74 IOWA ACADEMY OF SCIENCES. 



glomerate near Augusta, Iowa, which was apparently brought 

 from north of Lake Huron. The evidence of an extension of 

 the western lobe over the same district was found in eastward 

 bearing strias along the brow of the Mississippi bluff at points 

 farther east than the site of this bowlder, Mr Pultz argued 

 tl: at if the strias are not the product of the latest invasion they 

 would not have been preserved in such an exposed situation. 

 He also referred to some bowlder- strewn terraces in the Mis- 

 sissippi valley, at and above Keokuk as moraines, and corre- 

 lated them with striae as the product of the last ice invasion. 

 The following summer Mr. Fultz and the writer, while examin- 

 ing some rock outcrops in Burlington, found a striated surface 

 in which the bearing is westward This was evidently pro- 

 duced by the Illinois lobe, and as it is in a section about as 

 exposed to obliteration by a subsequent invasion as those cited 

 by Mr. Fultz in his paper, it became necessary to readjust the 

 views set forth in that paper. This was done at the tenth meet- 

 ing of the academy, in December, 1895, and the question of the 

 relation of the two invasions WdS there left somewhat in 

 doubt(l). The bowldery terrace interpreted by Mr. Fultz to 

 be a terminal moraine has been examined by Prof. T. C. Cham- 

 berlin and Dr. H, F. Bain, as well as by myself, and to each of 

 us it seams best explained as a residue of coarse material 

 formed by stream excavation along the Mississippi valley sub- 

 sequent to the last ice invasion. The evidence that the Illi- 

 nois lobe was last on this ground seems conclusively shown in 

 the relation of its till sheet to that of the sheet formed by the 

 western lobe. The latter can be traced under the Illinoian 

 sheet as indicated below. In addition to this evidence there is 

 found an abandoned river channel in the district immediately 

 west of the limits of the Illinoian drift which carried southward 

 the drainage outside the Illinois ice lobe. The banks of this 

 channel are well defined and the channel evidently has not 

 been filled by the drift of any subsequent invasion. 



Extent of the loioan Loess. — By the term Ibwan loess is meant 

 that sheet of loess which connects at the north with the lowan 

 till sheet. A till sheet of lowan age has been found in northern 

 Illip.ois as well as in eastern Iowa, and it probably covers the 

 greater part of the northern half of Illinois. It is, however, 

 covered by the Wisconsin till sheet from Bureau county, Illinois, 

 east and south. How much of Indiana and Ohio was covered 



(1) Proceedings Iowa A.cad. of Sciences, Voi. Ill, 1896, pp. 60-63. 



