in house construction. It
is found that the most convenient height for the rectangular slab (Fig.
1) is 12 inches and the breadth 18 inches, as the parts of a structure
built with slabs of these dimensions more often correspond with
architectural measurements. The hexagonal slab (Fig. 2) is made to
measure 12 inches between its parallel sides. Where combinations of
these slabs will not coincide with given dimensions, portions of slabs
are moulded to supply the deficiency. The moulds in which the slabs are
made are simple frames with linings having a thin face of India-rubber
or other suitable material, by the use of which slabs with their edges
as shown, and also of the greatest accuracy, can be manufactured. That
portion of the back of the slab which is undercut is formed by means of
soft India-rubber cores. The moulds for making portions of the slabs
have a contrivance by which their length may be adjusted to suit given
dimensions.

During the process of casting the slabs, and while they are in a plastic
state, mouldings (if required) or other ornaments, having a suitable
key, are inserted in the plastic surface, which is finished off to them
(Figs. 7, 8, and 10). The slabs may also be cast with ornaments, etc.,
complete at one operation (Fig. 11), but it is more economical to have
separate moulds for the mouldings and other ornaments, and separate
moulds for the slabs, and to apply the mouldings, etc., during the
process of casting the slab. Corbels (Fig. 9), sets off (which would be
somewhat similar to the plinth course slab No. 10), and other
constructive features may also be applied in a similar way, or may be
provided for during the casting of the slab. A thin facing of marble or
other ornamental solid or even plastic material may be applied to the
face of the slabs during the process of casting, thus enabling the work
to be finished as it is carried up, or a key may be formed on the face
of the slab to enable the structure to be plastered afterward.

[Illustration: FIG. 19. FIG 20.]

In Fig. 20, the structure from the bottom of the trenches is shown with
the sides of the trenches removed. It will be seen that the footings are
constructed in the most economical manner by not being stepped. As no
damp-course is required in concrete work, when the aggregate is of a
non-porous material, one is not shown. Upon the top of the footings is
generally laid a horizontal slab, called the wall-base slab, the special
feat