552 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



and deeper than the present river valley. In this section the 

 thick till-bed immediately underlying the loess bluff-capping 

 was that aftenvards called the Kansan Drift. Discovery at that 

 time of heavy, stratified, orang-e-colored sands and gravels be- 

 neath this Kausan till appears to be the first record of the actual 

 existence of what was subsequently denominated the Aftonian 

 inter-glacial deposits, although of course in the early eighties 

 and nineties of the last century this was not yet suspected. 

 Owing to a then recent land-slide on the bluff a very dark till- 

 layer displayed under the gravels at the base of the section, 

 was thought to be a part of the deposit higher up. Its subse- 

 quent reference to the Sub-Aftonian, or Nebraskan, till was the 

 later suggestion of Dr. H. F. Bain^ after the great complexity 

 of the Glacial Period had become firmly established. 



Fig. 175. — Rock gorge of present Des Moines river at l>es Moines. 



When the personal studies of the glacial deposits of South- 

 eastern Iowa were made in 1887-8, when I was li\'ing in that 

 part of the State, investig'^ations extended far beyond the con- 

 fines of Burlington.^ The existence of an ancient gigantic, 

 drift-hidden gorge of the INIississippi river was recognized below 

 the mouth of the Skunk river. Soon, however, I found that in 

 this discovery IVIajor G. K. Warren had anticipated me by a 

 full decade.* Subsequently by means of deep-well borings the 

 depth of this ancient canyon was reported by Dr. C. H, Gordon'* 

 to be about 125 feet below low-water level in the present Mis- 

 sissippi river, and six miles wide in place of one mile as at 

 Keokuk at the present time. This was, then the clue to the 



2Proc. Iowa Acad. Sci., Vol. VII. p. 338, 1897. 

 •American Naturalist, Vol. XXII, pp. 1049-10,54, 1888. 

 ♦Rept. U. S. Army Eng., 1878, Vol. IV, pp. 916-917, 1878. 

 eiowa Geol. Survey, Vol. Ill, p. 247, 1895. 



