/ 
726 Ci« - On the Production of Caft, Iron, Y 
coals will be equal to 198,000 lb. When we refleét that thts 
vaft body of ignited matter is replaced every third day, when 
the furnace is properly at work, a notion may be formed ,of 
the immenfe quantity of materials requifite, as alfo the con- 
fequent induftry exerted to fupply « one or more furnaces for 
the fpace of one year. 
When the furnace is fuficiently heated. throughout, {pe- 
cific quantities of cokes, iron-{tone, and blaft- furnace cinders 
‘are added: thefe are called charges. The cokes are com- 
monly filed in bafkets, which, at all the various iron-works, 
are nearly of a fize. The weight of.a bafket, however, de- 
pends entirely upon the nature and quality of the coal, being 
from 70 to 1121b. each *.. The iron-ftone is filled into boxes, 
which, when moderately heaped, contain 561b. of torrefied 
iron-ftone; they often exceed this when the ftone has been 
feverely roafted. The firft charges which a furnace receives, 
contain but a fmall proportion of iron-{tone to the weight of 
cokes: this is afterwards increafed to a fuli burden, which is 
commonly 4 bafkets cokes, 3201b.; 2 boxes iron-ftone, 112 ]b.; 
i box blaft-furnace cinders, 60 or 7olb.t. At new works, 
where thefe cinders cannot be obtained, a {imilar graphy 
of limeftone is ufed, 
The defcent of the charge, or burden, is facilitated by open-. 
ip the furnace below two or three times a-day, throwing 
out the cold cinders, and admitting, for an hour at a time, 
a body of frefh air. This operation is repeated till the ap- 
proach of the iron-ftone and cinder, which is always an- 
nounced by a partial fufion, and the dropping of lava through. 
the iron bars, introduced to fupport the incumbent materials” 
while thofe on the bottom are carried away. The filling. 
above is regularly continued, and when the furnace at the 
* This fame variety in te coal renders it almoft impoffible, under one’ * 
defcription, to give a jult idea of the proportions ufed at various blaft-.” 
furnaces: to avoid being too diffufe, I fhall confine my defeription con-. 
ne€ted with a coal of a medium quality, or a mixture of fplint and free~ - 
coal, a bafket of which will weigh from 78 1b. to 84lb. 
+ A preference at firft is always given to blaft-furnace cinders in place 
of lime; being already vitrified, ‘they are of much eafier fufion, and tend to’ 
; pater. the furface of the hearth by glazing it over with a black vitrid 
chat. j 
top. 
