434 Prof. E. Edlund on the Thermal Phenomena of the 



The mean, 18124, of the numbers found in the above expe- 

 riments differs only about 300 heat-units from the last-men- 

 tioned sum ; wherefore the two may be regarded as equal. 

 But according to both views, No. 1 and No. 2, this equality 

 must exist ; and so we have no clue to enable us to judge in 

 what way the galvanic current is produced ; whether we take 

 No. 1 or No. 2 as the correct way of considering, in this re- 

 spect we come to the same result. The calculation of the 

 quantity of galvanic heat developed by the current in the 

 entire circuit (a calculation not carried out by Favre in these 

 experiments) shows that it amounts on the average to 10837 

 thermal units, not much more than the half of the chemical 

 heat. 



The circumstance that, as results from the above experi- 

 ments, the galvanic heat gw developed by the current in the 

 entire circuit increases when the resistance is increased and 

 consequently the current-intensity is diminished, is confirmed 

 by Favre's later experiments with Smee's pile *. In one 

 of these experiments, the length of the platinum wire being 

 shortened from 7000 to 250 millims., the galvanic heat was 

 lessened from 18018 to 14424 thermal units ; the chemical 

 heat he found somewhat greater than before, namely 19834 

 units. While the chemical heat, as we know beforehand, is 

 constant and independent of the inserted resistance, the gal- 

 vanic heat, on the contrary, became less when the resistance 

 was diminished and consequently the intensity of the current 

 was augmented. In all these experiments, however, the che- 

 mical was greater than the galvanic heat. 



In the following experiments, on the contrary, the galvanic 

 exceeded the chemical heat ; for there appeared in the pile an 

 actual consumption of heat, so "that its temperature sank on 

 the passing of the current, instead of rising f. One of the 

 pole-disks of the pile employed consisted of platinum, the 

 other of zinc or cadmium ; and both were immersed in hydro- 

 chloric acid. The closed pile was first put into the calorimeter 

 without any exterior resistance, by which a measure of the 

 total chemical heat was obtained. Afterwards the pile was 

 furnished with a considerable exterior resistance and then en- 

 closed in the calorimeter, but so that the resistance was left 

 outside. The chemical heat amounted, for the cadmium-pla- 

 tinum pile, to 7968 units, and for the zinc-platinum pile to 

 15 89 9 ; but when the resistance was left outside of the calo- 

 rimeter, there was observed, in the cadmium-platinum pile, a 



* Comptes Rendus, t. xlvii. p. 599 (1858), and t. lxvii. p. 1012 (1868). 

 f Ibid. t. lxviii. p. 1300 (1809). 



