﻿l6o NEW YORK STATE MUSEUM 



recently exposed with perfectly preserved polish. While it is 

 possible that this difference in surface characters may be the effect 

 of differences in present conditions of drainage and solution, though 

 improbable, it seems more likely that we have here another illustra- 

 tion of multiple ice work. 



In the Potsdam areas the impression is given of general ice 

 abrasion by the frequent patches of polish and striae; but the un- 

 scored surfaces far outnumber the striated. Here, again, we have 

 the uncertainty as to the degree of weathering and destruction of the 

 latest glacial records, because exposed surfaces, apparently of iden- 

 tical quality of rock and equality in exposure exhibit partly highly 

 polished and partly unscratched surfaces. The fact of a general 

 grinding and smoothing of the rock is clear, but quite certainly not 

 by the latest ice sheet. 



Direction [see pi. 44-47]. Near the St Lawrence the average 

 direction of striae is about parallel with the river. Leaving out the 

 extreme and aberrant marks they may be generalized as follows : 

 at Chippewa Bay, s. 25 ° w. ; Alexandria Bay, s. 25-40 ° w. ; Clayton, 

 s. 40-50 w. ; eastward from the river and from the axis of the val- 

 ley the striae are more variable and swing more southerly. About 

 Redwood some striae are s. 40 w., probably representing the 

 stronger flow of the deeper ice, but a great number range within 

 s. io-20>° w. About Theresa the greater number lie within s. io° w. 

 and s. io° e. East of Chaumont the striae are s. 35 ° e. ; at Evans 

 Mills, 10-20 east of south and at Sanfords Corners, 30 east of 

 south. The Leraysville moraine [pi. 44] clearly shows the south- 

 easterly push of the latest ice in the district. This easterly swing of 

 the ice in the eastern part of our area was due to the well known 

 spreading or radial flow of a lobation in the ice front. As the ice 

 sheet waned the last portion resting over the area was a broad lobe 

 occupying the St Lawrence depression and having spreading flow 

 toward the east side of the valley. Along the east side of our maps 

 the most westward striae represent the general direction of the maxi- 

 mum flow while the eastward striae are later scratches by the ice 

 margin. 



Curved scorings. A remarkable example of curved scorings 

 may be seen on a broad, flat, smoothed surface of Potsdam sand- 

 stone 2}4 miles east-southeast of Alexandria Bay, about y 2 mile 

 west of three corners. The bare area lies in the track and on the 

 north side of an abandoned highway, on land of John Bogert. The 

 locality is indicated by three converging arrows on plate 47, and one 

 photograph is given in plate 59. 



