Canon Moseley on the steady Flow of a Liquid. 357 



It is the object of the following Tables to verify this formula 

 by comparison with the experiments of M. Darcy. 



In Table V., from the value of the discharge Q : given by ex- 

 periment for a given head of water h in the case of aoy given pipe, 



the value of — ■ is calculated. That is the value of the coefficient 

 of h? in equation (34). Call it A. Then, if the formula be true, 



will represent the discharge from the same pipe for any head 

 of water. This calculation is made in respect of three different 

 pipes ; and the results are compared with those given by expe- 

 riment. 



In Table VI., from the value of Qj (the discharge per 1" from a 

 pipe of given radius R under a given head of water h) the value 



of = — T is calculated. That is the value of the 



(€""*— 2-25R—l)Ri A* 



coefficient of (e 2,25R -2-25R-l)RU2 in equation (34) . Call it B. 

 Then, for all pipes of the same material and state of their in- 

 ternal surface and of the same length, whatever may be their 

 diameters and heads of water, (if the formula be true) the exr- 

 perimental discharge ought to be represented approximately by 

 the formula 



Q 1 =B(e 2 - 25R -2-25R^l)RUi 



These calculations are made in respect of two new cast-iron pipes, 

 whose radii were respectively '0685 and '094, and the results com- 

 pared with experiment. 



In Table VII., from given corresponding values of Q,, R, h, I 

 substituted in equation (34), the value of X^ is determined for 

 pipes of different material and for different states of the surface 

 of pipes of the same material. If two pipes of different diameters 

 and under different heads of water be of the same material, and 

 their internal surfaces in identically the same state, and if the 

 joints of the separate lengths which compose the pipe be equally 

 well (or ill) made (conditions exceedingly difficult to be realized), 

 then the values of \* t as determined by the formula, ought (if it 

 be true) to be nearly the same. They may be compared by re- 

 ference to the Table. All the experiments of M. Darcy with 

 pipes of the same material were made with the same length of 

 pipe. It is impossible therefore by means of them to verify that 

 condition of equation (4) by which (other things being the same) 

 the discharge per 1" ought to vary inversely as /^. 



