“_ 
Tron-Stones ufed at the Blaft-Furnace. 373 
pofed to the ation of a compreffed current of air, is unfit for 
conveying the carbonic principle to the metal; and as it fre- 
quently belongs to the juft proportion of charcoal neceffary 
to {melt the ores, and to carbonate their iron, its lofs muft be 
felt, and the quality of iron impaired. 
When cokes of any quality are expofed. to a moift atmo- 
{fpheric, fo as to abforb water, their effects in the blaft-fur- 
nace become much reduced, and the prefence of the water 
is productive of the moft hurtful confequences in the produc- 
tion of carbonated crude iron. I have found, by repeated 
experiment, that 1 1b. of well-prepared cokes will, when laid 
in water, take up 13 ounces in the {pace of half an hour; at 
this rate, a bafket of cokes weighing 8olb. faturated with 
water, will contain 140 ounces of water, or 8]b. If the 
charge contains fix bafkets, then we fee that upwards of 
50 lb. of water is introduced regularly along with the charge, 
furnifhing an additional quantity of oxygen equal to 42+ lb., 
_ and of hydrogen equal to 7! 1b.: it frequently happens that 
the cokes contain a larger portion of water than is here fiated. 
When cokes thus furcharged are introduced in quantity into 
the blaft-furnace, the quality of the metal is not always in- 
flantaneoufly changed, and frequently thecolour and form of 
the cinder remain long without any great alteration. The con- 
tact of wetted cokes with the ore is firft feen by the great dif- 
charge of pale-blue gas, with the whiter flame at the top of 
the furnace ; next, the accumulating oxyde upon the furface 
of the pig when confolidating indicates their prefence. Iron 
thus oxygenated frequently exhibits, while fluid, that agitation 
and delicate partings peculiar to carbonated metal: the 
remelting of this iron is never attended with advantage, and 
is always unprofitable to the founder. 
From the propertics affigned to pit-coal in this and in 
former papers, the following faéts may be deduced :—That 
charcoal ig the bafis of the manufaéture of crude iron; that 
its proper application produces the moft valuable qualities of 
pig-iron; that, by diminifhing its relative proportion, or con- 
taminating its quality by heterogeneous mixtures, the value 
and fufibility of the metal is loft; but that, by a proper in- 
. creafe, 
