130 
The Ohio Naturalist. 
[Vol. X, No. 5, 
this limestone has the peculiarity of being interposed between 
two beds of coal both of which reach mineable thickness in some 
places. The Pennsylvania geologists have said this limestone is 
sparing in outcrop in Mercer County and seldom seen where the 
Lower Mercer is found. Had the excellent expression of this 
stratum in Mahoning County been seen at that time, the name 
Upper Mercer would quite probably never have appeared. In 
both counties it is sometimes absent but is present equally as 
often as the Lower Mercer. 
Rogers states that this limestone is interposed immediately 
under the Tionesta sandstone (Homewood sandstone) in the 
vicinity of New Castle, Pennsylvania, [Geology, Pennsylvania, 
Vol. II, Part I, p. 489], and White in his section on the Ohio- 
Pennsylvania line on the Mahoning River shows the top of the 
Homewood sandstone to be 30 feet above the top of the Upper 
Mercer limestone. [U. S. Geol. Sur. Bui. 65, p. 191]. These are 
important points in correlating the horizons traced across the 
two counties with those beyond the state line. The horizons of 
doubtful correlation are, particularly, the Brookville coal, 
Clarion coal, and Putnam Hill limestone. 
5. The Howenstein is the fourth limestone and is traceable 
across the two counties. It is last seen in full development, and 
Avithout suggestion of disappearing, on Burgess Run. Its hori- 
zon is certainly marked by the coal at 1043 on Furnace Run. 
From White’s section and the Furnace Run section the writer is 
unable to reach any other conclusion than that the Howenstein 
limestone caps the Brook\dlle coal. The Homewood sandstone 
so conspicuous in Pennsylvania thins down on entering Ohio and 
becomes shale in the Furnace Run section but regains its massi\ r e 
character locally as seen at Club Lake where it is 28 feet thick, 
and rests upon a remnant of the Upper Mercer coal. Failing as 
it does it is no longer a guide to mark the top of the Potts\ T ille 
formation in these counties, but the Howenstein limestone 
directly overlying the Brook\ r ille coal comes in to be the guide in 
finding the horizons. 
6. The Putnam Hill, first recognized by Andrews, 1869, in 
Putnam Hill at Zanes\ r ille, Ohio, is the fifth limestone. It lies 
in rather heavy body through .Stark County and in western 
Mahoning County. It thins out toward the east and is absent 
in the eastern part of the county. The last trace of it was found 
at the Ewing mine in southwestern Canfield Township by Dr. 
Orton. The coal at 1078 feet aboA^e sea in the Furnace Run 
section marks its horizon and appears to be the Clarion coal of 
western Pennsyhmnia. It is worthy of note that in the interval 
between the Brook\ r ille, and clarion coals sandstone prevails 
through Mahoning County and is present through central 
