18 GEOLOGY OF OHIO. 
Clarion coal is found from 15 to 30 feet below the limestone. By some 
of the Pennsylvania geologists the Scrub-grass coal is held to be a split 
from the Clarion. (Second Penna. Survey, V.V., p. 49). From this 
point of view the seams can well be designated the Lower and Upper 
Clarion coals. The lower seam has considerable economic value in 
Western Pennsylvania. 
At a general distance of 30’ to 40’ above the limestone, but some- 
times coming within 10’ to 15’ of it, there is found a coal seam that is 
as persistent and as largely worked as perhaps any seam of the lower 
series. It is the Kittanning coal of Rogers or the Lower Kittanning 
coal of the Second Pennsylvania Survey. 
Below the Kittanning coal oceurs the Kittanning clay, by far the 
most important deposit of its kind in Western Pennsylvania or Kastern 
Ohio. This seam is the basis of a large manufacturing industry in the 
Ohio Valley. 
The elements named above, beginning with the Lower Kittanning 
coal, and ending with the Clarion coal, constitute what may be called 
the Ferriferous Limestone Group, a set of beds so well characterized, 
possessed of so much and so varied economic value, and so largely 
worked, that to follow them through the districts which they occupy is 
comparatively a plain and easy task. 
The Ferriferous Limestone Group is represented in the accompany- 
ing general section, Rapes We 
FIGURE Y. 
rE RRI FERROUS LimEsTONE GROUP 
! Kittoonind lesa Gace bent es 
Kitewtiug Clay aa 
Ss ondy Sh ale Sx Sandskome)___4 Sh eed Be 
| Bulve se eerie fyssi isi ch sect ae a 
| Ferviterous Wanenowe AS _----- Ee 
| Secul Grass Gea useccusesty alae IIIA \\\ 
| Shales ete. : 
Clea hy ow ex Casal. eR LES SN Seyee Dhue 3 ere pawecne os 
Bee oes | 
