BULL. GEOL. SOC. AM. 



Vol. 21, 1909, PL. 26 



Figure 1. — Natural Bridge across Arch Creek^ near Miami^ Florida 

 Composed of oolitic limestone 



Figure 2. — Natural Bridge formed by Gravity, Big Horn Mountains, Wyoming 

 Photograph, hy Walcott, U. S. Geological Survey 



ILLUSTRATIONS OF NATURAL ROCK BRIDGES 



