236 



TRANSITION ROCKS. 



New- York, in a narrow ridge, through which the 

 Mohawk makes its way at the Little Falls. A few 

 miles south of this it meets the western bend of the 

 Catskill's, and spreads out to a breadth of 200 miles 

 between the Pine Orchard and Lake Canandaigua. 

 The southeastern limit is the Shawangunk Mount- 

 ains and the Blue Ridge of Pennsylvania, parallel 

 with which it extends to Georgia and Tennessee m 

 a broad belt, forming the loftiest summits of the Al- 

 leghany. Of all these ridges it constitutes the east- 

 ern face, and dips with more or less rapidity to the 

 northwest, being in some places almost vertical." 



Prof. Renwick says, that " the anthracite coal for- 

 mation of Pennsylvania rests immediately on the 

 red sandstone." Prof. Hitchcock observes, that he 

 " suspects the Pennsylvania anthracite occurs in the 

 higher beds of the graywacke, perhaps even in the 

 millstone grit, and the Rhode Island anthracite in the 

 lower beds of the graywacke." M'Clure simply 

 states, that both the Rhode Island and Pennsylvania 

 anthracite occur in the transition formation, while, 

 again. Prof. Renwick remarks, that " those who con- 

 sider the anthracite of Pennsylvania to belong to 

 the transition order, err." We shall hereafter con- 

 sider this subject more in detail. Prof. Henry D. 

 Rogers, of Pennsylvania, remarks, in relation to the 

 sandstone under consideration, that " it is not con- 

 fined to the Appalachian region of Pennsylvania, 

 but that it possesses a prodigiously extensive range, 

 not only through Maryland and Virginia, but in a con- 

 trary direction through New-Jersey and New-York, 

 and, I believe, beyond those limits, constituting 

 everywhere the lowermost formation of the wide- 

 spread secondary strata, which it encircles in a 

 somewhat interrupted belt, following the primary 

 boundary of these rocks from Tennessee to Lake 

 Champlain, and thence northwestward to the north- 

 ern shore of Lake Huron and Lake Superior." 



