HOCKING VALLEY COAL FIELD. 913 © 
Map OF THE CoAL FIELD. 
A map accompanies this chapter, in which the Hocking Valley 
field is shown, together with some contiguous territory. The areas 
occupied by the Middle Kittanning seam in this district are laid down, 
and that portion of the seam which is 5 feet or more in thickness, and 
which by the definition here given constitutes the? Hocking Valley 
field, is separately distinguished. The outer margin of the Lower 
Mercer limestone and the boundary of the coal measures are also laid 
down upon the map. These last outlines agree closely with each other 
in some parts of the field. 3 
The most important feature of the map is the representation of 
the areas of thick coal. A few statements will here be in place as to 
the methods employed and the principles recognized in assigning the 
boundaries of these areas. 
On the north-west and west, the outcrop of the seam is easily 
followed, and here, therefore, comparatively little difficulty is found in 
laying down the boundary. ‘The line was not, however, instrumentally 
determined for this part of the field, but was fixed by reference to farm 
and section lines and to roads and streams, the scale of the map, viz., 
2 miles = 1 inch, not demanding nor rewarding minute accuracy. 
From Shawnee eastward, the boundary between the thick and the 
thin coal of the seam lies mainly under heavy cover, and for its loca- 
tion we are dependent upon the information gained from mines and 
drill holes. There are often reasons why those who have expended 
money in drilling do not choose to make public the knowledge that 
they have gained. There may, therefore, be facts in the possession of 
some parties, with which the boundary, as here laid down, will not 
exactly match. All, however, agree that the transition from thick 
coal to thin is abruptly made, and it is believed that future develop- 
ment will not greatly change the line as here given. Many of the 
facts used in determining this boundary were furnished by Col. James 
Taylor, of New Lexington, and Messrs. Black, of Buchtel, and Cor- 
coran, of Corning, but these gentlemen are not made responsible for 
the boundary as here laid down. 
The boundary between 5-feet coal and thinner coal in the south- 
west corner of York township and in the south-east corner of Starr 
township, is not as definite as could be desired. There is a more 
58 G: 
