﻿GEOLOGY OF THE THOUSAND ISLANDS REGION 163 



^hort. The longer lines have an arc of 6 inches or a radius of about 

 3^ inches. 



Another excellent illustration of the chatters is on the highway 

 3 miles north of Redwood on the road to Chippewa Bay, at the point 

 indicated on plate 47. Several very large examples occur in 

 the middle of the street in Redwood village, just below the Dollinger 

 House. Smaller examples are so very numerous that no notebook 

 record was made of them. Fine examples occur with the curved 

 scorings. 



The chatter fractures dip so steeply into the rock that rarely is 

 there any flaking of the surface rock. In many instances no axial 

 grooving or crushing of the rock is visible, the appearance being 

 as if the rock had been abraded and resurfaced and polished so as 

 to leave merely the clean-cut concentric fracture lines. Such 

 abrasion is more than possible but is very slight, as early striae hav- 

 ing the direction of the axes of the chatters are not obliterated. 

 Commonly there is some evidence along the axial line of the pres- 

 sure by the unsteady or chattering tool. 



The other class of fractures, having the concavity facing upstream 

 toward the tool, are much less regular or true than the chatter frac- 

 tures. In both classes the cracks dip downstream or away from the 

 point of the tool, but in these gouge fractures the angle of dip is 

 much less than in the chatters, and commonly there is considerable 

 flaking of the rock or removal of the feather edges of the surface 

 rock. These cracks fall in the class of " concentric gouges " or 

 " disruptive gouges " of earlier writers. 1 The action seems to have 

 been a sort of drag or pull on the surface of the rock by pressure 

 of a boulder with broad area of contact, but without pounding or 

 percussive force. The process was a plucking by dragging pressure. 



These gougings are not as common as the chatters, and only two 

 good localities were noted. One of these is ^ mile south of the 

 county line between Jefferson and St Lawrence counties, on the west 

 road to Chippewa Bay. The other occurrence is on the road east of 

 Goose bay and on the south side of Crooked creek valley. The 

 first mentioned is on the south end of a plain, the latter on a sur- 

 face facing north, where the ice was pushing against an upslope. 



The gouge fractures are rarely true circular curves, in which cases 

 they may be mistaken for chatters, but commonly they are irregular 



1 A full description and discussion of these singular phenomena con< 

 nected with glacier mechanics is given in Professor Chamberlin's paper 

 Rock Scoring of the Great Ice Invasion. U. S, Geol. Sur. An. Rep't 1888. 

 p. 216-40. Reference to other writings is there given. 



