320 
COAL-FIELDS OF OHIO. 
The geological structure of this coal-field is very 
similar to those already described. Some parts of 
the valley belong to the tertiary, some to the car- 
boniferous, and some to the red sandstone group. 
The remains of fossil plants are very numerous and 
beautiful, and the beds of red marl are of immense 
thickness, often as much as 40 feet, which, on ex- 
posure to the air and frosts, decompose into a red 
clay highly charged with iron, and disclosing nod- 
ules of red oxide of iron in considerable quantities, 
and shells of the genus wmo, which shows that the 
deposites were made in fresh water. In boring for 
salt water six miles above the mouth of the Mus- 
kingum in 1834, after passing through 40 feet of 
clay, they came upon a softer clay, mixed with sand 
and small fragments of wood, leaves, and seeds of 
monocotyledinous plants ; and under this a bed of 
woody materials, composed of the fragments of 
trunks and branches of trees, grapevines, seeds, 
and leaves. Under this was a deposite of 10 feet 
of fine sand mixed with clay, precisely such as we 
find in the beds of our ponds, and mixed with nu- 
merous fresh- water shells. The reader may learn 
the nature of the strata of the coal-fields of Ohio by 
recurring to the sections given in our chapter on the 
coal measures. An excellent species of coal, simi- 
lar to that of the Cumberland beds, and called by 
some Cannel coal, has been discovered on Will's 
Creek, in Guernsey county, of which an account is 
published in the 18th volume of Silliman's Journal. 
Hocking Valley Coal-field. — The Hocking River is 
about 80 miles long, and, with its tributary streams, 
drains a valley about 20 miles in width. The val- 
ley is generally hilly and broken, the hills rising 
from SOO to 300 feet high. In the centre of this 
valley bituminous coal is found in abundance, and 
with its associated minerals, iron and salt, will soon 
be extensive and lucrative articles of commerce. 
It is found in three principal beds, pursuing the 
