chemical Agencies of Electricity. 45 
which are attracted by the positively electrified zinc, exert 
similar agencies to the copper, but probably in a slighter de- 
gree, and being capable of combination with the metal, they 
produce a momentary equilibrium only. 
The electrical energies of the metals with regard to each 
other, or the substances dissolved in the water, in the Voltaic 
and other analogous instruments, seem to be the causes that 
disturb the equilibrium, and the chemical changes the causes 
that tend to restore the equilibrium ; and the phenomena most 
probably depend on their joint agency. 
In the Voltaic pile of zinc, copper, and solution of muriate 
of soda, in what has been called its condition of electrical 
tension, the communicating plates of copper and zinc are in 
opposite electrical states. And with regard to electricities of 
such very low intensity, water is an insulating body : every 
Copper-plate consequently produces by induction an increase 
of positive electricity upon the opposite zinc plate ; and every 
zinc plate an increase of negative electricity on the opposite 
copper-plate : and the intensity increases with the number, 
and the quantity with the extent of the series. 
When a communication is made between the two extreme 
points, the opposite electricities tend to annihilate each other; 
and if the fluid medium could be a substance incapable of 
decomposition, the equilibrium, there is every reason to believe, 
would be restored, and the motion of the electricity cease. 
But solution of muriate of soda being composed of two series 
of elements possessing opposite electrical energies, the oxy- 
gene and the acid are attracted by the zinc, and the hydrogene 
and the alkali by the copper. The balance of power is mo- 
mentary only ; for solution of zinc is formed, and the hydro- 
