fire-proof, vermin-proof, and nail-proof, and in dwellings for the poor
will therefore resist the destructive efforts of the "young barbarian."
Nothing, therefore, can be better as a building material. The system
ordinarily employed to erect structures in concrete consists of first
forming casings of wood, between which the liquid concrete is deposited,
and allowed to become hard, or "to set." The casings are then removed,
the cavities and other imperfections are filled in, and the wall
receives a thin facing of a finer concrete. If mouldings or other
ornament be required, they are applied to this face by the ordinary
plasterer's methods. This system finds favor in engineering
construction, and also in very simple forms of architectural work, but
with very complicated work the waste in casings is very great. Besides
this, however, the face is found sometimes to burst off, especially if
it has been applied some time after the concrete forming the body of the
wall has set, and the method of applying ornament is not economical.

[Illustration: 1.-18.]

A system of building in concrete has recently been invented by Messrs.
F. & J.P. West, of London, illustrations of which we now present. To
this system Messrs. West have given the name of "Concrete Exstruction,"
from the Latin "exstructio," which they consider to be a more
appropriate word than "constructio," as applied to concrete building in
general. In Messrs. West's system of building in concrete, instead of
employing wood casings, between which to deposit the concrete or beton,
and removing them when the beton has become hard, casings of concrete
itself are employed. These casings are not removed when the beton has
set, but they become a part of the wall and form a face to the work. In
order to form the casings, the concrete is moulded in the form of slabs.
Figs. 1 to 18 of our engravings show various forms of the slab, which