Nov., 1910.] 
An Open Valley near Harrisburg , 0. 
213 
a larger valley and a broader valley floor upstream than has this 
little stream in question. Thus we conclude that it must have been 
made by a much larger and longer stream. 
Another theory is that the Darby itself flowed through this 
valley at one stage of its development, and later changed its 
course for the present one. But the question arises, if the Darby 
had this valley for its course in some period of its history, why is 
the valley so much smaller than the present Darby valley? The 
Darby valley is from a quarter to one-half mile or even more in 
width, while the open valley is only one-eighth of a mile in width. 
Again, the Darby for many miles farther up its course has a much 
wider valley than this open valley. This width of the Darby 
valley north of the point where the open valley enters, opposes 
the idea that the river in some period of its history flowed through 
the open valley. So we must abandon that theory. 
A further solution is proposed, namely, that at an early period 
in its history, perhaps while still under the ice, the Darby divided 
its course so that about one-third or one-fourth of its waters went 
through this present open valley, while the greater portion of the 
river flowed in its present channel. After time enough to make 
this valley, the eastern branch succeeded in cutting below the 
western and thus captured its waters. The open valley was 
thereby left as an abandoned channel of a portion of the Darby. 
The floor of this open valley at the point where it joins the Darby 
is about fort}' feet above the present level of the flood plain of the 
Darby. This shows how the Darby in its eastern branch was able 
to take the waters of the western branch. 
These open valleys occur along the Scioto River in several 
places in its course and are attributed to the same cause as the one 
along the Darby. The division of the streams sometimes, no 
doubt, took place under the ice sheet during its last stages. Some- 
times an island may have been the cause, separating the stream 
into parts and causing it to find two separate courses. In such 
cases the inter-stream area should be sandy. 
This Big Darby valley has been abandoned long enough for 
the present northward stream to have graded a slope for its 
entrance into the Darby while the stream following southward 
down the slope once led by the old stream now has in its lower 
course a considerable flood plain some thirty or forty feet below 
the abandoned valley floor, leaving the old flood plain beautifully 
terraced as is that of the Darby itself. 
