AA? GEOLOGY OF OHIO. 
whole region they have evidently been dropped in a very miscellaneous 
way, as if from floating icebergs. 
The largest bowlder seen in the Second IDiletrtions 3 is in a valley about a 
mile north-east of Lancaster. It is where it could not have been brought 
by any motive force acting in the immediate valley of the Hocking. 
High hills lie to the northward. An approximate measurement gave 
eighteen feet for its larger and sixteen feet for its smaller diameter. 
Smaller bowlders are not uncommon in the neighborhood, and one meas- 
uring seven by five feet is seen almost on the top of Mt. Pleasant, or 
about two hundred and fifty feet above the large bowlder just referred to, 
which lies near the base of the hills. The bowlders of this region show 
all the lithological characters of northern bowlders, being granites, 
quartzites, etc. Over the more western portion of the Drift area in the 
Second District we find more or less gravel on the high grounds, but to- 
ward the extreme eastern limit of the Drift no gravel has been observed. 
In the Hocking valley, and probably over a very considerable portion 
of the Second District, there is found in the low grounds a blue clay in 
which bowlders are occasionally seen. This clay is variable in thick- 
ness. It is sometimes only two or three feet thick, and, indeed, it is 
often not found at all. There is proof that in some places channels were 
cut through it, and much of it carried away, after deposition by currents 
of water during the Dritt era. I have never seen any of this clay upon 
the hills within the Drift areas. In this blue clay are remains of ancient 
vegetation in the form of trunks, roots, limbs, and twigs of trees, generally 
remarkably well preserved. In some localities nearly every deep well re- 
vealed fragments of such vegetation. The wood is apparently allied to 
the cypress of the lower Mississippi valley. It was buried by the mud 
brought in by the waters in the earlier portion of the Drift era. In the 
valleys of the Second District this Drift clay seldom, if ever, rests upon 
the rock bottom, but upon what I suppose to be the old alluvial sands and 
clays of the pre-glacial period. Above the Drift clay are the gravel and 
bowlders of the modified Drift, or terrace Drift, which were not deposited. 
until long after the deposition of the Drift clay. We have thus two 
features of the original Drift—the gravel and bowlders scattered upon 
the higher grounds, and the Drift clay found in the low valleys. 
The Valley or Terrace Drift—This is simply the sand, gravel, and 
smaller bowlders brought down the leading valleys and distributed along 
the banks in great sand-flats and gravel-bars. The materials in all 
cases come from the general Drift, except such as would naturally come 
from the valleys and adjacent hill-sides, and become intermixed with 
the rest. In the terraces of the Muskingum valley we find pebbles of 
