379 
WiptHs AND DreprHs, CHILLICOTHE TO Foot or PreortA LAKE, 
Low WaArTER, 1901 
* zi | F Depth 
ae Sa e Station wae tt. 
rafton | 5 nae 
Unwidened river— 
180.2 500 yds. below boat-landing, Chillicothe 494 24.0 
179.6 Foot Chillicothe Island 439 22.5 
Upper lake— 
178.4 Head Peoria Lake, one half mile above Rome 1,000 17.0 
aby rer) Rome 3,960 14.0 
175.5 One and a half miles above Spring Bay 5,463 1 
Middle lake— 
173.4 500 yds. below Spring Bay 1,024 10.8 
173.1 About half a mile below Spring Bay 1,850 16.8 
169.5 Three miles above Peoria Narrows 5,627 10.0 
168.0 One and a half miles above Peoria Narrows 5,280 » 20.1 
Lower lake— ) 
166.5 Peoria Narrows (above bridge) 658 D545 
164.2 Opposite work-house 3,922 12.5 
162.5 Opposite foot Main St. 1,760 10.8 
162.2 Lower wagon-bridge 870 5.1 
As we should expect, the upper soil strata in the channel through- 
out most of this section consist of dark-colored mud of a good depth. 
The mud layer is four feet deep in the channel at Chillicothe, and ranges 
from 7.5 to over 22 feet in depth at boring stations (U. S. Engineers, 
1902-05) in the upper, middle, and lower lakes, if we except a stretch 
of less than two miles in and immediately below Peoria Narrows. At 
the Narrows and just below, cap-rock comes to within four or five feet 
of the surface, and the upper stratum consists of a well-packed mix- 
ture of mud and shells. This is followed for about a mile by a deep 
upper layer of dirty sand and shells, after which (between Mile 165 and 
Mile 164) deep mud begins again and is continued to the foot of the lake. 
At the foot of the lake rock comes again to within eight feet of the sur- 
face, and the floor of the river just above the mouth of Farm Creek is 
formed by gravel fifteen feet deep—hard bottom of sand or sand and 
shells continuing from this point all the way to Pekin. 
Findings regarding bottom deposits at our collecting stations in 
1915 agree very well, as far as they go, with the data from the government 
borings, and are satisfactorily consistent with such data as we have on 
slope and velocity. The mud brought up by the dredges, except at Pe- 
oria Narrows, was all very dark in color, and the recent origin of much 
of it was indicated by the softness of the upper layers. Measurements 
