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

412 HISTORY OF THE AMERICAN TELEGRAPH.
stations twenty miles apart. At station 1 are two mercury
cups, N o, into which the forked wire at c descends and closes
the circuit. The battery current of station 1 follows the wire
to N, through the forked wire c to o, thence to the magnet a,
and after passing around the soft iron, it returns to the battery
at 1. When the current passes around B, the magnet attracts
the armature of the right angle lever D, which causes the forked
wire to descend into the mercury cups of the station 2, which
puts in action the battery of 2. The second twenty-mile circuit is then charged and the magnet at E attracts the armature,
and thus another circuit is put in motion. The three equilateral
triangular pieces attached to the right-angled levers are weights
to draw from the mercury cups the forked wires when the
magnets cease to attract the subtending part of the armature
lever. The levers D are fixed to pivots as fulcrums at their
angles. This arrangement was termed the "combined circuits," and was publicly exhibited at the University in March,
1837. The plan represented could telegraph only in one direction. To communicate back another combination of circuits
would have to be organized upon the reverse order. At that
time there was no evidence on record demonstrating that a circuit as great as twenty miles could be operated. The apparatus, therefore, was based upon theory, but that problem has
long since been solved by the practical extension of the circuit
several hundred miles for telegraphic purposes.
Prof. Morse further deposed that, "In 1836 and the early
part of 1837, I directed my experiments mainly to modifications of the marking apparatus, contrivances for using fountain
pens, marking with a hard point through pentagraphic or
blackened paper, varying in the modes of using and moving
the paper; at one time on a revolving disk spirally from the
centre, at another on a cylinder, by which means a large ordinary sheet of paper might be so written upon that it could be
read as a commonplace book, and bound for reference in volumes, and devising modes of marking upon chemically prepared paper. As my means and the duties of my profession
would admit, the spring and autumn of 1837 were employed
in improving the instrument, varying the mode of writing,
experimenting with plumbago and various kinds of ink or
coloring matter, substituting a pen for a pencil, and devising
a mode of writing on a whole sheet of paper instead of upon
a strip or ribbon; and in the latter part of August or the
beginning of September of that year, the instrument was
shown in the cabinet of the University to numerous visitors,
operating through a circuit of one thousand seven hundred
feet of wire running back and forth in that room."