The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

TIHE FIRST EXPEDITION FOR LAYING THE CABLE. 633
facility in this laborious and important, but somewhat tedious
and obstructive operation.
The arrival of the vessels at Plymouth, and the unship.
ment of the whole of our cable, to be stored there during the
winter, afford the opportunity which I have so long deemed
necessary, of submitting the working powers of our instruments to the most rigid tests through the whole circuit, under
every conceivable condition. I have, therefore, with the sanction of the directors, removed thither the workshop, retaining
a few of our most skilled hands for repairs and alterations of
instruments, and the construction of any new ones deemed
desirable. With these I have also removed our superintendent,
and the whole staff of manipulators or instrument clerks, proposing to give them, during the winter, constant occupation in
the transmission of actual dispatches through the whole length
of the cable, thus rehearsing what will be the routine of their
duties when our line is in operation.
The facilities afforded by the government authorities at
the dockyard at Keyham have enabled me to fit up a complete
telegraphic station here, in one of the buildings devoted to
our use, in which the superintendent and staff of clerks are
now constantly engaged in transmitting dispatches.
I have been able to examine most critically into the question of the highest speed of transmission attainable, carefully
eliminating all mere instrumental or manipulative error from
the results.
In doing this we have made use of an arrangement by
which the accurate correspondence or otherwise of the transmitted with the received signal shall be most readily ascertained. The electric signals, on their entrance into the cable.
are made to pass through an instrument, by means of which
they record themselves upon the same slip of paper and side
by side with those of the receiving instrument at the other or
distant end of the line. We are thus enabled to scrutinize
most closely the behavior and transit of every signal. If a
dot or dash be lost, it is instantly detected; and if even the
slightest discrepancy occur in the length of the relative marks,
it cannot fail in this way to be at once made evident.
The power of our apparatus, as already made, is seen to be
ample for the purpose; the speed with which it can be worked
so as to insure accuracy in the transmission of a dispatch is
found, however, to depend so greatly upon the steadiness and
mechanical truthfulness of the manipulating clerk, that I have
been induced to devise an addition to the transmitting part of
our apparatus which shall render manipulative error almost
impossible.