50 NEW YORK STATE MUSEUM 



elevation determined by the aneroid barometer to be 270 feet, 

 abundant shells of Saxicava rugosa were found in a fine state of 

 preservation in gravel at depths from 18 inches to over 3 feet 

 below the surface. Many of the shells were standing in attitudes 

 of growth in the spaces between the pebbles. The deposits were 

 very rudely stratified. 



The discussion of the bearing of these and other shell deposits 

 on the New York side of Lake Champlain is given in full in my 

 report on the marine submergence. 



RECENT CHANGES 



Since the glacial deposits were strewn over this district and 

 the old shore lines marked out by waves, it is evident that the 

 land has risen in relation to the sea. According to the data 

 gathered in this survey, this elevation amounts to about 450 feet 

 along the international boundary, being somewhat less in the 

 southern part of the area because of the tilting to the south. 

 There are reasons for believing that this change of level is still 

 in progress but no local evidence of it has been observed. 



The exposure of the rocks to the atmosphere in postglacial time 

 has produced a slight amount of weathering and consequent dis- 

 integration. In many places over the flat rock spillways the 

 Potsdam sandstone has broken down, affording loose white sand 

 or white quartz pebbles but always in very small quantities. A 

 more noticeable effect in this area has arisen from the action of 

 frost in prying loose the angular joint blocks or slabs of the rock. 

 On the whole the drift strikes an observer from the southern part 

 of the glacial field as little altered by weathering but the resistant 

 character of the Fotsdam sandstone which forms so large a part 

 of the coarse material tends to Lighten this impression. The 

 amount of work done by glacial torrents and by waves gives in this 

 region a far longer vista of late glacial and postglacial time than 

 does the degree of weathering. 



Streams and stream deposits 



All of the streams of this quadrangle, except the brooks (lowing 

 down the south slope of Rand hill in Beekmantown, discharge 

 across the zone of abandoned and elevated beaches. The courses 

 of the streams thus present that irregularity which arises from 



