40 Larmor, Physical Aspect of the Atomic Theory. 



but that they can be drawn out into the open by electric 

 shock, and securely manipulated (J. J. Thomson, Lenard, 

 etc.) as atoms of pure disembodied electricity in those 

 cathode streams across highly rarefied gases which Sir 

 W. Crookes long ago insisted on calling a fourth state of 

 matter. 



In the electrolysis of an acid we are to imagine the 

 negatively charged massive hydrogen ions, which happen 

 sporadically to be free in the solution, as being slowly 

 drawn towards the negative electrode by the electric field 

 pervading the medium, as accumulating there with pro- 

 duction of polarisation reacting against this impressed 

 electric field, until they are so crowded together by the 

 constraint that some kind of instability arises, whereby 

 one of them takes over, but without violent disturbance 

 such as could diffuse away, two positive unitary charges 

 from the electrode. Surely these charges must in ultimate 

 analysis be positive electrons, or else the power of losing 

 negative ones must be unlimited. At any rate, in virtue 

 of them, the ion can associate with another and become 

 released as a free self-contained molecule of hydrogen, a 

 very different thing from the mutually constrained ions 

 that gave rise to it, — the energy required for the electro- 

 lysis being expended mainly, as Helmholtz insisted, and, 

 as we have seen, usually without much necessary waste, 

 in this requisition of the two positive charges. 



The relevance of the mode of operation of the Grove 

 gas battery will here occur to mind ; the finely divided 

 or porous platinum surface promotes ionisation of the gas 

 alongside it through the opportunities arising from intimate 

 contact in confined spaces {cf. p. 37), and so manages 

 to utilize much of the available energy of gaseous 

 combination, which in gases is very different from the 

 heat of combination on account of the change occurring 



