386 
(b) Foor or Peorta LAKE To Pexin (9 Mites) 
Hydrography—After passing over the high bar above the mouth 
of Farm Creek (foot of Peoria Lake) the river follows a comparatively 
swift and narrow channel to Pekin, the average velocity at a flood gage 
of eighteen feet, Peoria, being 191.64* feet per minute for the 9.8 miles 
between the foot of Main St. and the wagon bridge at Pekin, and the 
width (at low water of 1901) usually under six hundred feet. The aver- 
age slope of the water surface at the low levels of 1901 was two inches 
per mile, and 4.36 inches per mile at the high water of March, 1904. 
These average slopes and velocities are much greater than are met with 
in any other considerable section of channel in the one hundred and 
twenty-five miles between Chillicothe and Florence, and are four to 
seven times the figures for the 18.5 miles between Chillicothe and the 
foot of Peoria Lake. 
DECLINE IN ELEVATION OF WATER SURFACE 
Av. slope 
Reach Pee 1s a Ng inches 
per mile 
Low water 
Foot of Peoria Lake to Pekin 1901 9.2 2.00 
Flood stage 
i Mar, 15, 1903 9.2 3.45 
Flood stage 
oie Mar. 31, 1904 9.2 4.36 
Low water 
Chillicothe to foot Peoria Lake 1901 18.3 0.26 
Flood stage i 
f Mar. 31, 1904 18.3 0.64 
The channel floor is sand and shells, nearly denuded of mud, for 
most of the nine miles. At our 1915 collecting stations between Wesley 
and Pekin the bottom was hard, but opposite Pekin the hard bottom was 
overlaid with a very thin covering of soft silt. Between the 4- and 7- 
foot lines at Wesley in 1915 hard gravel bottom washed clean of mud 
was found both on the east and west sides. At the shore stations below 
the wagon bridge at Pekin six inches of soft mud was found on the west 
side and 12 to 36 inches on the east. Shore vegetation, except an occa- 
sional narrow fringe at the bank edge, is wanting. 
At the low water of 1901 the bank to bank width of the river be- 
tween Peoria and Pekin was usually between 400 and 600 feet, only 
a very short stretch just below the mouth of Farm Creek much exceed- 
ing 600. Depths in the wider and shallower stretches ranged from 7 
to 8% feet; and in the deeper and narrower ones betwéen 10 and 18 feet. 
Average depths at recent low levels (gage of July—October, 1910-1914) 
have been about 314 feet more than these figures. The connecting lake 
* Table, p. 377. 
