UNIVERSITY OF IOWA STUDIES 

 IN NATURAL HISTORY 



Professor Charles Cleveland Nutting, M. A., Editor 



Continuation of Bulletin from the Laboratories of Natural History of 

 the State University of Iowa 



Volume IX Number 3 



THE EROSIONAL HISTORY OF THE 

 DRIFTLESS AREA 



by 

 ARTHUR C. TROWBRIDGE 



PUBLISHED BY THE UNIVERSITY, IOWA CITY 



