lexington and Eastern Railroad 



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Figure 2. 



-Configuration of the Country near the Station Natural Bridge, 

 Powell County, Kentucky 



Showing the conditions favorable to the formation of bridges by the headward cutting of 

 streams. (See text figures 6 and 7) 



ILLgSTRATIONS OF NATURAL POCK BRIDGES 



