Kirchner — Bacteriological Examination of River Water. 291 
The water of the Drainage Canal after discharging itself 
over the bear trap dam, II, flows over the modified bed 
of the Des Plaines river. Near Ruby St. bridge at Joliet, V, 
the Illinois and Michigan canal and the Des Plaines river 
unite, but the old canal is continued on the opposite side 
of the stream, where it is controlled by locks. At I, 
the Des Plaines river, except during the rainy season, is 
merely a creek, and it seems more reasonable to consider 
the water below bear trap dam as a continuation of the 
Drainage Canal, although it follows the old bed of the 
Des Plaines river. The bear trap dam controls the flow 
of the canal which is about 250,000 cubic feet per minute, 
and the canal itself receives a large portion of the sewage 
of Chicago. Since a certain part of the sewage of Joliet 
finds its way into Hickory creek, samples were taken at 
VI to determine, if possible, its effect on the water of 
the canal. In most cases daily observations were made, 
but in the following table the results have been condensed 
by giving only averages for each of three consecutive days. 
