547 



Des Plaines River 



Morris 



Marseilles 



Hennepin 



Chillicothe 



Mid- 

 summer 

 1911 



1.21 



1.15 



.67 



2.85 

 3.47 



Nov. 1- 

 1911 



4.7 

 4.6 

 9.9 



9.8 

 9.8 



This is an average increase of 5.7 parts per million, or oi 

 300 per cent., of November over midsummer ratios for this part of 

 the Illinois River. 



February and March, ipi2. — A trip was made for chemical deter- 

 minations February i to 8, 19 12, from Lockport to Chillicothe, and 

 another, March 18 to 28, from Lockport to the mouth of the Illinois 

 at Grafton. The water temperatures averaged 34° F. on the first 

 trip, and 35° on the second, the upper river being quite frozen over 

 much of the time. 



The oxygen determinations of these trips differ widely from those 

 of the preceding midsummer in the much higher ratios found in the 

 winter and in the fact that the lowest point for oxygen was very 

 much farther down the stream. In all our midsummer trips this 

 lowest point was reached at the Marseilles dam, but in February there 

 was less oxygen at Chillicothe than at Marseilles, and in March, 

 when the whole length of the river was traversed, the oxygen ratios 

 declined down stream from Marseilles to Havana, rising then grad- 

 ually to the mouth of the Illinois. At Morris the ratio' of oxygen 

 was more than six times as great in February as in midsummer; 

 above the dam at ^Marseilles it was more than eight times as great; 

 below the dam more than three times ; and at Chillicothe it was 30 

 per cent, greater. The ]\Iarch ratios from Morris down were much 

 higher still, reaching a maximum of 10 parts per million below the 

 Marseilles dam, falling thence rapidly to Peoria (6.8), dropping a 

 trifle only at Peoria below the outlets of the sewer system (6.5), 

 declining slightly to Havana (6.2), and then rising steadily to the 

 mouth of the Illinois (9.4), the water of the Mississippi standing at 

 the same time at 10.5. In the entire distance from Lockport to 

 Grafton the percentage of oxygen saturation on this Alarch trip did 

 not fall below 44 (Peru), nor rise above 75 (south shore at Morris). 



July, ipi2. — A single trip was made July 11 to 15, 1912, in 

 company with the chemists of the Sanitary District of Chicago, com- 

 mencing, unfortunately for our purposes, at Peru, and giving us no 



