Here you see there is a mud hearth, a wall of clay plastered over the
stones of the fireplace. This will prevent the fire from cracking and
chipping the stones, but clay is not absolutely necessary in this
fireplace. When, however, you build the walls of your fireplace of logs
and your chimney of sticks the clay _is_ necessary to prevent the fire
from igniting the woodwork and consuming it. For a log-framed fireplace,
make a large opening in the wall of your house and against the ends of the
logs where you sawed out the opening, erect jamb pieces of planks two or
three inches thick running up to the log over the fireplace and spiked to
the round ends of the logs (see plan, Fig. 272). Next, lay your foundation
of sill logs on the fireplace, first two side logs and then a back log,
neatly notched so as to look like the logs in the walls of the cabin.
Build your fireplace walls as shown by Fig. 271, after which take your mud
or clay and make the hearth by hammering the clay down hard until you have
a firm, smooth foundation. The front hearth may be made, as shown in the
diagram, of stones of any size from pebbles to flagstones, with the
surfaces levelled by sinking the under-part down into the clay until a
uniform level is reached on top. The fireplace may be built with bricks of
moist clay and wet clay used for mortar. Make the clay walls of the
fireplace at least one foot thick and pack it down hard and tight as you
build it. If you choose you may make a temporary inside wall of plank as
they do when they make cement walls, and then between the temporary board
wall and the logs put in your moist clay and ram it down hard until the
top of the fireplace is reached, after which the boards may be removed and
the inside of the fireplace smoothed off by wiping it with a wet cloth.