Fire-bridge
A hollow cast frame, encased in fire-brick, which is built between the hearth and the grate of a reverberatory furnace. See REVERBERATORY FURNACE.
Fire-clay is the kind of clay which, when mixed with other refractory ingredients, is used for the manufacture of fire-bricks, crucibles, glass pots, retorts, etc., which require to withstand intense heat. It is found abundantly near the surface of the ground, but chiefly in the coal measure. Fire-clay to be of value should be comparatively free from ferrous oxide (or combination of iron with oxygen), calcium carbonate (or substances such as limestone, chalk, marble, etc.), and iron pyrites, because at very high temperatures these bodies would combine with the silica of the clay with the formation of fusible vitreous silicates. See REFRACTORY MATERIAL. Fire-sand is the name given to all foundry sands that are composed principally of coarse grains of quartz, intermixed with more or less alumina or clayey sand. Because of the highly refractory nature of these siliceous sands they are usually termed "fire-sands." See FACING-SAND; REFRACTORY MATERIAL. Flame is the luminous phenomenon produced by the combustion of gases and is, hence, fire in motion. Substances which burn with flame are either gases already or they contain a gas which is set free by the heat of combustion. But flame does not necessarily produce light. In the burning of pure oxygen and hydrogen there is intense flame, but the light is so weak that it can scarcely be seen. If we sift a little charcoal-dust into this non-luminous flame, the particles of solid carbon are instantly heated to incandescence, a bright flash of light resulting. Therefore the conditions of illumination are, first, an intense heat, and, second, a solid placed in the midst of it, which remains fixed and gives out the light.
The lighting power of a gas depends upon the proportion of carbon it contains, the particles of which become glowing hot before being consumed. See COMBUSTION; HEAT; CARBON.