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, thie 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. . lhave 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 flat 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 
