On the Source of Power in the Voltaic Pile. 337 



the sole exception of silver positive with respect to copper. The 

 inconsistency of these I'esults with any theory of contact electromo- 

 tive force is then strongly insisted on by the author. 



The next division of the paper treats of the order of the metallic 

 elements of voltaic circuits when different electrolytes are used. It 

 is usual to say, that metals are positive or negative with respect to 

 each other in a certain order ; but Davy, and afterwards De la Rive, 

 showed that, in certain cases, this order must be inverted. The 

 author, by using ten metals and seven different exciting electrolytic 

 solutions, shows that in no two solutions is the order the same ; but 

 that changes of the most extreme kind occur in exact conformity 

 with the changes in chemical action, which the use of the different 

 solutions occasions. 



The next division of the paper considers the very numerous cases 

 in which voltaic circuits, often such as are able to effect decompo- 

 sition, are produced without any metallic contact, and by virtue of 

 chemical action alone ; contrasting them with the numerous cases 

 given in the previous series, where contact tcithout chemical action, 

 whether it be the contact of metal with metal, or with chemically 

 inactive electrolytes, can produce no voltaic current. 



There then follows a consideration of the sufficiency of chemical 

 action to account for ail the phenomena of the pile. It is shown 

 that chemical action does actually evolve electricity ; that according 

 as chemical action diminishes or ceases, so the electrical current di- 

 minishes or ceases also ; that where the chemical action changes 

 from side to side, the direction of the current likewise changes with 

 it ; that where no chemical action occurs, no current is produced, 

 but that a current will occur the moment chemical action com- 

 mences ; and that when the chemical action which has, or could 

 have produced a current is, as it were, reversed or undone, the cur- 

 rent is reversed or undone likewise ; that is, it occurs in the oppo- 

 site direction, in exact correspondence with the direction taken by 

 the transferred anions and cathions. The accordance of the chemi- 

 cal theory of excitation with these phenomena, is considered by the 

 author as of the strictest kind. 



The phenomena of thermo-electricity are considered by some 

 philosophers as atlording proofs of the efficacy of mere metallic 

 contact in exciting an electric current. The author proceeds, there- 

 fore, to examine these phenomena in relation to such an action, and 

 arrives at the conclusion, that they in fact disprove the existence of 

 such a power. In thermo-electricity the metals have an order which 

 is so different from that belonging to them m any electrolyte, that it 

 appears impossible to consider their succession, in any case, as due 

 to any mutual effect of the metals on each other common to both 

 modes of excitation. Thus, in the thermo-circuit, the^lectric cui'- 

 rent is, at the hot place, from silver to antimony, and from bismuth 

 to silver ; but in a voltaic series, including dilute sulphuric or nitric 

 acids, or strong nitric acid, or solution of potash, the electric current 

 is from silver to both antimony and bismuth ; whilst if the 

 yellow sulphuret of potash be used, it is from both antimony and 



Phil. Mag. S. 3. Vol. 16, No. 103. April \M0. Z 



