﻿Lord Rayleigh on x^Eolian Tories. 



439 



stand resting on the bottom of the basin and rising slightly 

 above the level of the water. 



The pendulum (fig. 2), of which the lower part was im- 

 mersed, was supported on two points (A, B) so that the 



W 



B 



W 



possible vibrations were limited to one vertical plane. In 

 the usual arrangement the vibrations of the rod would be 

 radial, i. e. transverse to the motion of the water, but it was 

 easy to turn the pendulum round when it was desired to 

 test whether a circumferential vibration could be maintained. 

 The rod C itself was of brass tube Sh mm. in diameter, and 

 to it was clamped a hollow cylinder of lead D. The time of 

 complete vibration (t) was about half a second. When it 

 was desired to change the diameter of the immersed part, 

 the rod C was drawn up higher and prolonged below by an 

 additional piece — a change which did not much affect the 

 period t. In all cases the length of the part immersed was 

 about 6 cm. 



Preliminary observations showed that in no case wore 

 vibrations generated when the pendulum was so mounted 

 that the motion of the rod would be circumferential, viz. in 



