202 
Iron . 
part of the furnace, and instead of descending regularly to 
the focus of heat, falls down by pieces, and at irregular in- 
tervals, so that part of the metal is detained too long be- 
fore the blast, and in consequence is decarbonized and 
oxydated, while other portions pass so rapidly through the 
furnace as never to be thoroughly reduced, hence the 
amount of the produce is diminished and its quality great- 
ly deteriorated. Nor is it of less importance that the coke 
should be perfectly dry when put into the furnace, other- 
wise the water which it contains will be decomposed, the 
hydrogen and part of the oxygen will dissolve their re- 
spective portions of carbon, and escape in a gaseous state, 
while the remainder of the oxygen will combine with the 
iron; which will thus be injured, not merely by the pri- 
vation of carbon, but the poshive addition of oxygen. It 
is further requisite that the proportion of fuel be adapted 
to the richness of the ore, so that there may be sufficient 
both to keep up the necessary degree of heat as well as to 
carbonize the metal : hence as the charges of ore and fuel 
are always proportioned by measure, if an ore somewhat 
richer than usual happens accidentally to be employed 
without a corresponding addition of fuel, the produce, 
though somewhat increased in quantity, will be more than 
equivalently reduced in quality. Another circumstance 
that the manufacturer must carefully attend to, is the pro- 
per choice of ore with regard to fusibility, for as it is not 
only requisite that the iron should be melted, but also 
highly carbonized, and as coke gives off its carbon with 
much more difficulty than charcoal does, it is manifest that 
a very fusible ore would melt long before it arrived at the 
focus of the furnace, and passing rapidly through, would 
reach the hearth without having had time to imbibe the 
proper quantity of carbon. Hence it is that the rich haema- 
tites, although they afford an excellent quality of iron 
when smelted with charcoal, produce nothing but white 
