193 



ceeding in intensity, but deficient in quantity. We however think, 

 that it would be more in accordance with the phenomena to state, 

 that as some effects require continuous action, they can only be ob- 

 tained from ordinary electricity by rendering the quantity accumu- 

 lated on a given surface (which quantity is a measure of the inten- 

 sity,) available as a source of such action. 



Although we agree with the author in the conclusions which he 

 draws respecting the identity of electricities, yet there is one point, 

 the mode of their conduction, in which they have been said to differ, 

 on which we wish that he had made some remarks. The current 

 of voltaic electricity runs through the mass of the conducting wire, 

 and its intensity is diminished by increasing the length of that wire ; 

 and the same is the case with magneto-electric currents: but common 

 electricity, in a state of tension, resides at or near the surface of a 

 body, and has been considered to be so conducted *j and the shock 

 has been found not to be diminished by the length of the wire through 

 which it takes place. We would however ask, whether it is not a 

 gratuitous assumption to state that electricity is conducted on the 

 surface, because it exists there in a state of tension ? That it exists 

 near the surface when in a state of tension, is due to the repulsive 

 force which its particles exert upon each other 5 and when they are 

 relieved from tension, will not the same repulsive force spread them 

 through the mass of the conducting body ? W T ith regard to the shock 

 from a battery not being diminished by the length of the wire through 

 which it takes place, does it not arise from the same quantity of elec- 

 tricity on a given surface being passed, when the equilibrium is re- 

 stored, between the outside and inside of the battery, whatever may 

 be the length of the conducting wire ? We regret that the author's 

 attention was not drawn to this part of the subject ; for we feel as- 

 sured, that had it been so, he would have met the objections which on 

 this ground have been urged against the identity of the electricities. 

 Possibly he was so fully convinced of the futility of these objections, 

 that he considered it unnecessary to notice them. 



The second section of this paper details experiments for deter- 

 mining the relation, by measure, of common and voltaic electricity. 



The author first determines that the magnetical effect of a given 

 quantity of common electricity from a battery is independent of the 

 surface over which it is spread ; and next, that this effect is propor- 

 tional to the absolute quantity of electricity. The measures by the 

 galvanometer are not professedly very accurate ; but it is to be ex- 

 pected that experiments more accurate in this respect, and more va- 

 ried with regard to the quantity of electricity, would confirm these 

 conclusions. Determining, then, the quantity of voltaic electricity 

 which in a given time will produce the same deflection of the needle 

 as a given quantity of common electricity discharged from a battery, 

 he shows that voltaic electricity of the same intensity will also, in 

 that time, produce the same degree of chemical decomposition which 

 that quantity of common electricity will when passed from the con- 



* Phil. Trans. 1832, p. 280. 

 p 2 



