Electromotive Forces in the Voltaic Cell. 185 
Hdlund has published a long paper* in which he investi- 
gates experimentally the Peltier effect; he points out clearly 
at the end that there is no relation between the Peltier and 
Voltaeffects; and he suggests that this is because of the contact- 
force between the metals and the gas or air in which they are, 
the fact of such contact-force being, he thinks, sufficiently 
established by gas-batteries and galvanic polarization f. 
Majocchi, in a paper printed in Phil. Mag. xxx. p. 97, 
regards the H.M.F. of contact as due to the “adhesion”’ of 
the two metals for each other: pretty much the same idea as 
Sir W. Thomson’s chemical action ata distance, an idea which 
makes the energy of the Volta effect Zn /Cu depend on, and 
be calculable from, the combination-heat of zinc and copper in 
making brass. I must return to this matter later, because it 
is important in itself and crucial as regards theory. 
(yassiot | made an experiment intended to show that there 
could be a difference of potential excited between metals by 
proximity without actual contact, or at any rate without 
metallic contact. Grove§ also made a similar experiment. 
Hoorweg |, and also Nobili4], have a theory that all galvanic 
currents are really thermoelectric. 
In the article “ Electricity” in the Encyc. Brit. p. 99, 
Professor Chrystal gives some clear general considerations 
regarding the seat of H.M.F. and the opposing views which 
are held with regard to it. He is judicial in his attitude with 
regard to them; but the mere statement of the position in so 
* Edlund: Pogg. Ann. cxxxvil. p. 474; cxl. p. 435; exliil. pp. 404, 
534. See also Phil. Mag. [4] xxxvii. p. 268; xl. pp. 81, 218, 264, 
especially p. 273. 
+ Sundell investigates the E.M.F. of alloys in contact with copper, 
employing Edlund’s method, and finds, like him, that for alloys as well as 
for simple metals the Peltier corresponds with the Seebeck force. The 
peculiar language used in this and the preceding paper may easily cause 
it to be imagined that they have found Volta force to agree with Peltier. 
In fact, Sundell is so quoted in Watts’s 8rd Suppl. p. 708, Von Zahn 
. quotes Edlund in the same sense; and indeed it is probable that Edlund 
himself at first thought he was investigating Volta forces thermoelectrically 
(Pogg. Ann. exlix. p. 144). 
{ Gassiot, Phil. Mag. xxv. 1844, p. 283. 
§ Grove, ‘ Literary Gazette,’ Jan. 21, 1843 ; Wiedemann, E/ek. 11. p. 988. 
|| Hoorweg, Wied. Ann. ix. p. 552, 1880; xi. p. 233; and xii. p. 75. 
q Prof. Wiedemann notes as interesting that in 1828 Nobili held a 
notion that all galvanic currents are thermoelectric, thus vaguely antici- 
pating the modern thermodynamic theory of E.M.F. See Wied. Elek- 
tricitit, ii. p. 985, and Nobili, Bibl. Univ. de Geneve, xxxvii.p.118. But 
Prof. Hoorweg seems bitten with the same idea in recent times, and in 
1879-80 writes long papers in proof that all current-energy is due to 
absorption of heat at junctions! 
Phil. Mag. 8. 5. Vol. 19. No. 118. March 1885. O 
