58 Notes upon the Geology of the Western States. 



ward, only two or three of its members being distinguishable at 

 the Niagara river. 



The second or " Onondaga salt group," is in greatest force 

 about the central part of New York, being about one thousand 

 feet thick, consisting mostly of shales and marls containing the 

 gypsum beds, and all the important salt springs of the state. In 

 the eastern part of the state it is nearly lost from thinning out, but 

 westerly it suffers but little diminution as far as the Niagara river. 

 The Niagara limestone and its accompanying shale, are 

 scarcely recognized in the eastern part of New York, and even 

 as far west as the centre, they form only masses of a few feet in 

 thickness. The whole however gradually increases westward, 

 and on the Niagara river, as well as at Lockport, the two masses 

 are not less than two hundred feet thick. 



These three groups are traced far into Canada with little vari- 

 ation, except that the Niagara limestone becomes thicker and the 

 shale more calcareous. The line of outcrop or strike of this 

 limestone is from Rochester westward, along a torraee known as- 

 the mountain ridge and which extends by Lewiston and Clueens- 

 ton into Canada, and is distinctly traced as far as the head of 

 Lake Ontario. 



Near the western end of Lake Erie the Niagara U?nestone 

 appears above the surface of the water, having been elevated, 

 and forms a continuation of the axis before alluded to, as extend- 

 ing from Lake Erie to the S. W., along the borders of Ohio and 

 Indiana. In the central and western parts of Ohio it is the most 

 important rock, and is designated the "cliff limestone" by Prof. 

 Locke. Among its numerous localities may be named Spring- 

 field, Dayton, the vicinity of Columbus, and several places in 

 Adams county. In Kentucky, at Louisville, and the falls of the 

 Ohio, at Madison and other places in Indiana, it appears as the 

 limestone of greatest thickness. 



In examining the upper part of the " cliff limestone" I found 

 it, so far as lithological characters are concerned, a continuation 

 of the Helderberg group, the Onondaga salt formation having 

 thinned out almost entirely, having in fact no re})resentative ex- 

 cept a thin layer of water-lime, which is seen at the falls of the 

 Ohio and the canal below Louisville, but in other localities is of 

 less importance and often scarcely to be recognized. We have 

 here then this condition of things — the Niagara limestone, 



