Iron . 
117 
ted by the blast inversely according to the proportion of 
fuel with which it is mixed (for the oxygen of the air by 
preference unites with the loose carbon of the coaks, ra- 
ther than with that which has combined with the iron). 
The fluid mass soon sinks down below the influence of 
the blast, and while it remains in quiet at the bottom of the 
furnace the globules of iron are precipitated from the slag 
in which they were enveloped, and occupy the lowest 
place, while the covering of scoriae thus interposed be- 
tween the metal and that portion of the blast which is re- 
flected downwards, prevents it from suffering any further 
loss of carbon. In proportion as the melted matter accu- 
mulates, the Sag being the uppermost, flows out at the aper- 
ture made for this purpose, and the iron is let out at regular 
intervals into furrows made in sand, where it forms what is 
called pig iron, or into a large reservoir whence it is poured 
by means of ladles into moulds, forming all the various 
articles of cast iron ware, from cannons and steam engine 
cylinders, to lire grates and common iron pots. ( Aikins.) 
Figure 1, (Plate 1.) represents a blast-furnace, with part 
of the blowing-machine. ( Musket . ) 
A, the regulating cylinder, eight feet diameter and eight 
feet high,— B, the floating piston, loaded with weights 
proportionate to the power of the machine. — €, the valve, 
by which the air is passed from the pumping cylinder into 
the regulator : its length 26 inches, and breadth 1 1 inches. 
— D, the aperture by which the blast is forced into the 
furnace. Diameter of this Tange of pipes 18 inches. The 
wider these pipes can with conveniency be used, the less 
is the friction, and the more powerful are the effects of the 
blast.— E, the blowing or pumping cylinder, six feet dia- 
meter, nine feet high : travel of the piston in this cylinder 
from five to seven feet per stroke.— F, the blowing piston, 
and a view of one of the valves, of which there are some- 
times two, and sometimes four, distributed over the sur- 
