130 Notice of Geological Sur'veys. 



the surface so much lime as we should anticipate, and rarely, if 

 ever, when undisturbed, does it eifervesce with acids. On the 

 tops of the hills around Cincinnati, the loam lies seven to nine 

 feet deep before any stones are mingled with it, and this loam is 

 not effervescent ivith acids. As soon as a layer of stone has been 

 passed, all below it is highly so," By ordinary processes, the 

 lime has been undoubtedly removed from the upper part of the 

 soil ; " hence the yellow loam near the surface is more useful 

 for the manufacture of bricks that that which comes from be- 

 tween the layers of stone ; the latter is uniformly effervescent, 

 and contains from 12 to 25 per cent, of carbonate of lime." 



The blue limestone, though classed as a transition rock by Dr. 

 Locke, received no particular designation, while Mr. Conrad con- 

 siders it as the Trenton limestone of New York, and the equiva- 

 lent of the Caradoc sandstone of Murchison.* No specific enu- 

 meration of its organic remains is given, although they differ from 

 those of the " cliff limestone" as below. There is a series of 

 rocks, eight hundred feet in thickness, between this foundation 

 rock and the coal formation of Ohio, and at its point of greatest 

 altitude already referred to, it separates the coal basins of Ohio 

 and Indiana into two distinct and well characterized formations. 



The " cliff limestone^^'' that lies on the " hlue^'' limestone, is 

 separated from it as in the section of Adams county, by extensive 

 deposits of marl and intermediate limestone, which are much less 

 in other places, and is not fissured like the latter, but is entire 

 throughout its whole thickness of eighty feet, and where it is cut 

 through by the rivers, presents mural bluffs or " cliffs," whence 

 its name ; or when it forms the bed of the streams it often causes 

 cascades and occasions falls, as in the Ohio, at Louisville. It is 

 less hard and compact than the lower limestone, often soft and 

 friable like a loose sandstone, and even porous, spongy and arenace- 

 ous ; of various colors, yellowish, reddish gray, and almost white, 

 and is highly fetid and bituminous. In some places, it is without 

 fossils, in others highly fossiliferous. The organic remains of 

 both limestones are marine, and consist of corallines, univalves (?) 

 bivalves, and trilobites — sometimes the species are identical in 

 both, although generally different. The Corallines of the blue 

 limestone are small and branched ; those of the " clilf ' are in large 



* Vide this Journal, Vol. xxxviii, p. 87 — 88. 



