500 Sir Oliver Lodge on the 



density of aether may turn out to he fifty thousand million 

 times the ordinary material density of platinum. In which 

 case every cubic millimetre of space contains the equivalent 

 of a thousand tons, and every part of it must be internally 

 squirming with the velocity of light. 



Appendix A. 



Quotations from earlier writers on the subject of a 



hypothetical magnetic flow. 



The experiments above described are referred to by Professor 

 Larmor in his paper on "A Dynamical Theory of the Electric and 

 Luminiferous Medium," in the Phil. Trans, for 1894, vol. 185, 

 p. 778. A fairly high value of density for seiner is there contem- 

 plated with equanimity ; though it is pointed out that such density 

 would require the aether to be absolutely stationary, except in a 

 magnetic field, in order to avoid hydrodynamical systems of force 

 between moving bodies. But since everything tends to indicate 

 that the aether is the most stationary substance in existence, at least 

 as regards locomotion — probably the absolutely stationary thing, 

 in so far as the phrase means anything — this necessity involves no 

 difficulty whatever. 



27. To illustrate the theoretical bearing and expectation of a 

 magnetic drift, it may be useful to make a few extracts : — 



First I will quote from § 73 and 74 from the above 1894 paper 

 of Prof. Larmor's (Phil. Trans, vol. 185, p. 773, &c). 



" On the present theory, magnetic force or rather magnetic 

 induction consists in a permeation or flow of the primordial 

 medium through the vortex-aggregate which constitutes tho 

 matter; apparently it has not been tried (see however §81) 

 whether light-waves are carried on by this motion of the 

 medium and their effective velocity is thereby altered, as we 

 would be led to expect. It has been shown, however, by 

 Wilberforce that the velocity of light is not sensibly altered by 

 motion along a field of electric displacement, so far negativing any 

 theory that would connect electric displacement with considerable 

 bodily velocity of the aether ; and it has also been verified, by Lord 

 liayleigh, that the transfer of an electric current across an electro- 

 lyte does not affect the velocity of light in it 



"As motion of the aether represents magnetic force, the fact that 

 the magnetic permeability is almost the same in all sensibly non- 

 magnetic bodies as in a vacuum, must be taken to indicate that the 

 sether flows with practically its full velocity in all such media, so 

 that there is very little obstruction interposed by the matter ; it 

 follows that, in the motion of a body through the aether, the outside 

 sether remains at rest instead of flowing round its sides 



" The notion of illustrating magnetic induction by the permeation 

 of a fluid through a porous medium containing obstacles to its 

 motion has been shown by Lord Kelvin to lead to a complete formal 

 representation of the facts of diamagnetism.*' 



