Weight and Fate of Light. 557 



the energy o£ the light, which is c 2 times its mass, will 

 become the constitutional or vortical energy of the electron, 

 whose intrinsic circulation must therefore be of the same 

 order as c. 



Einstein's presentation of the kinetic energy of matter is 

 harmonious, for it takes the form mc 2 + ^mv 2 , the first term 

 being apparently the intrinsic or constitutional energy of 

 each ultimate particle. 



On this view the interior of an enormous stellar system 

 could be the seat of the generation of matter, on rather 

 different lines from those suggested by Prof. Eddington in 

 his Address to Section A at Cardiff last year. If the 

 concentrated and controlled luminosity were locked up 

 satisfactorily as an electron, its existence would be per- 

 manent : but is it possible that under exceptional conditions 

 a portable collection of half- formed, either half-materialised 

 or half-shattered, units could go about together in an un- 

 stable state, as globe-lightning, and be liable to explode back 

 into light again ? 



Dr. Barlow questions whether the stoppage of light here 

 considered need be very different from ordinary stoppage 

 by absorption, and asks whether the /3 particle ejected by an 

 impinging X or y ray is liberated merely, or manufactured ! 

 I do not attempt to answer any of these questions at present, 

 but I may refer to page 466 of the Phil. Mag. for May 1919 

 (where there is a misprint in the footnote of 10~ 12 for 10 12 ), 

 and also to the Phil. Mag. for February 1920, pp. 172 & 173, 

 especially to these words : — 



"A wave-front is an evanescent kind of matter— a sort of attempt 

 of an accelerated electron to reproduce itself; the question is how 

 such a peculiarity, when generated, can be made permanent and its 

 violent locomotion checked. We must find out how to disturb the 

 ether in such a way that the modification shall remain concentrated, 

 and not instantly rush away and disperse itself with the speed of 

 liofht. The electric and the magnetic components must be separated, 

 the one kept and the other annulled." 



Or, at least, they must be put out of phase. The simul- 

 taneous electric and magnetic displacements which constitute 

 a light-wave start from a Hertz vibrator with 90° difference 

 in phase, though the electric rapidly overtakes the magnetic, 

 and the two get into step. Retardation should reverse the 

 process set forth by Hertz in his Electric Waves, Chapter IX, 

 (especially pp. 142, 146), and cause them to finish in a modi- 

 fication of their original predicament — absorption corre- 

 sponding to emission, — thus reproducing the kind of etherial 

 singularity whence they arose. 



