224 , GEOLOGY OF OHIO. 
a thin streak of coal, which, however, is of no value in this county. In 
no other portion of the county was this limestone observed. 
Coal No. 7a is of value only in Liberty, Jefferson, and Monroe town- 
ships, where it is between three and four feet thick, and in these town- 
ships is used only because no other coal is accessible. Usually it is of 
poor quality. Overlying it is a heavy sandstone, containing many vege- 
table remains, and apt to be conglomerate. As in Harrison county, iron 
ore is not unfrequently found above this bed, but, as far as observed, the 
quantity is unimportant. Occasionally, blackband is found over No. 7, 
and that may prove to be an ore horizon of some local value. 
Coal No. 7 is of little importance north of the Central Ohio Railroad, 
and its variations are exceedingly perplexing. At one locality it is five 
feet thick ; two miles north-west it is eight inches; three miles farther 
north it is three feet; after which to the north it varies from ten to 
eighteen inches. It can be traced through Cambridge, Center, Liberty, 
Monroe, and Adams townships, but is worked only in Center and Cam- 
bridge. South of the railroad it is of considerable value. The sandstone 
above this bed is very massive, and apt to be conglomerate. The shales 
resting on the coal are dark-colored, and occasionally become true black- 
band. ; 
Coal No. 6 was observed only in Liberty, Wheeling, and Knox town- 
ships, in each of which it is extensively worked for domestic use. It varies 
from thirty-three inches in Liberty to four feet in Knox. The coal is 
usually of good quality. The shales. overlying it are full of ferruginous 
nodules, having fragments of zinc blende as their nuclei. At the junc- 
tion of the shales with the sandstone above a large quantity of nodular 
iron ore occurs, but it is so intimately associated with the sandstone as to 
be practically worthless. 
Coal No. 4 was seen at several localities in Liberty and Wheeling town- 
ships. The gray limestone above it contains great numbers of Spirifer 
lineatus, and is not persistent. The coal varies from eighteen inches to 
five feet, and is worked only in Liberty township. The distance between 
this bed and No. 6 is very variable in this county, and equally so in Mus- 
kingum county, as will be seen by reference to that report. In south- 
east Liberty No. 4 is only twenty-eight feet below No. 6. Five miles to 
the north-west the distance is somewhat more than forty feet; while five 
miles farther to the north-west it is one hundred and five feet. This evi- 
dently shows that the subsidence which put a stop to the formation of 
a coal-bed bore no fixed relation in its local extent to the length of time 
intervening before the formation of the next bed above. 
Coal No. 3 was seen only in Wheeling township, the blue limestone 
