W. J. Miller — Ice Movement and Erosion. 291 



Direction of Ice Movement. 



Chamberlin, in the report above referred to, makes the ten- 

 tative statement" that massive ice currents having their ulterior 

 channels in the Cham/plain valley, on the one hand, and the 

 Saint Lawrence on the other, swept around the Adirondacks 

 and entered the Mohawk valley at either extremity, while a 

 feebler current, at the height of glaciation, probably passed 

 over the Adirondacks and gave to the whole a southerly trend." 

 Observations by later investigators have tended to bear out this 

 view, and the evidences from the southwestern Adirondacks 

 herewith presented have an important bearing upon the propo- 

 sition. 



The direction of flow is best shown by the glacial striae 

 which have been observed at a number of different places 

 through the district. The striae are best preserved upon the 

 hard Precambrian rocks, but these are mostly drift-covered 

 except along the chief stream courses. The limestones are 

 next most favorable, while upon the shales none have been 

 found. Striations are present only upon those surfaces from 

 which the drift has been recently removed, because even the 

 hardest rocks exposed during postglacial times have been 

 weathered enough to cause an obliteration of the glacial marks. 



Striae pointing from south 25° to 40° east have been located 

 as follows : On Trenton limestone one mile south of Martins- 

 burg and also one-third of a mile east of Martinsburg (S. 25° E.) ; 

 on Precambrian near the mouth of Roaring brook; on Pre- 

 cambrian one and one-half miles northeast-north of Olenfield, 

 and also one-third of a mile southwest and three-fourths of a 

 mile southeast-south of the same village ; on Precambrian one 

 mile northeast of Denley station, one-third of a mile north- 

 east of Hawkinsville, on Big "Woodhull creek two miles north- 

 east of Forestport, and one mile north of Salisbury centre 

 (Cushing). Other striae, bearing nearly south, occur on Pre- 

 cambrian one mile east of Port Leyden and still others bearing 

 ]ST. 80° E. on the Trenton limestone two and a half miles north 

 of Middleville (Cushing). Beside these the observations of 

 Chamberlin, in the Mohawk Valley near Little Falls, are 

 quoted : " On the western slope of the ridge that stands athwart 

 the valley of the Mohawk at Little Falls are two sets of striae. 

 The course of the main series is S. 50° E. and of the minor 

 cross-set S. 45° W. North of Little Falls, two-thirds of the 

 way up the slope of the valley the course of the striae is S. 60° 

 E., the movement being apparently from the west. A little 

 farther up the slope, on an eastward inclined rock surface, the 

 main set runs S. 50°-55° E. crossed by feebler and later ones 

 S. 70° W. Four miles north of Little Falls, a varying group 

 runs S. 18°-28° E. and about six miles north S. 37° E." 



