442 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 District 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 Drift 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 wej.1 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-fiats 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 



