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

418 HISTORY OF THE AMERICAN TELEGRAPH.
upon the poles of the line. This monster form. of magnet was
continued for a short time, and replaced by another less in size,
devised by Professor Charles G. Page. These latter remained
in the service until substituted by some of the size now in use,
which had been purchased by Professor Morse in France in the
year 1S45.
INVENTION OF THE LOCAL CIRCUIT.
In regard to the invention of the local circuit, Professor
Morse deposed, viz.:
"I further state, that the combination of machinery in constructing my telegraph as put in operation in 1844, was different from that originally contemplated and described in my first
patent in the following respects, viz.: The combined circuits of
my first patent, were the combination of two or more circuits
as links in a main line for the purpose of renewing the power
and propelling forward, indefinitely, the electric current, in
such volume as to render the power more available at the distant point, and to charge an electro-magnet with sufficient
magnetic force to work a register or move the lever of a relay
magnet, suggested by the probability indicated by my own
experiments and the experiments of scientific men, that sufficient magnetic power could not be obtained from the electric
current through a very long circuit to make a mark of any sort.
This difficulty the undersigned proposed to obviate by means
of two or more circuits, each with a battery, coupled together
and broken and closed by means of the same principles as the
receiving magnet now used; these links of one main line are
to be made so short as to secure the necessary magnetic power.
The register was to be placed, not in a short circuit, as now
arranged, but on a link in the main line. But this arrangement wvas liable to the practical inconvenience that it would
always require two lines of wire, both always in order; because the receiving magnet would work only in one direction.
While preparing to build the line from Washington to Baltimore, I ascertained, by experiment upon one hundred and
sixty miles of insulated wire, and, sometime previously, upon
thirty-three miles of wire, that magnetic power sufficient to
move a metallic lever could be obtained from the electric current of a circuit of indefinite length, and that there was no
necessity for combining two or more circuits togetherfor the
purpose of renewing the power at short intervals on the main
line.
I then devised the present combination, which enables me
to work the sanme wire both ways, dispensing with one of''"'~~~~~