On the unequal Heating Effect of a Galvanic Current. 225 



invariably showed a different temperature, the one where the 

 electrical current quitted the bismuth to enter the antimony 

 being the lower, but always above tlie temperature of the sur- 

 rounding air. This property found in the bismuth bar, which 

 was directly derived from the examination of Peltier's law, ex- 

 tends to any other kind of matter, whether in the gaseous, fluid, 

 or solid state, traversed by a galvanic current ; the only condition 

 required for the experiment being that the current be brought 

 to the body tested by conductors which offer less resistance to 

 its passage than the body itself *. 



Thus, although my experiments gave a different explanation 

 of the observations of jNI. Peltier, they did not lessen their value ; 

 for through the study of this supposed absorption of heat during 

 the passage of a feeble galvanic current a yet more general law 

 was established, by which a consistent explanation was given to 

 a remarkable fact noted in Daniell's Introduction to Chemical 

 Philosophy, considered by the author of that work at the time 

 of its publication not to admit of illustration. The fact in 

 question is one of the conducting wires from a powerful battery 

 becoming red-hot, while the other wire remains comparatively 

 cool ; in this case the galvanic current has to pass across a short 

 space of air, where it encounters great resistance, and thus heats 

 the wire, where it meets this resisting force much more than the 

 wire where it quits the obstructing medium ; the result being 

 the same as those exhibited in the case of the bismuth bar cited 

 above, the difference being only one of degree. 



In studying the effects presented to us in thermo-electrical 

 arrangements, the force designated \>^ the term attraction of 

 cohesion is constantly found to form at the present time an im- 

 penetrable barrier ; the various properties of metals in their rela- 

 tions to the imponderables, to tenacity, elasticity, &c., show 

 what modifications the force of cohesion of attraction can un- 

 dergo ; yet in the present state of science there are no means of 

 ascertaining what alteration in this force has taken place, save 

 through the final effect shown by changes in the metal or its 

 alloys. Any one who may reflect on the subject will perceive 

 what an extensive range of pha^nomena is here hidden from view ; 

 and they will probably think that there the laws, which at present 

 cannot be traced so as to connect the generation of electricity by 

 chemical action with that derived from thei'mal sources, may 

 ultimately be developed. 



Yours very respectfully, 



Richard Adie. 



* Edinb. New Phil. Magazine, vol. xxxvii. p. 301. 

 Phil, Mag. S. 4. Vol. 4. No. 24. Hept. 1852. Q 



