History, theory, and practice of the electric telegraph (1866)
Prescott, George B.(George Bartlett),1830-1894 · Boston, Ticknor and Fields · leaf 148
d with the earth, and the positivepole, by the depression of the key, with the line. The paper is prepared with a solution of cyanide of potassium,made after the following recipe : Six parts prussiate of potash, BAINS ELECTRO-CHEMICAL TELEGRAPH. 129 dissolved in water, two nitric acid, two ammonia.… … Fig. 67. well insulated, will decompose the salts, and, uniting with the ironstylus, leave a light blue mark upon the paper at a distance oftwo hundred and thirty miles. The positive pole only producesa colored mark; the negative bleaches the paper. The call, or alarum, commonly used on the Bain…
Telegraph
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