180 T. C. Chamberlin — Diversity of the Glacial Period. 



beds of sea-retreat. There was a general retreat in botli cases, 

 but there were advances in both cases, and the recognition of 

 these constitutes the essence of the science in both cases. 



Besides the implications involved in the attempt to make 

 the older moraines — even undiscovered ones — do duty as cor- 

 relatives of what others regard as obviously much younger 

 ones of different character, there is a specific erroneous im- 

 pression conveyed by the statement that closer observation is 

 not unlikely to carry the exterior moraine farther south still 

 which would be " all that is necessary to make the extreme 

 boundary stand related to the moraine there as it does through- 

 out the eastern part of the Mississippi Valley." This carries 

 the implication that there is a constant relation between the 

 extreme boundary and the outer terminal moraine in the 

 eastern part of the Mississippi Yalley. This is not the case. 

 The fresh stout moraine that lies near the border in the upper 

 Ohio region departs from it in going westward and disposes 

 itself in a strongly looped fashion that is not coincident with 

 that of the border. It is precisely because of this lack of 

 coincidence and because of the marked differences in the char- 

 acter of the drifts that a distinction between them is urged. 

 In Illinois there is nothing within a hundred miles of the border 

 that presents any rational grounds for correlation with the outer 

 terminal moraine in Western Pennsylvania. Professor Wright 

 claims to have spent live seasons on the border between Penn- 

 sylvania and the Mississippi River,* and yet he has not found 

 in Western Ohio, Indiana and Illinois any such moraine-and- 

 " fringe " in any such relationship as he has so often described 

 in Western Pennsylvania. One would think that five seasons, 

 work would give a better suggestion of what is likely to be 

 found true respecting a moraine-and- u fringe " border, than 

 the one offered to the effect that Mr. Leverett or some one else 

 is not unlikely yet to find a moraine of some sort somewhere 

 near the border. In Bulletin 58 U. S. Geol. Survey (p. 75) 

 Professor Wright says, "■ In Illinois nothing like a moraine 

 was encountered in any portion of the State which I traversed, 

 which included Randolph, Perry, Franklin, Jackson, William- 

 son, Saline, Gallatin and White counties " 



Mr. Leverett recognizes the following stages applicable to 

 the region between its limit of drift in southern Illinois and the 

 the head of Lake Michigan. 



lst^tage. Sheet of drift averaging perhaps 20 feet in thick- 

 ness. Intervals of slight or partial deglaciation shown by 

 occasional presence of soil between sheets of till. 



2nd stage. Interval of deglaciation of great length. Sur- 

 face of old drift sheet deeply oxidized, leached and much 

 eroded. Thick and widespread soil. 



*The Dial, Dec. 16, 1892, p. 380 ; Jan. 1, 1893, p. 7. 



