168 GEOLOGY OF OHIO. | 
backs,” which are the great drawbacks in the working of this seam. 
The sandstone seldom cuts out the whole body of the coal, but it reduces 
the seam to 2 feet or less in thickness. The boundaries of the channels 
are quite abrupt, the coal running down in a few yards from full thick- 
ness to unmineable size. 
The seam is also disturbed by clay veins to a considerable extent. 
Despite these drawbacks, it ranks second among Ohio coal seams as to 
quantity. The Brush Creek coal (Salineville Strip Vein) is commonly 
worked and classed with the Freeport coals, but as already shown, it 
does not really belong to the Lower Measures, and it will accordingly 
be considered elsewhere. 
