Stream Pollution 51 



Results of Experiments in Polluted Streams 



On the other hand, it must be pointed out that experiments have 

 already been carried out on a grand scale in connection with wastes, 

 from many industries, and an examination of the territory subject 

 to the influence of the wastes discharged will yield better evidence 

 than any such laboratory experiment, for in such a place one can 

 see not merely the results of brief exposure to the influence of a 

 waste product, but rather the cumulative effects of long continued 

 stimulation by these substances under the varying influence of winter 

 and summer, low water and freshet, open water, ice-blanket, and all 

 other conditions that obtain in the given region. A study of the tern 

 tory will show what has been the result of the experiment and the 

 records of the manufacturing plant will probably always furnish 

 evidence at least as to the length of time that the waters have been 

 subject to this influence. In most cases it will also be possible to 

 determine in rough fashion from the manufacturer's data what 

 fluctuations in the composition of the wastes have occurred within 

 that period. The unfortunate total destruction of the organisms 

 characteristic of pure waters and their replacement by species which 

 are equally characteristic of polluted streams, as observed in various 

 places, is incontrovertible evidence of the effect on aquatic life of 

 this particular waste. While in the case of a request for a permit to 

 discharge new industrial wastes into a stream the method of labora- 

 tory experimentation should always be utilized to determine the 

 probable result of the practice, yet in the instances where the experi- 

 ment has already been tried the results displayed in the stream are 

 important enough to demand careful examination and detailed 

 record in order that the evidence may be available for use in dealing 

 with this and similar plants in future. 



Our general knowledge of animal life would lead us clearly to the 

 conclusion that certain stimuli which do not appear to have an 

 immediate serious effect upon animal life may clearly be harmful 

 if their influence is exerted, upon the same organisms continuously 

 over a long period of time. Bad air and bad water undoubtedly 

 influence in a similar way the organisms that are confined to the one 

 or the other environment. It is impossible to doubt that dilute 

 poisons in the water exert precisely the same sort of an influence on 

 the fish and on the other organisms contained in it. It would be 

 impossible to give here a complete summary of all the observations 

 and experiments that are on record with reference to the influence 

 of pollution on aquatic organisms or even on the fishes alone. I shall, 



