508 



refort — 1884. 



subtract Peltier forces from the observed numbers before comparing them 

 with theory, but these forces are too small to make any appreciable 

 difference. 



Volta Effects in Air. 



The alternative calculated number sometimes given is merely to show 

 the kind of variation probable in those cases from uncertainty of data. 

 In each case of agreement the calculated number is a little higher than 

 the observed, as -was to be expected. No reason occurs to me for the 

 breakdown, and apparent interchange, in the case of lead and iron but 

 such vague guesses as may occur to everyone. 



Measurements of the E.M.F. between clean metals plunged into dis- 

 tilled water or weak acid have been made by Clifton and by Beetz. 1 I 

 suppose one is justified in calling them — 



Volta Effects in Water. 



I do not wish to blink the fact that some of the numbers in the former 

 of the above tables afford a rather poor support to my theory; but it must 

 be remembered, on the other hand, that they are not relative numbers 

 only that we have calculated, but absolute ; and the fact that the heats of 

 •combustion reduced to volts are numbers of the same order of magni- 

 tude as the Volta effects, is of itself a strong confirmation of the belief 

 that chemical strain at the air contacts is the real cause of the apparent 

 •contact force at the junction of two metals. 



1 Eeetz, Ann. der Phyxih, x. 348, 18S0. 



