The earthy matter of ores consists mostly of silica (sand), silicate of aluminum (clay), limestone, and magnesia. All of these are seldom found in the same ore, but almost all ores contain (1) silica and silicate of aluminum, or (2) limestone and magnesia. The ores containing a predominance of the materials of group (1) are acid ores, and those containing a predominance of the materials of group (2) are basic ores. Acid ores are in much greater abundance than basic ores.

Fig. 6a. - Base of a Blast Furnace.

B - Boshes. E - Peep hole. H - Hearth. M - Blast main.

P - Bosh plates.

T - Tapping hole.

U - Mud gun.

V - Water valves for bosh plates.

W- Mud gun crane.

Y - Tuyere holes.

Z - Furnace supports.