14 NEW YORK STATE MUSEUM 



due to ice, the stoss side of the rock mass, against which the ice 

 moved, having suffered more wear than the lee side. Similar ex- 

 posures of rock, showing in their shapes and surfaces the effects of 

 glacier erosion, were observed in other localities; for example, 

 along the road that crosses the mountainous tract south of Lake 

 Bonita. Also on the southern slope of the highlands, in Woodlawn 

 park and westward, along the line of the railway, outcrops of worn 

 rock are frequent. 



The crystalline Precambric rocks of the highlands region were 

 resistant to ice erosion but there is evidence that the soft shale 

 rocks which underlie the village of Saratoga Springs, in its south- 

 western portion, were deeply gouged out by the ice. The records of 

 borings made by one of the companies formerly engaged in pump- 

 ing carbonic acid gas show that at points near South Broadway, 

 about a mile southwest of Congress park, shale rock lies at a 

 depth of 162 and 140 feet below the present surface. 1 Taking into 

 consideration that the harder limestone (dolomite) rocks appear at 

 the surface immediately north and west of Saratoga Springs it is in- 

 ferred that as the deeper ice of the Hudson plain passed beyond 

 the wall of the scarp and merged with the general mass, changing 

 its direction of movement to the southwest, the soft underlying 

 shales were powerfully eroded. 



The effects of glaciation are in places conspicuous on the south- 

 ward facing slopes of the Greenfield tract. An interesting work 

 done by the ice is the exposure and planing down of the remarkable 

 Cryptozoon reef beds of the limestone by the roadside near the 

 Hoyt quarry, 2.y 2 miles due south from Greenfield Center. A 

 photograph of this exposure is given in New York State Museum 

 Bulletin 173. 2 



DESCRIPTION AND INTERPRETATION OF THE 



DEPOSITS 



Unmodified till. Materials derived from the ice sheet and left 

 at the time of melting now overlie bedrock and form the surface 

 mantle of soils and rock fragments of the uplands region generally. 

 The composition of the till varies markedly in different regions and 



1 These data were obtained through the courtesy of Mr Frederick G. 

 Edwards, engineer for the Commissioners of the State Reservation at Sara- 

 toga Springs. They were taken from the well book of the company formerly 

 operating, the book being now in possession of the commission. See also 

 page 17 of the present report. 



2 Since the above was written this area has become the property of the 

 New York State Museum and has been named Lester Park. 



