290 GEOLOGY OF OHIO. 
named, a two-benched coal, the lower bench averaging 1 to 13 feet, and 
the upper bench running from 3 to 6 feet in thickness. The upper 
bench has no regular slates or partings, but it is seldom found without 
irregular bands that give rise to considerable “ dirt” in mining. 
It cuts easily, but does not bear powder in excess. ‘Three cents 
worth of powder is enough for a ton of coal. Like the coals above 
named, also, it has a definite chemical type. It averages 53 per cent. 
of fixed carbon, and about 37 per cent. of volatile matter. It is mode- 
rate in water and ash, but rather high in sulphur. These facts have 
been already shown to belong to the seam generally, and to be as 
characteristic of it as any facts in its physical structure. 
It remains to describe in brief terms the leading mines established 
in this field. There are two sections of them, viz., those established 
on the Baltimore and Ohio Railroad, along Leatherwood Creek, east 
of Cambridge, and those established on the Wheeling and Lake Erie 
Railway (formerly Cleveland and Marietta Railroad), in the valley of 
Will’s Creek, and its tributaries south of Cambridge. 
There are four mines in operation along the line of the B. & O. 
Railroad, east of town. They are named as follows: 
Guernsey mine. 
Cambridge mine. 
Scott mine. 
Central or Norris mine. 
The first three of these have been established for a number of years, 
and a large acreage is already exhausted. 
The Central or Norris mine includes 350 to 400 acres of coal, in 
the southwestern corner of Center township. The coal has a natural 
thickness ofe5 feet. It sometimes gains two inches, and sometimes loses 
one or two in its undisturbed portions, but in the main it holds the 
measures above given. The structure of the seam is shown in the 
following figure. , 
The bottom bench is thought to contain the best coal, but it is 
somewhat more tender than the top coal, and as the “bearing in” is 
done in this portion of the seam, it is brought out mainly as small coal. 
The upper bench mines in large blocks, but it bears neither transporta- 
tion nor storage well. It is used almost exclusively for the production 
of steam, a large part of it being taken by the railroad company for its 
locomotives. It is well approved for this purpose, kindling easily, 
