408 PALAEOZOIC TIME. 



Lower Silurian limestone and conformable to it in dip. This fault 

 continues on for eighty miles. (W. B. & II. I). Rogers.) 



Several such examples might be cited from Pennsylvania as well 

 as Virginia. One occurs near Chambersburg, Pa., and is thus 

 described by Lesley in his "Manual of Coal and its Topography" 

 (p. 147). "The western side of the anticlinal Cove canoe has been 

 cut off and carried down at least twenty thousand feet into the 

 abyss, along a fracture twenty miles in length ; the eastern side 

 must have stood high enough in the air to make a Hindoo Koosh ; 

 and all the materials must have been swept into the Atlantic by 

 the denuding flood. The evidence of this is of the simplest order 

 and patent to every eye. The highest portions of the Upper Silu- 

 rian wall against the lowest portions of the Lower Silurian. The 

 thickness of the rocks between is, of course, the exact measure of 

 the downthrow, which is therefore twenty times as great as the 

 celebrated Pennine Fault in England. Yet a man can stand astride 

 across the crevice, with one foot on Trenton limestone and the 

 other on Hamilton slates, and put his hand upon some great frag- 

 ments of Shawangunk grit, caught as it was falling down the 

 chasm, held fast in its jaws as it closed, and revealed by the merest 

 accident of lying suspended in the crack just where the plane of 

 denudation happened to cut it." 



Passing now farther north, to New England, we find the same 

 system of flexures as occurs to the south. The rocks are generally 

 crystalline, and it is not at first obvious that they were ever Palaeo- 

 zoic strata and have been metamorphosed into their present con- 

 dition. But this is proved by the portions of the strata which 

 remain undisguised by the alteration. 



The western part and summit of the Green Mountains have 

 already been shown to be altered Lower Silurian, and fossils have 

 been referred to that prove it (p. 392). 



Again, Devonian (Upper Helderberg) rocks have been identified 

 by their fossils in northern Vermont and at Bernardston in Massa- 

 chusetts. It is probable that from the former position a line of 

 Devonian rocks extends south through eastern Vermont ; and the 

 Bernardston beds are supposed to be part of the same formation, 

 but on the opposite side of an anticlinal. (Hitchcock.) 



Between Worcester, Mass., and Newport, R.I., the Coal forma- 

 tion occurs with its usual fossil plants, and conglomerates of the 

 Coal measures stretch on towards Boston (p. 325). 



South of Boston, at Braintree, fossils of the Potsdam period 

 have been found (p. 184). On the northern margin of New Eng- 

 land the rocks graduate into those of British America, which are 



