70 Economy of Fuel. (January, © 
which led to a saving of fuel through an increase in size 
were at that time not clearly understood, yet the practical 
results obtained were so beneficial that they culminated in 
a revolution unparalleled in the blast-furnace history of any 
district, in which all the original furnaces and plant were 
razed to the ground, and new ones on the now established 
improved principles were built in their stead. Furnaces 
have been built over 100 feet in height, and some of them 
as wide as 30 feet in the bosh; and it is the opinion of those 
best competent to judge of the matter, that the useful 
maximum of both height and diameter have been attained, 
if not exceeded. The object of increasing the size of the 
Cleveland furnaces was twofold; first, to increase the make ; 
and, secondly, to economise fuel; a third has followed 
gratuitously, viz., improvement in quality. The saving of 
coke from this cause has been considerable, and may be 
put down at from 7 to 8 cwts. of coke per ton of iron made. 
Mr. Isaac L. Bell, in investigating the causes which led to 
this economy of fuel in the larger furnaces, discovered that 
in a furnace one or two combinations are possible—that of 
one equivalent of carbon uniting with one or with two 
equivalents of oxygen; and that in the latter case as much 
heat is developed by 20 cwts. as is done by 71°14 cwts. 
when the carbon only unites with one equivalent of oxygen. 
The cause of the saving in fuel in large furnaces is two- 
fold; first, by the interception of a considerable portion 
of the heat formerly carried away in the gases—the products 
of combustion of the old furnaces; and, secondly owing to 
a better state of oxidation or combustion of the carbon,—a 
state of things proved by a great number of chemical 
analyses of the gases themselves as they leave the furnaces. 
Mr. Bell has also proved that no subsequent additions to 
the size of the furnace, beyond a certain point, has been 
attended with anything like the saving which accompanied 
the first steps in that direction; and that this is due to the 
fact that the escaping gases have, by such increase in 
dimensions, been deprived of nearly all the heat they can 
be made to surrender for use in the furnace; and that the 
chemical action in a furnace of about 12,000 feet is as 
perfect, so far as numerous analyses of the gases could 
indicate, as it is in a furnace of 25,000 cubic feet. 
Next to the increased size of the furnace, the principal 
cause of economy in fuel in the manufacture of iron is the 
improved temperature of blast at the tuyeres, which has 
been increased up to 1400. In order to obtain this 
