Iron, 
187 
j the furnace, the power of the blowing-machine, or the 
1 compression and velocity under which the air is discharge 
ed into the furnace, and the genius or mechanical skill of 
the workmen. According to this division, I shall endea- 
vour to point out the very various effects which dispro- 
1 portion in any case produces, and vice versa . 
In the preceding papers, the coal and iron stone have 
been traced through their various stages of preparation, 
and that stage pointed out in which they were most suita- 
ble for the profitable manufacture of the metaL It will 
be necessary to carry along with us this fact, that in the. 
exact proportion which the quantity of carbon bears to 
the quantity of metal in the ore, and its mixtures, so will 
be the fusibility, and of course the value of the pig-iron 
I obtained. The importance of this truth will still farther 
appear, when we consider the very various qualities of pit- 
coal, the different proportions of carbon which they com 
tain, and the various properties attached to every species 
1 of this useful combusti ble. 
Among the many strata of coal which I have distilled, 
some I have found to contain 70 parts in the 100. This 
large proportion is peculiar to the clod-coal, used at some 
|| of the iron-works in England, and justly preferred, for 
j the purpose of manufacture, to the purest and hardest va- 
riety of splint-coal. The latter I have found to average 
from 50 to 59 parts of carbon in the 100 ; and the soft, or 
mixed qualities of coal, from 45 to 53 parts. Such vari- 
ous proportions of carbon plainly point out that the opera- 
tions to be followed at each individual iron-work ought 
not to rest upon precedent, unless borrowed from those 
works where exactly the same quality of coal is used. 
This analysis also, lays open part of the source from whence 
originates the widely different quantities of metal produc 
ed per week at various blast-furnaces, and the great dis- 
proportions of ore used to different coals. 
