Cast Steel . 
387 
exposed to combustion in open heaps, and which also par- 
tially, though in a less degree, takes place in the process 
commonly known by the name of Lord Dundonald’s pro- 
cess for preparing coal tar.” 
Notwithstanding Mu shot’s experiments fully support 
his theory, that steel, is pure iron united to pure carbon, 
and that the various kinds of steel, depend the various pro- 
portions of the carbon united to the iron, yet i am persua- 
ded that neither in the making of cemented steel, or of cast 
steel, or of case hardening, do the manufacturers confine 
themselves to the charcoal of wood. I have before ob- 
served, that the carbon united to animal charcoal, is more 
easily disengaged than that which is contained in vegetable 
charcoal, so that for case hardening, the charcoal of hoofs, 
horns, bones, clippings of leather, &c. is constantly and al- 
most exclusively preferred. We sadly want a set of ex- 
periments, shewing the effect of treating iron in a cruci- 
ble with equal weights of animal and vegetable charcoal — - 
iron enveloped with Prussian blue, and exposed to a conti- 
nued heat in a close crucible of common crucible clay : for 
the Prussic acid is always contained in animal charcoal.— 
Iron so treated with ammonia or volatile alkali, and its 
carbonats — and another series of experiments in addition 
A 
to those of Mushet, on the different results in black lead 
crucibles and common crucibles. Such experiments would 
throw new light on the theory of the combination of steel 
and charcoal, and of course on the practice of making steel. 
Until these are made, I think I may venture for various 
reasons to state it as probable, that in the making of blis- 
tered and german steel, the bars cue imbedded by some 
manufacturers in a mixture of well burnt charcoal of wood, 
with about one sixth of animal charcoal made from hoofs, 
horns, leather cuttings, &c. also, that in making of cast 
steel, out of the clippings of blistered steel, german steel, 
old files, &c. these articles are fused with limestone and bot- 
