MOTION IN RELATION TO THE SURFACE FRICTION OF FLUIDS. 
207 
Expekiments on Surface Friction. 
Diameter 
of 
pipe in 
centi¬ 
metres. 
Length 
on which 
the 
friction 
was 
measured. 
Fluid 
used. 
Method of 
producing flow, 
Method of 
measuring discharge. 
Method of measuring 
friction. 
1-255 
52-96 
Water 
(1, 2, 3) Centrifugal 
pump 
(4) Plunger pumps 
Meter 
(1) Mercury tilting gauge. 
(2) Water U-tube. 
(3) Mercury U-tube. 
(4) Bourdon pressure gauges. 
0-7125 
30-50 
55 
(1,2, 3) Centrifugal 
pump 
(4) Plunger pumps 
55 
(1) Mercury tilting gauge. 
(2) Water U-tube. 
(3) Mercury U-tube. 
(4) Bourdon pressure gauges. 
0-361 
22-86 
55 
Centrifugal pump 
Plunger pumps 
55 
Mercury U-tube. 
Bourdon pressure gauges. 
2-855 
61-2 
55 
Centrifugal pump 
55 
Mercury tilting gauge. 
1-255 
52-96 
Air 
Suction of gas 
holder 
Centrifugal fan 
Motion of gas holder 
Pitot tube in axis 
Water tilting gauge. 
0-7125 
30-50 
55 
Suction of gas 
holder 
Motion of gas holder 
55 55 55 
0-361 
22-86 
55 
Suction of gas 
holder 
55 55 55 
55 55 55 
Mercury tilting gauge. 
2-855 
61-2 
5? 
Suction of gas 
holder 
Centrifugal fan 
55 55 55 
Pitot tube in axis 
Water tilting gauge. 
10-10 
152-5 
55 
55 55 
55 55 55 
55 55 55 
10-10 
152-5 
Thick oil 
Centrifugal pump 
By direct weighing 
Mercury tilting gauge. 
Coming to the chief features of interest in the curves of n/p, ’ 2 it will be noticed 
that the inclination to the horizontal becomes gradually less as the value of vd/v 
increases, indicating that the law of resistance tends to become one in which the 
friction varies as the square of the velocity and therefore independent of the 
dimensions and temperature of the fluid. At what value of vdjv this becomes 
approximately the case the data available are not sufficient to predict. 
As the value of vdjv diminishes the corresponding values of it /pv 2 grow at an 
increasing rate, obtaining a maximum, for pipes of the smoothness used in these 
experiments, of 0'0054 when vdjv is equal to 2500 approximately. Throughout the 
whole of this range in vd/v of from 2500 to 470,000, with the exception of a few 
individual determinations due possibly to errors of observation, the variation of H/pv 2 
