Iron. 
21 
2>o-?3^ 
tures as a consequence of the metal existing of a variety 
of qualities ; but, a priori , we ought to consider, that, as 
a consequence of the nature and proportions of the mix- 
ture, the iron will be called into existence in a state more 
or less oxygenated or carbonated. 
When iron-stones are said to contain good or bad iron, 
the expression ought to be understood, which by the bye is 
seldom the case, only as a comparative assertion, confined 
to local rules, and judged by certain fixed local standards ; 
into the account of which many things must be taken, 
which are frequently overlooked. At every iron- work, a 
certain proportion of fuel, coaks, or wood char, by weight, 
is understood to be sufficient to smelt, and give principle 
to a determinate weight and quality of iron-stones com- 
bined together, in order that a certain quality of crude 
iron may be produced. In this case, should a new iron- 
stone be substituted for one whose quality and effects arq 
already known, and should its application be productive 
of iron less carbonated than formerly, it would instantly 
be denominated a bad iron-stone, or an iron-stone contain- 
ing bad iron — an assertion only true comparatively, so far 
as it would affect the interest of the manufacturer, unless 
corrected by an addition of fuel, a change of the mixtures 
of ores, or a varied application of the lime- stone used as a 
solvent or flux . But this is no proof that the quality of iron, 
as it exists in the ore, is bad, since a larger proportion of 
coaks, or a change of mixture, which incurs no addition- 
al expence, can correct the evil. It rather furnishes a de- 
monstration that the iron in all ores is the same ; but that, 
in calling it into a metallic form, the quality is affected 
chiefly by the reduction of those mixtures originally united 
with it. 
As the quality of the fuel is improved in a direct ratio 
to the quantity of carbon which the coal contains, and its 
purity, hence arise the great variety of coaks used in smelts 
