602 REVIEWS 



The paha which are distributed near the border of the lowan drift are found to be 

 composed in part of Kansan drift, and are thought to be probable Kansan drumlins, 

 thougli it is considered singular that they should be congregated around the border 

 of a later sheet of drift. The deeply weathered surface of the Kansan, with its ferretto, 

 is discussed very fully. Pre-Kansan drift is found in the deep part of the thick drift 

 filling the preglacial valleys, but seems to be very sparingly represented on the 

 uplands. 



A preglacial channel called Stanwood River is traced through the county along 

 a course parallel with and a few miles east of the Cedar River, the latter being largely 

 in a postglacial course. From what seems to the reviewer to be an insufficient 

 number of data, the gradient of the bed of this preglacial river is estimated to be 

 7 feet per mile, which is many times that of the neighboring portion of the pregla- 

 cial Mississippi. As the valley of Stanwood River appears to have been a prominent 

 tributary of the Mississippi, and since the valley of the Mississippi has a rock floor 

 descending about one-half foot per mile, one would scarcely expect the gradient of 

 this tributary to exceed one foot per mile. Attention is called to the incursion of 

 some of the streams of the county into the edge of rock bluffs, which is thought to be 

 due to an initial course given by the glacial drainage when the broad valleys were 

 blocked by ice. 

 Savage, T. E. Drift Exposure in Tama County . Proc. Iowa Acad. Sci., 



Vol. VIII. pp. 275-78, 1901. 



A railway cut three miles west of Toledo, la., exposes what appears to be the 

 Aftonjan soil between sheets of Kansan and pre-Kansan till. The pre-Kansan till 

 is thoroughly leached of its calcareous matter to a depth of 18 to 24 inches below the 

 soil and partially leached to a depth of 6 feet. It is also changed to a reddish color 

 to a depth of 3 or 4 feet, beneath which it is unoxidized. The soil is i^ feet 

 thick, dark brown in color, and carries numerous small fragments of wood and dark- 

 colored bits of organic matter. 

 Savage, T. E. Geology of Henry County. Iowa Geol. Survey, Vol. XII, 



pp. 237-302, igo2. 



The physiography is discussed on pages 241-53 ; Pleistocene deposits, on pp. 

 289-95; soils, on pp. 297,98; water supply, on pp. 301, 302; the remainder of the 

 report being given to hard-rock geology. The effect of the Illinoian ice invasion in 

 disturbing the drainage is discussed ; also a probable post-Illinoian deflection of 

 Cedar Creek into Skunk River. The Illinoian drift extends only a few miles into the 

 southeast part of the county, the remainder being a Kansan drift area. In general the 

 Kansan drift is greatly eroded, but in the northeast part of the county the channeling 

 is very shallow, a feature which is explained by remoteness from a master stream. 

 Gravelly deposits found at the surface of the Kansan drift are noticed and classified 

 as Buchanan gravels. These gravels are of very limited extent compared with a 

 deposit of gummy and slightly pebbly clay known as "gumbo," which caps the Kansan 

 and also the Illinoian drift, and underlies the loess, but which is not noticed in this 

 report. 



Shimek, B. 7721? Loess of Iowa City and Vicinity. Bull. Lab. Nat. Hist. 

 State Univ. Iowa, Vol. V, pp. 195-216, 1901. 



The loess at this locality, like that of much of eastern Iowa, is fine and homoge- 

 neous, and has a thickness of 12 to 15 feet. The loess fauna has perhaps been more 



