T. C. Chamberlin — Diversity of the Glacial Period. 179 



Having made it appear by such omissions that I had changed 

 my mapping to the amount of a hundred miles, Professor 

 Wright states that Mr. Leverett draws "his later moraine 

 line " one hundred miles still farther south. If by this ex- 

 pression it is meant that Mr. Leverett referred this moraine 

 line to my second glacial epoch, I think a reading of Mr. 

 Leverett's language will fail to show warrant for it. Mr. 

 Leverett distinctly recognized two groups of moraines coinci- 

 dent with two orographic attitudes. He did not discuss the 

 relations of either of them to my correlations. If it is meant 

 simply that this moraine was announced "later" than the 

 others, it has no pertinence, unless it is assumed that any 

 moraine of any sort is to be referred to my later epoch, which 

 is not Mr. Leverett's view nor mine. As to still more south- 

 erly moraines, Mr. Leverett and myself are quite aware of the 

 hilly belt at Greenville (whose course it may be remarked in 

 passing makes a high angle with the drift border) and also of 

 other more or less definable but obscure tracts of thickened 

 drift of a terminal or quasi-terminal kind. It is a part of our 

 hope and expectation to be able at length to trace out obscure 

 sub-marginal thickenings of the drift sheets, and other quasi- 

 marginal markings of one kind or another, over the whole 

 drift field, old as well as new, where the more pronounced ter- 

 minal moraines are absent. This has formed a feature of my 

 plans for many years and considerable preliminary data have 

 been gathered and some detailed tracing has been done in pur- 

 suit of it, in connection with work on the more important and 

 significant moraines which mark advances of the ice and define 

 glacial episodes if not epochs. Some of these moraines of 

 minor significance have been mapped, and others are yet to be 

 added. Some of them will lie not far from the border of the 

 drift at some points, and it is to be hoped that the more ob- 

 scure older drift will yield marginal indices in all districts 

 sufficient to show its history with approximate accuracy. With 

 this in view, I have developed new criteria of discrimination 

 and have proposed additional distinctions between marginal 

 moraines and have sought other marginal and submarginal 

 markings suited to the requirements of this more critical work. 

 Of course a map showing all these moraines and marginal 

 lines without indicating their differences, gives a more or less 

 anti-divisional impression, much as does the diagrammatic geo- 

 logical column of the text-books and dictionaries, and of 

 course it is possible to lump these all together as " moraines of 

 recession," or "receding moraines," just as all the sedimentary 

 strata south of the Archaean terrane may be disposed of as 

 deposits of sea-recession. These moraines are moraines of ice- 

 retreat in much the same sense as the Paleozoic sediments are 



