98 ^ ORTMANN— THE DESTRUCTION OF [April 23, 



bottom of a creek. But the worst are the oil refineries, which dis- 

 charge into the water chemicals which are utterly destructive to life. 



These are the two most important sources of the pollution of our 

 streams : coal and oil. In addition, there are others, which are more 

 or less local, yet may become quite important in certain sections. 

 These are various industrial establishments, such as glass factories, 

 china factories, different kinds of chemical factories, zuood-pulp 

 mills,^ saw mills, tanneries, etc. There are certain sections of the 

 state, for instance the region of the headwaters of the Allegheny 

 and of Clarion River, where establishments of this kind are the 

 chief source of contamination. 



It is not my intention here to treat of the chemical side of the 

 process, because it is rather complex, and needs careful investiga- 

 tion by experts. This investigation is rendered more difficult, since 

 in most of our streams it is not one cause, which contributes to the 

 pollution, but several, often all of them, which contribute their share 

 in a particular stream. 



Finally, a last cause of destruction of life should be mentioned, 

 which, however, is not connected with a deterioration of the quality 

 of the water. This is the damming up of certain rivers. This has 

 been done most extensively in the Monongahela River, and in a 

 part of the Ohio below Pittsburgh. The dams and locks have been 

 built for the advantage of the shipping interests, producing a more 

 uniform level of the water, permitting navigation all the year round. 

 By this process the rivers, which originally possessed a lively cur- 

 rent, with riffles, islands, etc., have been transformed into a series 

 of pools of quiet, stagnant water, and this change has driven out 

 certain forms of life. It is most destructive to mussels, most of 

 which require a lively current. Dams also prevent free migration, 

 for instance of fishes, and thus they must be an obstacle to the nat- 

 ural restocking of the rivers in periods of high water. 



^ See Phelps, E. B., Water Supply and Irrigation Paper no. 226. 1909. 



