KI.KcrUO.MOTIVli KOUCK.S IX TIIK VOLTAIC CKl.L. 



4.S!) 



ilectro- 

 itively, 

 Li'gcs it 

 [nity to 

 tiatevev 



case]. 

 expcri- 



to the 

 ^ortact. 

 n. I ilo 

 potho<i3 

 reversed 



2cment.s 

 does the 

 so woU 

 ry to ilo 

 rt's mcr- 

 catioii ot 

 niig. y2. 

 ouplo 11 !> 

 constraci 

 he Volta 



:al slcoldi 

 .3 well to 

 oirs as I 

 a with : it 

 ^it I liopi^ 

 views aiul 



etlcotiou 'low 

 isuremc'its ot 



nme of the 



tes expc'^i- 

 tit there i-^ 



more fully 

 Mr. ll;irt- 

 TroC. I^^-^ner. 



e also I'M- 



no relation between the Peltier and Volta effects, and he suggests that 

 this is because of the contact force between the metals and the gas oi" 

 air in Avhich they are, the fact of such contact force being, he thinks, 

 sufficiently established by gas batteries and galvrniic ])olarisation,' 



M.TJocchi, in a jiapor printed in ' IMiil. ^lag." \xx., p. 97, regards tho 

 E.M.F. of contact as duo to the 'adhesion ' of the two metals for each 

 other : pretty nuieh the same idea as Sir AVm. Thomson's chemical action 

 at a distance, an idea which makes the energy of the Volta eil'ect Zn/Cn 

 depend on and be calculable from the combination heat of zinc find cojiper 

 in making brass. I must return to this matter later, bec?ause it is import- 

 ant in itself and crucial as regards theory. 



CJassiot - made an experiment intended to show that there could bo a 

 diflference of potential excife<l between metals by proximity without 

 actual contact, or at any rate wiihout metallic contact. Grove'' also 

 made a similar experiment. 



Hoorweg ' and also Xobili ' have a theory that all galvanic currents- 

 are real'y thermoelectric. 



In the article ' Klccti'icity ' in the ' Eney. Brit.' p. 9I>, Profes.sor 

 Chrystal gives .some clear general considerations regarding the seat oi' 

 E.M.l*'., and the ojiposing 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 clear a form is in itself a powerful argument for the 

 views held by Maxwell.'' 



Fleeming Jenkin, in the last edition of his ' f^lectricity and Magnetism,' 

 p. 21(!, endeavours to reconcile th(> contact and chemical theories. Accord- 

 ing to the chemical theory the K.M.F. of a cell:=2 (J Oe) ; according to 

 the contact theory it is C/L-f-L/Z-|-Z/C. Oa these undoubted facts ho 



' Sniulell investigates tlio E.AI.F. of alloys in contact with copper, cmployini;- 

 Kdhind's method, and liiirls. like him, that for alloys, as well as for simple metals, tho 

 Peltier corresponds with the Sccbcck force. The jieculiar lan.irnage used in this am? 

 the preceding,'' paper may ea-^ily cause it to l)e ima.Lj:ined that they have foimd Voliii. 

 force to a^-ree with relticr. In fact, Snndcll is so (nioted in AVatt's iJnl Siippl., p. H)i*. 

 Von Zuhn (piotes Edlnnd in the same sens(% and indeed it is nrobabli^ that Kdlun<l 

 liiniselt' ;it first tlioiiijjht he was investigating Volta forces Ihermoelectrically.- 

 Sundell: Poi/r/. Ami. cxii.v. Ml. 



•' (Jassiot' :'/'////. Mor/. xxv. 1S44, p. 2S:{. 



■' Grove : Ltfrrdrj/ (imrffr, ,Ian. L'l, \><^^^. Wiedemann, EIcc, ii. 988 



* Ifoorweg : HVVy/. Aim. ix. .■j.')2, ISSO ; xi. p. '2Xi, and xii. p. To. 



' I'rof. Wiedemann notes, ;is interesting, that in 1S2S Nobiliheld a notion that all 

 fTilvanic currents are thermoelectric, tluis Viignely anticipating the modern thermo- 

 (lynaniic, theory of K :M.F. See Wied.. /-yrrfririf /if, u. '.^x^i, :im\ Nobili, /ill//. Ciiir. 

 (Ill (i'(!iilrr,\x\\\\..]\. 118. l>nt I'rof. I loorweg seems bitten with the s.amo idea in 

 recent times, . 'mil in 1879-80 writes long ]>apers in proof that all current eni'rgy i i 

 tliieto absorption of lieat at junctions I 



" Although this article is, or tmght to be, easily accessible to everybody, there is 

 'ine important suggestion in it which it is as well to quote, viz. that contained in tln^ 

 lollnwing sentence : ' We are so ignorant of tlie natur(> of the motion whicli is tin? 

 •■ssonce of tlu? electric current that the very form in which wc have put the question 

 [iH to the locality of the E.Jf.F.] may be misleading. If this motion bo in the sur- 

 I'ounding medium, as there is great reason to believe it to be, it would not be 

 surprising to lind that speculations jis to the exact locality " *he K.M.F. ?«. ///c 

 circuit were utterly wide of the mark.' I'rof. Willard (iibbs " .■ :r' ed something of 

 tlic same .sort at Montreal, though in a rather vagv.er form. myself feel any 



iloubt that a precise location can be given to the E.IM.F., notwi. . ..aiding that iiuieii 

 "f the current energy exists in the medium. The most complete attention to tlio 

 ilistribiuion of energy in circuits which has yet been bestowed (m the subject has 

 •i(!on given by I'rof. Poynting in his remarkal>le memoir, P/iil. Trans., 1884, and he 

 therein locates the K.M.F. of a battery exactly where I do myself. 



