i6 Gibson, Bodies floating ijt a Free or a Forced Vortex, 



elevation of the outer layers, and, in consequence, the 

 velocity of inward flow increases somewhat from the 

 surface downwards, and is a maximum at the bottom. 

 This increases the relative tendency to inward motion of 

 a body whose depth of immersion is relatively great. 



From the foregoing analysis it appears that, depending 

 on the relative magnitude of the forces called into play, 

 one body may be irresistibly attracted to the centre of 

 the vortex, a second may be actually repelled from the 

 centre, a third may circle in neutral equilibrium at some 

 definite radius, while a fourth, again, depending on the 

 size, shape, and distribution of weight, may be attracted 

 inwards to a certain radius of stable equilibrium at which 

 there is an exact balance between the inward and outward 

 forces, and within which the resultant force is outwards. 

 Others again, and this is very definitely shown by the 

 experiments, may have two radii of equilibrium, the space 

 between being one of neutral equilibrium. 



§ 4. Experiments on Forced Vortex. The forced vortex 

 experiments were carried out in a circular vessel 15 inches 

 diameter and 8 inches high. This was fitted to a 

 whirling table and was capable of rotation at any speed 

 up to 100 revolutions per minute by means of a small 

 electric motor. The same series of floats were used as in 

 the free vortex, and as a result of the experiments the 

 following conclusions may be drawn. 



{a) Small bodies approach the centre with a radial 

 velocity which is greater the greater the radius of 

 rotation and the intensity of the vortex. 



{b) In homogeneous bodies of the same size and shape 

 the heavier shows the less tendency to approach 

 the centre. 



