376 
In our opinion and that of the most intelligent and observant fisher- 
men, the lakes are_the favorite feeding grounds of the larger and more 
common fishes, and this opinion is supported by the fact that the lakes 
have a more abundant food supply per acre than the river, and that the 
heaviest fish-yields come from sections where the ratio of lake areas to 
Tiver is greatest. 
The average weights of the yields of the inshore bottoms of the 
Illinois River lakes in 1915 were about five times as great per acre as 
those of the glacial lakes of northeastern Illinois in 1916, and the com- 
position of the faunas was also widely different, mollusks occurring in 
the latter in relatively insignificant proportion and being nearly all of 
the smaller species. The weed faunas of Fox and Pistakee lakes were 
almost wholly made up of small crustaceans and insects, the former 
predominating, although the total weights were not very much less than 
those of the Illinois system. 
Hydrography and Bottom Fauna, Illinois River, — 
Chillicothe to Grafton, July—October, 1915 
(a) CHILLICOTHE To Foot or Peoria Laxe (18.5 Mires) 
Hydrography.—tii the Illinois River is a sluggish stream considered 
as a whole, in comparison with most other important American rivers, 
the grand prize for local leisureliness of movement belongs to the short 
stretch between Chillicothe and the lower end of Peoria Lake, where, 
in March, 1903, at a flood stage of approximately eighteen feet above 
old low-water marks at Peoria, it took ball floats twenty-nine hours and 
fifty-nine minutes to make a total distance of 17.7 miles, the average rate 
per minute being 51.94 feet, and per hour, 0.59 mile. At a gage of nine 
feet, Peoria, which is almost exactly the mean level of the month of 
August, 1914, and represents the lowest water in this part of the river 
in the past seven years, these rates would be reduced to 25.97 feet per 
minute or 0.29 mile per hour—a total time in transit of fifty-nine hours 
nw 
and fifty-eight minutes for the 17.7 miles. 
These velocities compare with an average of 229.47 feet per minute 
or 2.60 miles per hour at a corresponding flood gage for the 33.9 miles 
Morris—Utica ; and with 115.43 feet per minute or 1.31 miles per hour 
for the 229.6 miles between Utica and Grafton. Above Peoria only 
the 12-mile section Henry—Hennepin has a current approaching the low 
figures found between Chillicothe and Peoria. In the other short reaches 
above Peoria, and in all below Peoria except the section of 8 miles between 
Liverpool and Havana (with 66.00 feet per minute, or 0.75 mile per 
hour), average flood velocities are over 100 feet per minute (1 mile per 
hour). The greatest velocities below Utica occur in the 9.8 miles between 
Peoria and Pekin (with 191.64 feet per minute or 2.17 miles per hour) ; 
and in the reaches below Florence, which have over 180 feet per minute, 
or more than 2 miles per hour. 
