rromanganese. The ferromanganese may contain as much as 80% manganese.
These varieties of cast iron are much used in the manufacture of steel.

~Wrought iron.~ Wrought iron is made by burning out from cast iron most of
the carbon, silicon, phosphorus, and sulphur which it contains. The
process is called _puddling_, and is carried out in a furnace
constructed as represented in Fig. 86. The floor of the furnace F is
somewhat concave and is made of iron covered with a layer of iron oxide.
A long flame produced by burning fuel upon the grate G is directed
downward upon the materials placed upon the floor, and the draught is
maintained by the stack S. A is the ash box and T a trap to catch
the solid particles carried into the stack by the draught. Upon the
floor of the furnace is placed the charge of cast iron, together with a
small amount of material to make a slag. The iron is soon melted by the
flame directed upon it, and the sulphur, phosphorus, and silicon are
oxidized by the iron oxide, forming oxides which are anhydrides of
acids. These combine with the flux, which is basic in character, or with
the iron oxide, to form a slag. The carbon is also oxidized and escapes
as carbon dioxide. As the iron is freed from other elements it becomes
pasty, owing to the higher melting point of the purer iron, and in this
condition forms small lumps which are raked together into a larger one.
The large lump is then removed from the furnace and rolled or hammered
into bars, the slag; being squeezed out in this process. The product has
a stranded or fibrous structure. _The product of a puddling furnace is
called wrought iron._

[Illustration: Fig. 86]

~Properties of wrought iron.~ Wrought iron is nearly pure iron, usually
containing about 0.3% of other substances, chiefly carbon. It is tough,
malleable, and fibrous in structure. It is easily bent and is not
elastic, so it will not sustain pressure as well as cast iron. It can be
drawn out into wire of great tensile strength, and can also be rolled
into thin sheets (sheet iron). It melts at a high temperature (about
1600 deg.) and is therefore forged into shape rather than cast. If melted,
it would lose its fibrous structure and be changed into a low carbon
steel.

~Steel.~ Steel, like wrought iron, is made by burning out from cast iron a
part of the carbon, silicon, phosphorus, and sulphur which it contains;
but the process is carried out in a very different way, and usually,
thou