404 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



nounced as farther to the north. In Clay township, the lowan 

 border, figure 106, according to earlier workers of the drift, has 

 been drawn to the east. After some detailed study of the lowan 

 border in this vicinity, the writer is convinced that it extends much 

 farther to the south. From investigation in the vicinity of Eldora, 

 it would seem as if a tongue of the lowan extends as far south as 

 the new bridge across Iowa river, south of the city. Further study 

 will be necessary before any definite line can be drawn. There are 

 many difficulties in the way of fixing positively the lowan border. 

 The lowan drift thins out gradually so that it becomes difficult to 

 distinguish, (1) its topography, in many places its surface features 

 being determined by the topography of the underlying drift, (2) its 

 complete state of oxidation, owing to its thinness, and, (3) its 

 great similarity in lithological characters to the Kansan. Much 

 more detailed work must be done before the boundary of the lowan 

 can be drawn definitely. 



