IKON AND STEEL. 
69 
called blast-furnaces, which stand like the fiery wardens guard- 
ing the giant’ s castle, in those Teutonic legends that still five in 
Northern Europe. The blast-furnace, as usually constructed, 
is a circular brick tower, about sixty feet high, and at the 
boshes, or widest part, its width varies from fourteen to seven- 
teen or eighteen feet. Its interior section exhibits two 
frustums of cones, meeting each other at their bases, at the 
widest part of the furnace ; from which point it gradually 
contracts both upwards to the mouth and downwards to the 
level, where the tuyeres (small apertures for admitting air) are 
situated; within this are placed the fuel, the flux, and the mine, 
or iron ore. The bloving -in, as it is called, or the first starting 
of an iron-furnace, is an operation requiring great experience. 
A fire of wood is first lighted on the hearth, upon which 
coke is thrown, and when the whole is ignited, the furnace is 
filled by pouring in at the month regular charges of calcined 
iron ore, limestone, and coke. Blasts of air, urged by powerful 
steam-engines, are blown in through the tuyeres, and the whole 
becomes an intensely incandescent mass. The size and power 
of those bellows will be best understood, by stating the fact, 
that an ordinary furnace making white iron requires nearly 
7,500 cubic feet of air per minute, or it consumes 2,318 tons 
of our atmosphere in every week. 
As the iron ore is acted on by the intense heat produced, 
it yields up its carbonic acid and its oxygen, and fluid metal 
flows into the lower part of the furnace, where it is collected 
and preserved, until a sufficient quantity is obtained for casting. 
Moulds are made in sand, consisting of longitudinal channels, 
called sows, from which are formed lateral troughs, named 
pigs. The furnace is tapped by breaking away the clay which 
closes and secures the iymp-plate, on the removal of which, out 
flows a river of glowing whiteness, rushing onward through 
the sows, and rapidly filling the pigs with iron. The whole of 
the liquid contents having flowed out, the tymp-plate is again 
secured, and the operation of smelting goes forward as before. 
Furnaces are kept in blast for many years, yielding regularly 
from 200 to 400 tons of pig-iron per week ; every ton of iron 
requiring the following proportion of materials, or thereabouts. 
(Half a dozen examples are given, as they vary at different 
works, and also with the quality of iron.) 
1. 
2. 
3. 
4. 
5. 
6. 
CWT. 
CWT. 
CWT. 
CWT. 
CWT. 
CWT. 
Calcined Iron Ore ... 
48 
28 
46 
35 
27 
37 
Hematite do 
— 
10 
— 
[ 
10 
7 
Cinders 
— 
10 
— 
— 
— 
11 
Coal 
50 
42 
' 
40 
— 
36 
Coke 
— 
— 
34 
— 
34 
— 
Limestone 
17 
14 
16 
5 
15 
5 
