F U R N 
or four, inches under the level of the tuyere hole. The 
fpace betwixt the bottoiu of the tynipand the dotted line 
is alfo rarraned full of ftrong f;uid,'and I'oineritiies fire¬ 
clay. This is called the tymp-ffopping, and jireven'ts 
any'part of the blafl from being unnecefiurily expended. 
Thefquare of the bafe of this furnace is thirty-eight feet; 
the extreme height from the falfe bottom to the top of 
the crater is fifty-five feet. 
The furnace, round the bottbm and Tides, for two feet 
up the fquare funnel, receives a lining of common bricks 
upon edge, to prevent the ftone from fhivering or moul¬ 
dering when the fire conies an contact with it. On the 
front of the furnace is erefted a temporary fife-place, 
about four feet long, into the bottom of wliich are laid 
correfponding bars. The fide walls are made fo high as 
to reach the under-furface of the tymp-ftone; excepting 
fl fmall fpace, which afterwards receives'an iron-plate of 
one inch and a half thicknefs, by way of a cover: this 
alfo preferves the tymp-fione from any injury it might 
fufiain by being in contaft with the flame. The fire is 
kindled upon the bars, and is fed occafionally with fmall 
coals. ' As the whole cavity of the furnace ferves as a 
chimney for this fire, the draught in confequence is vio¬ 
lent, and the body of heat carried up is very confiderable. 
In the courfe of three weeks, by means of this fire, the 
furnace will, from its ereftion, become entirely free from 
damp, and fit for the reception of the materials: when 
this is judged proper the fire-place is removed, but the 
interior bricks are allowed to remain till the operation of 
blowing commences. Some loofe fuel is then throvi'n 
upon the bottom of the furnace, and a few bafleets of 
cokes are introduced ; tliefe are allowed to become tho¬ 
roughly ignited before more are added. In'this manner 
the furnace is gradually filled; fometimes entirely full, 
and at other times j Sthsor 3-4ths full. The number of 
bafkets full depend entirely upon the fize of the furnace; 
that reprefented in the engraving, will contain 900 baf¬ 
kets. If the coal is fplint, the weigh.t of each baiket-full 
will be nearly i lolb. x 900 = 99 >ooolb- cokes. As this 
quality of cokes is made with a lofs of nearly fifty per 
cent, the original weight in raw coals will be equal to 
•198,0001b. When we reflefl that this vafl: body of ig. 
nited matter is replaced every third day, when the fur¬ 
nace is properly at work, an idea 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 fuflnciently heated throughout, ■ 
fpecific quantities of cokes, iron-done, and blad-furnace 
cinders, are added ; thefe are called The cokes 
are commonly filled in bafleets, which, at all the various 
iron-works, are nearly of a fize. The weight of the 
bafket,’however, depends entirely upon the nature and 
quality of thb coal, being from 70 to iszlb. each. The 
iron-done is filled into boxes, which, when moderately 
heaped, contain 561b. of torrefied iron-done ; they often ' 
exceed this when the done has been feverely roaded.. 
The fird charges which a furnace receives, contain but a 
fmall proportion of iron-done to the weight of cokes: this 
is afterwards increafed to a full burden, which js com- 
monly four bafkets cokes, 3201b. two boxes iron-done, 
H2lb. one box blad-furnace cinders, 60 or 701b. At 
new works, where thefe cinders cannot be obtained, a 
firr.ilar quantity of limedone is ufed. 
The defeent of the charge, or burden, is facilitated by ’ 
opening 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 fredi air. This operation is repeated 
till the approach of the iron-done and cinder, which is 
always announced 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 top has acquired a confider¬ 
able degree of heat, it is then judged time to introduce 
VoJ.. VIII. N0.490. 
ACE. ' 1.S.3' 
the blad; the preparations necefT.iry for which are the 
following: — 
The dam-done is laid iri its place firmly imbedded in 
firc-clay ; the dam-plate is again imbedded on this witli 
the fame cement, and is fubject to the fame inclination. 
