466 GEOLOGY OF OHIO. 



county, it will be found somewhere between Boggs' mill-seat and the 

 Pontiac lime-kilns. The shortness of the distance, together with the 

 slight fall in the river, would preclude the existence of any extensive 

 strata in this locality. There may exist here a few feet of evenly layered 

 rock, corresponding with the upper layers of the Covington stone ; but 

 the hope of very much good stone, even if any is found, is too slight to 

 encourage much expense in searching for it. It will be thus seen that 

 the Niagara thins out in this direction, especially the lower strata, while 

 the upper strata maintain a considerable thickness. Indeed, it is possi- 

 ble that the upper strata of the Niagara lie here immediately upon the 

 Clinton. The thickness of the strata is not known with certainty, but 

 can be approximately made out. The Pontiac limestone is but little* if 

 any, above the surface of water in the river in its lower layers, and a 

 mile south of Sidney the top of it is about twenty-five feet above the 

 water. With a fall of fifty feet in that distance, there would be a thick- 

 ness of seventy-five feet of this quality of limestone. I think there is 

 as much as this. We do not know that this is its greatest thickness, for 

 it may rise higher under the Drift in some places. It is i, soft stone, and 

 has, no doubt, been plowed down by the forces which deposited the Drift. 

 It would not retain any marks of wearing forces on its surface. Although 

 not valuable for building purposes, it contains an inexhaustible store of 

 the best quality of lime. The lime manufactured from this stone is of a 

 pure white when slacked, and is suitable for all purposes for which lime 

 is used. From a previous volume of this Survey (1870, p. 449), I make an 

 extract, showing the composition of the, limestone taken from one of the 

 quarries of this county. I will add the remark, that the locality from 

 which the specimen submitted to examination was taken, is about mid- 

 way between the lowest and the highest strata. I will say, also, that 

 from the appearance of the weathered surfaces of the stone at Dugan's 

 quarries, I concluded that there was a larger quantity of oxide of iron in 

 the stone of this locality, than would be found either above or below, 

 especially below. The rusty color indicated the presence of iron. From 

 the porous nature of the stone, I supposed the iron may have been filtered 

 out of water which has run through it. There was an entire absence of 

 that rust color in the Pontiac quarry, and the same might be said of the 

 quarries near Sidney. 



