Iron o 
Si 
1 look upon it therefore to be a great desideratum in the 
preparation of iron-stone, to contrive a mode which would 
unite certainty and economy ; a mode which would either 
de-oxygenate the ore unexposed to external air, or which 
would dissipate its volatile mixtures exposed to air, with 
a degree of certainty which, with a small share of atten- 
tion, would preclude the possibility of the metal attract- 
ing more oxygen* 
In the present mode of preparing iron-stones, too much 
is left to chance and the discretion of subordinate work- 
men* The surface of the piles, being always in contact 
with the open air, is frequently exposed to perforations 
from winds, especially in those parts where the layer of ig- 
nited coals comes in contact with the current : a hollow 
space is soon formed ; the fuel, by means of the fresh air 
continually pouring in, becomes ignited to whiteness ; the 
surrounding stone is immediately fused : should this aper- 
ture be joined by a similar communication from opposite 
sides of the fire, a degree of heat will be excited beyond 
what could have been conceived possible in this mode of 
burning, and oxygen be combined with a mass of stone 
in such an high proportion as to form a very considerable 
part of the whole weight* This is an accident which will 
take place even where order, regularity and experience are 
conspicuous ; were it possible to avoid it by torrefying 
the iron-stone in that just temperature which has been 
formerly demonstrated as the most proper, uniting at the 
same time an equal degree of economy, it would contri- 
bute greatly to reduce to certainty and rule the operations 
of the smelting-furnace* 
TJie extreme of fusing the materials and combining the 
iron with an extra portion of oxygen, is not the only evil 
which an accurate mode of torrefaction would avoid : the 
same train of casualty often affords a considerable portion 
of the stone not enough prepared^ and some quite un- 
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