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^ on the hydraulic grade line. 

 In the same way the pressure at gauge No. 2 will lift a column to 

 elevation Eg. The difference between these elevations is the head 

 lost, hf, 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 stni 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 beheves 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 6 J 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 



