115 
CURRENT. 
The effect of this low gradient is seen in the slight current 
found in the Illinois, a current so insignificant that Mississippi 
River steamboat men are wont to refer contemptuously to the 
Illinois River as a “frog pond.” The current is further im- 
peded, especially when the water level is below eight feet, by 
the presence of the four dams, which at low water convert the 
river into a series of slack-water pools. 
DISCHARGE OBSERVATIONS ON ILLINOIS RIVER AT LAGRANGE LOCK, 1887-1890. 
(Gage referred to low water of 1879; Price current meter used in 1888-89.) 
aes M | Mean Time required (days) 
Date feer) velocity (feet) | velocity (miles) to move from Utica 
( per second per hour to mouth, 227 miles 
Low water, 1887*...| 0.00 0.600 0.409 23.14 
August I, 1887 ....} 0.20 0.600 0.409 23.14 
December 21, 1888) 1.98 1.329 0.906 10.44 
December 20, 1888} 2.00 10277 0.871 10.86 
December 31, 1888] 2.95 1.539 1.049 g.02 
February 4, 1889..| 4.33 1.758 1.1098 7-90 
May 20, 1889...... 5.40 1.942 1.324 7.14 
April 8, 1889...... 5.01 1.852 1.263 7.49 
March 30, 1889....] 5.85 2.053 1.400 6.76 
March 25, 1889....| 6.72 2.258 1.540 6.14 
May 30, 1889...... 16.98 2.011 Dost 6.90 
March 8, 1889..... 7.65 2.554 1.741 5-43 
April 22, 1889..... FSIS 2.406 1.640 5.77 
March 11, 1889....| 8.36 2.572 1.754 5.39 
July 15, 1889..... 8.37 | 1.857 1.266 7.47 
JUDE OS TSO: en 106 a1 10.00 2.520 1.718 5.51 
{NNSA}, Hustle Ao sase 10.33 2.053 1.400 6.76 
January 18, 1890 ..|/12.80 2.547 1.737 5.45 
*Computed. +Backwater from the Mississippi River. 
As shown in the above table, the mean velocity per second 
of the current at LaGrange, forty-three miles below Havana, has 
been determined by the U.S. Army Engineers (see Marshall ’90, 
p. 2443) to range from .409 of a mile per hour at low water to 
1.754 miles at 12.8 foot stage—1.8 feet above bank height at that 
point. The velocity, in miles, per hour and the time required to 
move from Utica to the mouth at this rate are given in the 
table, having been computed from the data in the second col- 
umn, quoted from Captain Marshall’s Report. It will be noted 
that in a general way the velocity of the current increases as 
the river rises. This increase is, however, modified by the rel- 
ative heights of the water in different parts of the stream ; thus 
