130 Mr. A. Mallock. [Dec. 13, 



dv icA.v r% x-jx 



dr ~ ^ 27n^Ji 



where v' is the velocity at r 2 . 



Integrating between r x and r 2 with the conditions that when r = r, 

 v = 0, and when r = r 2 , v = v', 



whence ' u, = *A-J ^ (3). 



ZTrr^fl 



The numerical value of A is that of d0/dv at the origin of the curve 

 in Diagram 1. The ordinate being the circular measure of the 

 angle through which the cylinder B is turned by the viscosity of the 

 water when the cylinder A has the velocity v represented by the 

 abscissa in centimetres per second. 



To determine K the following measures were made : 



In fig. 2 let w = weight of "W, 



ED = Z>, 

 D'D = a?, 

 POP' = 0, 

 OP = B. 



x is the displacement of w from the vertical caused by the torsion of 

 the wire C through the angle acting at radius B. 



^B , oj 



. .K-.0=,-, 



aild = w 4 - 



The experiments gave the following values for x and : 



x c.m. 0. log #/0. 



Experiment 1 10'51 316'6 2-51109 



2 8-08 245-4 -51759 



3 .... 9-2 .... 276-8 .... '52162 



4 .... 9-88 .... 298-0 .... -52044 



5 .... 10-8 .... 324-0 .... -52287 



6 10-62 321-0 -51961 



Mean '52092 



