13° 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 expres.~i:/n 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 

 without 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 Brookville coal. The Homewood sandstone 

 so conspicuovis in Pennsylvania thins down on entering Ohio and 

 becomes shale in the Furnace Run section but regains its massive 

 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 Pottsville 

 formation in these counties, but the Howenstein limestone 

 directly overlying the Brookville coal comes in to be the guide in 

 finding the horizons. 



6. The Putnam Hill, first recognized by Andrews, 1869, in 

 Putnam Hill at Zanesville, Ohio, is the fifth limestone. It lies 

 in rather heavy body through vStark 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 above sea in the Furnace Run 

 section marks its horizon and appears to be the Clarion coal of 

 western Pennsylvania. It is worthy of note that in the interval 

 between the Brookville, and clarion coals sandstone prevails 

 through Mahoning County and is present through central 



