IRON MANUFACTURE. 549 
vent this as far as possible, but evidently they only partially correct 
the evil. | 
Hence, one reason for this silvery character of the iron would ap- 
pear to be the high temperature necessitated by the large amounts of 
ore and slag in the hearth; in other words, the mixture must be such 
as to give a slag so basic that it can absorb the coal ashes without pass- 
ing beyond a proto-silicate. This condition is only possible when the 
volume of slag is large and the hearth very hot. 
The second point from which the smelting was to be considered, 
was the fuel consumption and heat distribution. 
The fuel used was stated at about 3 times the iron made. Assum- 
ing a yield of 60 per cent. in coke, this gives 1.8 tons of coke for 1 ton 
of iron, or, in the case above discussed, 1.9 tons of coke.. If an estimate 
of the heat required in the furnace be made, as in the case of the char- 
coal furnaces before discussed, it appears that this amount of fuel is 
very excessive. 
Bell estimates the heat required to make iron from Cleveland ore 
at 4,670 units per unit of iron (Chemical Phenomena of Iron Smelting, p. 
151). With the ores of this State, and raw coal, this requirement would 
be greater, as the slag would be a little, and the amount of gases con- 
siderably increased. The amount of gas produced from the coal fur- 
naces per ton of iron made is from 9 to 10 tons, as against 6.9 to 7.5 
tons in Bell’s coke furnaces. This would mean an increase of heat re- 
quirement of perhaps altogether 200 units, making the total perhaps 
4,870 units. Now, against this requirement, the fuel consumption shows 
an enormous heat production; to tell just how much, the analysis of the 
furnace gas would be necessary. Now this excess means two things— 
first, a great waste of fuel, due to bad working, letting the iron reduc- 
tion take place in such a way that carbon instead of carbonic oxide re- 
duces iron. This can be corrected by better lines for furnaces, greater 
height and more capacity, but there is probably another source of heat 
| consumption not allowed for by Bell, and unavoidable with the fuel. 
The heat required to coke the coal in the top of the furnace is probally 
larger than usually supposed. If 4,870 heat units be assumed as re- 
quired to do this work of the furnace, an approximate calculation of the 
heat production in the furnace under discussion may be made as fol- 
lows: Of the 1.76 tons carbon, 1.4 tons are assumed to burn at the 
tuyeres, .386 tons being enough to reduce all the carbonic acid of the 
