THE FIREPROOFING OP CITY BUILDINGS. 583 



cut nails. The importance of this development is very great, 

 as hitherto root's have been confessedly the most ditiicult portion 

 of a building to deal with. 



m. In a thoroughly fire-proof structure, the material of the 

 walls is of much importauce. A stone containing much carbonate 

 of lime or magnesia, is turned by tire into quick lime, and crumbles, 

 (iranite if heated and drenched with water, disintegrates. A 

 sandstone, free from lime, will usually stand fire, but well burnt 

 bricks, especially if they are not too dense, and are laid in lime 

 mortar, are, about the best material available. Their only superior 

 are firebricks laid in fireclay cement, but for any ordinary 

 purposes the latter are unnecessary. 



n. Where a large quantity of highly inflamable material such 

 as oil, turps, varnish, spirit, tkc, is stored, the only safe plan \i\ 

 addition to the foregoing is to rigidly limit the size of the structure 

 and subdivide by brick walls into sections. The doors of com- 

 munication then become an important feature. In London \ inch 

 plate iron is the minimum thickness allowed and there must be a 

 door on each side of the wall. The frames also have to be of iron 

 and fit closely. Iron, however, buckles under great heat, and 

 various alternatives have been suggested as iron frames filled in 

 with concrete or wire lathing, or better still, with porous terra-cotta 

 panels. The closing of the doors is however the great difficulty, 

 at the critical time they are never shut, hence the Americans 

 have devised slidiag tracks and bolts, stays or fastenings with a 

 link fusible at a low temperature. For slow burning construction 

 doors of two li" thicknesses of wood cased with galvanized or 

 tinned iron may be adopted. They are much cheaper than iron 

 andwould last quite as long as the floors. 



o. In addition to any of the foregoing suggestions for fire- 

 proofing buildings, such accessories as fire hydrants, sprinklers 

 and fireproof paints and coatings are always of much value. With 

 the former an adequate supply of water devoted solely to this 

 purpose is of the utmost importance; also the periodical testing 

 of the hose and valves. Sprinklers are another American notion, 

 consisting of lines of water-pipes throughout a building fitted 

 with numbers of valves closed by a fusible plug or link. Undue 

 heat releases the link and the water is discharged in a shower. 

 One serious objection, however, is raised against automatic 

 sprinklers — viz., that more property is destroyed by watei-, than 

 is saved from fire. Another mode, where iron columns form the 

 supports is to charge them with water, from an overhead tank, and 

 apply circular jets, opeiated by fusible plugs as just descrilied. If 

 automatic sprinklers are adopted, an escape for water should be 

 provided, and more especially if the goods consist of iutiammable 

 liquids.* Of fireproof paints and coatings I can only say their 



* Sec ApiK-ndix E. 



