1 7 4 ERA NK LE VERE TT 



Academy, held December 1894, Mr. F. M. Fultz read a paper 1 

 in which the interpretation was presented that the ice lobe* 

 alternated in the occupancy of the district south of the driftless 

 area, and that the latest occupancy was by the western lobe. 

 The extension of the eastern lobe into Iowa had been inferred 

 by him through the discovery of a bowlder of red jasper con- 

 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 striae along the brow of the Mississippi bluff at points 

 farther east than the site of this bowlder. Mr. Fultz argued 

 that if the striae 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 Mississippi 

 valley at and above Keokuk as moraines, and correlated them 

 with the striae as the product of the last ice invasion. The fol- 

 lowing summer Mr. Fultz and the writer, while examining some 

 rock outcrops in Burlington, found a striated surface in which 

 the bearing is westward. This was evidently produced by the 

 Illinois lobe, and as it is in a section about as exposed to oblitera- 

 tion 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 meeting of the Academy in 

 December 1895, and the question of the relation of the two 

 invasions was there left somewhat in doubt. 2 The bowldery ter- 

 race interpreted by Mr. Fultz to be a terminal moraine has been 

 examined by Professor T. C. Chamberlin and Dr. H. F. Bain, 

 as well as by myself, and to each of us it seems best explained 

 as a residue of coarse material formed by a stream excavation 

 along the Mississippi valley subsequent to the later ice invasion. 

 The evidence that the Illinois 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 



1 Proc. Iowa Acad, of Sciences, Vol. II, 1895, pp. 209-212. 



2 Ibid., Vol. Ill, 1896, pp. 60-62. 



