336 
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 
Oatskill'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 in 
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." 
