30+
��DEVELOPMENT OF HEAT.
��CHAP.
��with carbon plates, A ; a thick carbon rod, K, stands upright in the middle, and is surrounded by the carbon plates B and B\. The charge ^S^ is introduced between K and jS, and it gradually sinks as it is transformed into a liquid mass, T, by
���Fig. 56.
��the action of the arc light L The large quantity of gas evolved escapes through the channels V and Fi between A and BBi,
If the fused carbide is not run off at a tap-hole, the molten mass must be allowed to cool after some time, and the process thus becomes discontinuous. As the melting point of the carbide is high, and its heat conductivity is small, it is extremely difficult to prevent stopping up of the tap-hole.
Furnaces have been constructed which can be continu- ously worked, although they theoretically functionate dis- continuously. King's furnace is of this type ; in it the hearth consists of an iron box, covered inside with plates of carbon, and mounted on wheels which run on rails. A receiver of this sort forms one of the poles, and it is run in imder the other pole consisting of a bundle of carbon rods, which are then lowered so as to form an arc. The charge is introduced through channels into the carriage, and is gradually transformed into carbide. When the carriage is full it is removed, and its place taken by a fresh one. The whole apparatus is set in a large furnace built of fire-proof, bad-conducting material, and provided with an
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