in manufacturing the Siemens-Martin steel in England, namely, the Landore, the Parkhead Forge, those of the Steel Company of Scotland, of Messrs. Vickers & Co., 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. Mathiessen and others have since enunciated the law according to which this rise of resistance varies with rise of temperature; and Siemens has further perfected his apparatus, and applied it as a pyrometer to the measurement of furnace fires. It forms in reality an electric thermometer, which will
