South Dakota School of Mines 



Bulletin No. 13. Plate No. 54. 





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Photograph by O'Harra, 1909. 





A. Sun-cracked surface of an alluvial flat showing loosening and curling 



of the drying mud. 



Photograph by Todd. 



B. Spongy surface of disintegrating Titanotherium clay. The gumbo lily, 

 as here shown, not infrequently finds root in the porous material. 



