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

STRENGTH OF TELEGRAPH WIRES. 519
plates would answer if it did not so quickly decay. Sheet iron
electro-plated with zinc or copper would answer fully the purpose required. The earth plate, of whatever metal it may be,
should be buried in moist earth, and the greater the moisture
the better will be the circuit. The iron wire next to and in the
earth, ought to be coated with tin or zinc to prevent its decay.
I have, in the foregoing, briefly considered the component
parts of the electric circuit; and the practical telegrapher can
readily see that he cannot too well understand the philosophy
of the media, composing the conductors of the voltaic circuit.
A uniformity of the conducting powers will always prove of the
greatest value in the attainment of telegraphic success.
STRENGTH OF TELEGRAPH WIRES.
During the winter of 1858-'9 I instituted a series of experiments testing the strength of various sizes and qualities of iron
wires. In these I was most liberally aided by Messrs. Ichabod
Washburn & Co., wire manufacturers at Worcester, Massachu.
setts. This old established firm provided the various qualities
of wire and the necessary appliances and help to enable me to
effect the most thorough investigation. The average results of
Fig. 1.
D
B
C