288 



The Rev. Canon Moseley on Uniform Flow. 



[Feb. 2, 



in height from 0^*027 to 30 m, 714, include (together with numerous experi- 

 ments on the quantity of water which flows per second from such pipes 

 under different conditions) experiments on the velocities of the films of 

 water at different distances from the axes of the pipes, made by means of 

 an improved form and adaptation of the well-known tube of Pitot. These 

 last-mentioned experiments afford the means of verifying the above-men- 

 tioned formulae. With a view to this verification, the author has compared 

 the formula with sixty of the experiments of M. Darcy, and stated the re- 

 sults in the first two Tables of his paper. 



The discharge per 1" from a pipe of a given radius may be calculated 

 from the above formula in terms of the velocity of the central filament. 

 This calculation the author has made, and compared it with the results of 

 eleven of M. Darcy's experiments. 



Where in the formula which thus represents the discharge from a pipe 

 of given radius, in terms of the velocity of the central filament, the radius 

 is made infinite, an expression is obtained for the volume of liquid of a 

 cylindrical form, but of infinite dimensions (laterally), which would be put 

 in motion by a single filament of liquid which traversed its axis ; and, con- 

 versely, it gives the volume of such a liquid in motion which would be held 

 back by a filament of liquid kept at rest along its axis. Thus it explains 

 the well-known retarding effect of filaments of grass and roots in retarding 

 the velocities of streams. 



It is the relation of the velocity of any film to that of the central fila- 

 ment which the author establishes in the above formula. To the complete 

 solution of the problem it is necessary that he should further determine the 

 actual velocity v of the central filament. This is the object of the second 

 part of his paper. This velocity being known, the actual discharge per 

 1" is known. The following is the formula finally arrived at : — 



where 



Q— discharge per l"in cubic metres. 

 R= radius of pipe in metres. 

 I = length of ditto. 

 h =head of water. 



C=a constant dependent on the state of the internal surface of the 



pipe. 



The values of this constant C, as deduced from the experiments of M. 



2nd, for the same covered with deposit ; 

 3rd, for the above cleaned ; 



4th, for iron pipes coated internally with bitumen ; 

 5th, for new leaden pipes ; 

 6th, for glass pipes. 



Darcy are given, 



1st, 4 for new cast-iron pipes ; 



