a Metal drum driven by a weight and train of wheels, for the purpose of drawing the chemically-prepared paper. This drum revolves in a trough of water.
b Roll of chemically-prepared paper, enclosed in a circular box; lid removed to display the paper.
c Arm carrying four steel styles, or tracers, of Geneva mainspring, carefully insulated from each other, which press upon the paper. The styles are parallel to each other, and the points are placed in a line directly at right angles to, or across, the slip of paper.
d Pressing or biting roller, to prevent the paper slipping on the drum.
e Trough of water.
f Clock movement driving the pendulum.
g seconds pendulum.
h A “Bain’s break-piece and bar,” somewhat modified and arranged so as to change the contact, at every beat of the pendulum, from No. 1 to No. 4 style, or vice versa.
i Receiving apparatus, or relay, in connection with the home circuit: this makes connection between the printing battery and style No. 2.
j Similar apparatus in connection with the long circuit current, and placed in the middle junction of the wires. This makes connection between printing battery and style No. 3.
k Local printing battery, which may be of any required number of cells. From the zinc terminal (z) a wire goes direct to the frame-work of the metal drum. From the other end of the battery three wires proceed — one to each relay, and one to the “constant” end of the break-piece (h); while, from the alternating end of the break-piece two wires proceed, carrying the current to No. 1 and No. 4 styles, alternating at every beat of the pendulum.