workmanship, retain their original sharpness as cleanly almost as the day on which they might have been cast. The reason of this was that they had been preserved in the bed of lime in which they had so long lain. Lime, therefore, will preserve steel from corrosion. The only difficulty has been in a perfect means of packing it around the shafts or beams. However well prepared and set the concrete may be that is used to protect the steel, concrete will draw moisture. Hence the imperative use of some coating of lime properly packed around the steel. But the more immediate difficulty in regard to steel is as to its strength when affected by heat and the sudden cooling effects of the fire squelching element, water. For the purpose of intervening means of preventing those effects of fire and water concrete is used. Concrete is, indeed, the saving-grace of fire-proof construction. Extensive experiments have proved the merits of what is called "cinder" concrete. This is superior to all other forms of cement. It is composed of one part Portland cement, two parts of sand and five of cinders (the residue of anthracite coal consumed in boilers). It weighs 75 to 90 pounds per cubic foot. It quickly sets and constitutes an encasing formation, so that foundation, walls, ceilings and roof, may, in a sense, be considered as continuous. Hence the name "monolithic" which has been applied to construction in which it enters largely. Burnt clay products, of hollow brick, (hard burnt clay) porous terra cotta, etc., are also largely used, for floors and encasing. Ordinary brick weighs 130 pounds per cubic foot, and does not withstand sufficiently high temperatures (such as from 2,500 to 3,000, required in a perfect fireproof material) to recommend it as a firstclass material (3). Hollow brick are of course lighter, but are also, like solid brick, disintegrated on exposure to sudden fire and the cooling stream of water. Stone cement, weighing 140 pounds per cubic foot, also disintegrates easily, and undergoes changes on exposure rendering it undesirable. The various plasters need only be referred to-they have their place, being in themselves non-combustible. One other substance may be mentioned glass. Generally understood glass has been considered as not entering into the category of fire-resisting materials. However, we now possess a form of glass which has been creating an important place for itself, namely what is known as wire-glass. For strength, and resistance to fire it has proved a most welcome adjunct. No building should be without wire-glass, the use of which has already been (herein) indicated. Its light diffusibility makes it all the more valuable. Other auxiliary materials, artificial but non-combustible, may be noted. Asbestos and alignum, for instance, belong to the fire retardant class. Flintkote and magnite, the (3) PORTION OF BRICK WALL AFFECTED BY HEAT. former a roofing material, the latter a paint, are tested auxiliaries. Durex and other tiling are valuable in hallways or in bathrooms as flooring. Glazed tiling may be introduced in many places instead of wood for paneling. In a fire-proof building where floors, walls and partitions are all made of fireproof materials, the doors should also be fire-proof. The De Man door is designed to accomplish this and at the same time match in appearance any wood finish which may be used. It is composed of a core, which is a monolith slab made of a fireproof composition and veneered with thin wooden facings which match the wood trim in the respective rooms. The door frames are treated in a similar manner. In case the contents of a room take fire, the facing of the door and frame may be destroyed on the side of the room where the fire originated, but the monolith fireproof core will arrest the progress and will prevent the spreading of the fire. hence such a tensile member as that used by Fire-proof construction may be of two classes: Complete fire-proof construction -in which non-inflammable materials are exclusively used; and semi-fire-proof construction-in which the inflammable materials are rendered fire-retardant by different methods of treatment and construction. But these may be further differentiated into three systems. The first is what is called the monolithic, in which concrete enters most largely; the second that in which is necessitated the assembling of various parts, which may consist of brick, blocks, tile, etc.; and, third, that in which metal constituents are introduced. In monolithic segmental arches or slabs, between or over steel floor beams, the material (cement) is placed in position while in the raw or plastic condition on temporary wood or permanent metal centering, and allowed to set. By this system settling or displacement of parts is avoided for the thrust is to a great extent eliminated. In the second system of construction the assembled parts are laid with mortar and may be in the form of segmental or flat arches, wood centering being generally used to support the work while the mortar sets. Great care, it need hardly be repeated, has to be taken in this system, as with imperfect joints arches will settle, causing cracks in mosaic or other expensive floor finish and in the plastered ceilings if the plaster is applied directly to the under side of the arch. In the third system, in which metal constituents are introduced, the metal is imbedded in the material itself while in the plastic state, in monolithic constructions; while in assembled constructions it is imbedded in the mortar of the joints. This form of construction adds greatly to the strength, while by it a much thinner and lighter construction can be secured. We are now prepared to consider the methods in general use in the construction of fire-proof floors and walls-the main portions of a building. Of these methods we have selected two of the most typicalthe Roebling and the De Man methods. In complete fire-proof construction concrete or cinder concrete and steel are, of course, the requisite materials. In constructions of former years concrete had only to resist compression stresses as in walls, piers and arches. In modern buildings, however, the construction has to sustain both compression and tensile stresses, as in a beam or a supported floor slab. In these cases the material of the beam or the floor slab is subjected to compression stress on the upper part and to tension at the bottom part. The compression resistance of concrete is sufficient to withstand most stresses, but its tension resistance is slight, hence one of the chiefest innovations in modern construction has been to increase the tensile strength of concrete by the introduction of steel "tension members" in its mass. This form of construction is known as "reinforced concrete." Great attention has been paid to tension members as to their shape and form, for the purpose of presenting locking shoulders to enable them to engage firmly with the concrete and to diffuse the stresses throughout. Different forms of tension members have been introduced by different engineers, either of twisted bars or "expanded" metal. Ransome of California proved that by twisting the bars in a cold condition the molecular strength of the metal was not lessened a fact that very much surprised some French engineers; ROEBLING CONSTRUCTION.