541 



the water of the latter stream at its mouth contained but 1.21 parts 

 of oxygen per million, the ratio for the Kankakee was 11.21; and 

 when the oxygen in the Des Plaines rose to 4.90 in November, that 

 of the Kankakee was 10.90. Our lowest reading for the latter stream 

 was 9 parts per million, in February, when the Kankakee was mainly 

 covered with ice. Most of the oxygen ratios in the Kankakee were 

 above those which the water will absorb directly from the air, and 

 indicated a "supersaturation" varying from 105 to 133 per cent. 



The differences between the two waters thrown together at the 

 origin of the Illinois were reflected in oxygen ratios from the two 

 sides of the stream just below the junction, as reported November 

 14, 191 2 — 4.6 parts per million for the water of the northern or 

 Des Plaines side, and 11.3 parts per million for the water of the 

 southern or Kankakee side. 



Morris to Marseilles. — In the seventeen-mile section of the Illi- 

 nois from Morris to the upper dam the river reaches its lowest point 

 of pollutional distress, becoming, when very hot weather coincides 

 with a low stage of water, a thoroughly sick stream. Its oxygen is 

 nearly all gone ; its carbon dioxide rises to the maximum ; its sedi- 

 ments become substantially like the sludge of a septic tank ; its sur- 

 face bubbles with the gases of decomposition escaping from sludge 

 banks on its bottom; its odor is offensive; and its color is gray with 

 suspended specks and larger clusters of sewage organisms carried 

 down from the stony floor of the polluted Des Plaines, or swept from 

 their attachments along the banks of the Illinois. On its surface are 

 also floating masses of decaying debris borne up by the gases de- 

 veloping within them, and covered and fringed with the "sewage 

 fungus" (Sphcerotilus nafans) and the bell animalcule (Carchesiuin 

 lacJinianni) usually associated in these waters. The vegetation and 

 drift at the edge of the stream are also everywhere slimy with these 

 foul- water plants and minute filth-loving animals. The two sides 

 of the stream differ materially in condition at Morris, and sometimes 

 also at Marseilles, the waters of the Kankakee and the Des Plaines 

 not becoming completely mingled until they have passed these points. 



The normal life of the stream practically disappears in the ab- 

 sence of oxygen ; its fishes withdraw to neighboring unpolluted 

 waters ; its mollusks, crustaceans, ordinary insect larvge and other 

 more or less sedentary forms disappear to be replaced mainly by 

 slime worms and Chironoiuiis larvre in the sludge; and its chloro- 

 phyll-bearing plants linger only along the edges in shallow water. With 

 the advent of cooler weather and higher river levels, most of these 

 marked symptoms disappear, and a few fishes may even make their 



