76 ILLINOIS BIOLOGICAL MONOGRAPHS [174 
that after rains, when the stream rapidly rose, putrescible matter was 
washed down stream, cast on shore, and the odor was then very bad. This 
lasted until the water subsided. In the fall of 1920, the same people were 
again interviewed and conditions were reported to be much worse than 
previously, the unusually low stage of the water causing the putrescible 
matter to decay on the exposed sand bars in the river, from which some 
odor was noticed. 
Stream measurements of the velocity of the current were made by the 
Water Survey at several points along the Salt Fork. These were made by 
Habermeyer on October 1, 1917, when the water was low in the stream. 
All data given in feet. 
TaBLE IX. Moura oF THE BONEYARD 
Distance from east bank............... 1 2 3 
Depthrofiwatercrrerreleliiteieis se lela 0.6 0.7 0.4 
Blow Per ROUT yore tsretet fare (ceels teil eterale ei 4608 4500 4320 
Salt Fork, Four Miles below Champaign Sewer Outlet 
Wistancelfromy Davey els eeetesla viele ie) 2.9 2.4 1.8 Ae7) 
Hlowaperhourrn esi ciscteletersisioes verte 3888 4320 4212 2412 
These measurements indicate a very slow current, from about one half 
to nearly a mile an hour. At high water the rate of flow is undoubtedly 
several times as great. This slow rate of flow would cause much of the 
heavy matter in the sewage to be precipitated to the bottom and form 
sludge banks, and this has occurred at many places below both the Urbana 
and Champaign outlets. High water and more rapid current probably 
moves some of this sludge farther down stream, also carrying the fresh 
sewage farther down at such times. A recent examination made at very 
low water indicates that this has been the case, for hundreds of bars were 
observed out of water, each covered with a sludge formation of greater 
or less size. 
Analyses of water from various places in the Salt Fork and tributary 
streams have been made by the Water Survey. The two tables that fol- 
low, taken from Habermeyer’s report, indicate some of the conditions of 
the upper waters of Salt Fork (Tables X and XI). 
In Table X the low percentage of dissolved oxygen (saturation) in 
the ditched stream above Lincoln Avenue is noteworthy as compared with 
the larger amount at Cunningham Avenue. At both localities, however, 
the water is relatively pure, there being little or no pollution. The sample 
from a mile and a quarter below the champaign outlet is striking because 
of the total absence of oxygen. The sudden rise in saturation at four 
and eight miles is also notable, and indicates that at these points on this 
date little decomposition was taking place. The sample from Salt Fork 
near Spoon River shows a marked fall in the amount of dissolved oxygen, 
