IN VOLTAIC ELECTRICITY AND ELECTRO-MAGNETISM. 
297 
positive, it will absorb nearly twice as much heat from the water in that 
chamber as the oxygen does from the water in the other. The temperature of 
the water in the negative chamber must therefore be kept lower than that in 
the other compartment. If liquids could conduct voltaic electricity without 
suffering decomposition, the temperature of the whole mass between the poles 
would have its temperature equally elevated in every point ; but the two 
unequal cooling processes going on in the extreme chambers, occasion the 
striking inequality of temperature in the three divisions. But this experiment 
appears to me to establish another point of vast importance in the theory of 
voltaic electricity. If the hydrogen which is set at liberty at the negative pole 
traversed the fluid between the two poles, it is obvious it must have acquired 
its specific heat at the positive pole, and consequently could not have lowered 
the temperature in the negative cell. The oxygen, then, which is disengaged 
at the positive pole must have belonged to the film of water in contact with 
that pole, and the hydrogen set at liberty at the negative pole must have been 
the hydrogen belonging to the film of water in contact with the negative pole. 
There appears, therefore, to be no actual transfer of the component parts of 
w r ater, but, agreeably to the views of M. Grotthus, a continued series of 
decompositions and recompositions along the whole chain of aqueous particles 
between the two poles. 
24. The explanation now given of this curious phenomenon receives the 
strongest confirmation from the decomposition of other substances besides 
water. When a solution of sulphate of copper was placed between the poles 
of a powerful battery, and the temperatures of the cells examined as before, 
it was found that a much greater difference between the temperatures of the 
extreme chambers took place ; but the temperature of the negative chamber 
was now higher than that of the positive. In some of my experiments the 
temperature of the negative cell rose eight or ten degrees above that of the 
positive, whilst the middle chamber was nearly of the same temperature with 
the negative compartment. The same striking difference was observed when 
a solution of acetate of lead was employed. 
The cause of this change of temperature depends, as in the case of water, 
on the specific heats of the elements separated at the two poles. When a 
metallic salt is decomposed by the agency of voltaic electricity, the pure 
