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 of 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=0 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 

 formula 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 water at various depths in two sections 

 of the Sudbury Aqueduct. 1 He wrote it: V= 127 R - 62 I - 50 . 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 



