South Dakota School of Mines 



Bulletin No. 13. Plate No. 68. 





2X 



Photograph by O'Harra, 1910. 



A. Erosion forms north of the Great Wall near Cedar Pass. 



..,.-.:. _ 



nma 



' 



Photograph by O'Harra, 1910. 



B. Erosion forms north of the Great Wall near Big Foot Pass. The flat 

 remnants are protected by a thin covering of well-rooted grasses. 



