53 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 inapphcable to the same in other places from the great 

 change in Hthological character. Thus far, httle 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, 1st. The limestone along the Mo- 

 jiawk 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- 

 haiok 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 

 groiip, 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 



