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

490 TELEGRAPH ELECTRIC CIRCUITS.
of the battery. The plates used by Professor Morse were five feet
long, and two and a half feet broad; at Baltimore, it was buried
in the water at the bottom of the dock, near Pratt street; at
Washington it was placed in the earth under the Capitol.
A subsequent experiment demonstrated the practicability of
working the two wires, arranged as represented in the follow-.
ing diagram.
Fig. 6.
-'-'- >. Eeast Wi-e >
8- A_~~~~~~~~~~ ~~A
B -'- -- C b —-- a.. o —-.. C''\
>:
^ V N, O
TT6est im.
By this arrangement the keys were not required to be closed.
Each station had its wire, independent of the other. At that
time it was a discovery of great import, and to Mr. Alfred Vail
the credit is due. They were called independent circuits. It
will be seen that the west wire was used for transmitting from
Baltimore to Washington, and the east wire from w to B. The
battery at B was used in common for both circuits. When
B transmitted to w, the current proceeded from P of the battery to k, then over the west wire, then to m' at w, thence to
c', thence through the earth to c at B, and thence to the N, or
negative pole of the battery as shown by the arrows. When
w transmitted to Baltimore, the current proceeded from the P
of the battery to rn, then over the east wire, then to k', at w,
thence to c', thence through the earth to c at B, thence to the
N, or negative pole of the battery, as shown by the arrows. In
the above arrangement Mr. Vail used but one battery, and the
same earth-plates common to both lines. The circuits were
called;" open circuits," because the keys at each station were
always open, unless when used for transmitting intelligence.
In 1844, Mr. Vail experimented on the line between Baltimore and Washington, with the two telegraph wires then erected.
There were none others in America. When he ascertained that
the two wires could be practically worked, as described hereinbefore, he advanced the opinion, that several circuits could be
operated with one battery, or by a series of batteries.
In the following fig. 7, let the right-hand side represent
Washington, and the left Baltimore. The lines 1, 2, 3, 4,