46 
Iran . 
another conclusion, that without the presence of carbon, 
either in chemical union in the ore, or attracted from the 
ignited gas by the particles of metal, crude iron will not 
separate from the ore or stone ; and that, in proportion as 
the metal is exposed to inhale this principle, its produce 
is increased and its quality improved* 
It will further appear obvious, from the various natures 
of scoriae which the different iron-stones afford when fu- 
sed per se, that there exists a want of mixture in most 
of them to form, when fused, a fluid so sufficiently divi- 
ded that no portion of iron may be retained, either in a 
metallic state, or in that of an oxyde. This deficiency of 
mixture is greatest in the siliceous iron-stones, less in the 
argillaceous, and least of all in the calcareous. The prin- 
ciple, therefore, I proceeded upon was, to ascertain what 
proportion of additional mixture, and of what nature, was 
necessary to give the proper equilibrium to form a transpa- 
rent slag or scoria. When silex predominated, it was found 
that a major proportion of calcareous earth, in the solvent or 
flux, supplied the natural deficiency ; and that the whole 
contents in iron were justly revived, and fully saturated 
with carbon : when at any time it was wished to revive 
the metal, contained in such ores, possessing strength with 
carbonation, I found that this could be easily effected, in 
all proportions, by the addition of calcareous earth with 
a mixture of pure clay. In short, in every experiment 
I have made with ores, the various natures of lime- 
stones, or chalk, with certain proportions of bottle glass, 
have been found capable of reviving the iron contained in 
all the ores w hich have come under my knowledge, and of 
conferring upon their respective products every degree of 
strength and fusibility *. In order to form an accurate 
* Although I have frequently had occasion to mention the com- 
bination of clay with iron-stone, as the mixture which in fusion con- 
veyed strength to the metal, yet I have not ventured a conjecture 
