perceive, that, while the length of the cable is,
electrically and practically, reduced to one-fifth of its former length,
the retardation of the current is also decreased in the same proportion.
Therefore, if, with the old cable, three words per minute could be
transmitted, with the new cable we shall be able to transmit five times
as many, or fifteen words per minute. This is not equal to our Morse
system on the land-lines, which will signal at the rate of thirty-five
words per minute, still less to the printing system, which can signal at
the rate of fifty words per minute; but, even at this rate, the
cable would be enabled to transmit in twenty-four hours one thousand
despatches containing an average of twenty words apiece. Mr. Field,
however, claims for the cable a speed of only twelve words per minute,
which would reduce the number of despatches of twenty words each
that could be transmitted in twenty-four hours to eight hundred and
sixty-four. We will suppose, however, that the cable transmits only five
hundred telegrams per day; this number, at ten dollars per message,
would give an income of five thousand dollars per diem, or one million
five hundred and sixty-five thousand dollars per annum. Quite a handsome
revenue on an outlay of about one million of dollars!

The only instrument which could be used successfully in signalling
through the old cable was one of peculiar construction, called the
Marine Galvanometer. In this instrument, momentum and inertia are almost
wholly avoided by the use of a needle weighing only one and a half
grains, combined with a mirror reflecting a ray of light, which
indicates deflections with great accuracy. By this means a gradually
increasing or decreasing current is at each instant indicated at its
due strength. Thus, when this galvanometer is placed as the
receiving-instrument at the end of a long submarine cable, the movement
of the spot of light, consequent on the completion of a circuit through
the battery, cable, and earth, can be so observed as to furnish a curve
representing very accurately the arrival of an electric current. Lines
representing successive signals at various speeds can also be obtained,
and, by means of a metronome, dots and dashes can be sent with nearly
perfect regularity by an ordinary Morse key, and the corresponding
changes in the current at the receiving end of the cable accurately
observed.

A system of arbitrary characters, similar to those used up