ANCIENT GLACIERS. 83 



cant for the ice-sheet ; and the clayey element, especially, 

 co-operating in many cases with the pent-up subglacial 

 waters, must have greatly facilitated the onward progress 

 of the ice." He concludes, therefore, that the onward 

 movement of the vast ice-sheet greatly exceeded that of 

 the main part of the ground moraine, the ice-sheet slipping 

 over the till, the whole being in some degree analogous to 

 that of a great land-slip. " In both cases the progress of 

 a somewhat yielding and mobile mass is facilitated by an 

 underlying clayey layer saturated with water." 



New York, New Jersey, and Pennsylvania. 



West of New England the glacial phenomena over the 

 northern part of the United States are equally marked all 

 the way to the Missouri River, and the boundary-line of 

 the glaciated region can be traced with little difficulty. 

 It emerges from New York Bay on Staten Island and 

 enters New Jersey at Perth Amboy. A well - formed 

 moraine covers the northern part of Staten Island, and 

 upon the mainland marks the boundary from Perth 

 Amboy, around through Earitan, Plainfielcl, Chatham, 

 Morris, and Hanover, to Rockaway, and thence in a 

 southwesterly direction to Belvidere, on the Delaware 

 River. That portion of New Jersey lying north of this 

 serpentine line of moraine hills is characterised by the 

 presence of transported boulders, by numerous lakes of 

 evident glacial origin, and by every other sign of glacial 

 action, while south of it all these peculiar characteristics 

 are absent. The observant passenger upon the railroad 

 trains between New York and Philadelphia can easily 

 recognise the moraine as it is jDassed through on the 

 Pennsylvania Railroad at Metnchen and on the Bound 

 Brook Railroad at Plainfielcl. Near Drakestown, in Mor- 

 ris County, there is a mass of blue limestone measuring, 

 as exposed, thirty-six by thirty feet, and which was quar- 

 ried for years before discovering that it was a boulder 



