448 GEOLOGY OF OHIO. 
vegetation. The Drift gravel terraces which often overlie the blue clays 
were formed long afterwards. The subsidence increased so that the 
waters in the Second District were several hundred feet—probably not less 
than five hundred feet—above the present level of Lake Erie, as shown by | 
the heights of the bowlders on the hills. A few facts would indicate a 
somewhat deeper submergence than this. There is no proof that at any 
time was there in the Second District any great continuous sheet of 
glacier ice. There is no general planing off of the rocks, but every 
where among the hills where the northern bowlders are most abundant, 
are projecting knobs or outliers of soft rocks, which would naturally be 
an easy prey to such a destructive force as would be exerted by the 
movement of a vast glacier. Fine exhibitions of such outlying knobs 
and cliffs of soft sandstone rock are seen on the high table-land west of 
Lancaster dividing the waters of the Hocking and Scioto rivers. The 
Drift sea was around these small knobs, for all about are Drift bowlders 
and gravel. The small knobs could not have survived the abrading 
power of a great glacial sheet moving on irresistibly from the north. 
At the time of the greatest submergence, all, or very nearly all, of the 
Second District was below the water, and at that time no local glaciers 
were possible; but such glaciers would be possible both during the 
progress of the subsidence and that of the emergence. I have, however, 
found no strie upon any rock surfaces in the Second District. These, 
however, if made, would hardly remain in the soft rocks of the Waverly 
or of the Coal Measures, which are readily disintegrated under atmos- 
pheric influences. If found, however, they might have been made by 
the ice-rafts where they ground along the bottom or impinged against the 
slopes of the hills, or by the movements of shore ice. Pres. Orton reports 
such glacial striz in the high lands west of the Scioto, in Highland 
county, which he considers the work of a great continuous northern 
glacier. The great current in which the great ice-rafts floated appears 
to have moved in a southerly direction a little west of south, the eastern 
limit being in the western part of Muskingum county, and Ashland, on | 
the Ohio River. East of this general line I have found but a single 
bowlder on high ground, that‘in Washington county. This line was not 
the eastern limit of the water, but the limit of the floating ice. 
The Drift phenomena of the Second District connect themselves, with- 
out any perceptible change, with those of the great general Drift of the 
North. There is nothing wanting except striation of surface rocks, and 
these may have once existed. Local glaciers on the highest unsubmerged 
lands, the moving ice-rafts, and doubtless vast quantities of shore ice, 
may well explain the striz and their varying directions. The Drift 
