566 GEOLOGY OF OHIO. 
always be found and recognized in its proper place in the column, it does 
not follow that it should always maintain the same character, even ap- 
- proximately. On the contrary, it is not unusual for it to change in the 
course of a few miles—sometimes even in the same hill—from a workable 
bed of several feet, to a worthless seam ofa few inches in thickness. 
Hence, there is no safety in figuring up an aggregate of so many feet of 
workable beds, in any locality, until these beds have there been actually 
opened and proved. The indications afforded by borings, are generally of 
very uncertain character, as respects the thickness of the coal beds and 
the quality of the coal. It is, without doubt, often the case that the beds 
of black shale passed through are called coal, and when one occurs as the 
roof of a coal bed, it serves to add so much to the thickness of the latter. 
By remarking, in the description of the townships, how rare it is for 
two workable beds to be found in the same locality, and how seldom any 
bed at all is worked below the sixth bed of the series, it can hardly be 
safe to estimate the total average distribution of the workable coal in the 
county, at much more than the thickness of this one bed; and this, 
taking into consideration the probability that some of the lower beds 
will yet be worked below the level of the valleys, where their range is 
unbroken. It is to be hoped that the lowest bed of all, about which very 
_ little is now known, may be found as productive and valuable as it is in 
the counties to the north, in which event the estimate given above would 
prove too low. The sixth bed is a very remarkable one, for the regular- 
ity 1 maintains, not only through this county, but over several others— 
even to the Pennsylvania line, and into that State. It here varies but 
little from four feet in thickness, and is everywhere depended upon as 
the most valuable bed of the lower Coal Measures. Throughout its great 
extent, even into Holmes county, and to the Ohio River, at Steubenville, 
it may be recognized by the peculiar purplish-ash. The heaps of it seen 
by the farm houses, show to the passer‘by, almost always without fail, 
whether it is this coal, or some other bed that supplies the neighbor- 
hood. 
Of all the strata, the limestones are the most persistent, and serve as 
the best guides for identifying the coal beds that accompany them. 
There are two bands of these, in particular, that are most useful in 
this respect. Both are fossiliferous, often abounding in crinoids and 
shells. The upper one, called the Gray limestone, is found varying in 
thickness from one foot, or less, up to six feet ten inches. It lies imme- 
diately on the coal bed known as No. 4. The lower one, called the Blue 
limestone, has about the same range of thickness as the gray, and is 
sometimes only twenty feet below this. 
