Nothing else, indeed, happens when we make the process continuous by
using a galvanic source of electricity. All that distinguishes a
galvanic cell from the sources of electricity used before the time of
Volta is its faculty of immediately re-establishing the field which
prevails between its poles, whenever this field becomes extinguished by
the presence of a conductor. Volta himself saw this quite correctly. In
his first account of the new apparatus he describes it as 'Leyden jars
with a continuously re-established charge'. Every enduring electrical
process, indeed, consists in nothing but a vanishing and
re-establishment of the electrical field with such rapidity that the
whole process appears continuous.

Here, also, pure observation of the effect of a conductor in an
electric field tells us that its action consists in the annihilation of
the field. There is no phenomenon which allows us to state that this
process takes place along the axis of the conductor. If we wish to
obtain a picture of the true direction, we must consider the condition
of space which arises in place of the electric condition that has
disappeared.

With the possibility of turning the cancellation of the electrical
condition of space into a continuous process, it became possible to
observe that the neutralization of electric charges entails the
appearance of heat and magnetism. We must now ask which are the
qualities of electricity on the one hand, and of heat and magnetism on
the other, which account for the fact that where electricity
disappears, the two latter forces are bound to appear. Since magnetism
is the still unknown entity among the three, we must now deal with it.

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