e than ordinary
firebrick. From this material a soft heat is given off, differing in
quality from that obtained from iron. An iron furnace, however, requires
less thought in design, gives less trouble in fitting up, and is cheap,
economical, and expeditious. Stoves, therefore, with an iron radiating
surface, have been largely adopted in the past, in spite of the
objection that, when super-heated, particles of metal are thrown into
the air of the hot rooms. Of iron furnaces there are many placed before
the public; but though all are doubtless suited to ordinary
requirements, there are few that are capable of creditably fulfilling
the conditions indispensable for the hygienic heating of the air of a
Turkish bath.

These conditions may be summarised as follows:--

1. A maximum of heating-surface, with a minimum of grate space.

2. Perfect immunity from the danger of leakage from the furnace into the
hot-air chamber or conduit.

3. Freedom from the defect of liability to overheat the air.

4. Inability to adulterate the air by throwing off matter from the
heating surfaces.

Such primary essentials must be constantly borne in mind by the designer
of furnaces for the Turkish bath. Their importance must be obvious to
all.

Of the many iron stoves, Messrs. Constantine's "Convoluted" stove has
been adopted the most frequently, as an eminently practical furnace for
the effective heating of the sudatory chambers. The appearance of this
stove is familiar to all architects, and it will be unnecessary, in
these pages, to minutely describe its construction.

[Illustration: FIG. 6.

View of a small Furnace Chamber, with portion of wall broken away to
show the "Convoluted" Stove.]

The method of constructing a furnace suitable for a small public bath
is, however, shown at Fig. 6. The excavations for stokery and heating
chamber being completed, and the position of the furnace determined a
solid foundation of concrete must be prepared, upon which the brickwork
to support the stove must be laid. At the same time, the foundations for
walls of furnace chamber, stokery, coke store, and the side walls for
the horizontal cold-air conducting flues will be prepared. These latter
must then be built in half-brick with glazed interior face, and the
furnace inclosed in similar work, as shown in perspective sketch. The
flues must be covered with York stone slabs 3 in. thick, up to within
three inches or so of the convolutions of the stove