PLATE XI. FIG. A. DRIFT TOPOGRAPHY. Contour interval, 20 feet. 

 Scale, about 1 mile per inch. (Dexter, Michigan, Sheet, V. S. Geol. Sun.) 



FIG. B. TOPOGRAPHY DEVELOPED BY STREAM EROSION. Contour inter- 

 val, 50 feet. Scale, about 2 miles per inch. (Lawrence, Kansas, Sheet, 

 U. S. Geological Survey.) 



