OCrémieu-Pender Discovery. 407 
1—1/y? of that of the body, whose index of refraction is p. 
By Maxwell’s law p?=K, and so Fresnel’s law makes the 
velocity of the ether 1—1/K of that of the transparent di- 
electric. This formula of Fresnel’s is the one verified by 
Fizeau’s experiment with running water, repeated by 
Michelson and Morley. Thus, then, the phenomenon which 
presented itself in ‘“Tonization &ec.” and has just been 
discussed in a simpler form, turns out to be an electrical case 
of Fresnel’s law. The Crémieu-Pender effect is another 
ease. Consider the rotating charged disk in their experi- 
ments. The electricity at any point of the disk takes the 
velocity v of the disk at that point. The solid dielectric 
attached to the. disk imparts to its ether at that point the 
velocity v(1—1/K). Thus the velocity of the electricity on 
the disk relative to the ether in the rotating disk is v/K. 
If, then, this slip »/K of the electricity past the adjacent 
zether is the cause of the magnetic effect of electric convec- 
tion, we see why Crémieu’s use of solid dielectrics reduced 
the magnitude of the effects he was investigating. One 
gathers by implication that Crémieu and Pender are investi- 
gating the ettect of the dielectric quantitatively. In one 
quantitative result given (loc. cit. p. 460) a magnetic effect 
measured by 140 when air was the dielectric was reduced 
to 15 when mica was attached to the metallic surfaces ; these 
are in the ratio of 1: 9, while the corresponding ratio of v/K 
with v the same in both cases is the ratio of the dielectric 
capacity of air to that of mica or 1: 6°6. As further experi- 
mental results are tobe expected soon, it will be better to 
await their appearance before proceeding with the theory 
that the magnetic effect of electric convection is due to the 
slip between electricity and ether, and not to the relative 
motion of electricity and remote ether. Crémieu and Pender 
have secured evidence of a phenomenon noticed by Himstedt, 
that beyond a certain density of charge the magnetic effect 
ceases to be proportional to the density of the moving charge. 
‘This will doubtless receive the experimental attention it 
merits. Meanwhile it may be pointed out that the results 
calculated from many of the recent experiments on ionic 
velocities in gases will need to be revised in order to take 
account of the dielectric capacity of the stuff of the atom, as 
1 have attempted to do in the case of ions moving through 
water. 
Melbourne, January 1904. 
