378 Prof. Oliver Lodge on the Seat of the 



which he has improved and elaborated since (see Faraday 

 Lecture of 1881). 



This fascinating theory has a small hypothetical basis, viz. 

 Nos. 3 and 9 of the above list; and on this foundation is erected 

 an explanation of the Volta effect, a theory of electrolysis, and a 

 great part of a theory of chemical combination. 



Once grant, (1) that every substance has a specific attraction 

 for positive or for negative electricity which can be exerted 

 only through molecular distances, and (2) that the laws of 

 electrostatics may be applied to the charges of atoms in a 

 liquid ; and the ease with which a multitude of phenomena are 

 explained is surprising. I do not feel certain that a little too 

 much is not explained ; but we can postpone the consideration 

 of possible objections until the theory itself is briefly stated. 



Metals, and " electropositive " elements generally, attract 

 positive electricity or positively electrified atoms whenever 

 these come within range, L e. within some molecular distance 

 of the surface. Potassium and zinc attract strongly, copper 

 and gold feebly. Oxygen, chlorine, and other " electronega- 

 tive " elements, attract negative electricity in a similar manner. 



Bring now two metals, say zinc and copper, into contact, 

 and the superior attracting-power of zinc for positive elec- 

 tricity will at once charge it at the expense of the copper, so 

 that the zinc touching-surface becomes strongly positive, and 

 the copper surface strongly negative. Separate the metals, 

 and they mostly discharge into each other; but a feeble 

 charge remains if the surfaces in contact were large, and if 

 they have been neatly separated ; and this is the Volta effect. 



Moreover since each metal has a definite attracting-power 

 depending on itself only, Volta' s series law is an obvious 

 necessity. 



If one of the substances had been an insulator much less 

 loss need take place while separating them, and accordingly 

 high charges are then found upon them even after separation 

 (" frictional electricity "). 



Now consider similarly two atoms in contact, forming, say, 

 a water molecule. The hydrogen will be positively charged, 

 the oxygen negatively. If some atoms should get knocked 

 asunder they retain their charges and therefore tend to unite 

 again, but, while separate, their mutual attractions and repul- 

 sions will preserve a uniformity of distribution throughout the 

 liquid — e. g. the repulsion of similar charges will prevent a 

 number of oxygen molecules crowding together ; and if any 

 cause should remove oxygen atoms from any part of the liquid, 

 the vacancy will be instantly supplied by similar atoms repelled 

 there. 



