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

12 CONTENTS.
CHAPTER XXXV.
TELEGRAPH ELECTRIC CIRCUITS.
Electric Circuits on European Lines-Circuit of the Main Line described-Adjustment
of the Line Batteries-Early Experimental Circuits —The Stager Compound Circuits
-Combining of Electric Circuits....................................... 480
CHAPTER XXXVI.
ELECTRIC CURRENTS.
Electric Currents Explained-Electric Circuits-Quantity and Intensity CurrentsPhenomena of the Return Current-Retardation of the Current Illustrated-Estimated Velocity of the Current-Working of the Mediterranean Telegraphs-Scale of
the Velocity of the Current on Subaqueous Conductors....................... 496
CHAPTER XXX II.
ELECTRIC TELEGRAPH CONDUCTORS.
Composition of Telegraph Circuits-Conductibility of Metals and Fluids-Conducting
Power of different sizes of Copper Wire-Conducting Power of Telegraph WiresAdvantage of Zinc-Coated Wires-Conductors composing a Voltaic Circuit-Strength
of Telegraph Wires-Scale and Weight of Telegraph Wires.............. 513
CHAPTER XXXVIII.
GUTTA-PERCHA INSULATION.
Application of Gutta-Percha as an Insulation-Discovery of Gutta-Percha, its Nature,
Qualities, and Chemical Properties.........2......................... 524
CHAPTER XXXIX.
TELEGRAPH INSULATION.
English Telegraph Insulators-The American, the French, the Sardinian, the Bavarian
the Holland, the Baden, the Austrian, the Seimens and Halskie's, and the Hindostan
Insulators-Tightening the Wires in Asia, England, and on the Continent...... 529
CHAPTER XL.
PARATONNERRE, OR LIGHTNING ARRESTER.
Lightning on the Telegraph-Highton's Paratonnerre-Reid's American ParatonnerreVarious Apparatuses on American Lines-Attachment of Paratonnerres at River
Crossings-Incidents of Lightning'striking the Line-Steinheil's, Fardley's, Meisner's,
Nottebohn's, Breguet's, the French, and Walker's Paratonnerres.............. 564
CHAPTER XLI.
SUBTERRANEAN TELEGRAPHS.
Subterranean Lines in America, Prussia, Russia, Denmark, and France-Lines in Great
Britain-Underground Lines in Hindostan-Mode of Testing-Subterranean Telegraphs
Repairing the Insulated Wires............................... 587