120 
IOWA ACADEMY OF SCIENCE 
fore would not tend to settle rapidly. Further, many forms are 
endowed to a high degree with the power of motility, and there is 
no reason to assume that they would seek the bottom of a stream 
rather than the higher portions of the water. It is true that the 
sediment of a river may be found higher in bacteria than the water, 
but this would follow from the fact that this sediment contains 
large quantities of organic matter, food for the bacteria, and that 
they would increase enormously in this habitat. This purification 
goes on to a marked extent, even in the course of a few miles, as 
witness, for example, the numbers for August below Columbus, 
195,100, and at Shadeville at the same time, seven miles below, 
where the number drops to 885.” 
Burrill, Jordan, Zeit, Long, and others concluded that the dis- 
charge of the Chicago sewage into the valley of the Illinois had no 
effect whatever upon the Illinois River at its mouth beyond increas- 
ing the chlorine and other mineral constituents. They found that 
between Chicago and Peoria, that some of the streams flowing into 
the Illinois, had as many organisms as the Illinois River above 
Peoria which had been richly charged with sewage organisms from 
Chicago drainage canal. 
It was my privilege, last Summer, to investigate, along with Prof. 
Bissell of Ames, John W. Alvord of Chicago, Prof. W. T. Sedgwick 
of Boston, Mr. J. R. Freeman of Providence, Rhode Island, Prof. 
A. C. Abbott of Philadelphia, Prof C. Harrington of Cambridge, and 
Prof W. J. Roberts of Pullman, Washington, the supposed pollution 
that would follow the construction, maintenance and operation 
of the Chicago, Milwaukee & St. Paul Railway, through a portion 
of the Cedar River watershed from which the city of Seattle obtains 
its water supply. The case is of particular interest because the 
question had not been raised prior as to the possibility of pollution 
from a railroad by merely passing through a watershed and along- 
side a stream supplying a large city with water. The railroad was 
particularly anxious to obtain a right of way to the city of Seattle, 
which owned a portion of the territory of the watershed, in order 
to get an easy grade into the city. The writer had been in corres- 
pondence with the president of the road in Washington, concerning 
the danger of such pollution, and he gave it as his opinion that if 
the stream was properly safeguarded, during construction and 
maintenance, pollution would not occur. The city council finally 
passed an ordinance granting a strip of land 100 feet wide to keep 
within certain distances from the river bed, that the bridges should 
be solid-decked structures, and approaches to them and trestle 
should be so constructed and maintained as to prevent anything 
