1000000030

breadlh. Th& holes 010ulo be placc I fo Ihal neilher

of Ihem ma)' open inlo Ihe fire' rlaec when Ihe IIVO

plates are joineo logether in Ihe middlc of Ihe door

/huI il c1ofc.

Fifthly, 10 terminale the furnace above, Ihere mufl

be a pyramid,

f~rmed

ohhe fame malcrials wilh the furo

nace, hollolV, quadlangul.r, lhree ínches high, on a bJ(e

of (even inehes, whieh ha(e mufl exaaly Gt tI,e upper o·

pening of Ihe furnace : Ihe

lO?

of Ihis pyramidal eOYl r

Dlufl end ina luheof Ihree

ioeh~s

in diam((e(' ano IWO in

heighr, whieh mufl he

~Imofl

eylindrieal, and yet a

liuJe incliniog la Ihe eonical furol. This tube fcn'es,

as in Ihe furnaces already d"ferihed, 10 carry Ihe eonical

funnel, whieh is Gned to the upper par! IVllen a Gre of

eXll aordinary aai\ ily is lI'anled.

The furMee Ihus eonflruaed is Gt la fen'e all the pur–

pofes for whieh it isueGgned; yer, btfore il can be u:td,

ano,her pie,. mnfl be proYided, which, Ihongh it does

nOI properly bclong la the furnace, i, nevenhele(s neeef·

Caey

in all Ihe opclalions performeo by il; ar.d Ihat is a

piece eonlrived tO eonlaio Ihe eupels, or olher verrds

",hieh are 10 be expn:ed 10 Ihe fi'e in Ihis futnaee.

is eallcd a

lII:.fflt,

"n:!

is made in ¡he fo!lowing manner.

On an oblor.g (quue, of four inches io breadlh, aod

fix

f~ren

in Icnglh, a eooeave fCllIi.cylinder is

cre,~ed,

in Ihe ;urm of a v.luh , which mak.:s a (emi·eircular ca

oal, open al bOlh e"ds. One of thtfe is almofl enlirely

clufed, rxcerl Iha¡ near Ih.: l:otlom IWO (m,1I femi·eir·

rular hales are lef:. In caeh of its fides likewife two

fuch hales are made, aod the other end is 1& quite open.

T he mulRe is intended lO hear and commllnicale the

6ereefl heal; and Iherefore it muft be made Ihin, and of

ao eanh thal will refift the violenco of fire, fueh as that

of which crucibles are made. Thomullle being Ihus coo·

lIruaed, and Ihen well bak..l, is lil for ufe

Wheo il is la be ured. il mufl be pm iota Ihe furnace

by thc upper openinJ, and ret upon IIVO iron bm, intro·

oueed through Ihe hob made for thal purpofe bclow lhe

door of Ihe fire.place. The mnl!le mull be placeo on

Ihefe bars in Ihe fire place, io fu ch a mJnner

tila!

its o·

ptn eod Ihall !land nexl lO aod oirealy .gainn Ihe door

of Ihe Jire·place, and m?y be joincd la it wilh IlIIe.

Then Ihe eupels are ranged ín it, and the furnaee is filled

up, la Ihe heighl of IIVO OT Ihree inches aboye the muf·

Be,

wilh fm.1I co.lls not bigger Ihan a IValnul, tO Iheend

.hal Ihey mal' lie clofe round Ihe mul!lc, and procure it

an equal heat on ewy fide o The chicf nfe of Ihe muf–

fie

is le preveol the eoals and ,lhes froOl f'llhng inlo the

cupeh, which IVould he very prejurlicial la Ihe operalions

earrying on in Ihem: ror Ibe Icad would not vitrify as it

ough., becaufe Ihe immediate contaa of Ihe coals would.

eontinually refiore ils phlogifion; or e1fe Ihe glIJ, of lead,

which ought '0 penetrate and pafs Ihrongh Ihe ellpels,

would be renderco incapable of fa doing; becaufe Ihe

alhes mixing IhereIVilh IVould give it fueh

cooliftence

and lenacily " would de!!roy thal property, or al leal!

eonfiderahly lerrón il. The openings, I[¡erefore, which

are left in the lowtr pan of Ihe muIRe, OlOuld oo. be fa

Iligh as tO admit coals or alhes '0 gel inlo the cupels ;

