STREAM-FLOW 



65 



For measuring the velocity the current meter is now most 

 generally used. This meter is primarily an instrument for 

 measuring the velocity of moving water, and consists essentially 

 of a wheel with vanes, which may be shaped like those of a wind- 

 mill or of a screw, or with caps like those of an anemometer, the 

 necessary qualification being that the moving water shall easily 

 cause the wheel of the meter to revolve. The velocity of the 

 water is then determined from the revolutions of the meter in 

 unit time. The meter which has been adapted by the U. S. 



2000 1000 6000 8000 10000 12000 1400016000 18000 20000 5 



Discharge In Second Feet 





Fia. 24. Discharge, Mean Velocity, and Area Curves for James River at 



Cartersville, Va. 



Geological Survey after years of experience and improvements is 

 the Price Current Meter, which is manufactured by W. & L. E. 

 Gurley. It is illustrated in Fig. 23. 



The curves in Fig. 24 show a method of plotting the values 

 of discharge, mean velocity and area in relation to the gauge 

 height. 



Where a current meter is not available or its expense not jus- 

 tified as in minor preliminary investigations, the float method may 

 be used for approximately determining the velocity. This may 

 be done by laying off 100 feet of the bank and throw a float into 