-Their arch type of construction with flat ceiling consists of a wire cloth arch (stiffened by woven-in steel rods) which is sprung between the floor beams, and abuts into the seat formed by the web and lower flange of the I beams (4). On this wire centering Portland cement concrete is deposited and allowed to harden. The result is a monolithic construction, adapted for a fire-proof floor. The ceiling consists of a system of supporting rods attached to the lower flanges of the floor beams by a patent clamp which offsets the rods below the I beams. Under these rods, and securely laced to them is wire lathing, with the woven-in 4inch solid steel stiffening ribs crossing the supporting rods at right angles. This con gether every 16 inches and obviates the necessity of tie rods. The cinder concrete as regularly furnished receives and holds nails admirably. Lightness and economy may consequently be further realized by dispensing with the usual nailing sleepers and the sleeper fill, and nailing the rough under-flooring directly to the concrete; the finished flooring being laid over the rough flooring as shown. The wire centering is always preferred if the work is to be erected during cold weather, as it permits the moisture to drip away rapidly and prevents the concrete from being injured by freezing. The wire. centering also produces an exceedingly rough surface, affording an excellent key for the plaster when applied directly to the under side of the concrete. -3SLEEPERS (4) ROEBLING ARCH CONSTRUCTION. A suitable foundation for ornamental plaster effects is obtained by light iron furring and wire lathing. The furring usually consists of brackets or profile pieces made from flat or half oval iron, bent to correct outline, and is secured in position by means of clamps or clips to the structural iron or by nailing or stapling to the concrete fireproofing. The massive effects in the interior of the Broad Street Station of the Pennsylvania Railroad in Philadelphia, Pa., were produced entirely by such a system of furring and wire lathing. When furring and wire lathing is erected in connection with the hollow tile fire-proofing the brackets or profile pieces are so designed and adjusted that the greater portion of the weight of the false work and plaster is supported by the structural iron. The THE NEW RESIDENCE OF ANDREW CARNEGIE, 5TH AVENUE AND 91ST STREET, NEW YORK. (Roebling fire-proof floors throughout.) tile blocks are never injured and a rigid construction is secured. This wire lathing is well adapted for exterior wall furring. Heavy sheet iron is bent in the form of a V rib and woven in the wire lathing at intervals of every 71⁄2 inches. This furring is readily attached to the wall by nails driven through the angle of the rib into the mortar joints. The angle of the rib offsets the wire surface an inch from the wall and, when plastered, leaves an air space of 3/4 of an inch between the plaster and the wall. Arches, domes and alcoves, up to spans of 12 feet, and false beams, coves, cornices, etc., for ornamental effects in vestibules and hallways can readily and economically be constructed by such a system of furring and wire lathing. The light steel furring, in such cases, is supported directly by the walls or by means of clamps and hangers from the floor beams and girders. ance to fire. The principal advantage of The Roebling fire-proof partitions are strong, transmit very little sound, are vermin-proof, light, and, being constructed of incombustible material, offer great resist These partitions are adapted for elevator enclosures, vent shafts, pipe covering, etc. A solid fire-proof partition finishing 4 inches thick when plastered, has a core, 2/2 inches thick, of cinder concrete, both sur faces of which are plastered in the usual manner. As the concrete will receive nails, no wood furring is necessary in order to attach the base-board, chair-rail or picture moulding. Vertical spaces for piping, speaking tubes and electric wires, can also be provided in this partition. Only two coats of plaster-a "brown" coat and a "finishing" coat-are required as a finish. DE MAN CONSTRUCTION.-Another system of fire-proof construction which has been successfully introduced in the West, is place. In this system monolithic arch floors. are used when the spans between the floor beams are small. The covering of the lower flange of beams can be left off where fire proofing is not essential, thus reducing the cost. The top can be surfaced with cement or asphalt. The monolithic flat floor slab in reinforced concrete, supported by steel beams, is suitable for wide spans. It is composed of a concrete slab, reinforced with the De Man steel tension member (5). Again a com the De Man system. One of its chief characteristics is the treatment of the tension members. This system takes into consideration the fact that the natural cohesion of concrete is sufficient to support the stresses on lines parallel to the floor beam, for which reason there is no need of reinforcing concrete by tension members running in that direction. In the De Man system the tension members run from beam to beam in the line of stresses, no tie rods being necessary as the tension members take their paratively large space without steel beams can be floored with a monolith reinforced concrete floor. In this it is necessary to increase the depth (that is the distance from the upper surface of the floor to the tension member in the lower part) until a proper proportion is obtained between the span and the depth. In order to avoid an unnecessary waste of material in the lower part of such a floor construction, the tension members can be placed into the bottom part of ribs which are added to the under side of 2 |