Ihe ufe of them is

procure an eafier p.trrdge for the

dod the air tO

Ih~fc

velreh. The mulRe is Icft quite.

lIS

opco in ils fore-part, that the operator may be al liberty

examin~

what parres in Ihe cupels, to fijr their con'

lel1lS, to remove themfromone place la anolher, 10 coo–

vey new maners inlo them,

&c.

and alfo to promote the

frce aceefs of the air, whieh mufl concur wilh the 6re

lo..arus Ihe evaporadon necerrary to Ihe vitrification of

Ic:td; which air, if frtlh were nOI of,eo enough admit–

~eu,

",ould he incapableof produeing that c/Teé!; becaule

IVo.ld

foon be loaded IVilh fuch a quaDtily of vapou"

thJ( il eould 001 take up· any more .

T ile governmcnt of Ihe 6re in Ihis furnace is founded

on Ihe general principies .bove laid dOIVn for all furnaces.

Yet

as Ihere are fOllle linle dilfereoccs, and as it is very

trrential to Ihe fueeef, of the operadons for which Ihis

furn ace is intended,

I~lat

Ihe arrin Ihould he abfolulely

maner of his degree of heal, we {hall iA fewwords /heW'

halO Ihat mal' be raif.d or 10lVel ed.

When Ihe (urnace is fiIIed wilh coals and kindled, ir

the door of Ihe alh·hole be fet \Vide open, and lha¡ of the

lire

pl~ce

/hUI very clofe, Ihe force of Ihe 6re is inerea–

fed; and if, morcover, the pyramidal cove, be put on Ihe

tOp, and Ihe conieal funnel added la il, Ihe fire will be–

come fliJl more ficrce.

Seeing Ihe mallers ecntained in this furnace are en–

conlpafled \Vilh fi re on all fides, exeept in Ihe fore part

oppofite la the door of Ihe fire place, and as there are–

oecafions which require Ihat Ihe force of Ihe fire Olould

be applied la Ihis pa" al(o, ao iron box, of the /hape

and fize of Ihe door, halh been contrived tO aofwer that

purpofe. T his box is filled wirh lighled coals. and ap–

plied imOlediately to the door.place, by which means the

beal there is confiderablyaugmented. This help mal' he

ruade ufe of al Iht heginning of the opemion, in arder to

accelerate it, and briog Ihe heat fooner to thedefired de–

gree; or in ca(t a very fi"rce hl'at be required; or at

lime whcn Ihe air

hein.~

hOI aod moill will not make Ihe

fire buro wilh Ihe nccdf. ry ,'igour.

The heat mal' he I. rrcned,

removiog Ihe iron box,

ano Iholling Ihe door of

Ih~

fire.place quile clofe. It

may be Ilill funh':r aod gradually diminilheJ, hytaking .

off Ihe conical fuonel f,om Ihe IOp; byOluniog Ihe doo.

cf Ihe fire· ?laee wilh one of ils plates only, Ihal which

has t:1e lealt. or ¡hat

hi, h hds Ihe grcattfl 'puture io

il ; by laking off Ihe pyramidal cO"er; by Oluuing the

a/h·hole door wholly or in par!; and lanly, hy fwiog

Ihe door of Ihe fire.plaee wiJe open : hUI, io this lall

cafe, Ihe eold air penmates in:o Ihe eavily of Ihe mullle,

and refriger'lcs die eupel, more Ihan is almoll ever ne–

celrary. If it be oblmed, during the operalion, that

Ihe mllllle grows cold in any particular part, it is a fign

Ihere is a vacuity lefl by Ihe eoals in tha! place: in this

cafe aniron IVi,e mol! he Ihrufl into Ihe furn aee, Ihrough

the hale whieh is over the door of Ihe fire.place, and Ihe

eoals nirrtJ dlerewilh, fo as 10 make them fall into Iheir'

pldees and fill up Ihe

va~ant

inlerlliees.

is plOp" 10 ohferve, Ihal, befides what has heeo

fdid conmning Ihe ways of inereafing Ihe aaivity of the

fire in the tupelling fmlMce, fevenl other caufes alfo mal'

Coneur 10 procure to Ihe mallers eontained in Ihe mullle

a greater degree of hw: for example, tho fmaller the

ruulRe is,

lbe

IVider

amI.

DUlCe numeroU$ !be hob in it

are