Stream Pollution 13 



the shallows are eliminated and the beds of gravel may be covered 

 too deeply for their utilization as spawning grounds by many fish. 

 In case the dams are located close together, so that the water from 

 one backs up close to the foot of the next above, this difficulty 

 becomes very real. The construction of works for current regula- 

 tion, such as lateral dikes, shutting off the shallow shore areas, 

 also modifies the general character of the stream so radically as 

 to put serious obstacles in the way of the spawning and development 

 of many kinds of fish. Conditions of this sort may be seen between 

 Albany and Troy and at other points along the Hudson. The 

 elimination of shallow areas near the banks affects aquatic life more 

 than might appear at first thought. These are the places where 

 aquatic plants grow abundantly and where small aquatic animals 

 are bred in multitudes. They afford spawning ground for certain 

 of the fishes and furnish hiding places to the young fish of all sorts 

 and to the smaller species. Finally they are the regions which hold 

 out longest against the pollution of the water and in which suitable 

 conditions of existence are found longer than in the open stream. 



A little reflection will show clearly the extent to which natural 

 conditions have been modified within recent years. The increase in 

 population in New York state within fifty years is the first element 

 in the change, but the influence of this is much less conspicuous 

 than that of other factors. During the same period the character 

 of the state has changed somewhat rapidly. The cities have grown 

 greater ; general farming is relatively a less conspicuous occupation 

 of the citizens of the state. On the other hand the amount of manu- 

 facturing has increased enormously. 



Increase of Chemical Wastes 



Even this, however, does not bring out the most conspicuous 

 element in the situation. The manufacturing of the present day is 

 characterized in a conspicuous way by the chemical processes 

 involved. These lead to the production of quantities of peculiar 

 waste materials, and while the industrial wastes of the past were 

 small in amount, relatively simple and stable in composition, those 

 of the present are conspicuous for their volume and for the variety 

 and changeful character of the materials produced. Where formerly 

 the addition of such wastes resulted at most in the destruction of 

 life in a small stream and in poisoning or polluting a relatively 

 limited area surrounding the outlet, at the present time the frequent 

 addition of new and powerful poisons in large quantities has 



