THE FLOW OF WATER IN WOOD-STAVE PIPE. 17 
Bureau of Standards the year previous, but had been used only a few 
times, and then as a standard. Its rating curve was checked by the 
writer and his assistant in the channel of the hydraulic laboratory at 
Cornell University, just prior to these tests. No change was found 
necessary. 
Fluorescein. 1 — Direct measurements of velocity of water in a pipe 
were made by injecting solutions of fluorescein and timing the passage 
of the resultant green-colored water through the reach tested. 
Weirs. — Where weirs had been installed to measure the quantity 
of water from pipes the writer made use of them. Each is described 
in the report of the test in which it was used. 
Hook gauge. — A small hook gauge of the Boyden type, with vernier 
reading to thousandths of a foot, was used to determine surface 
fluctuations for head on a weir. (See PL 1, fig. 1.) 
Piezometers, — Two types were used: 
Water column : This was employed where the pressure in the pipe 
was low. A simple glass manometer-tube, engine-divided to tenths 
and hundredths of a foot, was connected to the tap in the wood pipe 
by a piece of rubber pressure tubing. (See PL II, iig. 1.) 
Mercury manometer: Where otherwise the pressure would have 
compelled the use of a long water column, a mercury manometer of 
the U-tube pattern was selected. Two of these U-tube mercury 
gauges, as shown in figure 3, were provided. They consisted of 
wrought-iron U tubes "with unequal legs. The short leg was a glass 
manometer tube surmounted by a tee connection provided with the 
necessary cocks for manipulation. The long leg was formed of 2-foot 
units of one-eighth inch wrought-iron pipe until a length had been 
attained which permitted the top of the high mercury column to 
show in another glass tube. 
These glass tubes were engine-divided into tenths and hundredths 
of a foot, the tenths and half-tenths fines extending completely 
around the tube and the other lines but half way around. By sight- 
ing through the tube across the front and back of any one line, all 
tendency toward parallax was removed and the mercury column 
could be correctly read to thousandths of a foot. The relative vertical 
positions of the two sets of graduations were of immaterial conse- 
quence as the graduations on each gauge glass were brought into the 
general scheme of levels above an assumed datum, as shown in 
figure 2. 
All abutting pipes screwed against fiber gaskets. The ends of the 
gauge glasses were permanently set into sleeved couplings with sealing 
i The writer is indebted to R. B. Dole, of the U. S. Geological Survey, for suggesting the use of this won- 
derful coloring matter. See " Use of Fluorescein in the study of underground waters," R. B. Dole, Water 
Supply Paper No. 160, U. S. Geological Survey. 
68796°— Bull. 376—25 2 
