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 stria? 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 striae 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 unsubroerged 

 lands, the moving ice-rafts, and doubtless vast quantities of shore ice, 

 may well explain the striae and their varying directions. The Drift 



