188 Mr. G. J. Knox on the Direction and Propagation 



ture of sulphur was, that it was "a compound of small quan- 

 tities of oxygen and hydrogen, with a large quantity of a 

 basis, that produces the acids of sulphur in combustion, and 

 which, on account of its strong attraction for other bodies, will 

 probably be difficult to obtain in its pure form*." To put the 

 question beyond any further doubt, I will mention some ex- 

 periments which I tried in the laboratory of the Royal Dublin 

 Society in the year 1837, having had, through the kindness of 

 Professor Davy, a galvanic battery of sixty pair of plates, five 

 inches square, put at my disposal. 



When fused phosphorus, sulphur, selenium and iodine, 

 were submitted separately to the action of this battery charged 

 with a strong acid solution, they conveyed the electrical cur- 

 rent freely during the whole time, giving a spark whenever 

 contact was broken ; yet at the end of two hours they showed 

 not the 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 pro- 

 pagation 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'sf opinion that the contact of the metals was 

 the pri7}i2im mobile of voltaic excitement, having been proved 

 by Dr. Faraday:^ to be erroneous, chemists are now pretty 

 generally agreed that the electrical force developed in the vol- 

 taic 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. Fara- 

 day's§ and Mr. Becquerel'sH. 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 

 regard 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 action 

 of the acid or alkali upon the platinum plates; but the latter 

 has shown that the electrical current is produced equally when 



* Bakerian Lecture, 1809. f Phil. Trans., Bakerian Lecture, 1826, 



+ Eighth Series, (880). § Eighth Series, (927) (928). 



\\ Tom. ii. from page 77 to 81. ^[ Phil. Trans., Bakerian Lecture, 1826. 



