﻿8 Mr. A. R. McLeod on Unsteady Motion produced 



The motor was driven from a 200-volt accumulator circuit. 

 Three sizes of cylinders were used : 



Small cylinder c = c x = 2*40 cm. = radius. 



Middle „ c = e 2 = 7'48 „ 



Large „ c = c 3 = 12*69 „ 



Three angular velocities were selected for each cylinder : 



Low speed £2 = 12! = '1396= 1^ r.p.m. 



Middle „ n=n 2 =ro47 =10 „ 



High „ O = H 3 = 3-770 =36 „ 



The large and middle cylinders were painted inside. 

 They were bored with an error of a small fraction of a 

 millimetre at the upper rim. The small cylinder was true 

 to 0'05 mm., and its length was four diameters. The others 

 were slightly more than two diameters long. The bases of 

 all were plane and smooth on the inside. 



Experiments were made when the water began to rotate 

 from a condition of rest, and also when it was coming to 

 rest from a condition of uniform rotation, the uniformity 

 being ascertained before the cylinder was stopped. 



In reducing the observations, the watch- reading was 

 corrected by subtracting half the stop-watch reading to 

 give the mean time t, and the values of vtjc 2 and 0/X2 were 

 calculated for each observation. The viscosity of the water, 

 at the mean temperature during the experiment, was taken 

 from Kaye & Laby's Tables. The values of 0/12 were 

 plotted on squared paper against the values of vt/c 2 , each 

 observation being represented by a dot. Hence for a 

 selected circle corresponding to the selected value of r/c, 

 for each value of 12 there corresponds a series of dots 

 which lie in a narrow band. This band defines a curve 

 by its median line. Observations were made on the four 

 circles corresponding to r/c = 03, 0*5, 0*7, and 9 for each 

 of the three cylinders. Thus for each cylinder there were 

 finally eight sheets of curves — four for " starting " and 

 four for " stopping- " experiments. Each of these sheets 

 contained three curves corresponding to the three selected 

 velocities, and corresponded to one of the values of r/c. 

 The theoretical curve from Table I. was also added for 

 comparison. Several experiments were made for each set 

 of conditions, to secure a sufficiently dense band of points 

 for each curve. Apart from a number of preliminary 



