﻿GEOLOGY OF THOUSAND ISLANDS REGION l6l 



A considerable area of planished rock is covered by striae which 

 have various directions, from s. 56 w. to s. 16 w. Apparently the 

 markings with the more westerly trend are the older and prevailing 

 ones over most of the surface, the later and more southerly abrasion 

 having softened the older groves and given a cross polish. But the 

 later motion is also represented by a few strong chatter bands which 

 quite obliterate the older scorings where the latter are crossed. 



The curved markings lie in a belt about 10 feet wide and over 50 

 feet in length now exposed. The scorings are strong, clean-cut, 

 and perfectly parallel. At the north end they lie for several yards 

 perfectly straight, with direction 56 west of south, then they gently 

 curve, southing with steady uniform curvature until the direction is 

 s. 42 ° w. The curving is still continued where the belt of scorings 

 passes under the turf on the south side of the wagon track. The 

 strong furrow r s may not be confidently traced throughout the entire 

 length of the curve in distinct individuality, as later abrasion has 

 somewhat obscured them in places, but they are practically con- 

 tinuous and retain their relation and character. The belt of curved 

 scorings is exceptional to the general striae of the broad surface and 

 surrounding bare patches, the prevailing direction being s. 30-35 ° w. 



The curving lines have no angularity and show no hesitation nor 

 pauses or spasms in the ice motion. In one place a few of the 

 strong scorings in a narrow strip exhibit a perceptible variation 

 from the true curvature, or a tendency to straightness, but taking 

 the belt as a whole the curvature and the parallelism of the lines 

 appear to the eye to be true. The radius of the curve is about 60 

 or 70 feet. The chord of the exposed belt, including about 15 feet 

 of the straight beginning of the scorings, is 54 feet; and the ordinate 

 is 23 inches. 



This glaciated surface is the northern side of a broad rock plain, 

 with no apparent cause in the surrounding topography for the de- 

 flection in the ice flow. A narrow valley lies near on the north, 

 across which is a somewhat higher plain. The map, plate 44, shows 

 the general topography. 



A significant fact is that the curving belt of scorings, even at the 

 southern deflected end, so far as uncovered, is much more westerly 

 in trend than the prevailing ice movement, not only in the immediate 

 locality but in the great area. 



Chatter marks and gouges. The innumerable exposures of 

 the Potsdam sandstone, often of large extent, coupled with the very 

 hard and brittle texture of the rock, furnish many excellent ex- 



