quality of the iron* On the other hand, it is said that 
sulphur is of difficult expulsion from the centre of the 
stone 3 as it is never seen going off till a bright red heat 
forcibly expels it ; and therefore it is highly requisite the 
iron-stone should be long and violently exposed till the 
last portion is got rid o£ T o effect this, therefore, the heat 9 
say they, ought to be urged till such time as the stone has 
indicated signs of fusion, or has partially suffered thereby. 
In order to give strength to this opinion, those who adopt 
it add, that, by such severe calcination , the volume of 
stone is reduced, becomes heavier, and that it will conse- 
quently occupy less room in the blast-furnace ; of course 
it is imagined that, bulk for bulk, the iron-stone becomes 
richer in iron than when in a raw state* 
Those who are acquainted with the oxydation of me- 
tals, and the consequent increase of weight, will at once 
discover the source of this error, and readily conceive, 
that, after the metal in the iron-stone has become partially 
disengaged by the expulsion of water, carbon acid, sul- 
phur, See. forming frequently a third part of the whole 
weight, it will become an object of attack to the oxygen 
of the atmospheric air, the combination of which with 
the iron, alone adds to the actual increase of weight, and 
not the transposition of the particles of metal from one 
piece of from stone to another. It must also be obvious 
that, where such fallacious prejudices have taken root, the 
consequences must frequently be fatal to the interests of 
the manufacturer ; as such iron-stones, literally calcined, 
must require an additional portion of fuel to furnish carbon 
to carry off the superadded oxygen. 
It is somewhat remarkable that the phenomena attend- 
ing the oxydation of iron should be entirely unknown at 
iron manufactories. Such a process is never dreamt of, 
and even the declaimers against severe torrefaction only 
account for the increase of weight, by asserting that the 
K 
