THE LOWER COAL MEASURES. 263 
tion of the coal field of Ohio where there has been a tithe of the dis- 
turbance that occurs in the vicinity of Mineral Point. The disturbance 
is shown in its most marked phases in a cut of the Valley Railway, a 
mile above Mineral Point. The rocks of the Kittanning Group, and a 
part of the Freeport Group are here found in a synclinal fold, the 
structure of which is complex. There is a northwesterly dip of 60° to 
75° in part of the series. The Lower Freeport coal and limestone are 
shown in the railroad cut, as well as the Middle Kittanning, No. 6, the 
former being 18 inches thick. The Upper Freeport coal does not 
appear, but a coarse sandstone, apparently the Mahoning, is shown in 
the upper portion of the section, lying horizontal and unconformable 
on the edges of the upturned series. This fact fixes the date of the 
disturbance, if the reference of the sandstone is correct. In any case 
it brings out clearly the fact, not hitherto recognized in Ohio geology, 
that a considerable disturbance occurred near the end of the Lower 
Coal Measure period in this portion of the State. 
The results of this movement affect quite seriously all mining opera- 
tions in this field. The disturbance is shown in Holden’s old mine, at 
Mineral Point, in “clay veins” without number, in rolls and breaks in 
the coal, and sometimes in a doubling of the coal seam for a short 
distance. The coal has been found to rise at an angle of 45° in the 
mine, and to pitch downwards after a short distance at an equal angle. 
In short, there is not another mine in the State that makes any near 
approach to such irregularity as is shown here. The seam throughout 
this field is more or less involved, but the trouble seems to have 
culminated in the vicinity of Mineral Point. 
The seam is not opened in Lawrence township to any extent, but 
there is proof of its presence there at some points in fair development. 
Its horizon is reached in Fairfield in several of the valleys, but the coal 
has not been reported here. In Dover townst.ip it is again quite largely 
worked, and the characteristics already given for the seam will apply 
without change to this locality. It is cut by many “clay veins,” and 
every mine in it meets with more or less trouble, but still it is a basis 
for quite extensive work. ‘The largest amount of coal has been taken 
from what is known as the Bodey or Wilhelmi Bank, opposite Canal 
Dover. The structure of the seam is shown in the accompanying figure. 
The deposit of pyritous slate represented in it is abnormal, and is only 
