200 GEOLOGY OF EASTERN WISCONSIN. 



cut channels from one to three hundred feet deeper than those which 

 they now occupy. These preexisting features of the surface, exerted 

 a very marked and peculiar influence upon the direction of glacial 

 movement. 



FIG. 2. 



A striated half-cone of rock on a glaciated surface of limestone, seen at Pelton's quarry, Pewnn- 

 kee. The parallel lines represent the strife . The base of the cone is not striated and the adjacent 

 surface is at first rough, but becomes gradually smoothed, and at length merges into the polished 

 plane surface, demonstrating the direction of glacial movement. 



In its progress the ice mass abraded the surface of the rock, carry- 

 ing away and grinding up the material detached, and by means of it, 

 embedded in its base, polishing and scoring the ledges below, there- 

 by indicating the direction of its movement, and leaving us its own 

 history engraven on the surface of the rock. By careful observation 

 of these scratches or strise, it has been found possible in all except a 

 few cases to tell the point of compass towards which the movement 

 took place. By such observations it appears that the movements of the 

 ice in this region were of an exceedingly interesting character. On 

 the east side of the Kettle Range, with some unimportant exceptions, 

 the direction of movement was in a westerly or southwesterly direc- 

 tion, or towards the Range. The exceptions are cases in which two 

 sets of strias are present, the one set corresponding to the general di- 

 rection just indicated, the other to the general trend of Lake Michi- 

 gan. On the other side of the Kettle Range, between it and the crest 

 of the ledge that borders the Green Bay valley, heretofore described, 

 the direction is to the southeasterly toward the Kettle Range. With- 

 in the great Green Bay valley the direction is uniformty parallel to 

 its trend, and the cutting and planing indicates a long continued and 

 powerful action. To the west of this valley, the striae have a west- 

 ward and southwestward direction, the tendency being in general 

 more to the westward as the slope is ascended. It appears then that 

 the movement on the east side of the Kettle Range was up the slope 

 obliquely towards it; that on the west side of the Range, between it 

 and the margin of the Green Bay valley, the movement was obliquely 

 down the slope toward the Range ; that within the Green Bay valley 

 the ice moved up it until it reached the dividing ridge between it and 

 the Rock River valley, when it descended the latter, the lines gradu- 



