582 PROCEEDINGS OF SECTION J. 



the iron, when the weight to be carried is heavy, the iron joists 

 are far apart, or the tilling in is weak. These, however, occupy 

 space, and afford fuel for a fire, so that is better to fix rebated 

 fillets under the top flange of each joist, (PI. XXXIX., fig. 9), well 

 wedged, and bed intermediate bearers on the filling. A more fire- 

 proof mode is to fill up to the top of the iron joists with concrete, 

 floatthe same with cement, and lay solid wooden blocks or parquetry 

 in one of the many forms in which they are now prepared and used 

 in England. There being no interstices, the chances of ignition 

 are much modified, and the quantity of inflammable material is 

 greatly reduced. A perfectly incombustible floor, laid directly 

 on the concrete, such as cement, asphalte, slate, tiles or marble, 

 is, of course, the best from a fire-resisting point of view, and is 

 especially desirable in the passages of public buildings. 



i. The supports of the floors are equal in importance to the 

 floors themselves, and if insufficiently fire-resisting, the building 

 is but little better than one of ordinary construction. Cast iron 

 is notoriously treacherous, giving way altogether if suddenly 

 cooled. Wrought iron and steel columns have lately been intro- 

 duced, but these are liable to buckle under heat. They may be 

 partially protected by plaster or wire-lathing, or, better still, by 

 porous terra-cotta blocks, (PI. XXXIX., figs. 13a and 136.), which 

 maybe secured either by grooved joints and bonding, or by clips and 

 bolts. In all cases, an air space should be allowed between the blocks 

 and the metal, and with these precautions metal columns may be 

 considered practically fire-proof. Another mode of rendering 

 columns fire-proof without casing, is to keep them charged with 

 water. The oxidation is a fatal objection with wrought iron 

 columns, but in cast is not so serious. 



j. As in slow burning buildings, staircases and lifts should be 

 enclose! by brick walls, and kept outside the main walls of the 

 buildings, and in addition the materia] of the staircase itself should 

 be incombustible, as iron, stone, or marble, or, better still, of a 

 fire-pi'oof material, as concrete or terra-cotta. The form of the 

 staircase is also of importance, especially if placed within the 

 building, the most perfect being that enclosed by walls on both 

 sides of each flight. An open well in the centre becomes, during 

 a fire, a vertical flue, and enormously increases combustion. 



k. Instead of using wood for the internal divisions of a 

 building, the Americans now largely adopt partitions of hollow 

 porous terra-cotta (PI. XXXIX., fig. 14), three, four, or six inches 

 in thickness. They are very light, strong, sound proof and fire- 

 resisting, and can be built on any of the floors just described. 

 These I'educe the risk of fire very materially. 



I. By the use of flat tiles of the same material and light _[_ or 

 |_ iron, roofs may also be rendered entirely incombustible, as the 

 slates or other covering can be nailed or secured directly to the 

 porous terra-cotta, which can be sawn with a saw, and will hold 



