116 



backwater from the Mississippi River or from a tributary may 

 cause the river to rise and at the same time check the current 

 above to some extent. Such modifications are often, however, 

 local and temporary, and soon give way to the rush of the current. 



Mr. C. A. Abrams, a steamboat man of many years' experi- 

 ence upon the Illinois River, writes me that the current is as 

 much as three miles an hour at high water and on a rising river, 

 while at low water it amounts to "nothing" except on the 

 bars and in the narrower and shoaler parts of the stream such 

 as those near Havana. 



Capt. J. A. Schulte, of Havana, 111., whose experience in 

 steamboating on the Illinois River, especially near Havana, is 

 extensive, has kindly sent me data which indicate that at high 

 water the current from Copperas Creek down to Havana is about 

 2.5 miles per hour, and at low water about 1.28 miles. He 

 further states that he has observed that the current above 

 Havana is strongest when the river is bank-full and slackens 

 somewhat when the river overflows, while below Havana the 

 current is strongest at times of overflow. It is probable that 

 the elevated bottom-lands above the mouth of Spoon River 

 cause this difference. 



A slightly greater rate than the mean quoted from the U. 

 S. Engineers' Report is indicated in mid-channel by a few in- 

 adequate tests which we have made at the plankton station, near 

 Havana, by means of a vertical float reaching within a foot of 

 the bottom and projecting but a short distance above the sur- 

 face of the water. A test made September 29, 1897, — when the 

 river had been standing at the lowest levels reached since the 

 dam at LaGrange was built (1.7 — 2.05 above low-water mark on 

 gage) for forty-eight days and had not fluctuated during the 

 week preceding, — showed a current of .720 of a mile per hour. 

 Steamboat men say that, owing to the proximity of the Spoon 

 River bar, the current is as rapid at low water at this point as 

 at any place on the river. A similar test made June 22, 1898, 

 when the river was at 10.7 feet and was falling at the rate of 0.2 

 of a foot per day, showed a current of 1.033 miles per hour. At 



