278 IDENTITY OF THE WESTERN FORMATIONS 



that this mass may represent the Clinton group, as Dr. Locke 

 showed me specimens from the same, in the eastern part of Ohio, 

 which, as I understood from him, forms the lower part of the 

 cliff limestone. This rock, which plainly succeeds the shales and 

 limestones equivalent to the Hudson river gi'oup, is marked by 

 patches and laminae of green shaly matter, strongly resembling 

 some portions of the intermediate mass betw^een the Medina 

 sandstone and the Clinton gi'oup, being an intermixture of the 

 green shale of the one, and the sandy matter of the other. 



Time, how^ever, did not admit of going into detailed examina- 

 tions, regarding the individual rocks, or groups, composing the 

 cliff limestone, the object being a general identification of larger 

 subdivisions. From examinations made at a short distance from 

 this place, I learned that the friable sandy mass just noticed was 

 succeeded by a harsh, porous limestone, apparently magnesian in 

 composition, and possessing the general characters of the Niag- 

 ara limestone in New York. At this place I was unable to find 

 any fossils save a few crinoidal columns, which gave to the rock 

 much the appearance of the lower part of that at Niagara Falls 

 and Lockport. The examinations of this rock in other places, 

 where I found fossils, and w^as able to trace the succession up- 

 w^ards, left no doubt of its identity with the Niagara mass. 

 . It should be remarked, that soon after leaving Cincinnati, the 

 rocks are seen to dip to the west or southwest; and at Madison 

 the base of the cliff limestone has approached within one hun- 

 dred and fifty or two hundred feet of the river. From this point 

 it continues to dip in the same direction, gradually approaching 

 to the river level, and finally entirely disappearing beneath it at 

 Louisville or the falls of the Ohio. The river, at the time, being 

 high, did not permit an examination of the rock directly at the 

 falls, but the excavation of the canal below Louisville has devel- 

 oped, in the loose fragments, the character of the rock, which 

 consists, apparently, of the water lime, and perhaps some portion 

 of the Onondaga salt group, with the limestones above. The 

 most satisfactory exhibition, however, was a few miles further up 

 the river, where the rocks are very well exposed. Along the line 

 'of rail-road, and in the banks of a small stream about three miles 



