crucible having two carbon electrodes entering it in such a manner that the voltaic arc could be produced within it. He succeeded in fusing a variety of refractory metals in a comparatively short time: thus, a pound of broken files was melted in a cold crucible in thirteen minutes, a result which is not surprising when we consider that the temperature of the voltaic arc, as measured by Siemens and Rosetti, is between 2,000° and 3,000° Centigrade, or about one-third that of the probable temperature of the sun. Sir Humphry Davy was the first to observe the extraordinary fusing power of the voltaic arc, but Siemens first applied it to a practical purpose in his electric furnace.
Always ready to turn his inventive genius in any direction, the introduction of the electric light, which had given an impetus to improvement in the methods of utilising gas, led him to design a regenerative gas lamp, which is now employed on a small scale in this country, either for street lighting or in class-rooms and public halls. In this burner, as in the regenerative furnace, the products of combustion are made to warm up the air and gas which go to feed the flame, and the effect is a full and brilliant light with some economy of fuel. The use of coal-gas for heating purposes was another subject which he took up with characteristic earnestness, and he advocated for a time the use of gas stoves and fires in preference to those which burn coal, not only on account of their cleanliness and convenience, but on the score of preventing fogs in great cities, by checking the discharge of smoke into the atmosphere. He designed a regenerative gas and coke fireplace, in which the ingoing air was warmed by heat conducted from the back part of the grate; and by practical trials in his own office, calculated the economy of the system. The interest in this question, however, died away after the close of
