382 Prof. Oliver Lodge on the Seat of the 



copper with which it is put into contact, where does it all 

 come from ? And why does it not leave the copper strongly 

 negative instead of only feebly so, as evidenced by Sir W. 

 Thomson's electrified-needle form of experiment? Why, again, 

 does this method of observing the Volta-effect, with the plates 

 permanently in contact, agree so well with the old method of 

 observing it by separation of the plates, if a great but uncer- 

 tain part of the charge leak back as soon as separation beyond 

 molecular distance is attempted ? 



These and similar difficulties occur to me in connection with 

 this most interesting theory ; and I state them, not with any 

 idea that they are final and unanswerable, but because it is 

 always serviceable to point out the apparent defects of a theory 

 as well as its merits. 



It will be seen that, w^hereas Helmholtz's theory starts with 

 a hypothetical differential attraction of matter for electricity, 

 and explains the chemical attraction of matter for matter on 

 the strength of it, my view starts with a differential chemical 

 attraction of matter for matter (i. e. zinc attracting oxygen 

 more than copper attracts it), and on this basis works out the 

 theory of the voltaic cell and of the Yolta-effect. 



In electrolysis proper both views may be at one, because 

 here we are concerned with electrical attractions only ; but 

 Prof. Helmholtz's has the advantage, because it explains the 

 fact of atomic charges, w T hich mine has to assume. My view 

 of electrolysis has hitherto been much less electrostatic than 

 Prof. Helmholtz's, but also it has been much more vague. A 

 great deal is to be said for the assumption of ordinary electro- 

 static attraction over molecular distances, and by adopting 

 such more definite ideas I am in hopes of improving my theory 

 further. And though, after all, none of these views can be 

 really absolute, because they begin and end with action at a 

 distance, still electrostatic attraction is a fact, and we know 

 that it can be accounted for by a strain in a continuous 

 medium. Hence phenomena reduced to electrostatics may be 

 held to be provisionally " explained." 



But beyond electrostatic attraction some other primary 

 force is necessary ; either chemical affinity, the attraction of 

 atom for atom, or electrical affinity, so to speak, the attraction 

 of atoms for electricity. 



Chemical affinity is a fact, however it be accounted for ; 

 but, to enable it to explain everything, the fact of atomic 

 charge must be permitted to likewise go without explanation. 

 These are the necessary data for my view. 



" Electrical affinity " is not known to be a fact ; but if it be 

 granted, everything is explained (barring a few outstanding 

 difficulties), even the fact of atomic charge itself, though not 



