Queries. [Volume: 8, Issue: 1, 1888, pp. 21-28]

No. 1.] CHARCOAL IRON WORKERS. 27
and cause to alloy with the iron, the higher the melting point of
the slag must be.
Third. Upon the mineralogical condition of the constituents of
the mixture. The temperature of formation of the slag is more
important than the melting point with regard to the grade of iron
produced, and depends upon the amount of silica in the slag, and
the condition in which the slag-forming constituents exist. The
different reducibility of different ores also must be taken into consideration. In smelting difficultly-reducible ores, more iron is
slagged off than when smelting easily reducible ones. It is also
harder, in the first case, to produce iron high in silicon, carbon or
manganese.
Fourth. Upon the temperature of the melting zone of the furnace. The reduction of manganese and silicon in large quantity
requires high temperatures, so that high silicon or manganese pig
cannot be produced in a furnace working cold. The temperature
of the furnace depends upon the temperature of the blast, the
nature of the fuel, the proportion between fuel and ore, and the
heat consumption of the furnace. The latter is greater when large
amounts of manganese and silicon are reduced, and when smelting
difficultlv-reducible ores, than in the reverse case. All these conditions together, cause a larger fuel consumption and the employment of a more highly heated blast, the higher in silicon or manganese the pig is desired to be.
Fifth. Upon the quantity of blast which the furnace receives in
unit of time, or more correctly, upon the proportion this amount
of air bears to the cubic capacity of the furnace. The more air a
furnace receives the quicker the smelting proceeds and the greater
the quantity of iron produced, but the more easily unreduced iron
may be slagged off, and the less the amount of silicon and manganese reduced. Therefore a furnace making white iron requires
closer watching than when making grey iron or high manganese
iron. By the proper mixing of several ores, or by mixing the
same with suitable flux, different grades of iron may be produced
from the same ores, even when the original condition of the ores
appears to be more suitable for one purpose than the other. Bog
ores, intimately mixed with quartz or quartzy red hematite
ores nearly always promote the production of grey iron; on the
other hand high manganese spathic ores when used to produce