24 
Iron . 
4. Iron-stones which unite a large proportion of sand 
with sparing proportions of clay and lime, which, upon be* 
ing slightly exposed to heat, exhibit masses of semivitrifi- 
cation, neither obedient to the magnet, nor adhesive to the 
tongue, having a refractory disposition to part, and pos- 
sessing a dark-blue or black colour, always afford, with 
the usual proportion of fuel, crude iron of the worst qua- 
lity, either as to strength or fusibility* Such metal is 
commonly highly oxyginated, and brittle ; incapable of 
being used alone for any melting purpose ; and, when ap- 
plied to the Use of the forge, affords malleable iron, which 
possesses the cold short quality. 
These are the four principal classes under which I have 
arranged our iron-stones, with regard to their tendency to 
afford their iron carbonated, possessing strength, or other* 
wise, when smelted in the blast-furnace with a determinate 
quantity of fuel. As this classification is exactly analo- 
gous to the results obtained in the large way, it may serve 
as a ground-work to those who may wish to attain a prac- 
tical knowledge of these ores, so far as it relates to their 
manufacture. 
It is however easy to counteract the natural tendency 
which every iron-stone has in this case, to afford its iron of 
a certain quality, and to make each of them yield crude 
iron of all the different degrees of fusibility and strength. 
Is it not obvious, that since the qualities of crude iron de- 
pend upon the mixtures and their kinds composing the 
stones, that if nature be assisted by adding or subtracting 
from them in the blast-furnace, every quality of crude iron 
may be produced from the same iron-stone ? I have seen 
most of these results determined in the large way, and the 
whole of them beautifully confirmed in the assay-furnace* 
It remains with the present manufacturer to consider 
whether it will be more his interest to reject such iron- 
stones as are of difficult carbonation, or to apply the neces- 
