= 
52 Notes upon the Geology of the Western States. 
of the different states; it being evident that the same rock was 
known under different names, and the descriptions in many cases 
being inapplicable to the same in other places from the great 
change in lithological character. Thus far, little attempt has 
been made to identify the particular rocks of the lower forma- 
tions in distant localities by their fossils. In this condition of 
things we have the “cliff limestone” of Prof. Locke, a name 
applicable in Indiana and Ohio—and equally applicable, as will 
be seen, to another rock on the Mississippi river—and the ‘ blue 
limestone” of the same report, given as the lowest member of 
the series in Ohio. ‘Thus according to the report just quoted, 
and which in fact gives a very accurate account of the rocks of 
the state, we have in Ohio only two limestone formations, 
whereas in New York we have three very important ones, with 
some minor beds. These are, ist. The limestone along the Mo- 
hawk valley, the principal member of which is termed by Mr. 
Vanuxem, the ‘‘ Mohawk limestone,” a name which with much 
propriety might be applied to the whole mass, forming the Mo- 
hawk group. This would include the Mohawk, Birdseye, and 
‘Trenton limestones, and the calciferous sandrock might also be 
included as the lower member of the group. 2d. The Niagara 
group, called in the reports Lockport limestone and Rochester 
shale. 3d. The ‘ Helderberg limestone group” of Mr. Mather, 
including all those limestones of Schoharie and the Helderberg 
mountains, or all the rocks between the Onondaga salt group and 
the fossiliferous shales of Ludlowville, Moscow, &c. Between 
either of these groups in New York, there are thick deposits of 
other rocks, (shales and sandstones,) while in Ohio, the two 
limestones there named are separated only by a few feet, accord- 
ing to the report. Now it becomes very important to know, to 
which of the New York groups these two masses belong, and 
whether, in progressing westward, certain groups become more 
or less important. We have already seen from the New York 
reports, enough to anticipate that great changes might be ex- 
pected when we should trace the same rocks over twice or thrice 
the extent of that state. 
The extension of the great coal basin of Pennsylvania be 
came another object of interest, from the fact that it. borders the 
southern counties of. New York, the lower member of the car- 
boniferous system extending within that state, and for the most 
