444 GEOLOGY OF OHIO. 



action which carried southward Drift materials and left them in terraces 

 along the streams, modified to some extent the old Drift, giving it a some- 

 what terraced character. 



There is in the Second District another and very distinct system of 

 terraces found on streams emptying into the larger streams bordered by 

 true Drift terraces. They may be called back-water terraces. When in 

 the Ohio, Muskingum, Hocking, etc., rivers, the water in the Drift era stood 

 eighty or ninety feet higher than at present, the back-water would set 

 back up all the tributaries. In this still water the sand and sediment 

 brought down these tributaries were depoisted, or, in other words, the still- 

 water areas were silted up, as mill-ponds often are. When afterward the 

 main streams gradually fell to their present level, these affluents cut 

 through the back-water beds and carried away much of the soft materials, 

 but left in many places fringing terraces, which tell very plainly how they 

 were formed. In these back-water terraces we find no true Drift sand and 

 gravel. The beds are entirely of home origin. Such terraces I have seen 

 on the Little Scioto River, above its junction with the Ohio at Scioto- 

 ville, on Duck Creek, and on the Little Muskingum River, in Washing- 

 ton county, and on Sunday Creek, in Athens county. I have no doubt 

 they are to be found on a large number of streams. 



When we carry back the study of our surface geology to the period 

 immediately antecedent to the Drift, we find that all the leading valleys 

 had been eroded by the same system of surface drainage which now ex- 

 ists. The general surface features of the whole State were the same as 

 now. The Scioto, Hocking, and Licking rivers drain by their upper 

 waters much of the central and level portions of the State, a region now 

 thickly covered with a mantle of Drift materials. They drained the 

 same area before the era of the Drift. The Drift agencies could not have 

 planed down or essentially modified this upper fiat country to any appre- 

 ciable extent — they merely covered it with debris. The same reason- 

 ing applies to the northern slope of the State. The Cuyahoga River, for 

 example, had, as shown by Dr. Newberry in Vol. I., in his report on Cuya- 

 hoga county, eroded a very deep channel, which was subsequently filled 

 with Drift. This stream flowed northward into a deep valley now occu- 

 pied by Lake Erie and by the Drift clays which form its bed. Similar val- 

 leys and channels of streams emptying into the Lake were doubtless filled 

 by the Drift. These facts furnished by Dr. Newberry tend to show that 

 the surface features of the State were essentially the same before the Drift 

 era as now. The clays, gravel, and bowlders of that period were laid 

 down upon a surface already brought into its present form and contour 

 by agencies at work during an indefinite period antecedent to the Drift 



