may be manufactured with a surface of any dimensions and of rectangular
(Fig. 1), triangular, hexagonal (Figs. 2, 14, and 15), and indeed of any
other form that will make a complete surface, while for thickness it may
be suited to the work to which it is to be applied, that used for heavy
engineering work differing from that employed 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