On the top of this plate is a dight deprefllon, of a curved 
form, towards that fide fafthed didant from tlie blatt, 
for the purpofe of concentrating'the fcoria, and allowing 
if to flow off in a connefted dream, as it tends to fur- 
mount the level of the dam. From tliis notch to the 
level of the floor a declivity of brick-work is erefted, 
down which the fcoria of the furnace flows in large 
quantities. The opening betwixt tlic.dam and flde-wall.s 
of the furnace, called the fauld, is then built up with 
fa’nd, tlie loofe bricks are removed, and the furnace bot¬ 
tom is covered with powdered lime or charco.il dud. 
The ignited cokes are now allowed to full down, and are 
brought forward with iron bars nearly to a level with the 
dam. The fpace between the furface of the cokes and 
the bottom of the tymp-plate is next,rammed hard with 
drong binding fand ; and thefe cokes, whicli are expofed 
on the outfide, are covered with coke-dud. Thefe pre¬ 
cautions being taken, the tuyere-liole is then opened and 
lined with a foft mixture of fire-clay and loam ; the blafl 
is commonly introduced into the furnace at hid with u ' 
fmall difeharging-pipe, which is afterwards increafed as 
occafion may require. In two hours after blowing, a 
confiderable quantity of lava will be accumulated ; iron 
bars are then introduced, and perforations made in the 
cbmpreffed matter at the bottom of the furnace ; the lava 
is admitted to all parts of the hearth, and foon thoroujhly 
heats and glazes the furfaces of the fire-done. Shortly 
after this it rifes to a level with the notch in tlie dam- 
plate, and by its own accumulation, together with the ' 
forcible aftion of the blad, it flows over. Its colour is 
at fird black ; its fradlure denfe, and very ponderous ; the 
form it alTumes in running off is flat and branched, fome¬ 
times in long dreams, and at other times lefs extenlive. 
If the preparation has been yrell condu6led, the colour of 
the cinder will foon change to white; and the metal, 
which in the date of an oxyd formerly coloured, will 
be left in a difengaged date in the furnace. When the 
metal has rifen nearly to a level with the dam, it is then 
let out by cutting away the hardened loam of the fauld, 
and conveyed by a channel, made in fand, to its proper 
dedination; the principal channel, or runner, is called 
the fowt the lateral moulds are called thep?>i. 
In fix days after the commencement of blowing, the 
furnace ought to have wurougkt herfdf dear, and have 
acquired capacity fufficietit to contain from 5000 to 7000 
weight of iron. The quality ought alfo to be richly • 
carbonated, fo as to be of value andedimation in the pig- 
market. At this period, with a quality of coal as for¬ 
merly mentioned, the charge will have increafed to the 
following proportions:—five bafkets cokes, 4Gblb. fix . 
boxes iron-done, 3361b. one box limedone, loolb. 
An analyfis of the fmelting operation, and the ten¬ 
dency which the individual .agents have to . produce 
change in the quality and quantity of the iron, next de¬ 
mand confideration. Let us, howeverj fird notice the 
charafleridic featiires'exhibited by the different kinds of . 
iron while in fufion, whereby the quality of the metal 
may be judly defined.—When fine i, or fupercarbo- 
nated crude iron, is run from the: furnace, the dream of 
metal, as it iffues from the f^uhj, throws off an jiifinife ' 
number of brilliant fparkles pf carbon. The I'uffacp is ' 
covered with a fluid pellicleTif'carburet of iron, wIIujcIi, ; ■ 
as it flows, rears itfelf up in tHe mod delicate, fqlds j at \ 
fird the fluid metal appears like'a denfe ponderous 
dream, but, as the collateral fnoulds become filr,ed,j.it;ex- 
hibits a general rapid mptioh from the furface of the pigsr • 
to the centre of many points ; mjlUoris of the fined- un,^ 
diilations move upon each mould, dirpTaying the greatisfl ^ 
nicety and rapidity of movement, conjoined'H’ifli an un~ ' 
commonly beautiful variegation of colour, which lan- 
M m 
