ROOFS VULNERABLE POINTS IN FIRES.
The San Francisco fire taught emphatically that the most vulnerable part of a building, in the case of a big conflagration, is the roof. Several forms of fireproof roofing are now being put forward, and at least two styles are guaranteed to resist flames under all conditions: These two forms are metal shingles and clay tiles. A third, and probably the greatest achievement in tileroofing from a utilitarian as well as esthetic point of view, is the use of glass. In the first place glass tiles are of the same pattern as clay tiles, and in factory work, upon an open-steel construction, may he inserted just as a clay tile would be in any number or in any position required. This does away with the cost of sheet-metal work, and the absence of this, or even of wire work, is important in many other respects. Galvanised iron and tin fields quickly when it comes in contact with the gases that arise almost invariably from reduction works, factories and the like. The life of this customary support to the skylight is three years: the glass tile, moreover, washes clean, while glass surrounded by sheet-metal work never does. Finally, the light obtained from the use of the skylights is far superior to that obtained in the old way, the corrugated surfaces of the tile acting prismatically, and perfect dissemination of light follows.—“Mining and Scientific Press.”