230 Wisconsin Academy of Sciences^ Arts, arid Letters. 



broken outline would be the result. If masses of the ice becama 

 incorporated in the drift, as has been suggested, their melting 

 would give rise to depressions, constituting one form of the kettles 

 that characterize the range. The suggestion just made, with ref- 

 erence to the irregular advance of the ice mass, accounts for other 

 forms, and, at the same time, for the irregular hills, mounds, and 

 hillocks. Certain of the kettles may be due to underdrainage, 

 through the action of strong underground streams that occasion- 

 ally flow, as full brooklets, from its base. The drainage of the 

 glacier, while it was advancing and pushing the debris before it, 

 was probably quite general and promiscuous over the moraine, and 

 this would give rise to the stratified sands or gravels, and other 

 evidences of the action of water, among which may perhaps, be 

 reckoned some of the minor mounds, ridges and depressions. 

 The changing attitudes, which the debris would be likely to as- 

 sume, as it was forced along, would, perhaps, give peculiar force 

 to torrential effects. 



The gaps in the range, attended by plains, or long streams 

 of gravel and sand, appear to represent the more considerable 

 points of discharge of the glacial floods. When the surface 

 about the margin of the glacier permitted the accumulation of 

 water, the moraine would doubtless be much modified by it and 

 present a subdued aspect. 



The Alpine moraines, above referred to, are regarded as minia- 

 ture exemplifications of the process by which the Kettle moraine 

 was formed. 



Bat, in addition to the structure of the range, the change in the 

 relative position of the Green Bay and Lake Michigan glaciers, 

 already alluded to, affords evidence of an exceedingly interesting 

 character, which has a significance much beyond what can be here 

 indicated. It appears that the junction between the Green Bay 

 and Lake Michigan glaciers at the last observable stage, preceding 

 the formation of the Kettle moraine, was about twenty-five miles 

 farther west, than at the time of the latter's formation, or, in other 

 words, there is an abrupt easterly shift of the line of junction. It 

 appears, also, that the width of the ante-morainic Green Bay 

 glacier, measured just south of the Kettle moraine, was only half 



