350 POLLUTION OF THE POTOMAC RIVER 



probabl}' contributes not more tban six per cent of the water 

 carried l\y the Potomac at Great Falls, and this small percentage 

 traverses about 190 miles of broad river bed, agitated and broken 

 ' by numerous shoals and diluted by fresh waters bearing more or 

 less oxygen and sediment tending to its purification. While 

 these influences contribute to ameliorate the quality of the water, 

 it cannot be contended tliatthe supply for this city is entirely as 

 it should be. 



Sufficient has been said to indicate that a considerable amount 

 of filth of all kinds is habituall}' dumped into the river, and that 

 this is stead ih'- increasing. It is not desirable to describe or 

 characterize this material under any stronger term than sewage, 

 as the details are too disgusting to be given in a public address. 

 It may properly be claimed, however, that no matter how bad 

 the material is at the point where discharged, it becomes neutral- 

 ized or destro3'ed before the water containing it reaches the Wash- 

 ington aqueduct. The self-purification of rivers is a phrase Avhich 

 has been made the excuse for much carelessness or indiff"erence, 

 but there is no doubt that streams do tend to rid themselves of 

 much of their undesirable load. 



The conditions along the Potomac are particularly favorable, 

 for the water passes over many broad riffles where it is exposed 

 to light and air, and many deleterious substances are unques- 

 tionably burned up, while others may i)ossibly be dragged down 

 by the finel}' divided sediment which is usually present. Thus 

 the chemicals used in the i)ulp mills, tanneries, and other facto- 

 ries are greatl}' diluted, and b}^ reaction upon each other and 

 upon the small amount of lime carried in solution probably form 

 harmless compounds. The momentous question therefore is as 

 to the behavior of the small micro-organisms, to which the modern 

 students of disease attribute such potent influence on the human 

 system. Take, for example, the typhoid bacillus, which is said 

 to live even in ice for a hundred days or more and to develop in 

 soil, retaining its vitality for a 3'^ear and even increasing from a 

 single cell to 16 million individuals in 24 hours. It may be 

 questioned whether such an organism is rendered harmless in 

 the journe}'' of from two to four days or more from the sewers of 

 towns up the river to the mouth of the aqueduct. 



We are comforted by the assurance that harmful bacteria are 

 rarel}^ found in Potomac water; but still this ma}'' not set us 

 whoU}'' at rest, for negative evidence in such a case proves little. 

 The discussion of the probable danger from sewage must be left 



