Devonian Era in the Ohio Basin. — Claypole. 21 
and very extensive excavations have been made, especially 
along the river and in the upper beds. The full thickness of 
no feet is assigned to it here, that is, thirty-five feet to the 
upper and seventy-five feet to the lower portion. 
Slightly touching Madison county, the outcrop runs into 
Franklin county, occupying its western half and showing, 
along the Scioto, near Dublin and the capital city, some of the 
finest exposures and largest quarries along the whole line. 
Then, with a long rounded projection into Pickaway coun- 
ty, the outcrop comes to an end, being overlapped by the Black 
shale, which there stretches to the westward beyond the me- 
ridian of the Corniferous limestone. Nor does evidence derived 
through the drill, as at Lancaster, Jackson and Iron ton, give 
any proof of its continuance under cover to the southward, so 
that it probably runs no farther in that direction. Its apparent 
thinning and its absence in a large area, if not altogether, in 
northern Kentucky, according to Shaler,* are additional sup- 
port of this opinion. 
Coming back to the second line of outcrop, we find the 
Corniferous limestone entering the state from Michigan, in 
Lucas county, and continuing through Wood, Henry, Defi- 
ance, Putnam and Paulding counties to the Indiana state line. 
Exposures are so rare, owing to the deep covering of drift, 
that no data of importance are afforded thereby. 
Beyond the state line the Corniferous limestone is nowhere 
seen on the surface and has been nowhere reached by the drill 
to the south of this latitude, nor throughout the Appalachian 
region, until it reappears in northeastern Pennsylvania after 
an interval of nearly five hundred miles. Here it is thin but 
rapidly thickens up to 200 feet or more,f and in New York- 
it is reported of even greater thickness. Through that state 
it can be traced in a northerly direction to Albany, where it 
turns to the west, crosses the state and runs into Ontario coun- 
ty, continuing with its usual characters half way along the 
north shore of the lake. Here a thickness of 160 feet is as- 
signed to it.:|: Curving to the north, it passes under lake 
Huron and reappears in northern Michigan, where A. Win- 
chell gives it a thickness of 350 feet. Its outcrop underlies 
* Geology of Kentucky, vol. iii, p. 3S7. 
t I. C. White, Geol. Survey of Pa., G6, p. 116. 
X Geol. of Canada, 1863, p. 364. 
