silts over the old bed rock floor is much deeper than a normal stream of 
its size should have possessed. With the beheading of this ancient drain- 
age in the earlier stages of successive piracy the drainage remaining 
would not be able to retain as low a gradient as the previous larger more 
vigorous drainage. The result would be aggradation of the valley. If this 
is a correct interpretation, the fact that the present valley of Blue River 
is 380 feet below the old valley flat is not altogether a result of erosion down- 
ward of its bed since the stream adjustments have been made. Again this 
aggradation of the lower part of the valley will aid in explaining the ex- 
ceptionally low gradient of the old northwestwardly flowing stream as de- 
termined by the relative elevations of the remnants of the gradation plain. 
At Borden it is 755 feet and in the preserved lower portions it is 730 feet 
where it is lowest. This would be a gradient of less than five feet to the 
mile. 
The Potential Future of Muddy Fork of Silver Creek. 
When one realizes that the larger part of Muddy Fork of Silver Creek 
has been made at the expense of the Blue River drainage system, and that 
Fig. 5—View showing gravel and silt overlying the bed-rock floor of: the old 
abandoned yalley southeast of Pekin. Monon R. R. cut in the southwest corner of 
See. 29, about 2 miles southeast of Pekin. 
the last annexation was relatively recent, one must inquire whether the 
drainage adjustments are yet complete. It needs little more than casual 
observation to note that the piracy is far from complete in the Pekin- 
Borden region. The tiny stream shown on the topographic map in the 
southeast corner of section 30 was really the latest accession. This was 
a mere wash leading to the northwest before the Monon Railroad was built 
through the old col. The cut necessary for a more gradual descent into 
the Silver Creek system allowed the wash to send its waters into the 
