120 Canon Moseley on the steady Flow of a Liquid. 



From this it follows that, however different the actual velocities 

 of the films may be by reason of differences in the heads of water 

 and in the diameters and internal roughnesses of the pipes, their 

 relative velocities at equal distances from the axis are (in the 



same liquid) approximately the same. Since moreover 



'© 



is 



approximately independent of these differences in the heads of 

 water and the diameters and roughnesses of the pipes, it follows 



(U — — 1) \ o" 11)1 



— \\ and— are also independent of 



them, and that they must have approximately the same values 

 for the same values of r in respect of all the heads of water, and 

 all the kinds and diameters of pipes included in the range of M. 

 Darcy's experiments. 



This will be found to be the case. Table II. contains the 



values of (_ °j calculated with respect to the characteristic 



experiments of each group ; and its value will be seen to be in 



every case, approximately, unity; and, that being admitted, 



Table I. shows that the values of v calculated from equation (9) 



wi 

 agree with experiment when — is taken equal to the constant 



2*25; whilst Table III. shows the efflux also to correspond with 

 experiment when calculated on that supposition. 



Table II. 

















Values of (^-^oV 

 W-v 2 )> 



Index 



Diameter 













number 



of pipe. 



v. 



v Q . 



v v 



v 2 . 



v 3 . 



corres 



ponding 



'to 



v 3 . 



159. 



0-188 



2-69 



0-885 



0-845 



0-760 



0-758 



•99513 



•98375 



•9835 



171. 



0-2432 



814 



2-273 



2118 



1-833 



1-771 



•9944 



•9855 



•9835 



181. 



0-2447 



14-91 



5-212 



4-935 



4-497 



4-419 



•99288 



•98268 



-98212 





0-297 



118 



0-435 



0-410 



0-355 



0-355 



•99134 



•97473 



•97473 



187. 



0-297 



665 



2-708 



2-590 



2-355 



2-365 



•99164 



•97662 



•97662 



192. 



050 



109 



0-571 



0-535 



0-477 



0-475 



•97767 



•94734 



•92847 



197. 



0-50 



2-26 



1-319 



1-249 



1-133 



1-197 



•97433 



•93848 



•93482 



Since in M. Darcy's experiments it thus appears that, approxi- 

 mately, 



Gfe#-.. « 



it follows from equation (9) that, approximately, 



wir 



(12) 



