THE IOWAN DRIFT SEIEET. 139 



cuttings on the Chicago and Northwestern, 1 mile east of Belvidere. Here, 

 as at Stratford, the fossils are mainly of one species (Succinea avara). 



The pebbles and smaller rock constituents of the till appear to be 

 largely limestone whose native ledges are distant but a few miles to the east 

 and north. In this respect it conforms to the structure of the underlying 

 Illinoian sheet, and it seems not improbable that it has obtained much of 

 the material from the Illinoian. There is not found between the Iowan and 

 Illinoian till sheets of the Illinois lobe such a striking contrast in rock 

 constituents as is reported by McGee and by Calvin to be found in the 

 Iowan and Kansan of northeastern Iowa. The Iowan is reported by Calvin 

 to carry scarcely any pebbles or large rock fragments of local derivation, 

 while the underlying Kansan is thickly set with them, 



The paha ridges of western Whiteside and northeastern Henry coun- 

 ties usually contain a peculiar phase of loess. The basal portion is a fine 

 sand, rather than loess, in which many of the individual grains may be seen 

 by the naked eye, though with some difficulty. The great majority of 

 grains of ordinary loess are much too fine to be seen with the naked eye. 

 From Round Grove the fine sand at the base of the paha ridge has been 

 shipped to Chicag'o foundries for use as a molding sand. 



In some cases the upper portion of the paha assumes a sandy consti- 

 tution. As a rule, however, it consists of a loess similar to the bluff loess 

 of the main waterways, and its banks will stand in vertical walls for years. 

 Like the bluff loess, it is fossiliferous, but as yet, so far as the writer is 

 aware, no determination of the species of fossils represented has been made. 

 Before leaving this subject a few sections are presented from the debatable 

 district in central and southern Whiteside County, which serve to show the 

 freshness of the till and the occurrence of more than one drift sheet. 



A well made for Mrs. Seeley on the slope of the Round Grove Ridge, 

 at a level about 10 feet from the base, is reported by the driller to have 

 penetrated the following beds : 



Section of well of Mrs. Seeley at Bound Grove, Illinois. 



Feet. 



Earthy soil and subsoil • 3 



Fine yellow sand 5 



Yellow clay, no pebbles noted 5 



Sol't blue pebbly clay (probably Iowan till) 8 



Black dirt with wood embedded (probably Sangamon) 2 



Till mainly of blue- gray color (probably Illinoian) 17 



Limestone. 



