LINING AND DRYING OF FURNACES. 45 required to withstand. The life of fire-brick depends upon the purity of these ingredients. The silica should be pure quartz or anhydrous silica, and not incalcined or raw rock for a substitute as is often practiced by some. It can be readily seen that one kind of fire-brick may give excellent service with one character of work and very poor for others. flaking of the bricks due to decomposition of carbon from carbon monoxide around any iron particles reduced from impurities in the original bricks.''