230 
flood (as in September) concentrating the sewage and at the 
same time favoring the development of the plankton. 
That the sewage of Chicago is quite thoroughly rotted out 
before it enters the Illinois at La Salle, and that the contribu- 
tions from Peoria are also well advanced in decay before they 
reach Havana have been demonstrated by the chemical and 
bacteriological examinations made at the instigation of the 
Sanitary District of Chicago apropos to the opening of the 
drainage canal. The full results of this work have not as yet 
been published, but from the data published by Prof. A. W. 
Palmer (’97) from the analyses of the Chemical Survey and 
from the preliminary report of Jordan (’00) upon the bac- 
teriological examination it is evident that the nitrogenous 
matters of the Chicago sewage were in process of rapid oxida- 
tion in the upper reaches of the Illinois and Michigan canal 
near Lockport; that this process was largely completed before 
the canal waters entered the river at La Salle; and that the Pe- 
oria pulse of sewage is, during the summer months at least, well 
decayed before it reaches Havana, though in colder weather, 
when decay is less rapid, the sewage is not so well oxidized and 
the bacteria are more abundant than during the summer at 
this point. The following table, which has been made up from 
the averages in Palmer, ’97, exhibits to some extent these facts 
in tabular form. The increase in nitrates and decrease in free 
ammonia unite in indicating the extent to which decay has 
progressed. 
: Total | Total Albu- | Total 
J | ee residue {loss on| Chlo- ple minoid| Organ-| Ni- Ni- 
Station. Chicaso.|°% evap-| igni- | rine |“fj2'°|Ammo-| ic Ni- | trites | trates 
5°! oration. | tion nia. | trogen 
Lockport ..............-..-. 29 438.6 20.5 24. 092 417 84 .019 95 
orris. .... 57 359.4 23.4 29.7 | 3.55 709 1.44 149 1.72 
La Salle. 95 372.3 23.03 19.6 971 .612 1.26 +255 2.51 
WPeOniaijecceseeete ee ee 58 376.7 21. 1.8 +254 516 1.06 +209 2.59 
Havana.......... ratte 199 355.3 21.2 15.4 63 455 1.06 +135 2.35 
Kampsville* ............... 288 352.1 22.4 13.4 .261 .508 1.17 062 1.39 
*Average July 23—Dec. 29, 1896. 
The influence of the sewage of Peoria upon conditions at 
Havana, owing to temperature changes, is not uniform 
