Steel. 
279 
cooled from a state of ignition, it is malleable and 
soft, like bar iron ; but when ignited and plunged into 
cold water, it is the hardness and brittleness of crude iron. 
From the foregoing facts we are justified in drawing the 
same conclusions with Reaumur and Bergman, but which 
have been more perfectly explained by Vandermonde, 
Berthollet, and Monge, that crude iron is a reguius, the 
reduction of which is not complete ; and which conse- 
quently will differ according as it approaches more or less 
to the metallic state. Forged iron, when previously well 
refined, is the purest metal ; for it is then the most malle- 
able and the most ductile, its power of welding is the 
greatest, and it acquires the magnetic quality soonest* 
Steel consists of iron perfectly reduced and combined with 
charcoal ; and tire various differences in blistered steel, 
made of the same metal, consist in the greater or less pro- 
portion of charcoal imbibed. Iron gains, by being con- 
verted into steel, about tIo part of is weight. In order 
do harden steel, it must be put into a clean charcoal, coal 
or cinder fire, blown to a sufficient degree of heat by bel- 
lows. The workmen saw that neither iron nor steel will 
!| * 7 
harden properly without a blast. When the fire is suffi- 
! ciently hot, the instrument intended to be hardened must 
be put in, and a gradual blast from the bellows continued 
! until the metal has acquired a regular red heat : it is then 
to be carefully quenched in cold water. If the steel be 
too hot when immersed in water, the grain will be of a 
I rough and coarse texture ; but if a proper degree of 
heat, it will be perfectly fine. Saws and some other ar- 
ticles are quenched in oil. Steel is tempered by again 
subjecting it to the action of the fire. The instrument to 
be tempered we will suppose to be a razor made of cast 
steel. First rub it upon a grit stone until it is bright, then 
put the back upon the fire, and in a short time the edge 
will become of a light straw colour, whilst the back is blue, 
* 
