140 THE ICE AGE IN NORTH AMERICA. 



a considerable portion of Long Island. The exterior line, 

 beginning at Montank Point, forms the backbone of the 

 island as far as Brooklyn, N. Y., the city itself being built 

 upon it. The interior or parallel line, represented to the 

 east by the backbone of Cape Cod and the Elizabeth Islands, 

 disappears beneath the deeper waters of Buzzard's Bay, to 

 emerge upon the mainland at Point Judith in Khode Island, 

 and give variety to the whole coast of the State westward 

 from that point. This part of the moraine presents many 

 features of special interest at Watch Hill, Fisher's and Plum 

 Islands, and on the northern shore of Long Island as far as 

 Port Jefferson. Westward from Port Jefferson only the 

 external line of moraine hills is traceable, Staten Island in 

 New York Harbor being a most interesting development of 

 it. The northern and western portions of this island are 

 covered with the peculiar combination of rounded knobs and 

 circular depressions characteristic of moraines, while the 

 southeastern portion of the island was just beyond the reach 

 of the ice, and the deposits upon it are of an entirely differ- 

 ent character. 



Up to this point in our investigations some doubt may 

 attach to the inferences concerning the limits of the great 

 ice-sheet. For, since the ocean everywhere expands to the 

 south, it may be asked, What certainty is there that its 

 waters do not cover a belt of glacial deposits still farther out 

 than those now visible ? No positive answer can be made to 

 this objection. But, on striking the coast of New Jersey 

 opposite Staten Island, a fair field of investigation is at once 

 offered, and doubt as to the substantial correctness of the 

 deiineation farther on need be no longer entertained. The 

 line of moraine hills across New Jersey is a direct continua- 

 tion of these forming the backbone of Long Island, and 

 covering the northern half of Staten Island. Here they 

 form a sharp line of demarkation between the glaciated 

 region to the north and the unglaciated plains to the south. 

 Beginning at Perth Amboy, the moraine bends northward 

 through Baritan, Plainfield, Chatham, Morris, and Hanover, 



