STRATIGRAPHICAL ORDER. 51 
extends along the valley for more than half of the distance to be trav- 
ersed. The coal is known as the Clay Vein, the Potters’ Vein, the 
Sulphur Vein and the Creek Vein. Above it lies the Middle Kittan- . 
ning coal, here known as the Strip Vein or the Block Vein. The seam 
is thin, but its quality is generally excellent, and it is worked in many 
small mines. The interval between the two Kittanning coals ranges 
from 18’ to 30’, but the average would not be much more than 20 feet. 
A seam not before reported makes its appearance in almost all of 
these sections. It lies about 40 feet above the last named seam, and in 
accordance with the Pennsylvania notation may be designated as the 
- Upper Kittanning coal. It is commonly called the 18-inch vein, and 
though thin, is opened in many local banks for household supply. Its 
quality is good. 
The main coal of the valley is, however, the Lower Freeport seam, 
which is here known as the Roger Vein. The interval between it and 
the Clay Vein ranges from 86 to 140 feet, and averages about 110 feet. 
This seam is of fair thickness, viz., 3 to 4 feet throughout a good deal of 
territory, and the quality is also good. It is always underlain with its 
limestone. 3 | 
The Upper Freeport coal, the Big Vein of Salineville and the Yel- 
low Creek Valley, has but a very sparing development south of Yellow 
Creek. A “blossom” frequently marks its place, and its limestone is 
sometimes met, but the coal itself has not been found south of Yellow 
Creek Station. 
The Brush Creek coal, which is the Strip Vein of Salineville and 
the Groff Vein of the lower Yellow Creek Valley (Newberry’s No. 7, 
throughout this region) is a much more constant element. It is worked 
at a number of points, and is everywhere of good quality. Its elevation 
above the Clay Vein ranges from 192 to 225 feet, giving an average of" 
207 feet for the sections measured. 
Two other elements are reached in many of the sections, viz., the 
Crinoidal limestone and the Pittsburgh coal. The former lies at an 
average distance of 320 teet above the Lower Freeport coal (Roger 
Vein), and of 430 feet above the Lower Kittanning. The Pittsburgh 
coal at the most northerly point that it reaches in the State, viz., in 
Saline township, at the southernmost bend of Yellow Creek, is 468 feet 
above the Upper Freeport coal, which would make it about 530 feet 
above the Lower Freeport seam. This interval increases to the south- 
ward. 
