﻿Mechanism of Electrical Conduction. 69 



been said to show that the opacity of conductors must be far 

 less for luminous radiations than for electromagnetic dis- 

 turbances of long period, and we may fairly expect, I think, 

 that the transparency of metals is to be explained without 

 attributing any new properties to the electromagnetic field. 



The second part of this paper will deal with electrolytic 

 conduction and disruptive discharge. 



Note added April 30th. 



In the course of the discussion Prof. S. P. Thompson ob- 

 jected to the arrangement of molecules in rectangular order, 

 and he further suggested that the arguments might only be 

 applicable in two dimensions. I had omitted to mention that 

 the figures were intended to be sectional views of three- 

 dimensional models, while the rectangular arrangement of 

 molecules was merely adopted to save prolixity in the descrip- 

 tions, and was so far from being essential to the investigation 

 that the case of irregularly distributed coordinates and velo- 

 cities was constantly before my mind. Another point raised 

 by Prof. Thompson must also be considered here : in § 6 it 

 does not necessarily follow that two conductive particles 

 oppositely charged like A and B (fig. 1), approaching one 

 another and subject to the influence of an external E.M.F. 

 acting from right to left, would have the signs of their 

 respective electrifications reversed by a momentary contact ; 

 in some encounters the readjustment of electrifications might 

 even be in the opposite sense ; but I think we may safely 

 admit that in the long run the effect of innumerable collisions 

 amongst such conducting particles as A and B will be to 

 transfer electrification in the direction of the impressed 

 E.M.F. 



Prof. Riicker recalled a difficulty, which Lord Kelvin 

 pointed out some time ago, in connexion with the collisions 

 between molecules. If we suppose the molecules to be con- 

 stituted like little pieces of elastic solid, every collision will 

 cause some additional amount of translational energy to be 

 converted into energy of vibration, and heat-energy will be 

 continually running down into energy of shriller and shriller 

 vibrations, that is, into energy of a lower form. In the fore- 

 going pages, electrical contact between particles is supposed 

 to occur during a collision, and Prof. Riicker remarked that 

 the method suggested for avoiding an electromagnetic degrada- 

 tion of energy left untouched the corresponding mechanical 

 difficulty. 1 have made some attempt to deal with this 



