It is overcome by increasing the
number of cells in the battery, or, in other words, by increasing the
intensity or force of the current. The retardation in a telegraphic
cable, on the contrary, is proportional to the length of the
conducting-wire and the intensity of the battery. In the former case, by
increasing the electrical force you overcome the resistance; while
in the latter, by augmenting the electrical force you increase the
retardation.
From the foregoing law it will be seen that there are two ways of
lessening the resistance upon telegraphic conductors,--one by reducing
the length, and the other by increasing the area of the section of the
conducting-wire. Now, as already remarked, the copper conducting-wire in
the old cable weighed but ninety-three pounds to the mile, while in the
new cable it weighs five hundred and ten pounds to the mile, or more
than five times as much. If, then, by comparison, we estimate the
resistance in the old Atlantic cable to have been equal to two
thousand miles of ordinary telegraph-wire, the increased size of the
conducting-wire of the new cable reduces the resistance to one-fifth
that distance, or four hundred miles.
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