battery, the wire became charged with the electricity of that pole,
which, so long as it existed, gave rise to a current which was made
evident by a galvanometer: but, in order to obtain this result, the
second pole of the battery must communicate with the ground, or with
another long wire similar to the first.

In a second series of experiments, Professor Wheatstone interposed three
galvanometers in the middle and at the ends of the circuit, determining
in this manner the progress of the current by the order which they
followed in their deviation. If the two poles of the battery were
connected by the long conductor of six hundred and sixty miles, the
precaution having been taken to divide it into two portions of equal
length, it was observed, on connecting the two free extremities of these
two portions in order to close the circuit, that the galvanometer placed
in the middle was the first to be deflected, whilst the galvanometers
placed in the vicinity of the poles were not deflected until later.

By a third series of experiments, Wheatstone, with the galvanometer, has
shown that a continuous current may be maintained in the circuit of the
long wire of an electric cable, of which one of the ends is insulated,
whilst the other communicates with one of the poles of a battery whose
other pole is connected with the ground. This current is due to the
uniform and continual dispersion of the statical electricity with which
the wire is charged along its whole length, as would happen to any other
conducting body placed in an insulating medium.

It was owing to the retardation from this cause that communication
through the Atlantic Cable was so exceedingly slow and difficult, and
not, as many suppose, because the cable was defective. It is true that
there was a fault in the cable, discovered by Varley, before it left