EDITORIAL 873 



the elaborate investigations of Mr. McGee some years ago 

 demonstrated the existence of two sheets of till, separated by a 

 vegetal horizon. It was known that in southern Iowa there were 

 also two sheets of till separated by a vegetal horizon, but these 

 had not been studied in detail nor their connections traced out. 

 It was natural, as well as prudentially conservative, to suppose 

 that these two series were mutual equivalents, as they stood in 

 much the same geographic relationship to the later (Wisconsin) 

 drift. It was recognized that the amount of erosion upon the 

 south lowan series was greater than that upon the east lowan, 

 and also that the loess in eastern Iowa was intimately connected 

 with the upper till sheet, while the upper till sheet in southern 

 Iowa was separated from the loess by a definite interval, but the 

 importance of these differences was not fully appreciated. The 

 investigations of the Iowa geologists have led to the quite firm 

 conviction that the upper till sheet of the series in southern 

 Iowa is the lower member in eastern Iowa. They have also 

 become convinced that the upper sheet in southern Iowa extends 

 continuously across northwestern Missouri into Kansas, and is the 

 equivalent of the drift sheet that covers the northeastern part of 

 Kansas. State Geologist Keyes of Missouri concurs in this view. 

 They do not hold this to the exclusion of a possible lower 

 member in Kansas. In harmony with these views the upper till 

 in the southern part of Iowa has been designated Kansan in the 

 recent Iowa reports. 



During the past summer I have had the pleasure of making 

 two excursions with Mr. Bain of the Iowa survey to localities 

 where the above formations are advantageously exhibited, and I 

 have been impressed with the cogency of the arguments of 

 the Iowa geologists. While, therefore, the case cannot be said 

 to be demonstrative, as yet, it seems best to accept the applica- 

 tion of the nomenclature adopted by the Iowa survey. This 

 places the xA-ftonian beds below the Kansan series instead of 

 above them. It puts the sub-Aftonian sheet of till in an earlier 

 category, and, for the present, it may perhaps be regarded 

 tentatively as Albertan, although, of course, it cannot now be 



