346 
The location of the primary divide, if the preglacial drainage lines 
have been established correctly, can be followed in a general way by a 
glance at the maps (Pls. IV, V). The portion of the divide, and the most 
important portion, between the Wabash and Erie basins has not yet been 
satisfactorily located. Upon its accurate determination depends most of 
our knowledge of the outlet of the drainage of southern and southeastern 
Ohio. Some general facts concerning it will appear in the following dis- 
cussion. From near Mt. Vernon east and southeast to New Martinsville 
the divide is well located, and the area northeast and north drained to the 
northward. The present Ohio is seen to fall into two divisions on this 
basis. 
The portion of the Ohio above New Martinsville reached some northern 
outlet by three different streams (Pl. V). These are easily located, with a 
few minor exceptions, for the preglacial cols are usually apparent. Carll 
(17) called the attention to a narrowness of the Allegheny valley at 
Thompson’s gap and shows that the rock floor of the valley, now covered 
with drift, sloped northward from the divide, and he concluded that the 
headwaters of the Ohio once drained northward by this valley. He con- 
cluded that the outlet was through the Cassadaga valley, but Chamberlin 
and Leverett made later studies, found the Cattaraugus creek valley the 
deeper and more direct route to Lake Brie and concluded that the outlet 
was by that valley (65: 129-30; 21: 101: 159-60). 
Another prominent col just north of Parker separates another section 
of the Allegheny which included the Allegheny to a little below Oil City. 
French creek reversed to Meadville and an old valley continuing northward 
to some preglacial valley in the Eric basin were the main stream in the 
system, for here is an old, wide rambling valley in which Cussewaga creek 
flows south to join French creek. Leverett accepts this outlet, showing that 
the drainage could not have been up French creek above Martinsville, be- 
cause of a col in French creek valley a few miles northeast of Meadyille 
(65: 184-8). 
The next lower section of the preglacial system, whose main stream 
was the Beaver reversed, and the Grand, is variously known as the Spen- 
cer (35), Old Lower Allegheny, Pittsburg (109) and Grand river (21). It 
has been well studied and most authors agree upon its course. The drift 
is deep north of the source of the Beaver; but the old gradation plain 
slopes north to Sharon and then upward farther north, A depression 
