EXTENT OF IOWA PORTION OF IOWAN DRIFT. 147 



investigation, especially since in some of its features it suggests a terminal 

 moraine. 



During the past season (1897) the' writer, together with Mr. Oscar 

 Hershey, made further observations in eastern Clinton County, Iowa, as 

 well as in Hem - )-, Whiteside, and Carroll counties, Illinois. At Clinton the 

 glacial deposits on the bluff of the Mississippi are found to be very thin, 

 amounting usually to but 5 or 10 feet. These deposits, however, appear 

 to be capable of separation into two distinct till sheets. One is reddened 

 and leached at the junction with the overlying loess and apparently is 

 much older, while the other is scarcely at all leached or stained at the 

 junction with the loess and in one locality appears to graduate upward into 

 loess. The former deposit is probably of Kansan age while the latter 

 appears to be Iowan. The best exposure noted is found a short distance 

 northwest of the Clinton Brewery in sec. 1, Clinton Township. The loess 

 here has a thickness of 20 to 25 feet. At its base, near the east end of the 

 exposure, is a fresh-looking calcareous till, about 4 feet thick, resting upon 

 a bed of rotten, deeply stained gravel which there caps the older till. A 

 few rods west the older till comes up to the base of the loess and farther 

 west there are several exposures in which the loess rests directly upon the 

 older till. Had the exposure of fresh till not been observed, there would 

 have been nothing to indicate the presence of an Iowan drift at this locality. 

 Such being the case here, where exposures are extensive, it can scarcely be 

 affirmed that the Iowan drift is not present in the district immediately north 

 and west, where only slight exposures can be found beneath the heavy 

 covering of loess. The exposure just mentioned was visited in November, 

 1897, by Messrs. Calvin, Udden, Bain, and the writer, and the interpreta- 

 tion given above was assented to without reserve. Hershey and the writer 

 noted two exposures in the bluff in the north part of North Clinton (formerly 

 Lyons) in which a few feet of fresh-looking till rests directly upon the 

 residuary clay of the underlying limestone, a till which seems referable to 

 the Iowan rather than Kansan. Southwest of Clinton along the Burlington, 

 Cedar Rapids and Northern Railroad bowlders were noted by Messrs. Cal- 

 vin, Udden, Bain, and the writer near the east bank of the Mississippi. 

 They are of the large angular type recognized by Calvin as characteristic 

 of the Iowan, and they occur on a gently undulatory plain, such as is also 

 characteristic of the Iowan. Similar bowlders were observed by the same 



