348 POLLUTION OF THE POTOMAC RIVER 



stream into which it empties form tlie state boundary between 

 Maryland and ^^'est Virginia. Tlie South branch lies wholly 

 within this latter state. At their headwaters these two branches 

 flow in a general northeasterly direction, nearly parallel to each 

 other, the North branch being to the west of the Alleghany front 

 and the South branch to the east. The. total drainage area of 

 the North branch at Cumberland is 891 square miles, or about 

 8 per cent of the entire catchment area alcove the city of Wash- 

 ington. The total drainage area of the North branch at its 

 inouth, or where it joins the South branch, is 1,36-5 square miles, 

 being a trifle smaller than tlie area drained b}' the latter. 



The waters of the North branch of the Potomac, eyen near its 

 head, are naturally somewhat dark in color, and it is stated by 

 the older inhabitants of the region that it has always been thus, 

 owing jirobabl}^ to the presence of decaying yegetable matter 

 from the forests. This is further increased by the effluents from 

 the saw-mills, tanneries, and coal mines, so that at the old mill- 

 dam near Keyser the polluted water agitated by the fall boils 

 and foams, forming in the early morning a thick layer of whitish- 

 brown froth. 



In order to obtain a general conception of the amount of i)ol- 

 lution, it is necessary to know how much water is carried by the 

 riyer. This, of course, yaries from day to day and eyen hour b}^ 

 hour. These minor fluctuations are slight, and by taking special 

 care during time of flood it is i)0ssible to know how much water 

 is delivered by the main stream and its principal tributaries. 

 Without entering into a discussion of how this is accomplished, 

 it is sufflcient to state that the results are giyen in a table show- 

 ing the average dail}' flow throughout the year in cubic feetjier 

 second. 



The minimum flow of the riyer has been considered to be that 

 obtained by INIr William R. Hutton in 1856, 1,063 cubic feet per 

 second. It is probable that during the past fall (1897), owing 

 to the protracted dry ^v■eather, the discharge sank to about this 

 amount. At that time the water received into the conduit is 

 stated to have been from 75 to 90 second-feet, or from 7 to 9 per 

 cent of the total volume of the river. 



It is evident that the quantity of water in the Potomac, es])e- 

 cially at times of flood, is ver}^ considerable, and that sewage and 

 waste material dumped into it from towns and manufacturing 

 establishments must be greatly diluted, but in times of low water 

 this must necessarily become less so. The quality of the water 



