80 ILLINOIS BIOLOGICAL MONOGRAPHS {178 
RECENT EXAMINATION OF THE POLLUTED PORTION OF SALT FORK 
Figures 21, 36 to 45 
During the fall, winter, and spring of 1919 and 1920 Salt Fork was 
carefully examined from Urbana to St. Joseph. All parts of the stream 
were searched for macroscopic life and samples of the bottom and of the 
water were taken for microscopic study, to determine the character and 
abundance of the foul-water organisms present. Examinations were made 
during the months of May, September, October, November, and December. 
During the spring months the water is so high in the stream that collec- 
tions can not be made and examination of the water is difficult. The 
great volume of water, laden with both sewage and silt, is of a dark lead 
color and polluted conditions are not apparent, although some putrescent 
matter was observed on several occasions. In the fall months conditions 
are much more favorable for critical examination, the water being so low 
that one may wade over any part of the stream. It is at this time, which 
extends from July through the fall and winter to the rainy period in March 
or April, that the polluted conditions are very apparent and the most 
satisfactory studies can be made. The general conditions of the stream at 
this period are summarized below. 
The water in the Boneyard near the Big Four shops, below the Urbana 
sewage outlet is usually shallow, from a foot or less to two feet in places. 
The bottom is a mass of sludge with putrescent material covering all 
objects in the water and floating down the stream, which has an estimated 
flow of about half a mile an hour. Several large sludge banks are exposed 
and the odor is usually nauseating (Fig. 39). At the junction of the 
Boneyard with the Salt Fork the water varies from six inches to a foot 
in depth, there are several sludge banks and the putrescent matter covers 
all objects and lines the shores to a height of several feet, indicating former 
high water marks (Fig. 36). Samples of the sludge and green putrescent 
material from one of these sludge banks were examined by Professors 
Smith and Transeau and the following algae, Protozoa and other animals 
observed: 
Blue-green algae Animals 
Pediastrum simplex, common. Paramoecium, not common. 
Senedesmus abundans, rare. Euglena geniculata, very abundant. 
Phormidium inundatum, abundant. Limnodrilus (sludge worm), very abun- 
Diatoms dant. 
Navicula cryptocephala, common. Tubifex (sludge worm), one specimen. 
Synedea pulchella, not common. Nematode worms, several. 
Ciliate Protozoa were numerous, including Colpodium and a few 
hypotrichous and peritrichous species. 
