DRAINAGE OF SOUTHERN INDIANA 7, 
low pass was formed between the westward flowing streams 
and those flowing eastward which formed the corner of the cul de 
sac above referred to." 
During the glacial period the ice passed immediately east of 
the Knobstone hills in western Bartholomew county, through 
Jackson, and crowded up against the projecting knobs known as 
the Silver hills in Scott county (D, Plate VI). If the suggested 
conditions existed at that time, the triangular cu/ de sac in the 
Knobstone hills would have had its eastern outlet completely 
shut off by the ice, and the basin thus formed would have filled 
with water from the melting ice until it poured over the pass into 
the westward flowing streams; the pass would have been cut down, 
and finally the stream would have become firmly established in 
its new course, and into this it would have led the waters of its 
entire drainage basin as the ice retreated. 
The shape of the cud de sac, in which the Brownstown hills stand 
with the eastward projecting Silver hills (D, Plate VI), against 
which the ice was pushed to the south, makes this second hypoth- 
esis seem probable. The principal objection to it is found in the 
general width of the valley of East White River below the mouth 
of the Muscatatuck. There are no zarrows in the canyon to cor- 
respond with the position of the supposed original divide between 
the east and west flowing streams. The bottom, or present flood 
plain, of the valley varies in width from one-half mile to over 
one mile, and would certainly seem to antedate the ice invasion. 
THE WESTERN DRAINAGE AREA.’ 
The main drainage lines of the western area are such as 
would be developed by the structure of the country, and they 
‘A condition of affairs quite similar to that hypothecated here exists at the present 
time in townships Isouth and I north, 5 and 6 east,where Muddy Fork of Silver Creek 
forms a triangular valley opening out to the east, while the divide between this stream 
and Blue River, which flows southwest is quite low. (/, Plate I.) 
?The drainage of southern Indiana, in its relations to the glacial period, is dis- 
cussed and mapped by LEVERETT in Monograph XXXVIII, U.S. Geol. Surv., p. 97 
et seg. See also Mr. LEVERETT’S discussion, Pt. IV, Eighteenth Ann. Rept. U.S. 
Geol. Surv., pp. 446-58. 
