334. GEOLOGY OF OHIO. 
TIMBER. 
In the broad valleys of the streams the native timber was mainly hard 
maple and black walnut; of the latter a very large part was destroyed 
before its value was known, but very much has been cut and shipped to 
market. The large sugar maples in this district seemed a strange thing, 
but the thorough drainage afforded by the deep deposit of gravel fully 
explains their presence. If the alluvium rested upon clay, we should 
find soft maple, elm, and sycamore growing upon it, but no sugar maple. 
On the Waverly hills a mixed forest of maple, beech, hickory, oak, and 
pepperidge; in a few places on the borders of the stream hemlock, and 
on the ridges where the Waverly Conglomerate comes to the surface, 
chestnut. On the Coal Measure rocks the predominating timber is oak. 
On all the hills are scattered trees of whitewood, cucumber, black and 
white ash, and elm; the latter three being most abundant where the 
original glacial Drift remains. 
GEOLOGICAL STRUCTURE. 
The series of rocks exposed in the county comprise about two hundred 
and seventy-five feet of the Coal Measures, and about three hundred feet 
of the Upper Waverly, but borings for oil have extended our knowledge 
of the strata down to the Huron shale, and have afforded important in- 
formation in regard to the character and thickness of the sub-carbonifer- 
ous rocks. 
The following is a general section of the rocks underlying Knox county, 
as made known by observations of rock exposures and by the borings for 
petroleum: 
