Fitzgerald — On a Model Illustrating Properties of Ether. 419 



as the square of the distance from points spread over a plane. 

 Sir William Thomson has also pointed out a case in which a 

 polarised state of the vortex motion vsrill be in equilibrium as long 

 as it cannot produce motion of the boundary of the containing 

 vessel, but in which if it can expend its energy in causing motion 

 of the boundary, its energy, will be so expended. From this it 

 seems likely that there are modes of polarisation of a vortex 

 sponge which will be in equilibrium as far as the sponge is con- 

 cerned, and whose energy can only be spent on producing motion 

 of the boundaries. This is exactly the condition required in order 

 to explain the equilibrium of the strained ether, which itself in 

 equilibrium tends to move objects within it. If the vortex sponge 

 be otherwise disturbed, ii is obvious that the polarised state will 

 become distributed through the sponge, and this should be analo- 

 gous to the propagation of light. It is evident that inasmuch as 

 we could neither create nor destroy vorticity, all we could do would 

 be to polarise the motion, and that all such polarisation would have 

 this character of electric phenomena that we could not produce one 

 kind of electrification without producing somewhere an equal and 

 opposite electrification. 



I have not been able to work the theory out completely, but 

 have not come across any fatal objection to it. There are a great 

 many suppositions that can be made as to the nature of the polari- 

 sation that represents electrostatic phenomena; and it may be of use, 

 to anyone working at an hypothesis as to the nature of this polari- 

 sation, to recollect that it is allowable to suppose a flow continuously 

 in one direction between electrified bodies held apart by solids, for 

 the electric forces are then balanced by stresses in the solid sup- 

 ports, and these stresses may be due to the flow back of whatever 

 is supposed to be flowing out between the electrified bodies. I do 

 not expect that any flow continuously in one direction does take 

 place ; but there is danger of such a hypothesis being summarily 

 dismissed, because of its being supposed to lead to an accumulation 

 in the body towards which the flow takes place. 



In conclusion, I desire to reiterate that it seems that the only 

 way in which to impart to a perfect liquid properties at all analo- 

 gous to those possessed by the ether, is by supposing it full of 

 motion. 



