THE FLOW OF WATER IN CONCRETE PIPE. 97 
the pipe. In the writer's experience it has been found that reservoir 
waters carrying microorganisms sometimes foul pipes rapidly, and 
decrease carrying capacities to an important extent. This has been a 
vital matter with some pipe lines in this country and in England. The 
reduction in carrying capacity from organism may be in part, or 
mainly, temporary, and capacity may be restored soon after the 
organisms of the particular kind that cause trouble cease to be found 
in the water through natural causes, or by the application of copper 
sulphate. On the other hand, the conditions may become chronic 
with, some reservoir waters. The matter is one that must be taken 
into account, and it will not do to assume that the variation in 
carrying capacity of concrete pipe is only due to the character of the 
surface of the pipe itself. 
The author is to be particularly commended for making use of 
various approximate methods o£ measuring water. If he had insisted 
upon some one method thought to be more accurate than the others, 
it would have reduced the number of possible experiments. The 
methods used by him seem to have been sufficiently accurate. Efforts 
to obtain precision, while often commendable, may seriously limit the 
accumulation of useful data. 
The writer is pleased to see that the Williams and Hazen formula 
still holds its own. He has used it in all his hydraulic work for 15 
years, and found that, as an all-around working basis of estimate, it 
answers very well. 
There is a distinct advantage in using only one formula, for one 
becomes thoroughly accustomed to it, accumulates his data in its 
terms, can much better judge all varying conditions, and is less likely 
to make errors in its application. 
The formula proposed by the author for cement pipes, V— 8 
H°- 5 d°- G25 , is unquestionably a good one and well adapted to the use. 
As a practical matter, within the ordinary range of velocities, it would 
not make much difference whether it or the Williams and Hazen for- 
mula were used. ' Only at very low or very high velocities would 
the difference become considerable. 
The formula proposed by the author has some interesting ante- 
cedents. The number of exponential formulae has become so great 
in recent years that the range of exponents is well taken up, and any 
exponent that may be selected will be found to have been already used 
by someone. Thus the Moritz formula referred to by the author at 
length in his paper is, in reality, the old Lampe formula, which 
antedates its use by Moritz by several decades. In a similar way the 
"ormula now proposed by the author for cement pipe is an old one. 
In 1882, Alphonse Fteley, then city engineer of Boston, found that 
it best accounted for the flow of w ater at various depths in two sections 
of the Sudbury Aqueduct. 1 He wrote it : V= 127 R°- Q2 I -™. I stood 
for inclination, and is equivalent to s now used. (See pipe No. 63, 
p. 89.) 
The formula now proposed by the author was also reached by the 
writer in 1901 by a reconsideration of hydraulic data presented by 
Mr. Fenkell. 2 
1 Boston Water Works, Additional Supply from Sudbury River, City Document, p. 92. 
2 Jour. Assoc. Engin. Socs., vol. 26, p. 163. 
164725°— 20— Bull. 852 7 
