84 BULLETIN 376, U. S. DEPARTMENT OF AGRICULTURE. 
the pond above the intake and readings on a mercury U-tube manometer at- 
tached to the pipe about 6 feet above the surge tank. From the gross loss must 
be deducted the local loss through the racks at the intake and the velocity head. 
The rack losses were computed by comparison with some measured losses in a 
similar rack at another plant. In any event the incidental losses were very small 
compared with total loss in a 33^-mile line. Gauge elevations were checked by 
readings with the turbine gates closed so that practically a static condition re- 
sulted. 
The loss of head for the higher velocities agrees very closely with our formula 
loss, but as lower velocities are considered the observed losses of head are less 
than the formula calls for. 
No. 59. Expt. S-18. 96-inch Continuous- Stave Creosoted Douglas Fir Pen- 
stock. Wise Power Plant, Pacific Gas & Electric Co., near Auburn, Calif. — 
The Wise power plant is served with water from a f orebay at the lower end of an 
open canal, by means of a stave line for the first one-fourth mile, thence through 
a Venturi meter, and the balance of the distance of 13^ miles through a steel pipe 
of tapering diameters. 
In 1919 the writer, while making a series of tests on the friction losses in the 
steel penstock, set up mercury gauges near the ends of the stave line between 
the f orebay and the Venturi meter, giving a reach of pipe 1,238.9 feet long. 
The quantity of water was determined by readings of the Venturi meter cor- 
rected for leakage losses in the stave line. These losses were concentrated and 
measured over triangular notch weirs. They constituted only two-tenths of 1 
per cent of the total flow, so might have been neglected without materially alter- 
ing the results. This pipe is slightly sinuous in both vertical and horizontal 
planes. The internal diameter was determined by measuring the outside cir- 
cumference at four points and deducting the known thickness of the staves. 
The line was 2 years old at the time of test. W^hile the reach was short, compared 
with the diameter of the pipe, still the velocity was so high that experimental 
errors were minimized. The velocity found was some 6 per cent less than that 
called for by our formula for the same loss of head. 
No. 61. Expt. S-19. 120-inch Untreated Fir-Stave Penstock. Montana 
Power Co., near Ennis, Mont. — The power plant on the Madison River, below 
Ennis, Mont., offered an exceptional opportunity for tests. Between the reservoir 
and the surge tank were parallel lines of stave pipe, one 10 feet and the other 12 
feet in diameter. These lines were nearly 7,000 feet long and were 17 years old 
at time of test. The combination of large sizes, reasonably long reach of pipe, 
relatively great age, and low pressure heads was quite unusual. Informal coopera- 
tion of the Montana Power Co. enabled the writer to make a series of tests on these 
two lines in 1923. 
Piezometers leading to water columns in graduated gauge glasses determined 
the loss of head. At each end of the reach 6,698 feet long two piezometers, each 
containing four holes one-sixteenth inch in diameter, neutral to the current, 
were introduced through holes drilled in the staves at about 10 and 2 o'clock 
(regarding the section of the pipe as a clock dial). This gave the average pressure 
from eight holes. The piezometer tubes at the two ends of the reach were under 
the same dynamic condition. The velocities within the pipes were determined 
by timing the passage of fluorescein from a point near gauge 1 to its appearance 
in the surge tank a short distance below gauge 2. At the surge tank the stave-pipe 
outlets were submerged only from about 3 to 10 feet. Sunlight was admitted to 
the tank by the removal of boards from the roof. The first appearance of color 
was detected without difficulty, but in order to determine the last sight of color it 
was necessary to watch the "boil" from the pipe carrying color to see when the 
clear water cut through the green pool then resulting. Having two large pipes to 
