THE IOWAN DRIFT 



595 



the Wapsipinicon River. The valley of the Cedar River, the 

 anomalous characteristics of which are recognized and noted, if 

 not explained, in Iowa Geological Survey, XIII, 298, 306, affords 

 numerous examples (Figs. 5, 6). For some unaccountable reason 

 the parts of the state occupied by the Lime Creek shales have an 

 unusual number of driftless patches, some of which have dimensions 

 of several miles. A rather small, but typical area of the kind occurs 



Fig. 8. — View on ridge in Section 3, Washington Township, Chickasaw County, 

 Iowa, showing the largest bowlder in the county rising out of a heavy growth of small 

 grain. 



in Section 21, Township 84, Range 18 (Fig. 7). Large areas, 

 almost continuous, occur over the ten-mile stretch between Mason 

 City and Rockwell; and on the south side of Lime Creek there is a 

 belt, practically driftless, two or three miles wide, all the way to 

 Rockford. There may be bowlders in these areas, even where the 

 other constituents of the drift are absent; and in no small propor- 

 tion of the territory under consideration, "the soil through which 

 the farmer drives his plow is made up of decomposed shales of 



