10 Gibson, Bodies floating in a Free or a Forced Vortex. 



(i) Where homogeneous bodies have the same specific 

 gravity, depth of immersion, and shape of plane of 

 flotation, generally speaking the larger shows the greater 

 tendency to approach the centre. In bodies, the section 

 of whose plane of flotation approximates to a rectangular 

 form, this appears to be generally true, but in circular 

 cylindrical bodies floating with vertical axes, there appears 

 to be a critical diameter, — from lin, to i|in. in these 

 experiments — for which the repellent effect of the vortex 

 for small radii of revolution is very marked. Objects, 

 whether of a greater or less diameter than this, show a 

 greater tendency to be drawn into the vortex, though this 

 effect is more marked with increasing than with diminish- 

 ing sizes. Cf Experiments A (i to lo) ; B (i to 5) ; 

 C (i to 9). The same applies, in a lesser degree in the 

 case of bodies of square section, but here the critical size 

 appears to be somewhat less. Cf. A (23 to 26) ; C (24 to 

 28) ; A (27 to 32) ; C (14 to 17). Cylindrical objects of 

 a size somewhat larger than, but approximating to the 

 critical, appear to have a definite circle of rotation on the 

 lip of the funnel, in which, except when affected by ex- 

 traneous circumstances, they may rotate indefinitely. If 

 displaced outwards from this circle they return, while if 

 displaced inwards they are drawn down the funnel. 

 Objects somewhat smaller than the critical size — from 

 •Mn, to lin. diameter — have an equilibrium circle of 

 much greater radius, usually from 7 to 10 inches in these 

 experiments. The radius of the equilibrium circle for a 

 given object increases with the intensity of the vortex. 

 For objects of greater size than the critical, it increases, 

 within limits, with the size of object, the largest object to 

 have an equilibrium circle in these experiments being of 

 three inches diameter. 



