used to
express those relations of the electric forces in which progression of
either fluids or effects are supposed to occur (283.), _so long_ will the
idea of velocity be associated with them; and this will, perhaps, be more
especially the case if the hypothesis of a fluid or fluids be adopted.

1649. Hence has arisen the desire of estimating this velocity either
directly or by some effect dependent on it; and amongst the endeavours to
do this correctly, may be mentioned especially those of Dr. Watson[A] in
1748, and of Professor Wheatstone[B] in 1834; the electricity in the early
trials being supposed to travel from end to end of the arrangement, but in
the later investigations a distinction occasionally appearing to be made
between the transmission of the effect and of the supposed fluid by the
motion of whose particles that effect is produced.

[A] Philosophical Transactions, 1748.

[B] Ibid. 1834, p. 583.

1650. Electrolytic action has a remarkable bearing upon this question of
the velocity of the current, especially as connected with the theory of an
electric fluid or fluids. In it there is an evident transfer of power with
the transfer of each particle of the anion or cathion present, to the next
particles of the cathion or anion; and as the amount of power is definite,
we have in this way a means of localizing as it were the force, identifying
it by the particle and dealing it out in successive portions, which leads,
I think, to very striking results.

1651. Suppose, for instance, that water is undergoing decomposition by the
powers of a voltaic battery. Each particle of hydrogen as it moves one way,
or of oxygen as it moves in the other direction, will transfer a certain
amount of electrical force associated with it in the form of chemical
affinity (822. 852. 918.) onwards through a distance, which is equal to
that through which the particle itself has moved. This transfer will be
accompanied by a corresponding movement in the electrical forces throughout
every part of the circuit formed (1627. 1634.), and its effects may be
estimated, as, for instance, by the heating of a wire (853.) at any
particular section of the current however distant. If the water be a cube
of an inch in the side, the electrodes touching, each by a surface of one
square inch, and being an inch apart, then, by the time that a tenth of it,
or 25.25 grs., is decomposed, the particles of oxygen and hydrogen
throughout the mass may b