390 
Cast Steel. 
I cannot better close this collection on iron and steel, 
than by Dr* Aikin’s Summary* 
Manufacture and properties of Steel .- — Steel combines 
the fusibility of cast iron with the malleability of bar iron, 
and further possesses this very valuable property, that 
when heated and suddenly cooled, it becomes intensely 
hard, and is therefore much superior to simple iron for all 
kinds of cutting 1 instruments, files and various other tools. 
In the present section we shall describe the different me- 
thods of preparing and tempering steel, reserving for 
the next section an enquiry into the chemical compo- 
sition of this useful substance. 
The most ancient way of making steel is probably that 
related by Agricola. Take some highly carburetted bar i 
iron, cut it into small pieces and mix it with pulverized sco- 
riae, put the mixture into a crucible lined with charcoal, , 
and bring it to a state of fe *on in a blast furnace. When a 
both the iron and sc arias are thoroughly fluid, immerse in 
this metallic bath, four lumps of bar iron, weighing about 
thirty pounds each, and let them remain in this situation 
during five or six hours, stirring the bath occasionally 
with an iron rod ; by this time they will have become soft ii 
and spungy,upon which they are to be taken out and drawn 
down into bars by the forge hammer. A s soon as this ; 
is performed, the bars still hot, are to be plunged into cold 
water, by which they will be rendered brittle, and are 
then to be broken under the hammer into short pieces. 
The crucible in the mean time is to be replenished with 
the same mixture as before : and when its contents are be- 
come quite fluid, the pieces into which the bars have been 
broken, are to be again immersed till they become soft : 
each piece being then taken out and forged separately into 
a slender bar, is to be cooled while yet glowing hot, in 
cold water, and the process is finished. The above me- 
thod is we believe entirely obsolete, though with a few 
& > * <L>' 
