STEEL, AND THE BESSEMER PROCESS. 213 
recarboniser is set to melting in the small furnace. When the iron in 
the large furnace is melted, the converting vessel is turned on its axis, 
spout downwards, and the coal emptied out. It is then turned into a 
horizontal position, and an iron trough lined with loam, suspended on 
rollers, is swung, one end into the mouth of the vessel and the other 
under a spout leading to the tap-hole of the furnace. The furnace is 
then tapped, and the iron runs through the channel thus formed into 
the converting vessel. The air-blast is then let on, and the vessel 
turned spout upwards, the tuyeres or air-passages thus being underneath 
the melted cast-iron. The air is blown up through the cast-iron at about 
fifteen pounds pressure per square inch. Combustion, first of oxygen 
and silex, and then of oxygen and carbon, and a violent boiling, at once 
ensues. In from six to ten minutes, the flame blowing out of the mouth 
of the converter into the chimney changes from a dull red, full of sparks, 
to an intense white, with splashes of cinder. After five to ten minutes 
more the flame gets thinner, shows purple streaks, and finally drops 
away, not entirely, but very obviously to the practised eye. At this 
moment the metal is entirely decarbonised. More air blown in would 
begin to burn the iron itself. At this instant, then, which is so clearly 
defined that a dozen men tolerably familiar with the process, would cry 
" stop " at the same second, the converter is turned down into a hori- 
zontal position, and the air blast shut off. The recarboniser from the 
little furnace is then run into the converter by the same means, thus 
restoring to the metal the exact quantity of carbon; silicium, and man- 
ganese or its substitute required, the liquid cast-iron being only the 
vehicle for conveying these ingredients. The chemical mixture of the 
recarboniser with the decarbonised iron is complete and almost instan- 
taneous. It causes a momentary boiling of the mass in the converter. 
The ladle is then swung under the mouth of the converter, and the 
latter being lowered, the steel pours out into the ladle. While the ladle 
is being raised over the ingot moulds, the mouth of the converter is still 
further lowered to let the slag run out. Some of the slag runs out with 
the steel and forms a coating over it in the ladle, thus keeping it hot. 
The slag consists of such impurities of the iron as have not passed off in 
a gaseous form. 
The ladle is then moved over the tops of the moulds successively, 
and the steel let into them by the stopper and lever above mentioned. 
When a mould is full, a plate of thin sheet-iron is laid on the top of the 
steel, then a shovelful of sand, then a thick plate which is wedged 
down. In ten to sixty minutes, depending upon their weight, the 
ingots, still red hot, are removed from the moulds, and may be ham- 
mered, or rolled into rails, plate, shafting, or other forms, without 
reheating, except to warm the exterior, chilled by the moulds. Usually, 
the ingots are allowed to cool before hammering ; this cooling changes 
their crystallisation and improves their ductility. The ingot moulds 
are usually of cast-iron, from two to three inches thick. Some of -them 
