108 



The scarcity of algie can best lie explained by considering the nature 

 of the river itself. Along the lower part of the West Fork and the entire 

 course after the two l)ranches unite the river follows a meandering course 

 through a loose, sandy soil; and, by a gradual process of cutting the bank 

 on one side and piling up sandbars on the other, it is continually changing 

 its course. Then, along the straight parts of tlie stream the banks are 

 generally steep, and tliere is little shallow water. When we consider at 

 tlie same time that the current is comparatively swift, it is seen that only 

 when the river is at its lowest stage are conditions at all favorable for the 

 growth of alg:¥. Moreover, the conditions just preceding these investiga- 

 tions had been the worst possible, for the exceptional flood of the preceding 

 .'■•pring had made such changes in the ri\er bed that several years will be 

 required to bring the plant life of the stream back to a normal condition. 



Tlie abrupt disapi)ea ranee of algal growth just below Martinsville was 

 accompanied by an improved sanitary condition of the watei-. These two 

 conditions wei'e due. in itart. to a sciMcs of long, (leej) stretches of ((uiet 

 water which acted as septic basins foi- the polluted water and were also 

 loo deep for alga>. It is pi-obable. too. tliiit the alga' aliovt' these decii parts 

 aided materially in imi-ifying the water by releasing large .-inionnts of 

 oxygen which went into solution and hastened the i)utrefaction of organic 

 matter. 



