proportion
as the length of the wire increases. Thus, if the wire be continued for
ten miles, the current will have twice the intensity which it would
have, if the wire had been extended to a distance of twenty miles. It is
evident, therefore, that the wire may be continued to such a length that
the current will no longer have sufficient intensity to produce at the
station to which the despatch is transmitted those effects by which the
language of the despatch is signified. _But the intensity of the current
transmitted by a given voltaic battery upon a wire of given length will
be increased in the same proportion as the area of the section of the
wire is augmented_. Thus, if the diameter of the wire be doubled, the
area of its section being increased in a fourfold proportion, the
intensity of the current transmitted along the wire will be increased in
the same ratio. The intensity of the current may also be augmented by
increasing the number of pairs of the generating plates or cylinders
composing the galvanic battery.

All electrical terms are arbitrary, and necessarily unintelligible
to the general reader. I shall, therefore, use them as sparingly as
possible, and endeavor to make myself clearly understood by explaining
those which I do use.

All telegraphic conductors offer a certain resistance to the passage of
an electric current, and the amount of this resistance is proportional
to the length of the conductor, and inversely to its size. In order to
overcome this resistance, it is necessary to increase the number of
the cells in the battery, and thus obtain a fluid of greater force or
intensity.

On aerial telegraph-lines this increase in the intensity of the battery
occasions no particular inconvenience, other than by tending to the more
rapid destruction of the small copper coils, or helices, employed;
but upon submarine lines it has the effect of increasing the static
electricity, or electricity of tension, which accumulates along the
surface of the gutta-percha covering of the conducting-wire, in the same
manner as static electricity accumulates on the surface of glass, or of
a stick of sealing-wax, by rubbing it with a piece of cloth. The use of
submarine or of subterranean conductors occasions, from the above cause,
a small retardation in the velocity of the transmitted electricity. This
retardation is not due to the length of the path which the electric
current has to traverse, since it does not take pla