THE FLOW OF WATER IN WOOD-STAVE PIPE. 15 
1. Directly, by timing a given volume of water through a known 
distance. 
2. Indirectly, by measuring the discharge of the pipe, thus deter- 
mining the quantity, Q, and solving the equation V = ^. 
Where the velocity is tested by the direct method the error is 
smaller than where the indirect method is used. 
LOSS OF HEAD DUE TO RETARDATION. 
Most of the recent experiments on the flow of water in pipes of 
uniform size have been made with piezometer columns. This was the 
method used by the writer. If a piezometer (fig. 1) be properly 
attached to the pipe, the pressure in the latter will support a column 
of water whose surface is at elevation E x on the hydraulic grade line. 
In the same way the pressure at gauge No. 2 will lift a column to 
elevation E 2 . The difference between these elevations is the head 
lost, h f , due to the retarding influences. 
INTERNAL SIZE OF PIPE. 
It was not practicable to secure inside measurements of any of the 
pipe tested in the experiments conducted by the writer. The method 
used in ascertaining the inside cross-sectional area of the pipe is 
recounted in the description of each test. In some cases several 
joints of pipe, remaining from construction, were measured and their 
mean inside cross-sectional areas accepted as the internal sizes of the 
operated pipes. In other cases the external circumferences of the 
reaches tested were measured in several places and the mean inside 
cross-sectional areas computed, the thickness of the staves being 
known. This thickness runs very uniformly, being determined at 
time of manufacture by the use of the same templet. 
In still other cases, especially on pipes of small diameter, the nomi- 
nal diameter of the pipe was accepted. As the pipe runs very close 
to nominal size the writer believes that no appreciable error is intro- 
duced in accepting these areas, provided the conditions are such that 
the pipe is not liable to be more or less clogged with rocks, sand, or 
other debris. 
SCOPE OF THE EXPERIMENTS. 
The writer conducted 64 tests on 16 separate pipes, 13 of which 
ranged from 8 inches to 4 feet in diameter; one was 6i feet; one, 12 
feet; and one, 13^ feet in diameter. Six pipes were of the machine- 
banded type, put together in lengths, and 10 were of the continuous- 
stave type. Mean velocities ranged from less than 1 foot per second 
to more than 8 feet per second. 
From other sources, listed in summary Table 3, and briefly described 
in the appendix commencing on page 74, descriptions of experiments 
