[ 335 ] 



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

 Phenomena of ordinary Electricity, Voltaic Electricity, Electro- 

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

 M. Donovan, Esq., M.R.I.A. 



[Continued from p. 299.] 

 Section IV. 



THE foregoing experiments and reasonings are adduced by 

 Professor Faraday in support of his opinions relative to the 

 enormous quantity of electricity which he conceives is naturally 

 associated with matter. It was necessary to prove the existence 

 of a source so abundant as the vast quantity supposed to consti- 

 tute the current required. Without this peculiar character of 

 the current, it could not be applied to explain the difference be- 

 tween the effects of ordinary and voltaic electricity. In further 

 support of that opinion, his next object was to prove that sup- 

 plies of ordinary electricity equally abundant are required to 

 produce effects commensurate with those of voltaic electricity ; 

 and as the cause must equal the effect, he thus derives a new 

 argument in favour of the intensely electrical condition of matter. 



In furtherance of these views, he made many experiments in- 

 tended " to obtain a common measure, or a known relation as to 

 quantity, of the electricity excited by a machine, and that from 

 a voltaic pile, for the purpose not only of confirming their iden- 

 tity " by proving " that the differences of intensity and quantity 

 are quite sufficient to account for what were supposed to be their 

 distinctive quantities/' " but also of demonstrating certain general 

 principles*." 



To support the opinion of identity, and to account for the 

 dissimilarity of the voltaic and ordinary electrical current, he has 

 made it a chief object to adduce facts calculated to determine the 

 ratio in which the two kinds of electricity are required to act in 

 producing equal effects. A second object was to give additional 

 support to his view of the absolute quantity of electricity with 

 which matter is associated. To facilitate this and many other 

 inquiries, he makes use of the following law : — " If the same 

 absolute quantity of electricity pass through the galvanometer, 

 whatever may be its intensity, the deflecting force upon the mag- 

 netic needle is the samef." 



The general method adopted in his experiments, was to charge 

 a Leyden battery with a certain number of turns of a powerful 

 plate-electrical machine, occasionally varying the number of jars 

 employed, to transmit the charge through a galvanometer, and 

 to note the deflection. In the first experiment, eight jars were 



* Researches, pars. 861, 37B. t Ibid. par. 366. 



