lO 



NEW YORK STATE MUSEUM 



quarry near the Troy branch of the New York Central & Hudson 

 River Railroad, 42° west of south. 



2 In a quarry about a mile to the east of the former, 22° west 

 of south. 



3 Two miles north of Rexford Flats on sandstone exposed at the 

 roadside, 38° west of south. 



4 At the 600- foot level on a branch of road running north from 

 Hardin's crossing, on the Amsterdam trolley line, on sandstone ex- 

 posed at roadside, 35° west of south. 



5 Near the western margin of the sheet at an elevation of 780 feet 

 on the road running east-west from the north-south road that passes 

 through Town House Corners, on sandstone at roadside, 57° west 

 of south. 



The readings as above given are magnetic north. 



PROBABLE AGENCY OF ICE IN THE FORMATION OF THE BALLSTON 



CHANNEL 



Evidences that the Ballston channel is an old rock-channel have 

 been referred to above. It presents, however, a number of features 

 which indicate that the old stream-formed valley was deepened and 

 widened by ice erosion during the glacial period. The general shape 

 of the valley in cross section conforms rather to the type of an ice- 

 made valley. The bottom is broad and the slopes where the valley 

 is most fully developed, along the southern half of Ballston lake, 

 are somewhat steep and smoothly planed. It will be noted that the 



I 



r400 



f- 



-bOQft. 

 Z 85 ft. 



230/;. 



Fig. I Diagram showing topography and rock structure as seen in section across Ballston 

 hannel at about one mile north of the southern end of Ballston lake. Vertical scale lOO feet to 

 he inch. Horizontal scale one-fourth of a mile to the inch 



lake does not lie in the middle line of the trough, but to the eastern 

 side. West of the lake the shore, for the most part rocky, rises 

 somewhat sharply to a level of about 35 feet above the surface of 



