adily to close the throat entirely,
which is highly desirable in the summertime and frequently in the winter
when the fireplace is acting too strenuously as a ventilator. If the
cast-iron throat is not used, therefore, it will be well to lay an iron
plate on the smoke shelf in such a way that it could be drawn forward
across the opening to close it.

[Illustration: Perspective view of the fireplace, showing the
shape of the various parts as built without a cast-iron throat
damper]

There are other types of dampers, most of them patented and all of them
aiming to provide an adjustable opening in the throat in some way. One
or two of these have a knob or handle projecting through the brickwork
of the arch, permitting the convenient adjustment of the damper from
outside. As a general principle, however, it is well to choose the
simplest possible device that will secure the desired result.

The terra cotta flue lining which is shown in the sectional diagram is
not absolutely necessary, of course, as it is a rather modern
introduction and unnumbered fireplaces have served their purpose without
it. There is no question, however, regarding its worth, for it provides
a flue with smooth, regular sides that will not clog nearly so readily
as an ordinary brick flue. Besides that, it has the advantage of
permitting a thinner wall for the chimney. It is dangerous to build a
chimney with a single four-inch thickness of brick between the flue and
whatever may adjoin the chimney. Of course no wood should be allowed to
come within an inch or two of the brickwork in any event, but with a
single thickness of brick, unlined, there is always the danger that the
mortar will crumble from a joint and leave an opening through which it
would be an easy matter for sparks or flame to do considerable damage.
The introduction of a flue lining, however, into the chimney built in
this way makes it entirely safe, provided the joints between sections of
flue lining are carefully filled and made smooth with cement mortar.

The sectional diagram, it will be noticed, indicates a difference
between the main back wall of the chimney, eight inches thick, and the
brickwork laid inside the fire chamber to form the hearth and the back.
The reason for this separation is that the rough brickwork of the
chimney is always laid first as simply as possible, leaving the fire
chamber with its sloping back and sides and the hearth to be filled in
later wi