1 50 Mr. Knox on the Direction and Mode of 



slightest trace of decomposition, no gas being evolved at either pole, which would 

 have been the case had there been any water present. 



Having by these experiments shown the direction of propagation of the 

 electric force, I will now consider the source from which it originates in the 

 voltaic pile, the mode of its transfer, and its sustaining principle. 



Sir H. Davy's* opinion that the contact of the metals was \}a.Q 'pr'imum mobile 

 of voltaic excitement, having been proved by Dr. Faradayt to be erroneous, 

 chemists are now pretty generally agreed that the electrical force developed in 

 the voltaic pile is due altogether to chemical action, concerning which there are 

 different opinions ; of these, I will mention two, which are the most applicable 

 to the present argument — Dr. Faraday'st and Mr. Becquerers.§ The former 

 supposes that the development of electricity is due to decomposition alone, and in 

 no case to the chemical union of bodies, while the latter contends that it is due 

 to both, and in proof of his opinion shows that when an alkali unites with an acid, 

 with a neutral salt, and in fact with any solution whose natural state is with re- 

 gard to it electrically negative, a current of electricity will flow from the alkali 

 to that solution. Sir H. Davy|| has taken a different view of these experiments 

 from Mr. Becquerel, supposing that the electric current is produced by the ac- 

 tion of the acid or alkali upon the platinum plates ; but the latter has shown that 

 the electrical current is produced equally when no such action could take place, 

 the platinum poles being placed in separate cups filled with water.lj 



The accuracy then of Mr. Becquerel's experiments having been fully esta- 

 blished, the question arises, how are we to reconcile them with other well known 

 contradictory facts ? such as for instance those of Sir H. Davy,** — solid potash 

 and sulphuric acid combining in an isolated platinum crucible, and causing no 

 electrical development. Again, a plate of copper and of sulphur, when heated, 

 have their electrical states increased until chemical action begins, when they 

 cease. 



* Phil. Trans., Bakerian Lecture, 1826. t Eighth Series, (880). 



X Eighth Series, (927) (928). § Tom. ii. from page 77 to 81. 



II Phil. Trans., Bakerian Lecture, 1826. 



T He might have added another experiment, free from all objections — namely, the increased 

 intensity consequent upon an increased number of alternations of acid and alkali. 

 •* Phil. Trans., Bakerian Lecture, 1807. 



