914 GEOLOGY OF OHIO. 
gradual reduction of the seam here than on the northern boundary. 
Much of it is under cover, and in the outcropping portion but little 
mining has been done, so that the opportunities for observation are few 
and unsatisfactory. In several of the eastern and southern sections of 
Starr township, more than 5 feet of coal is claimed, and the claim is 
recognized upon the map, but in any case the area of thicker coal can- 
not be large. The Carbondale mines have been driven a long ways in 
this direction, and all of their entries show less than 5 feet of coal, the 
average, indeed, not exceeding 4 feet. 
In Sections 23 and 29, Brown township, Vinton county, coal 
measuring more than five feet is found at one or two openings of this 
seam, but nowhere else in the township is it known to yield even 4 feet 
of coal. A small area is credited with 5 feet coal in these sections. 
The continuity of the coal is inferred and is indicated upon the 
map for all areas upon the several sides of which the seam is found, 
either in outcrops or in shafts and drill holes. When, for example, 
the seam goes under cover in the direction of its dip and is found again 
as soon as its proper level is reached in the valleys to the south and 
east of the first-named outcrop, the whole intervening territory is 
represented as possessing the seam, unless there are known facts to the 
contrary. 
The final disappearance of the seam to the south and east is indi- 
cated upon the map by broken lines, but so far as its presence has been 
fully demonstrated by trial pits or by working shafts, it is not so 
designated. 
Where the seam descends in good volume and condition beneath 
its final cover, some extension of it in the direction of its descent must 
be inferred, but recent developments, especially in Monroe township, 
lead to the opinion that its entire eastern boundary is likely to prove 
abrupt. 
It is to be distinctly understood, that no claim is made that all of 
the territory marked as possessing the thick coal has been adequately 
proved. In those portions of the field most fully tested by mining, or 
by drilling, many breaks in the continuity of the seam have been found. 
The coal is reduced or irregular in thickness, or is entirely wanting. 
Where such “ wants” or irregularities are known, the fact is noted 
upon the map by broken lines, but exploration has not advanced far 
enough as yet to make it safe to lay down the boundaries of these 
