272 ILLINOIS ACADEMY OF SCIENCE 



supply, and in many places the very objectionable physi- 

 cal character of the polluted waters, have caused the au- 

 thorities of several states to pass laws governing the dis- 

 charge of these wastes into streams and the establish- 

 ment of penalties for disregarding these laws. New York 

 and Massachusetts have led in the framing of these laws 

 and other states are following the good example set 

 by these two older commonwealths, where the conditions 

 seem to have reached a maximum of harmfulness (see 

 Ward, 1918, 1919). 



During recent years stream pollution has enormously 

 increased and the problems arising from this condition 

 have been investigated by many biologists and sanitary 

 engineers. The former have studied the problem from 

 the viewpoint of its effect on the useful animal life, es- 

 pecially fishes and river mussels, and this phase prob- 

 ably bears as close a relation to human welfare as any 

 other. Of course, from the standpoint of health, the pol- 

 lution problem is of paramount importance because of 

 its bearing on such diseases as typhoid fever which may 

 be caused by a polluted water supply. 



Perhaps the worst effect of chemical pollution is to be 

 found in the streams of western Pennsylvania, where 

 mine water heavily loaded with oil or acid water from 

 coal mines is permitted to flow into the rivers and 

 streams of this part of the state. Studies by Ortmann 

 (1909) show that whole stretches of the Allegheny, Ohio, 

 and Monongahela rivers have been made into deserts, as 

 far as the animal life is concerned, by the large amount of 

 poisonous substances discharged into these streams by the 

 mines, oil industries, and chemical and other factories 

 that border these rivers. In the Susquehanna Eiver the 

 same condition prevails in many places (Leighton, 1904). 

 Such pollution causes a complete extermination of the 

 fauna (and largely of the chlorophyl-bearing flora) and 

 leaves the stream in such condition that restocking by 

 either natural or artificial means is practically impos- 

 sible, and if attempted is a waste of money. 



Pollution by sewage, when the polluting material is of 

 small percentage as compared with the pure water of 



