1883.] 



On the Motion of Water. 



97 



held in "both tubes, and through velocities ranging from 1 to 50, 

 where it showed no signs of breaking down. 



(4.) The most striking result was that not only at the critical velocity, 

 but throughout the entire motion the laws of resistance exactly corre- 

 sponded for velocities in the ratio of 



pc 



This last result was brought out in the most striking manner on 

 reducing the results by the graphic method of logarithmic homologues 

 as described in my paper on Thermal Transpiration. 



Calling the resistance per unit of length as measured in the weight 

 of cubic units of water i, and the velocity v, log i is taken for abscissa, 

 and log v for ordinate, and the curve plotted. 



In this way the experimental results for each tube are represented 

 as a curve ; these curves, which are shown as far as the small scale 

 will admit in fig. 9, present exactly the same shape, and only differ in 

 position. 



Fig. 9. 



Pipe. Diameter. 



No. 4, Lead (T- 0061 5 



„ 5, „ 0-0127 



A, Glass 0-0496 



B, Cast iron 0'188 



D, „ .... 05 



C, Varnish 0*196 



Either of the curves may be brought into exact coincidence with 

 the other by a rectangular shift, and the horizontal shifts are given 

 vol. xxxv. H 



