The Civil engineer and architect's journal, scientific and railway gazette (1839)
London : [William Laxton] · leaf 272
Figs. 2 and 3 show the application of the electric telegraph to tunnels.1 A, 2 A. Telegraphs fixed in policemens boxes near the entrances oftunnels. B. Intermediate telegraph near a shaft within a tunnel, always ready towork with 1 A, 2 A, in case of need. C. Protecting tube for conducting wires. C…
Architecture · Civil engineering · Science
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