Electromotive Forces in the Voltaic Cell. 261 
(say heat) is generated atthe junction. Thus there is a true 
Peltier effect at the junction despite the existence of V—V’ 
and its equality to the junction force, and yet no resistance 1s 
offered to the flow of water either way. Thus is the first form 
of the argument controverted. 
Fig. 14, 
Hydrostatic analogue of the true contact or Seebeck force, and of the real 
though small difference of potential which it maintains between two 
metals in contact. A and Brepresent the two metals, C their junction ; 
W is a weight driving a water-tight wheel until stopped by the dif- 
ference of potential set up. The hydraulic raising or lowering of the 
weight represents the Peltier effect. 
To pump water from A to B by any other pipe would need 
work to be done equal to Q(V—V’), and to pump water 
against the force of W, acting alone, would also need work EQ; 
but when the water goes from A to B wid W, or vice versa, no 
work is done on the whole. Quite true: but the conclusion 
that no work is done at the junction by no means follows. 
Work must be done at the junction in proportion to the force 
there (by inspection of the diagram); and accordingly the 
existence or non-existence of a Peltier effect has everything to 
do with the existence or non-existence of alocal E.M.F. This 
controverts the second form of the argument. 
If the argument be now considered upset, are we to pro- 
ceed to assert that the difference of potential, or force, con- 
cerned in the Volta effect, and the heat-destruction or gene- 
ration concerned in the Peltier effect, are closely connected, 
and in fact different ways of observing the same thing ? 
By no means. All we have proved is that the Peltier effect 
accurately and necessarily represents and measures the true 
contact-force at a junction. True we have considered a 
difference of potential V — V’ as produced by this contact-force 
in an incomplete circuit ; and so it is. But nothing has been 
said to imply that this difference of potential has anything to 
do with what is observed in electrostatic experiments as the 
Volta effect. So far from this, I will assert that what is 
