Wisconsin Kettle Moraine. 231 



that of the post-morainic glacier, north of it, measured at a dis- 

 tance just far enough to escape the terminal curvature. An in- 

 spection of the outline of the Green Bay glacier shows that this 

 eastward shift of the junction of the two glaciers was not due 

 ■simply to encroachment oq the Lake Michigan stream, nor to a 

 common movement of both in that 'direction, for the opposite 

 margin of the Grreeu Bay glacier lay close upon the borders of 

 the driftless re2;ion, demonstrating that there was no eastward 

 swaying on that side. Indeed, the indenture of the outline of 

 the driftless area strongly suggests actual encroachment on that 

 side also, and this view is not without independent support. 



In harmony with these phenomena are the fiords of the Green 

 Bay peninsula, which indicate that the Green Bay ice stream over- 

 flowed into the basin of Lake Michigan. These facts, taken al- 

 together, seem to warrant the belief that both glaciers retreated 

 sufficiently far to the northward, and within their respective 

 basins, to allow time and opportunity for the change in the rela- 

 tive size and position of the two ice streams, and that, under 

 slightly changed conditions that favored the Green Bay glacier, 

 they advanced to the position of the Kettle moraine, and, after a 

 series of oscillations, retreated permanently. This view seems 

 •also to be demanded by certain details in the distribution of the 

 -drift material that are otherwise enigmatical, but whose discussion 

 would too much extend this article. 



/Significance. — As forty-five years have passed since Dr. Hitch- 

 cock called attention to some of the phenomena under consider- 

 ation, or, at least, to some distinctly related to it, and yet, the matter 

 has received so little consideration, that our present knowledge is 

 limited to such a degree, that I lay myself liable to the charge of 

 undue temerity in attempting to correlate the observations, I may 

 be pardoned in attempting to indicate, briefly, something of the 

 significance and importance the foregoing conclusions, if sus- 

 tained, have in relation to the Quaternary history of the region 

 involved. The moraine constitutes a definite historical datum line, 

 in the midst of the glacial epoch, and becomes a basis of reference 

 and correlation for adjacen t formations. It is an historical rampart, 

 outlining the great dynamic agency of the period, at an important 



