10 
This is a constant level pool. There is no necessity for its being 
so, but the impression has got abroad that variation of the water 
level is productive of malaria, and to prevent this the power com¬ 
pany raises the gates whenever a flood is expected and closes them 
Fig. 3.—Section of poo! of Lock No. 12, Coosa River, above the Narrows. Elevation of water 
a little less than in figure 2, yet section overflowed by pool is greater. Water here is raised 
about 43 feet, the map covering the area from 7}-$ to 10 miles above the dam. 
when it has passed. As the flow in the river has been in excess of 
the requirements for power, the company has been able to keep the 
level ver} 7 nearly on the 1‘20-foot contour during the summer and 
