e of cold iron laid in a small
welding furnace momentarily lowers the temperature, will appreciate
the enormous amount of extra heat that must be maintained in the
central portion of this furnace to make up for the constant chilling
effect of the cold wall. Moreover, since there would have been
serious trouble had steam generated in this front, a steady stream
of water had to be run through it constantly to insure against
an approach to the boiling point. This is illustrated because of
its absurdity, and as a warning of something to avoid.

Water-cooled, tuyere openings, as mentioned above, which support
brick side-walls of the furnace, have proved successful for coal
furnaces used for forging machine and drop-hammer heating, since
they permit a great amount of work to be handled through their
openings without wearing away as would a brick arch. Great care
should be exercised properly to design them so that a minimum amount
of the cold tuyere will be in contact with the interior of the
furnace, and all interior portions possible should be covered by
the bricks. However, a discussion of these points will hardly come
in the flame-shield class, although they can be made to do a great
deal toward relieving the excessive heat to be borne by the furnace
worker.

FLANGE SHIELDS FOR FURNACES.--Such portable flame shields as the
one illustrated in Fig. 106 may prove serviceable before furnaces
required for plate work, where the doors are often only opened
for a moment at a time. This shield can be placed far enough in
front of the furnace, that it will be possible to work under it
or around it, in removing bulky work from the furnace, and yet
it will afford the furnace tender some relief from the excessive
glare that will come out the wide-opened door. To have this shield
of light weight so that it may be readily pushed aside when not
wanted, the frame may be made up of pipe and fittings, and a piece
of thin sheet steel fastened in the panel by rings about the frame.

About the most disagreeable task in a heat-treating shop is the
removal of the pots from the case-hardening furnaces; these must
be handled at a bright red heat in order that their contents may be
dumped into the quenching tank with a minimum-time contact with the
air, and before they have cooled sufficiently to require reheating.
Facing the heat before the large open doors of the majority of
these furnaces, in a man-killing task even when the weather is
moder