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. 



