Density of the JEther. 501 



Also on pages 779 and SOo : — 



" The residual forcive between bodies at rest in a field of aetherial 

 motion, dne to very slight defect of permeability, has already been 

 shown, after Lord Kelvin's illustration, to simulate diamagnetism ; 

 and the fact that there exist no powerfully diamagnetic substances 

 is so far a continuation of the present hypothesis. The view that the 

 magnetic field of a current involves only slight circulation of the 

 fluid aether is also in keeping with the account which has been 

 given (§ 46) of the genesis of such a field." .... 



"The idea of representing magnetic force in the equations of 

 electro -dynamics by the velocity of the electric medium has been 

 tried already, for example by Heaviside and by Sommerfeld, not to 

 mention Euler. The objection however has been taken by Boltz- 

 mann and also by von Helmholtz, that it would be impossible on 

 such a theory for a body to acquire a charge of electricity. A 

 cardinal feature in the electrical development of the present theory 

 is on the other hand the conception of intrinsic rotational strain 

 constituting electric charge, which can be associated with an 

 atom or with an electric conductor, and which cannot be discharged 

 without rupture of the continuity of the medium.'"' 



28. G. P. FitzGerald also recognized the possibility or probability 

 that the aether may have a high density ; as is shown by the 

 following quotation from his Helmholtz Memorial Lecture before 

 the Chemical Society of London in 1896 (page 347 of his Collected 

 Papers) while discussing the vortex theory of matter. After 

 explaining that a liquid with inteuse internal movement, or kinetic 

 structure, could propagate disturbances like light, provided there 

 were no diffusion of the motion, he goes on to point out that 

 '* as vortices move of themselves freely and independently of the 

 density of the liquid, there is no necessity for supposing that the 

 density of the liquid is small. In fact, the simple theory would 

 point to the conclusion that its density may be greater than 

 that of platinum. This would require the energy per cubic centi- 

 metre of the turbulent motion to which the propagation of light is 

 due to be very large indeed, approaching a million of millions of 

 kilojoules, i. e. it would be equivalent to a million horse-power for 

 10 hours a day for nearlr a month." 



This guess at intrinsic aetherial energy makes it 10 22 c.o.s. My 

 paper has now estimated it as several thousand million times 

 greater still. 



29. At an earlier date, Mr, Heaviside's ideas on a magnetic 

 analogue or model, based on fluid flow, may be typified by the 

 following extract from a paper of his in the l Electrician ' for 1883. 

 feee ' Electrical Papers,' vol. i. pp. 275, 277. 



" But by far the most interesting analogue is that presented by 

 the motion of a perfect incompressible liquid. Let it fill all space 

 (since the magnetic force of our rectilinear current extends without 



