8 o 
Journal of Agricultural Research 
Vol. II, No. 2 
Merely to make the data complete rather than to duplicate conditions 
of field use, the meter was again raised in the water until the center plane 
of the cups was just at the water surface. The curve for this condition 
shows that the meter runs slow when a low velocity is reached, and the 
difference between the curves rapidly becomes greater within the range 
of the experiments. 
Murphy, in the report of his experiments at Cornell University, 1 also 
pointed out the fact that the Price meter does not run true to standard 
rating curve when held near the surface. He compared the velocity as 
indicated by the meter with that of a surface float operated simulta¬ 
neously in running water. His general deduction was that this type of 
meter does not run true to standard curve when operated at depths less 
than 0.5 foot below the surface. The writer found, however, by actu- 
Fig. 3. —Vertical velocity curves, showing error due to using standard rating for points near the surface 
and bottom, Orr ditch, Nevada. 
ally rating the meter at various depths, that the behavior of the meter 
becomes normal somewhere between depths of 0.2 and 0.3 foot below the 
surface. 
A concrete example of the difference in results obtained when the 
proper correction for surface and bottom velocities is applied follows: 
The Orr ditch at Reno, Nev., was measured with a current meter, 
using the vertical velocity-curve method. The ditch channel was lined 
on the sides with rubble masonry. This channel was 10 feet wide and 
of nearly rectangular section. The vertical velocity curves for the right 
half of the section are shown in figure 3. The open circles and solid 
lines give the curves after the proper corrections have been applied to 
the velocities for the surface and the bottom. The dots and broken 
lines show the form the curves would have assumed if no corrections had 
been applied. The curves for the other half of the section were quite 
similar to these. The verticals were spaced 0.5 foot apart. The total 
discharge indicated by the solid curves is 45.80 second feet, while that 
1 Murphy, E. C. Accuracy of stream measurements. U. S. Geol. Survey, Water-Supply and Irrig. 
Paper No. 95 . i9°4» P. 90. 
