Papers on Contact Electricity. 



53 



experiments with simple cells ; and his electromotive forces 

 are: — 



Zinc and platinum. 



Zinc and copper. 



Zinc and silver. 



Open. 



Closed. 



Open. 



Closed. 



Open. 



Closed. 



1-52 



0-72 



0-98 



046 



1-23 



0-57 



And when he used sodium amalgam the difference of the elec- 

 tromotive forces of the closed cells was equally striking : — 



Sodium amalgam 

 and platinum. 



Sodium amalgam 

 and silver. 



Sodium amalgam 

 and copper. 



Sodium amalgam 

 and zinc. 



Open. 



Closed. 



Open. 



Closed. 



Open. 



Closed. 



Open. 



Closed. 



2-31 



1-33 



2-05 



1-22 



1-79 



114 



0-78 



0-68 



The nature of the negative metal must always have a great 

 effect on the initial electromotive force ; we are, however, 

 astonished that Prof. Beetz should find such great differences 

 in the columns headed "closed." Our impression has always 

 been that when the negative metal becomes sufficiently coated 

 with hydrogen, the contact between the thin conducting-layer 

 of gas and the metal was almost like that of a pair of metals ; 

 and if this is the case, then 



is the same as 



H|Pt + Pt|Zn 

 H|Cu + Cu|Zn, 



and almost any negative metal would eventually act like a con- 

 ducting hydrogen plate. 



Prof. Exner's second paper, like his first, we are com- 

 pelled to regard as wrong theoretically, and describing expe- 

 riments which do not lead to the conclusions he has deduced 

 from them. 



It is not necessary for us to follow Beetz into his dis- 

 proof of Prof. Exner's statements regarding the use of the word 

 polarization, which is employed in England in the vaguest 

 way to indicate a change of current whether from alteration 

 in the electromotive force or in the resistance, but to which 

 in Germany various philosophers attach distinct meanings. 

 Between the contact theory as properly understood and the 

 chemical theory there is really nothing antagonistic. The 

 " summation law " deduced from various experiments for 

 metals and one liquid, and extended by our own experiments 



