On General Relativity. 219 



the relative velocity of star and observer. The case is exactly 

 the same as locating an aeroplane by pointing a resonator in 

 the direction in which the noise of the engine is loudest; the 

 aeroplane will appear displaced behind the true position. If 



is the apparent latitude and 6' the true latitude, this 

 explanation makes v/c = sm(d' — 6)/sm6' } whereas the usual 

 explanation makes v/c = sin (6 1 — 6)j sin 0. But the differ- 

 ence is too small to observe. 



Thus the hypothesis accounts for aberration, and seems 

 to give a means of escaping from the Fitz Gerald -Lorentz 

 assumption and its consequence, the Principle of Relativity, 

 at the expense, of course, of a strictly electromagnetic 

 explanation of matter. 



XX. On General Relativity. 



To the Editors of the Philosophical Magazine. 



Gentlemen, — 



rpHE appearance of Dr. Silberstein's recent article * on 

 A " General Relativity without the Equivalence Hypo- 

 thesis " encourages me to restate my own views on the 

 subject. I am perhaps entitled to do this as my work on the 

 subject of General Relativity was published before that of 

 Einstein and Kottler, and appears to have been overlooked 

 by recent writers. In 1909 I proposed a scheme of electro- 

 magnetic equations f which are covariant for all trans- 

 formations of co-ordinates which are biuniform in the domain 

 we are interested in. These equations were similar to 

 Maxwell's equations, except that the familiar relations 

 B = //,H, D = kE of Maxwell's theory were replaced by more 



* Phil. Mag. July 1918. 



t Proc. Lond. Math. Soc. ser. 2, vol. viii. p. 223 (1910). 



