168 On the Excitement of Voltaic Plates. 



tact are in different electrical states 3" — in other words, that 3 

 difference of electrical state is produced by the contact of these 

 plates. Tliat the Voltaic plates indicate no degree of excite- 

 ment whatever while in contact, but that excitement becomes 

 evident after their separation, is not a supposilion, but a fact 

 demonstrated by the irresistible evidence of our senses; as much 

 a demonstrated fact, as that all bodies of wljatsoever nature fall 

 through a given space iii vac?in in the same time — the one alto- 

 gether as unconnected with anv particular hv))othesis concerning 

 the remote cause of electrical pha;nomena, as the other is un- 

 connected with any s})eculations relative to the remote cause of 

 gravitation. But Mr. De Luc has promised to show the converse 

 of my statement ; — " to demonstrate by a great number of experi- 

 ments, that these effects (the excitement of the Foltaic plates) 

 exist only during the contact, and that it is owing to extraneous 

 circtuiistances that any effect remains ai'ter their separation*/' 

 1 have naturally looked with much eagerness for this promised 

 demonstration ; but I have not been able to find one single ex- 

 periment which militates in the slightest degree against my 

 statement relative to the Voltaic plates, and which indeed, as it 

 is a bare expression of facts, I do believe, will for ever remain 

 incontrovertible. It however appears, tliat Mr. De Luc's pro- 

 mise to demonstrate the inaccuracy of my statement, has ori- 

 ginated in his having imaccountably mistaken it ; for he repre- 

 sents me as having asserted that excitement of the pile cannot 

 be produced while the metals are in contact : whereas every one 

 who has the slightest knowledge of the science of electricity, is 

 aware that, in tiic more ordinary combinations for the pile, two 

 metals have always been in contact; and that, in the kind of 

 trough which was until lately used, two metals are soldered to- 

 gether. I am ■sorry that my observations should have been so 

 misunderstood; as it has occasioned Mr. De Luc much pains to 

 refute an ojiinion, which I could never have advanced in open 

 defiance to common experience, and has induced him to sup- 

 pose that I am unacquainted, not only with his experiments, 

 and the very ordinary ])haenomena of the pile, but with the 

 earliest and simplest facts relative to the science on which I had 

 Avritten. In truth, sir, his experiments with the pile have no 

 reference whatever to mine with the plates. Let it be granted, 

 that excitement took place in every dissection of the pile, in the 

 manner and degree he describes, I yet affirm that there is no 

 analogy between the circumstances necessary for the excitement; 

 of the Voltaic plates, and those necessary for tlie excitement of 

 the pile; and that the hypothesis which attempts to explain the 



* Phil, Journal, vol. xxxii. 



excitement 



J 



