the beach be used, sound and dry walls will be obtained.  The use of concrete as a material for building will be found to meet all the defects set forth by practical people, as it may be made 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 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