LOWER SECONDARY ROCKS. 237 
The Catskill Mountains, from the base to near the 
loftiest summits, are composed of strata of this sand- 
stone, through a thickness of 3000 feet or more. 
CHAPTER XXII. 
GEOLOGY OF THE UNITED STATES. 
LOWER SECONDARY FORMATIONS. 
Carboniferous Group (De la Beche). Medial Order. 
Secondary Rocks— Their Division. — Carboniferous Limestone 
— Its Range. — Mr. Featherstonhaugh's Account of it. — The 
Coal Measures — Of what they Consist — Their Situation. — 
Anthracite Coal Measures — Prof. Rogers's Account of them.— 
The Shales. — Section of Coal Measures of Pennsylvania. — 
Section of Carboniferous System of Ohio. — Coal Measures 
on Kenawha River — At Wheeling, Va. — At Pittsburgh — At 
Kiskiminitas. — Millstone Grit and Shale. — May we expect to 
find Coal in New-York ? 
Having " worked our passage" through the con- 
torted strata of the transition series, we are now 
prepared to launch out upon the great secondary 
formation, where, if we mistake not, we shall find 
smoother saiUng. 
The lower secondary rocks consist of three series : 
1. Carboniferous Limestone. 
2. The Coal Measures, 
3 . Millstone Grit and Shale, 
Carboniferous Limestone, — Bearing in mind, then, 
that we are working our way upward, from granite, 
the lowermost rock, to the surface, we next come 
to the carboniferous limestone, resting upon the 
old red sandstone* just described. 
* At Lewiston, ten miles below the Falls of Niagara, we can 
see the old red sandstone immediately under the great carbon- 
iferous limestone formation. 
