444 Intelligence and Miscellaneous Articles. 



radial disturbance: or the intensity of the destructive effect on 

 leaves, branches, &c. increases radially towards an axial line, where 

 the effect is a maximum, or explosive. 



Before this observation, or in 1876, I had published two articles 

 in 'Engineering,' (March 17 and 31, 1876), where, in regard to 

 the lightning discharge, the above radial movement towards an 

 axial line — which constitutes the "spark" — was suggested on 

 theoretical grounds to be a fact ; so that I may be allowed to add a 

 few remarks on this point here, referring to the above-named 

 articles for more detail. The idea that static electricity is a " reso- 

 nance " of the aether (confirmed experimentally since by the dis- 

 coveries of Prof. Hertz) is speculatively advanced in these articles, 

 and it was mentioned in a work, ' Physics of the Ether ' (E. and 

 F. IS". Spon, London), published by me in 1875. I cannot do 

 better than quote the passage, as it bears on the present case ; 

 viz. : — 



"It is evident that friction or any molecular disturbance what- 

 ever would naturally throw the aether within a mass of matter into 

 vibration. The stationary vibration of a mass of aether has its 

 analogy in the stationary vibration — ' resonance ' — of a mass of air, 

 produced by friction &c. The change of 'static'' electricity into 

 1 dynamic' electricity, or the ' static' state into the l dynamic' 

 state, and conversely, is simply the change of stationary vibrations 

 into progressive vibrations, the one being necessarily always capable 

 of producing the other ('Physics of the Ether,' p. 133). 



As we may sometimes arrive at initiatory ideas of the modus 

 operandi of phenomena, which may usefully aid towards their final 

 solution, no further excuse is probably needed for the considera- 

 tions which follow. 



The spark or lightning-flash will be found at least, I believe, to 

 consist in the breaking, through loss of equilibrium, of a "reso- 

 nance " column of aether (which vibrated radially about a central 

 rarefied* axis, and partly longitudinally), the loss of equilibrium 

 being followed by the resolution of stationary waves into progres- 

 sive waves, with the movement of these waves radially (in the 

 main) from all sides towards a central or axial line, where they 

 rebound with explosive effect. In this way energy is drawn from 

 a wide radial extent or volume of the aether and concentrated sud- 

 denly on a single line (the axis), which produces a violent conden- 

 sation of the aether along this line, instantly followed by an 

 explosive rebound, as the aether recovers its equilibrium, with the 

 velocity of light. If the trunk of a tree, for example, happens to 

 be situated in this aether rarefaction (where che "attraction" is a 

 maximum just before the flash is observed), then, since the aether 

 is known to penetrate the substance of the tree freely, it becomes 

 clear enough, as a mechanical fact, that on such a violent conden- 



* The rarefied axis constitutes a point of stability to vibrate about, 

 just as the rarefaction in a column of air (in a ;npe) open at both ends 

 constitutes a point of stability for the resonance of the air-column. 



