OCCLUSION OF IGNEOUS ROCK 439 



which commonly swarm along the axis of extensive orogenic 

 movement, but probably over the roots of one of the oldest and 

 most violent volcanic craters ever existent upon the earth. 



In previous discussions of the eruptive crystallines along the 

 eastern border of the Appalachian belt, grounds have been 

 presented in favor of a prevalent hypothesis of the elevation of 

 a mountain range upon the western rim of an Archaean conti- 

 nent along the Atlantic, to which the name " Appalachia " has 

 been applied/ However, in view of the probable relegation of 

 these crystallines to Palaeozoic age, it has been recently urged 

 that " the location of this hypothetical range, which is supposed 

 to have supplied the sediments for the Appalachian sea during 

 Palaeozoic time, must be shifted, at least for the earlier Palaeozoic, 

 farther east where its roots would not lie buried under Coastal 

 Plain deposits." ^ Nevertheless the evidences of a huge moun- 

 tain range along the tract of these Palaeozoic crystallines remain 

 exactly the same, testifying, it would appear, toward the suc- 

 cession of that Archaean range by another enormous uplift 

 along this inner line, in advance of the main Appalachian uplift 

 on a line still further west. Its period, if estimated by that of 

 the igneous activity, fell probably, it is believed, in the earlier 

 part of the interval between early Silurian and late Carboniferous. 



From local evidences of intense vulcanism there is further 

 reason to believe that this range rose here and there into lofty 

 peaks. For the purpose of the physiographer, the one on the 

 site of New York City may be designated as Motuit Manhattan. 

 Some comprehension of its height and dimensions may be gained, 

 not merely from allowance for its apparently vast contribution of 

 secondary debris to the later Palaeozoic and Mesozoic within the 

 interior sea-basin, but from an estimate of the area apparently 

 covered by its base. To the north, rocks of exactly the same 

 character stretch for forty miles fill they blend with the Cort- 

 landt series at the Archaean Highlands on the Hudson river. 

 To the northeast, they extend over Westchester county and 

 beyond into Connecticut. To the east, on the shore of Long 



1 B. Willis, Nat. Geoi:. Map. 



2 E. B. Mathews, loc. cit., 159. 



