STATE OF TENSION BETWEEN THE ZINC AND WATER. 443 



with it, as to place the similar forces already active between these and the other par- 

 ticles of oxygen and the particles of hydrogen in the water, in a peculiar state of 

 tension or polarity, and probably also at the same time to throw those of its own 

 particles which are in contact with the water into a similar but opposed state. Whilst 

 this state is retained, no further change occurs ; but when it is relieved, by com- 

 pletion of the circuit, in which case the forces determined in opposite directions, with 

 respect to the zinc and the electrolyte, are found exactly competent to neutralize each 

 other, then a series of decompositions and recompositions lakes place amongst the 

 particles of oxygen and hydrogen constituting the water, between the place of relief 

 and the place where the zinc is active ; these intervening particles being evidently in 

 close dependence upon and relation to each other. The zinc forms a direct compound 

 with those particles of oxygen which were, immediately before, in divided relation to 

 both it and the hydrogen : the oxide is removed by the acid, and a fresh surface of 

 contact between the zinc and water is presented, to renew and repeat the action. 



950. Practically, the state of tension is best relieved by dipping a metal which has 

 less attraction for oxygen than the zinc, into the dilute acid, and making it also touch 

 the zinc. The force of chemical affinity, which has been influenced or polarized in the 

 particles of the water by the dominant attraction of the zinc for the oxygen, is then 

 transferred, in a most extraordinary manner, through the two metals, so as to re-enter 

 upon the circuit in the electrolytic conductor, which cannot convey or transfer it 

 without decomposition as the metals can ; or rather, probably, it is exactly balanced 

 and neutralized by the force which at the same moment completes the combination of 

 the zinc with the oxygen of the water. The forces, in fact, of the two particles which 

 are acting towards each other, and which are therefore in opposite directions, arre the 

 origin of the two opposite forces, or directions of force, in the current. They are of 

 necessity equivalent to each other. Being transferred forward in contrary directions, 

 they produce what is called the voltaic current : and it seems to me impossible to 

 resist the idea that it must be preceded by a state of tension in the fluid, and between 

 the fluid and the zinc ; ihe^rst consequence of the affinity of the zinc for the oxygen 

 of the water. 



951. I have sought carefully for indications of a state of tension in the electrolytic 

 conductor ; and conceiving that it might produce something like structure, either 

 before or during its discharge, I endeavoured to make this evident by polarized light. 

 A glass cell, seven inches long, one inch and a half wide, and six inches deep, had 

 two sets of platina electrodes adapted to it, one set for the ends, and the other for 

 the sides. Those for the sides were seven inches long by three inches high, and when 

 in the cell were separated by a little frame of wood covered with calico ; so that 

 when made active by connexion with a battery upon any solution in the cell, the 

 bubbles of gas rising from them did not obscure the central parts of the liquid. 



952. A saturated solution of sulphate of soda was put into the cell, and the elec- 

 trodes connected with a battery of 1 50 pairs of 4-inch plates : the current of electricity 



