In 1846, he was made a member of a commission organised in Berlin to
introduce electric telegraphs in place of the optical ones hitherto
employed in Prussia, and he succeeded in getting the commission to adopt
underground telegraph lines. For the insulation of the wires he
recommended gutta-percha, which was then becoming known as an insulator.
In the following year he constructed a machine for covering copper wire
with the melted gum by means of pressure; and this machine is
substantially the same as that now used for the purpose in cable
factories.
In 1848, when the war broke out with Denmark, he was sent to Kiel where,
together with his brother-in-law, Professor C. Himly, he laid the first
submarine mines, fired by electricity and thus protected the town of
Kiel from the advance of the enemies' fleet.
Of late years the German Government has laid a great network of
underground lines between the various towns and fortresses of the
empire; preferring them to overhead lines as being less liable to
interruption from mischief, accident, hostile soldiers, or stress of
weather. The first of such lines was, however, laid as long ago as
1848, by Werner Siemens, who, in the autumn of that year, deposited a
subterranean cable between Berlin and Frankfort-on-the-Main.
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