,
Sheffield, and others. These produced no less than 340,000 tons of
steel during the year 1881, and two years later the total output had
risen to half a million tons. In 1876 the British Admiralty built two
iron-clads, the Mercury and Iris, of Siemens-Martin steel, and the
experiment proved so satisfactory, that this material only is now used
in the Royal dockyards for the construction of hulls and boilers.
Moreover, the use of it is gradually extending in the mercantile marine.
Contemporaneous with his development of the open-hearth process, William
Siemens introduced the rotary furnace for producing wrought-iron direct
from the ore without the need of puddling.
The fervent heat of the Siemens furnace led the inventor to devise a
novel means of measuring high temperatures, which illustrates the value
of a broad scientific training to the inventor, and the happy manner in
which William Siemens, above all others, turned his varied knowledge to
account, and brought the facts and resources of one science to bear upon
another. As early as 1860, while engaged in testing the conductor of
the Malta to Alexandria telegraph cable, then in course of manufacture,
he was struck by the increase of resistance in metallic wires occasioned
by a rise of temperature, and the following year he devised a
thermometer based on the fact which he exhibited before the British
Association at Manchester.
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