96 THE WORLD-ENERGY 



be charged from a Voltaic battery, as from an electrical 

 machine. 



The real truth of the relation between statical and 

 dynamical electricity comes out in the estimate of Fara- 

 day,* that a current of dynamical electricity which would 

 decompose a single grain of water by acting upon it during 

 three and three-fourths minutes would, if its whole force 

 were expended instantaneously, be equal in intensity to a 

 powerful flash of lightning. Here the quantity of force 

 is evidently the same. Acting through a longer time, it is 

 extensive quantity; while the instantaneous expenditure 

 of its whole energy presents the same quantity of force 

 under the character of intensive quantity. 



Statical electricity, then, is a phase of force, whose 

 quantity is characteristically intensive, while dynamical 

 electricity is a phase of force whose quantity is characteris- 

 tically extensive. And, as is well known, all that is neces- 

 sary in order to concentrate the extensive quantity of the 

 latter, so that its manifestation shall be specifically inten- 

 sive, is to introduce into its circuit an induction coil. 



It is evident, then, that the "intensity" of statical 

 electricity is simply intensive quantity, while the " quan- 

 tity " of dynamical electricity is quantity manifested under 

 the specific character of extensive quantity. And when 

 it is said that quantity and intensity are inversely the one 

 as the other in electricity, it is evident that this is but 

 a loose way of saying that in any given quantity of elec- 

 tricity as of any other phase of force : the extensive and 

 the intensive aspects are reciprocals. 



*See his "Experimental Researches in Electricity," (3d Ed.) L, 250. 



