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



the motion on starting, on the other hand, appears to the eye 

 to be without appreciable irregularity, and it is very striking 

 to see the sharp dividing-line between quiescent liquid in the 

 centre and rotating liquid on the outside. This dividing-line, 

 represented by the steep part o£ the curve in the figures, 

 slowly moves towards the centre but becomes indistinct some 

 distance from it. It is best seen at the higher speeds when 



the velocity-gradient is greater. Its rate of travel depends 

 on the value of O. 



In the case of the large cylinder starting at the high speed, 

 large secondary eddies 3*5 cm. across were often observed 

 just inside the cylinder wall a few seconds after starting the 

 motor. These soon died out when the velocity-gradient 

 became less, and thereafter the motion travelled in towards 



