226 The American Geologist. ^p'"'^- ^^o- 
the Clinton is quite conspicuous. The formation in that part 
of the state is essentially a crystalline limestone. This is usu- 
ally delicately colored and is often highly fossiliferous. At 
places it is a building stone of high grade, but uneven bedding 
has been an obstacle to its use for this purj^ose. In one or two 
counties it is burned for lime, furnishing a product of excellent 
quality. The rock is calcareous in composition, becoming in 
some places the purest rock of this type in Ohio. The fol- 
lowing is an analysis of the limestone near Osborn, Green 
county :* 
Carbonate of lime 97-14 per cent 
Carbonate of magnesia 1.21 " 
Alumina and oxide of iron .41 
Silicious matter .70 
99.46 " " 
Occasionally in the part of the state under consideration, 
a thin bed of clay, called by Foerste the Beavertown marl 
forms the top of the Clinton, and at other points a lean deposit 
of Clinton ore occupies the same relative position. The earl- 
iest geological reports of the state spoke of the rock carrying 
the odor of petroleum, and about forty years ago wells v.-th 
this substance in view were drilled in it. The result, however, 
was total failure, t 
Lender cover in the northwestern part of the state the com- 
position of the rock changes, resembling very closely that of 
the overlying Niagara. This is well shown in the followmg 
analysis of the Clinton from near Bowling Green: J 
Carbonate of lime 49-19 per cent. 
Carbonate of magnesia 40-3 1 
Insoluble residue 7.76 " 
At Fremont, Sandusky county, the formation has been the 
source of a small reservoir of gas ;§ and occasionally it lias 
yielded a small quantity of oil or gas in adjacent countie--". 
In central Ohio the formation presents a complete change. 
The limestone has disappeared, and there are found in its place 
shales of various colors and compositions, and usually an inter- 
calated bed of sandstone. The shales contain a noticeable 
* GeoJ. Sur. of Ohio, vol. vi, p. 728. 
t Second An. Rep. Geol. Sur. of Ohio (1838), p. 225; also yoI. iii, (187S), p. 
407. 
t Geol. of Ohio, vol. vi, p. 728. 
§ Ibid., pp. 183-9. 
