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XXXI. On the supposed Identity of the Agent concerned in the 

 Phenomena of oi-dinary Electricity, Voltaic Electricity, Electro- 

 magnetism, Magneto-electricity, and Thermo-electricity. By 

 M. Donovan, Esq., M.R.I. A., formerly Professor of Che- 

 mistry to the Company of Apothecaries in Ireland. 

 [Concluded from p. 138.] 

 Section VIII. 



I HAVE in a former part of this essay made some observations 

 on the evidence afforded by the deflections of the galvanometer, 

 and will now offer some additional considerations on the same 

 subject, believing that it involves the whole question, namely, 

 whether these deflections are metrical indications of the opera- 

 tion of one undecomposable because uncompounded electric fluid 

 or agent, always the same in its natm'e, vaiying only in quantity 

 and intensity ; or are there conditions of the electric fluid differ- 

 ing from each other in respect of constitution or composition, 

 which, independently of quantity or intensity, are far more pow- 

 erful than ordinaiy electricity in producing deflections ? 



It appears to me, after considering the difficulties in the way 

 of the hypothesis of identity with as little prepossession or pre- 

 judice as I am able to view them, that deflections and voltaic 

 phsenomena in general are inexphcable according to the doctrine 

 of those who consider them due to the operation of ordinary 

 electricity, acting in great quantity at a low intensity, 



I shall now only advert to a few experiments out of a multi- 

 tude, not in the hope of proving anything, but merely with the 

 intention of submitting to the judgement of the reader whether 

 such striking effects can result from an ordinary electricity, so 

 feeble that its agency is altogether supposititious, and affords no 

 evidence of its presence except the phsenomenon which is the 

 subject of the doubt. Were it not for analogy, it could not be 

 maintained that in these experiments ordinary electricity is at 

 all concerned; its well-known properties are not recognisable; 

 nor is there any evidence of its presence but the effect on the 

 galvanometer, which it is the fashion to consider obedient to no 

 other power. Were it not for the circumstances that the agent 

 which affects the galvanometer is only transferable through con- 

 ductors of electi'icity, it would be as natm-al to believe that in 

 the following experiments the power concerned is that universal 

 property of matter called chemical affinity; for, so far as the 

 mode of action of the bodies is concerned, the deflections might 

 be viewed as measures of intensity of chemical affinity rather 

 than of electricity. The hypothesis which appears to me most 

 consistent with the facts, and perhaps least repugnant to modern 

 opinions, is to assume, as I have done, the agency of electricity. 



