FYRE-BRICKS

bricks used in furnace construction or for other purposes where a high temperature is used. The qualities required in good firebricks are as follows: “They should not me it or soften in a sensible degree by exposure to intense heat long and uninterruptedly continued. They should resist sudden and great extremes of temperature. They should support considerable pre ure at high temperatures without crumbling. They may be required to withstand as far as practicable the corrosive action of slags rich in protoxide of iron or other metallic oxides.” (T. Percy, Fuel, p. 144.) These qualities are not all shown in the highest degree by any one brick. In selecting a brick, therefore, attention must always be given to the special conditions in which it is to be used, for one which would be good under one set of conditions may ANALYSIS OF FIRE-CLAY SPECIMENS 1 2 3 4 5 6 7 8 Silica. oo e. (65°64 [56°42 158-00 |62-35 [44-37 165-10 148-04 |48:99 Alumina aw -» 127-50 126-35 130-85 118-47 138-59 129-22 134-47 132-11 Oxide of Iron.. oe 1-944 2°334 $557 4-77} 1:82 | 1°92) 3°05) 2°34 ime.. ate ane +32 60 80jtrace| -5i 14 66} -43 Magnesia ate on “79| 55] — { 1-36 30 *18))| 24:51) = 22 Potash.. ae ae “BI 48) — | 247; — 18] 1:94) 3-31 Soda ve ae a. <= a oa — aes == cme — Titanic acid.. aS 33] 115} — | 140} — — — — Organic matter or lo in calcinate a a 24] —- — _ —_— ‘58 — — Combined water ~. | $96 {10-95} 9-70} 5-22 141-78) 7-10 |11-15] 9-63 Moisture = as 2:12] 2-80; — } 4-15 } 269} 2°18) — 2°33 FIRE-BARS, bars of iron fitted into the bottoms ef furnaces to support the fire. Their shape and size depend very largely on the nature of the furnave. Fire-bars are not used in the furnaces of large land boilers. The grate consists of hundreds of links which are fastened together to form an endle iron belt about 7 feet wide, which is carried over two rollers, one at the back end of the grate, and one at the forward end. This endle belt of links is kept slowly moving, and carries new fuel into the fire and ejects the spent ash at the back.— BIBLioGRAPHY: W. Inchley, Steam Boilers and Acce ories; Modern Mechanical Engineering (Gresham Publishing Co.).