The upper surfaces of the floors are formed on battens filled in with mortar to an even surface for tiles in cement. It is impossible that fire can find its way between these solid surfaces of plaster, and in this way walls and floors may be made practically fireproof. Our own wrought-iron and concrete floors, composed of girders, joists, and T-bars, filled in with concrete, are more elaborate adaptations, and become fireproof when the iron is encased. Floors and walls of this description are also proof against damp, noise, and dust. Our common hollow wood floors are open to all these objections, and they are certainly far behind our age and science. If architects were to fill up their joists with plaster, and form good thick ceilings with battens for flooring, or cemented and tiled floors, we should hare solid instead of hollow floors everywhere, and fires breaking out in lower or other storeys would be confined between the floors, and prevented from spreading upwards, with all the disastrous consequences to bedrooms and their occupants. Good walls are essential, but the horizontal walls or floors of a building are no less so. There are some other kinds of floors and roofs that commend themselves to the building profession from their extreme simplicity and economy.

One plan consists in using earthenware tubes, square in section and about 1 ft. or more long. These are turned in flat arches, and rest on iron joists 8 ft. or 10 ft. apart. Two courses of these tiles, laid at right angles to each other in cement, form a strong floor 10 ft. or more wide. The tubular tiles give great rigidity and lightness, and by breaking joint a floor strong enough for any number of people is constructed. The floor and ceiling are afterwards coated in cement stucco. Frost introduced this plan. Another kind of roof or ceiling is formed of arched pots made square at top and round at the bottom, about 4f in. across and about 8 in. high, having the sides and bottom screwed, and a hole to give a key to the cement. The Bank of England, the Treasury Buildings, Whitehall, Buckingham Palace, the National Gallery, and other buildings have ceilings of this description. Stoneskew-backs have been used in some cases for the abutments. Again, roofs and flats of great strength, and perfectly fireproof, can be formed in a still more simple way. Two or more courses of plain tiles are laid in cement upon joists or rafters about 4 ft. apart, with battens 3 in. by 2 in., and at 11-in. intervals.

Upon these the first course of tiles is laid, the second and each following course breaking joint. The upper surface can be cemented or asphalted with an inch layer. Asphalte forms an admirable covering to a roof or floor. For floors it should be laid on a bed of concrete 3 in. to 6 in. in thickness, the concrete being of clean gravel and lime in the proportion of 7 to 1 in ground floors. If laid in joists, a finer layer is necessary. When quite dry, the asphalte should be laid to a thickness of 3/4 in. to 1 in., according to traffic and wear. Experiments have shown the value of asphalte in arresting fire. Although partially liquefied, the asphalte protects the timber from ignition; and a layer 1/2 in. thick is said to have preserved planks from ignition 1 1/2 hour. The only asphalte fit for roofs and floors, as a fire-proof material, is not any tar compound, but the rock asphalted mastics, as the " Seyssel" and "Val de Travers," containing about 7.50 of bitumen and 92.50 of carbonate of lime.

Thus one of the most effective roofs or floors is constructed of flat tiles over wooden or iron joists, concreting and then asphalting the surface.

D. 0. Boyd suggests that fireproof construction depends mainly on the following points: -

(a) That buildings, of the warehouse class especially, should be constructed wholly of incombustible materials, and of such as are unaffected by intense heat.

(b) That they should be built in compartments capable of instant isolation.

(c) That they should be proof against fire from without.

(d) That in the event of fire in any one compartment, and the inevitable consumption of its contents, an intense accumulation of heat, to endanger the building generally, should be impossible.

To secure the first in a strictly sound and scientific manner, the use of wood constructionally should be discarded, and our scientific men might do good service by discovering a mode of construction with known substitutes which should dispense with its employment. The too free use of iron in exposed situations has been found most objectionable; stone has equally failed; and good honest brickwork, especially when the mortar used is fire-resisting, would appear, after all, to be the most reliable. As, however, iron must enter into the construction to admit of the large rooms required in modern buildings, it would be essentia], and by no means difficult, so to isolate vertical columns, girders, and tension-rods, as to make them unaffected by the fiercest heat generated in their immediate vicinity.

The fact of the fragile wooden doors of ordinary buildings being the chief outlets- for the spread of fire has scarcely been adequately noticed. No sooner is the frail door burnt through, than the fire rushes up the staircase, which thus acts the part of a huge chimney in creating a draught and increasing the fire, being itself a vehicle for transmitting the fire to other parts of the building. Even iron doors buckle and twist under intense heat, and have failed lamentably. There is, however, a description of door (of which two have been fixed for some years in the Museum of Building Appliances in Maddox Street) absolutely fire-resisting. They are partly constructed of refractory fire-clay, and are made to slide into spaces left in the thickness of the walls. They overlap the door aperture by several inches on all sides, whereby their iron framework is well removed from any possible contact with fire.