Aug. 18, 1870] 
NATURE 
323 
- can be no better medium through which to effect the demo- 
lition of this mischievous error. 
By reference to almost any text-book on chemistry, it 
will be found that cast-iron is described as a compound 
or mixture of iron and carbon; that steel is another 
compound or mixture of iron and carbon, but with a less 
proportion of carbon; and that wrought iron is nearly 
free from carbon. Further, we are told that the ordinary 
method of making steel is, first to remove all the carbon 
from the cast or pig-iron by making it into wrought or 
bar-iron, and that this bar-iron is afterwards converted 
into steel by causing it to take up a new dose of carbon 
in the cementing furnace. The natural inference of a 
thinking reader is, that this is a clumsy complication, 
especially if he knows that the process of cementation 
is slow and costly, that on account of the irregular diffu- 
sion of the carbon in the blistered bars, other expensive 
processes of shearing, tilting, casting, &c., have to follow. 
Why not at once produce the steel from cast-iron by a 
process of decarburisation which shall stop at the right 
point, z.e., when the 3 or 4 per cent. of carbon of the cast- 
iron is reduced to the one or one and a half per cent. re- 
quired to produce steel? By doing this, not only the cost 
of converting wrought-iron into stecl, but also the cost of 
puddling to produce wrought-iron will be saved ; and steel, 
which is but a carburet of iron intermediate between cast 
and wrought-iron, instead of being so much dearer than 
either, should be made at an intermediate cost, or cheaper 
than wrought-iron. 
If he dips further into the literature of the subject, and 
reads the history of the manufacture of iron, he will find 
further confirmation of such reasoning, as he will learn 
thereby that the direct production of steel is an ancient 
art, and that weapons of renowned quality were made from 
steel thus produced. 
By reference to one of the most recent and elaborate 
English treatises on the subject, Dr. Percy’s “ Metallurgy,” 
he will find on page 778 that this is described as “the 
ancient method, which is still extensively practised on the 
Continent, especially in Styria ;” and further down on the 
same page that “if steel be regarded simply as iron car- 
burised in degrees intermediate between malleable and 
cast-iron, then it is obvious that the latter during its con- 
version into the former in the processes of fining and 
puddling, must pass through the state of steel.” On page 
805 of the same work he will find further confirmation of 
his theory in the words, “it is obvious that steel must be 
produced by melting malleable and cast-iron together in 
suitable proportions.” 
I might multiply quotations from this and every other 
work I have seen in which the chemistry of iron and steel 
is treated, and show by each of them that the thousand- 
and-one of unfortunate inventors who have struggled in 
vain to make steel directly from English pig-iron, have 
been encouraged in their delusion by the teachings of high 
chemical authorities. 
“Tf steel be regarded simply as iron carburised in 
degrees intermediate between malleable and cast-iron,” 
these inventors are perfectly justified in seeking some 
substance which at the melting heat of cast-iron shall give 
off a definite quantity of oxygen; and they have logical 
grounds for believing that by bringing such a substance 
in contact with the molten cast-iron, and properly regulat- 
ing its quantity, they may burn out just that surplus car- 
bon which makes all the stated difference between cast- 
iron and steel. As a multitude of compounds when thus 
heated do give off oxygen, a vast field of effort is open, 
and accordingly every available peroxide and decompos- 
able oxygen salt has been administered by strange devices 
to the melted iron, the same obvious substances used over 
and over again, and the same failures continually repeated 
by expectant inventors ignorant of what each other have 
done or are doing. Gas and vapours have been blown 
over the surface and under the surface, and through from 
bottom to top of melted cast-iron, and all (including Mr. 
Bessemer) have failed to produce merchantable steel from 
ordinary English cast-iron, without first making it into 
malleable or wrought-iron. 
The reason of this is, that the removal of the surplus 
carbon is only a small portion of the work which has to 
be done in order to convert cast-iron into steel of any 
commercial value. Several other substances have to be 
removed also; and no process has yet been discovered 
by which these impurities can be removed without at the 
same tine removing the carbon in corresponding degree. 
I put this in italics because I am convinced by experience 
of its great practical importance ; because I do not find it 
clearly and distinctly enunciated in any general or special 
treatise ; and further, because I have seen so plainly that 
the want of clearly understanding it is the rock upon 
which so many unfortunate inventors have split. 
These inventors have not been informed with anything 
like the necessary degree of distinctness, that the Styrians 
and others who have made, or are making, steel directly 
from cast-iron, have started with a very different mate- 
rial to that which bears the same name of cast-iron in - 
England; the difference being sufficiently great to alter 
totally the conditions of the problem. The cast-iron of the 
Styrian steel-makers is a nearly pure carburised iron ; 
our cast-iron is a carburised, silicised, phosphurised, and 
sulphurised iron; /¢/ezr problem in steel-making is, 
merely the partial decarburisation of their cast-iron ; owrs 
is the total desilicisation, the total dephosphurisation, and 
the total desulphurisation in addition to this. Now, the 
partial removal of carbon from iron is one of the very 
easiest problems in practical metallurgy, while the com- 
plete removal of silicon, phosphorus, and sulphur, is 
among the most difficult. 
To illustrate the grossness of the fallacy which repre- 
sents the difference between cast-iron and steelas merely, 
or * essentially,” due to carbon, I may state that on look- 
ing down a tabular statement of the analyses I have 
recently made of thirty brands of ordinary English pig- 
iron (excluding hematite pigs), I find that seven among 
them contain less than 2 per cent. of carbon, or an 
average of 1°77 per cent. Now this is below the per- 
centage of carbon which exists in some of the finest 
and most expensive samples of cast-steel. Therefore, to 
convert these particular brands of cast-iron into the 
finest steel, the carbon must neither be increased nor 
diminished, and if, as Dr. Percy says, the differences be- 
tween steel, wrought-iron, and cast-iron, “essentially de- 
pend upon differences in the proportion of carbon,” 
all these brands of pig-iron should be described as steel 
rather than cast-iron. 
Nevertheless they are utterly worthless for any of the 
purposes for which steel is used, and the common result 
of the costly experiments of the inventors who endeavour 
to make steel directly from English pig-iron, is to produce 
a material very much likethem. ‘They usually succeed per- 
f.ctly in their effurt partially to decarburise the pig iron. 
They take out, say one half of the carbon, and with it a con- 
siderable portion of the silicon, and sowze of the phosphorus, 
sulphur and manganese ; but to make a erect steel they 
must take out aé/ of these latter, and leave nothing but 
pure iron and carbon. Absolute perfection is not, of 
course, practically attainable in steel-making, but it is 
approximated in exactly the same degree as the purification 
of the iron from everything excepting the carbon is 
effected. 
The most notable modern attempt to produce steel di- 
rectly by the simple decarburisation of English cast-iron 
was that of Mr. Bessemer. His first idea was to blow 
air through melted cast-iron, and thereby to oxidise the 
carbon, and then, when a sufficient degree of decarburi- 
sation was effected, to stop the blowing. He supposed 
that when by this means the proportion of carbon was 
reduced to about one and a half per cent. the result would 
