VERTICAL FURNACES FOR TEMPERING
It would be very simple to change this furnace in the manner
shown in Fig. 100. Here the hot gases from the independent
firebox are set free in the heating chamber of the furnace and
drawn off from the bottom of the chamber. The circulation of
the heated gas is indicated by the arrows.
Certainly, this construction is not suitable for heavy artillery
tubes and jackets. A pit jn the neighborhood of 20 m in depth,
as required for the large naval guns, cannot be heated in such a
simple manner; but, in general, the problem may be very easily
solved if the radiation losses from the heating chamber are avoided.
Another type of vertical annealing furnace is that used for the
annealing of iron wire before and after it has been passed through
the drawing blocks. Fig. 101 shows the design of a furnace for