IRON. 
heat and more precaution, because more 
liable to break. 
This cast steel is almost twice as dear as 
other good steel. M. Duhamel says that 
it is not proper for all kinds of work, par- 
ticularly those which require much tenacity, 
as well as hardness to resist violent blows 
and strains ; but it is good for razors, knives, 
and all toys and small work which require 
an exquisite polish. It does not seem, how- 
ever, that the tenacity of this steel is inferior 
to that of the best.of the other kinds, and 
its uniformity of texture is for many works 
an invaluable advantange. It is daily more 
and more used in England, but must neces- 
sarily be excluded from many works of con- 
siderable size, on account of the facility 
with which it is degraded in the fire, and 
the difficulty of welding it, which cannot be 
done in the common way. We have been in- 
formed that the faces of anvils and broad 
hammers, for the use of silversmiths and 
other artists, have been made of cast stqel, 
and welded to iron by a particular manage- 
ment, which consisted in substituting be- 
tween the iron and the steel another kind 
of steel in the form of filings, or a thin 
plate. The steel plate intended for the 
face was made as hot as could be done with 
safety, and the iron being at the same 
time brought to the welding heat, was 
applied to the steel, and quickly united by 
hammering. 
When we consider the operations by 
which crude iron is brought into the mal- 
leable state, then converted into steel, and 
afterward into a fusible metal, which is not 
malleable ; we may perceive that steel- 
making is a kind of inversion of the process 
of refining iron, as practised in the first in- 
stance. When the oxide of iron is mixed 
in the smelting furnace with combustible 
matter and glass, it will either be complete- 
ly or partially revived, according to the 
management of the process. Much of the 
coal will however be so enveloped with 
the vitreous matter as to remain unburned : 
and the reduced iron, with which it may be 
in contact, will be in the same situation as 
forged iron in the cementing pot; that is 
to say, it will be in contact with coal at a 
very elevated temperature, and defended 
from the air. From the great infusibility 
of iron, it may reasonably be concluded, 
that the reduced metal does not flow into 
the bottom of the furnace, until the char- 
coal has converted it into a fusible matter 
similar to steel, by the same action which 
•takes place in cementation, whatever that 
action may be. Hence it must follow, that 
the various specimens of crude or cast iron 
will differ in their qualities, as well on ac- 
count of the degree of cementation they 
have undergone, as the degree of reduction 
which has taken place among the metallic 
parts, which are carried down, and form 
the whole mass. Since the coal, in the 
process of cementation, communicates or 
adds weight to the iron ; and since crude 
iron, as well as steel, exhibits sparkles, and 
is more easily burned that) other iron; it 
may therefore be concluded, that in the 
process of refining, that part of the inflam- 
mable substance which had united with the 
metal is burned, and leaves the iron much 
less fusible than before. Stirring the mass 
multiplies the contacts of the air with the 
burned substances; these surfaces of con- 
tact will therefore successively afford thin 
coats of infusible metal. In this manner 
it is found, that, if a large piece of crude 
iron be exposed to heat in a wind furnace, 
the external part will be deprived of its 
fusibility during the time required to pro- 
duce a strong heat in the whole mass; and 
the internal part will be melted, and run 
out, leaving the shell behind. Iron, which 
is of the consistence of paste, may there- 
fore be considered, like any other paste, as 
a mixture of a fluid with a solid. It will 
be easily understood, that the forging will 
bring the parts of difficult fusion together, 
and extrude the less refined and fluid parts : 
it will also be evident, that this operation is 
not likely to drive out the whole of the 
fusible matter. When the iron has arrived 
at that state, wherein the quantity of fibre 
or tough iron is sufficient to answer the me- 
chanical purposes to which it is intended 
to be applied, the artist will consider it as 
sufficiently refined ; and the residue of fu- 
sible iron contained in the bar, answers, in 
all probability, the valuable purpose of con- 
necting these infusible masses together. 
Thus we find that forged iron appears as 
if covered with a varnish, when urged to a 
white heat ; we find that this varnish is 
more abundant in steel ; and that iron and 
steel may be respectively welded together 
by application in this state; an effect which 
it would be very difficult to account for, in 
this most infusible of metals, if it were not 
for such an admixture. But past steel, steel 
over cemented, and crude iron, appear to 
be in the state of all other metals, platina 
excepted. They cannot be welded, because 
welding implies a partial fusion: or an 
effect similar to the gluing or uniting of 
