The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

84 VOLTAIC ELECTRICITY,
alone is employed; especially when the plates are at a considerable distance apart. By the addition of an acid or a neutral salt to the water, the conducting power is greatly increased, and the excitement is augmented in a corresponding
degree. It is a disputed point whether the increased action
from the addition of acids arises from the improved conducting
power alone, or whether it is to be attributed also to the increased affinity of the oxygen to the zinc. The effect is most
probably owing to the joint effort of the two forces.
In the opinion of Faraday, the conduction of electricity
through liquids is accompanied by, if it be not owing to, the
successive decomposition of the intervening particles. When a.
copper and zinc plate, for example, are connected together and
immersed in diluted acid, the oxygen in the particle of liquid
contiguous to the plate enters into combination with the metal,
and its equivalent quantity of hydrogen is disengaged. The
hydrogen is not immediately liberated, but is transferred from
particle to particle of the liquid in a continuous chain till it
reaches the conducting plate, where, not meeting with any
more liquid particles to which it can be transferred, it is liberated in the gaseous form. The intervening particles are supposed to undergo temporary decomposition during this transfer
firom plate to plate, and to assume a polar condition, the oxygen
and hydrogen occupying opposing places in each particle of
liquid.
The annexed diagram, fig. 4, shows, in an exaggerated form,
Fig. 4. the chain of particles of water
through which the decompop ot ^ ="^ siCng, influence is supposed to
be transmitted. Voltaic ac||. fA X tion having been established
- _through water in the vessel A
<j~ \p~ E~ tfrom the zinc plate z to the
copper plate at c, the particles
between the two metals are:~^^^^^^^^^ - j^'J thrown into a polar state; the
oxygen of each being directed toward z, and the hydrogen
toward c. The zinc plate absorbs the oxygen of the particle
nearest to it, and the liberated hydrogen combines with the
oxygen of the next adjoining particle, and in this manner a
continuous interchange takes place. According to this view
of the conducting power of fluids, no fluid can conduct electricity unless it be capable of being decomposedl; the conduction
being necessarily accompanied by a train of successively decomposed particles.