380 
Cast Steel. 
three hundredth, 1 four hundredth part the weight of the- 
iron, whereas in experiments No. XIII. and XIV. the loss 
of metal amounted to one 31 six tenth, and one 22 
eight tenth part the weight of the iron. 
I shall conclude this paper with a few remarks upon 
the state in which carbon exists in steel and in crude iron. 
When malleable iron is fused with 1 one hundredth thirti- 
eth or 1 one hundred fortieth part of its weight of carbon, 
the resulting product is considerably steelified. The frac- 
ture is lighter in the colour than it formerly was in the state 
of iron. When fused with an 8 0th to 1 one hundredth, steel 
of an ordinary quality is produced, the fracture of the me- 
tal still becoming whiter. When the dose of carbon is 
increased beyond this, the steel becomes so hard and dense 
as to be unfit for hammering. The fracture now will be 
found approaching to the colour of silver, and losing its 
granulated appearance, assuming, however, a crystallized 
form. In this state the metal will be found to resist the 
hammer and file, and to be unfit for any purpose. In- 
crease, however, the quantity of carbon to one twelfth or 
one fifteenth, the resulting product is no longer destitute 
of grain, nor possessed of the same degree of hardness. 
The fracture will be found grey, and the surface "easily 
reduced by the file. A further increase of the carbon is 
accompanied by an increase of these properties. At l-8th 
or l-6th, the filings of the metal, when thrown into water, 
leave a carbonaceous pellicle covering the whole surface, 
and of a considerable thickness. 
Thus we find that carbon hardens iron till it arrives at 
the highest pitch of density, which is indicated by the me- 
tal losing grain, and assuming a crystallized silvery frac- 
ture. At this point or maximum we may conceive that 
the respective proportions of mixtures are so nearly ba- 
lanced that the affinity exerted by the iron is just suffici- 
cient to deoxydate the charcoal, and that hitherto nothing 
