FUR 
the contre ; aes are coated with a layer of clay at the cir- 
cuamfeyence § onnbe of fa he bea Is of broken pipes are in- 
r r fragments are placed u 
S, are connie in 
faine time fo thin, as to require but little clay to conftru& it, 
and is lefs liable to {p lit es the heat, than a veflel formed of 
thic ker “mater nee method might, we think, , be advan- 
ds led ae upon rua: — of clay, r, whic 
mall bs are 
odlitenent ranges of pipes, without 
h other, as to endanger 
their being erufhed by the weight. By t this mode of are 
rangement, the furnace is made to contain 50 grofs, or etc 
Pipes: : thefe require to be burned from feven to nine hou 
e heat is at firft brought on gently, and afterwa ad 
eci 
mper 
applied over the — e fir ee 
lining... This age of horfe-dung, fand, and pipe-clay, 
well worked ovaler, and fpread in thin layers upon 
a fheet of this being on over the hole 
or lefs of it, will give the 
means of increafing or aoe the an. and, confe- 
quently, the heat of the furna 
ve 
a conclude this ere with fome ufeful hints — 
tive que mae of fuel, the oe ent of fur 
en a the quality and form sf crucibles 
fuel epoca: is af three kinds; namely » pit-coal, sae 
and charcoal ; the: firft of which ‘is idan employed b 
for reverberatory — — fubftances are to 
t "The nature of coaks varies 
1 t al 
required, the coaks are made to exhibit a bright, 
white, cryttalline fr fr acture. In other ciles, where" great heat 
ree coak, is el c seal is- ead exceee ingty 
Charcoal is alfo fometimes mixed with: coak, 
it ch ou rod, with a ho 
ufed for pias chs aay eae from. the grates -which 
otherwife would prevent the paffage of the air. After an 
-air-furnace has been ufed for feveral hours, when the fire is 
let cut, the bars ought to be taken out for the maple of 
oe all the flag ’y matter 
ing, perhaps, is of mo re importance, in the dr ry opera- 
Not 
tions of chemiftry, than Sad crucibles, a rmerly we had no. 
hat wh 
qT * mott enti pet in | making good 
“A crucible thould be capable of bearing 
it, without ome itfelf fo foft, as not to bear lifting out 
Vou. X 
the fubftance -put ‘into. 
FUR 
And it fhould alfo be ‘capable of pats: rae 
extremes of heat and cold, without cracking: The firft of 
thefe objeéts is attained, by Sate oa uch pure eg 
into its compofition as poffi Cruc bles. aa folely of 
ay how ever, are very liable to crack with ex tremes of heat 
evil has been 
of the fe. 
burne 
‘The crucibles ufed for melting feel, hich requires greater 
heat than is generally ufed, are fade with Stourbridge clay, 
and the powder of other toad coaks, which are ufed as fucl. 
hefe pots will fometimes bear four heats, or meltings, 
without cracking or a as their form. 
e infide of a crucible is in figure nearly a paraboloid, 
and the outfide a trun cated cone ; fo that the fides are gra- 
dually thicker towards The ftands and cavers 
of crucibles ought to be mee of the fam c material as the 
: the ftand fhould = A and of the dia- 
meter of the yonee * the cr 
Previoufl 
d 
oe heated till it aia to vitrify, can 
feldom he ite a fecond timesin t 
A crucible fhould never a. introduc a or taken out of tl 
fire ae tongs, holding it by one fide only, but by fuch as w “ll 
embrace it clofely on the outfide, by having the mouth of 
the tongs of the curvature of the crucible. Whena each 
is vey hot in vi furnace, the fire fhould not be fuffered to 
get y low, fince the introduction of a great quantity of 
cold ‘fuel will "be liable to break the crucible. Crucibles are. 
much more liable to crack when they have been baked very. 
ard. If they are merely hard enough to bear putting into 
‘he fire, and to bear the weight of the materials, it is fuf- 
fic io 
Furnace, Reverberatory. See above, Dr. Black’s, Mr. 
Muthet’s, and the article Ino 
Furnace, Simple. See ye RNACE, Plate I. figs 1 
Furnace, a See above, BLast-Furnace, TRoN, 
Ores, SMELTIN 
For RNACE, Wind. See Air-Furn ped 
URNACE for making Steel. See Situ 
F pe bs procuring Zinc from its On. See ZINC. 
Furnace of a mine, in the Art of War. See CHAMBER. 
and Mine. 
See See TORNAGE. 
FURNEAUX, Pump, in Biography, was born at 
Totnefs, in Devonfhire, in the year 1726. He received 
ee 
his dates education ae the free-{chool of his native town, 
€ 
fe n 
e bonds of friendfhip. ject of 
their purfuits was -fimilar, though they took different 
methods to attain it. Dr. Kengicod was a member of the. 
eftablifhed church, but Mr. Furneaux fought for learning, . 
and aimed to be a ae i Diffenters. He ftu di ed 
under the patrousg- 
Clapham, and fuccceded Mr. 
man, the well-known he the book of Revelation, . 
as 
aS 
a 
