324 Mr. E. H. Hall on the new Action of 



ferent plates of the same metal, we see from the experiments 



Mx V 



on both gold and silver that the basis — ^7 — is by far the 



better one. We may sum up the matter by saying that, 

 according to p*resent appearances, 



1st, there is no constant representative quantity for all 

 metals ; ,.. -^ 



2nd, the basis — - — does not give a constant representative 



quantity for different plates of the same metal ; 



Mx V 



3rd, the basis ■ R1/ gives for different plates of the same 



metal a representative quantity which is approximately a con- 

 stant. 



MxV 

 It is evident, upon consideration, that this ratio ^7 



could not be expected to give the same result for all metals. 

 We get the quantity V by dividing the nominal cross section 

 of our conductor by the strength of the current. We must, 

 however, think of a metal as not strictly continuous, but con- 

 sisting of metallic particles more or less compactly aggregated 

 in the space occupied by the body as a whole. Evidently, 

 therefore, the cross section effective in conduction would vary 

 in different conductors of the same nominal cross section. It 

 may therefore be found that different specimens of the same 

 metal, but of different densities, will give quite different values 



n MXV 



Of course the magnitude of the new action in the different 

 metals may be considered in connexion wtth various other 

 physical properties of the metal beside the specific electrical 

 resistance. One might, for instance, expect to find some 

 striking relation by comparing in this connexion the known 

 magnetic or diamagnetic properties of the metals. It is indeed 

 to be observed that the most strongly magnetic substance, iron, 

 does show the new action in a more marked degree than the 

 other metals ; and possibly nickel will come next in the list. 

 Here the clue is ent' y lost, however ; for the relative magni- 

 tude of the action in gold, silver, &c. is entirely out of propor- 

 tion to the magnetic capacities of these metals. 



On the whole, we cannot be sure that any relation has yet 

 been detected between the magnitude of the new action in 

 the various metals and any known physical property of these 

 metals. It is of course possible, however, that, when more 

 data shall have been obtained, analogies and relations at pre- 

 sent unsuspected will appear. It can hardly be doubted that 



