270 
Ohio Valley again between Enterprise and the eastern part of Warrick 
County. . 
To the erosive power of the river is to be attributed the greater part, if 
not the whole, of the valley now occupied by Lake Plain. In Pigeon Plain 
the worx done was simply the deepening, and it may be a little broadening, 
on the eastern side of a broad valley, extending from the northeast, which 
the river entered after cutting through the rock in Lake Plain. <A portion 
of this more ancient valley extending from the northeast still remains in- 
tact north of the terrace. The terrace being simply the northern boundary 
of the Ohio’s down cutting in the more ancient valley. 
The work done in cutting out the Lake Plain valley through solid 
sandstone, limestone and shale is probably just about equal to the deepen- 
ing of the more ancient Pigeon Plain. This would explain in great part 
at least the conspicuous difference in width which exists between various 
parts of the old river cut-off. 
Nearly all the swampy area mentioned above, that is the lands drained 
‘by Swan Pond, Lake Drain, Lake, Sweezer’s Cow Pond, and Hoop-pole 
ditches are simply portions of the old channel which have been but imper- 
fectly filled. They are in some respects similar to the half-filled old river 
‘cut-offs and marshes of the lower Mississippi, but differ in that the cut-offs 
of the Mississippi are made through soft, yielding alluvium, while this one 
has been made, in part at least, through solid rock. 
The ancient stream plains which the Ohio entered after cutting through 
the hills two miles east of Richland is locally called Pigeon Valley, but as 
has been intimated before, is not at present occupied by Little Pigeon 
Creek. A cross section (see Fig. 3) of the country running southeastward 
along a line drawn from a quarter east of the middle of section 35, town- 
ship 5 south, range 7 west, to a quarter south of the middle of section 6, 
town 6 south, range 6 west, shows Little Pigeon Creek in a young, nar- 
row, V-shaped, rock-bound valley separated by a hill of sandstone thirty 
(30) feet high from the broad flat alluvial-filled valley east of it. Well sec- 
tions in this valley reveal in a few places a depresson 60 feet deep filled 
with blue sand. 
Near the base of the hills, bounding the River Plain, north of Enter- 
prise is a series of gravels and sands which are of considerable value 
in determining the age of the old Ohio cut-off. The gravels rise 40 feet 
in the hills near the junction of River and Pigeon Plains, but after the 
hills along the eastern part of Pigeon Plain are reached they are nowhere 
