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114

H E

1\1

amining the con.lition of the maners

cont~ined

in his

u–

(ible, wilhout opening the door of the t\re-place: this

hole O\oulJ be mAde to open and (hut

e~lily,

by mcans

of a {lopple of eanh.

Foulthly, • circular apenure of .bout threeinches \Vicie

in the upper pan or vault of the furn, ce, \Vhich

f1JUIII,j

gradually lerren and

termin~te,

like that of thc dome

Ihe reverberating furnace, In a O'Ort contcal funnd of

abount three inches long, anJ fille(1tO enter the conic.1

pipe before defcribed, which is applied when the aaivity

of the 6re is to be increared.

When this fuenace is to be ufed, anJ

crucible to

be p!;\ceJ in it, care mu{l be taken tO fet on the grate a

cake of baked eanh fomewhat broader than the foot of

Ihe crucible. The ufe of this !laod is to fuppon Ihe

crucible, and Taife il above the

gT~te,

for which pllTpofe

it (hould be twO inches thick. Were it not fOT this

pTecaution. the botlom of the crucible, which wOlIlJ !land

immediately on the grate, could never be thoroughly

heated. becaufe it would be

alw~ys

expofed

Ihe IIream

of cold .ir which enters by the a(h·hole.

(hould

alfo be taken to heat this .eanhen botlom red·hot be·

fore it be placed in the fUI nace, in order tO free it from

any humidity, which might olherwife happen to be dli–

ven

.g~int1

the crucible during the opemioo, and oc–

cafion in breaking.

We omllled tO take notire, in fpeaking of the a(h hole,

that, befides its door, it (hould have about the middle of

itl height a fm,1! hole, capable of receiving the nofel

of a good perpetual bello\V!, which is to be introduced

ioto it aod worked, after the door is exa81y (hut, when

it i, thought proper

excite the a8ivity of the fire

the utmo!1violeore.

The forge i, nnly a mafs of bricks of

~boul

three

foot high, along whofe upper furface is dire(ted Ihe nofe

or pipe of a pair of !arge perpetual bellows, fo placed

Ihat the operator mayeafily blow the fire with one hand.

'íhe coals are laid on the heanh of the forge near Ihe

Do!.of the bellows; they are confined, if oecerrary, tO

plevent their being carried away by the wind of the be!·

lows, withina fpace inclofeJ by bricks; aod then by pull–

ingthe bellowi tbe fi,e is continually kept up iD its gre:.tt{l

aaivity. The forge i, of ufe when there is ocC'.fion to

apply a grm degree of heat fuddenly to any fubílance,

or when it is necerrary that the operator be at liberty tO

baodie

frcq~eotly

thematters which he propofes tO fufe

or calcine.

The cupelling fumace is thal in which gold and film

are purified, by the meaos of lead, from all alloy of o

Iher met.llic fubílances. This furnace mu{l give a heat

Ihong enough 10vitrifylead, and therewith aJl the alloy

which the pcrfea metal, may cootain. This furnace is

be built in the following manner.

Fir{l, of thick iron-plates, o, of fome fuch compofi–

lioo of earth as we recommended for the coo{lruaion of

fu rnaces, mu{l be formed a hollow quadrangular prifm,

whofe fides may

about a foot broad, and from ten to

eleven inches .high; and extending from thence upwards

may 'converge IOwards the tOr, fo

10 form a pyramid

Iluncated at the height of feven. or eight inches, and

,crmin~ted

a~erture

me widm

fmn

o¡

eight

incbes evcry

\V.ly

. The t:.wer pan of the prifm is ler–

minated and cI"led by a pldIC (Jf the fame mat'.rials of

which the fllrnace is ·on!l.·u,9d .

Secondly, in the fe'T. !ide or front of thi. prifm

there is an opentng of time or fOllr inc:,:s in height

by lil'e or fix inches in breadth: titis

op~ll!ng,

\Vhid\

Ihollld he

v.ry

near the htltlom, is the dnor of the

an\·hole. Inllnedtattly ol'er this opening is Vl.lced an

iroo gl.lte,

d\~

bm of which are quadr,ngular prifms

of half an inlh fquarc, !aid parallel lO

e.eh

other,

anrl .bout tight or nine inches afu nder. ano fo dil'vofto

Ihal t\VOof their angles are Iólmllynppofite, thetl'lOO–

thers looking one dire81y

~p\vd(ds,

and the other down–

lVolrds. As in this lituation Ihe bars of the grate pre–

fent to the fire·place very ohlique furface., the alhe.

and very fmall coalsdo nOI accumul. te bctween thelD, or

hin.!er the free entran.e of d\e "iT frum the a(h·hule.

This grale terminates Ihe an\·hole at its upper·p.J!l, aod

ferves lor the botlomof lhe fire-place.

l1\irdly, three ineh¡s, or three and a half, above the

grate. thele .is in the fore fide of the f'lrnace another

opcoing terminated by 3n arch for i:s upper pan, which

confequeotly

h~s

the figllre of a femi-Clfcle: it uught

be four ioches \Vide al bOllom. arod Ihree iD.hes a:\d an

half high at its middle. Thisopen:ng is the door of the

6re.place; yet it is not inlended for thefameules as the

door of the fire-place in other furnaces: the purpofe

for which it is aaually denined

(h.dl

be explained when

we come tO(hew f.OII the furnace is to be ufed. An

inch above Ihe door of the fire·plm ,. ílill in the forefide

of Ihe furnace, "e tWO holes of about ao inch diameter,

and at the di!¡ance of three inches and

half fromeach

other, tO which anfwer twn other I,oles of the fóme fize;

m~de

in the hioJer pan, dire81y oppoGte tO theCe.

There is, moreover, a fifth hole of the f.une width a–

bout an inch aboye the door of the fire-place. The de ·

figo of all Ihefe holes (hall be expl,ined whenwe defcribe

Ihe manner inwhich thefe furnlccs are to be ufed.

Founhly, the fore,pi\!! of the furnm is bouod by

three)ron braces, Ooe of which is fixed ju{l helowlhe

door 'of the a(h·hole; Ihe fecood occupies the IVhole

fpace betlVeeo the an,·hole door and .the dOGr of the fire–

place, and

ha~

t\Vo holes io it, anfwering to lhofe which

we direaed lO be made in the furnace ilfelf about thi.

place; and the Ihird i! placed immedimly over Ihe door

of Ihe fire·place. Thefe braces mu{l extend fro01 one

corner of the front of the furoue to the other, aod be

fa!lencd thcreto wilh iron pins, in fuch a manner that

their GJes next lO Ihe doors may 001 lie quite clofe to

the body of me furnace, bUI form a kiod of groovea

for the iron plates lO /Loe io, that are i1eGgned tO nlUl

the two doors of tbe furnace when il is neceffilry. Eaeh

of Ihefe iroo plates (hould have a baodle, by which it

may

conveniently moved; and to

e~ch

door therJ

(hollld be two plates, which meeting each other, anJ

joining

ex~aly

iu thu middle

the door.place, mRy (hut.

1t very clofe. Each of the two plates belonging tO tbe

door of the tire-place ought tO hl\ve a hole in iu Ilpper

pa" ; 'one of thefe holes (hould be a Oit of about two

Iines wide, and half an inch long; the other may be

fC\lli·eircuJar 0Eeoing of

Olle

¡¡

¡ell.in

hei~hl

aod (WO in

breadth.