described, the brick-work in the left-hand chambers will have become considerably cooled, and then the "melter" reverses certain valves (not shown in the figures), causing the currents of gas and air to be reversed—that is to say, the gas and air will now come in through the right-hand chambers and pass out through the left. In this way a very intense heat is maintained in the "melting hole," which can be regulated at pleasure by varying the amount and proportion of the gas and air used. The advan-
Fig. 52. Plan of Siemens Pot Furnace.
tages of this furnace are sufficiently numerous and important to make its employment compulsory in all well-administered establishments.
In whatever kind of a furnace the steel is fused, as soon as the metal in the "pots" is thoroughly melted they are removed therefrom by a pair of tongs similar to those shown on the "pot" at the right hand of Fig. 53. and the "teemer" then grasps the "pot" with another pair of tongs and "teems" (pours) the fluid steel into an ingot mold of cast iron, care being taken that the stream of metal passes down the center of the mold without coming in contact with its sides.
The heat of the whole operation of "pulling out" the "pots" and "teeming" the steel (which last is well represented in Fig. 53) is so great that the workmen envelop their limbs in thoroughly soaked woolen cloths (technically called "rags"), which require wetting repeatedly during the casting of a "heat" of steel.
When the manufacture of cast steel was first undertaken in
