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XXIX. An experimental examination of the electric and chemical theories of 

 galvanism. By William Ritchie, A.M. F.R.S., Rector of the Royal 

 Academy at Tain. 



Read May 7, 1829. j 



1 . J. HE continental philosophers still continue to adopt the electric theory of 

 galvanism proposed by Volta, whilst those in Britain as uniformly follow some 

 modification of the chemical theory proposed by Dr. Wollaston. From this 

 diversity of opinion we may safely conclude, that the experimental proofs for 

 the truth of either theory are not sufficiently powerful, to command the assent 

 of all capable of appreciating the weight of such evidence. I have therefore 

 ventux-ed to lay before the Society the following experiments and observations; 

 as they appear to me to establish the truth of some modification of the chemical 

 theory, and to demonstrate the fallacy of the principles on which the electric 

 theory rests. 



2. Tlie fundamental principle assumed by Volta, and supported by his fol- 

 lowers, is, that if dissimilar metals be brought into contact they are instantly 

 thrown into opposite electric states. This he conceives to be a new law of 

 nature, and claims to himself the honour of the discovery. He conceives that 

 its truth is proved by the following experiment. 



Let Z be a plate of zinc, and C a plate of copper, soldered together ^ 

 at the line of contact A B. Hold the plate of zinc in the hand, and 

 touch the under plate of a delicate electric condenser (le conden- 

 sateur a lames d'or) with the copper plate, whilst a moistened finger 

 is applied to the upper plate of the instrument. Remove the compound plate 

 and the moistened finger, and then lift the upper plate of the instrument by its 

 insulating handle, and the slips of gold leaf will be found to diverge. Taking 

 for granted the truth of the experiment, the conclusion which Volta deduced 

 from it by no means follows as a legitimate inference. Dr. Wollaston has 

 shown that a galvanic effect is produced by dissimilar metals with the moist 



MDCCCXXIX. 3 a 



B 



