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trenchment is not less than 200 feet. Remnants of the gradation plain are 
perfectly preserved on both sides of the present intrenched valley to the 
northwest of Borden. The remnants are more extensive farther up the 
stream where the piracy occurred at successively later periods. Finally the 
whole of the old yalley is seen for a stretch of about three-fourths mile in 
section 30 stretching southeast from old Pekin. Old Pekin is built on the 
Blue River wbrein of it. (See Figure 2, 3, and 4.) This portion of the 
old valley is more than one-half mile wide, as wide as the present valley of 
the Muddy Fork of Blue River. It was made by a stream comparable in 
size to this Fork of Blue River. It drained an area of approximately 35 
square miles while that of Muddy Fork of Blue River drains approximately 
40 square miles. 
The few tributaries of the old drainage course yet remaining are shallow 
streams. The largest one comes in from the south. It is not discernably 
below the old valley flat in the northeast one-quarter of section 31, (See Fig. 
4). On approaching Blue River it is trenched broadly into the old alluvial 
deposits, and enters Blue River accordantly. The small tributaries from 
the north have scarcely been able to transport their load across the old 
valley flat, and have the appearance of having slightly aggraded the old 
valley flat where they debouch upon it. 
Fig. 2—View of the old valley where it joins the valley of the Muddy Fork of 
Blue River near Pekin. View taken from the road on the hill in the northern half of 
Sec. 31. Old Pekin in the distance. 
The divide between the present streams on the old valley flat southeast 
of Old Pekin is only 30 feet above the valley of Blue River. ‘The old valley- 
flat projects above the valley or Blue River as a terrace. It appears that 
Blue River has cut its valley down something like 30 feet since the stream 
adjustment has taken place, but such is probably not the case. It is evident 
