OPERATING BLAST FURNACES.
ascends. The buggies used hold about 800 pounds of ore and of coke 450 pounds.- The men charging the furnace are called " top fillers " and those loading the buggies '' bottom fillers.'' The work is thoroughly systematized, each man knowing his part. Top fillers hold a somewhat hazardous position, as it is not uncommon for men to be " gased '' by the fumes escaping at the bell and hopper of a furnace. Some furnaces suspend a sheet iron stack about ten feet over the top
FIG. 8. — HOISTING APPARATUS OF A "MODERN FURNACE — LABOR ALL ACCOMPLISHED BY MACHINERY.
of the bell, on the charging platform, for creating a draught to carry off the escaping gases. Improvements have been made whereby all stock is carried up and dumped by machinery into the hopper, so that there is no need for men working on a furnace as " topwhat are called silica, carbon, ganister, coke, magnesia, and asbestos bricks, all of which have been experimented with, and, to some degree, all have advocates of their utility in certain lines of work. Carbon bricks, it is claimed, have worn well, made of fine coke (poor in ash), or charcoal mixed with clay with tar as a binder. If such bricks contain more than 70 per cent of silica, as used for high temperatures, they are generally very friable and disintegrate with the least friction, so that bricks of this character would be suitable only for the lower body of a furnace. As clay is chiefly silicate of alumina, which is also a good substance to resist high temperatures, it works well as a binder with silica in making fire-bricks. The other substances in clay are iron oxide, lime, magnesia, potash and soda, which, to some degree, decrease the durability of fire-bricks. As fire-bricks come to the furnace or foundry they are often composed of about equal parts of silica and alumina. Bricks should contain silica or alumina in proportion to the amount of heat or friction they are if j