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chimn~y to emy olr ~II fulinillofilics, and ~eecler~te rhe
tllmnl of lhe Jir. This patr..ge n).ly be !hut at pleafure
Wilh a Oal toVer. 1Ilor~over, as it is n~eetl'ary that the
dome OlUulJ be takcn 011' anJ pm on IVilh cafe, it OlUuld
bave til'O eatl or handb for that purpofe: 'a ponalÍve
or move.~I~ furnace tholllJ alfo have a pair of handlcs
lixed oppo{jte toeath oth~r bctwecn the . Ih·hole and the
're pLec.
Sixthlpnd la(lly, a eonical canll mllfl he provided of
about three foot lung, aad fufficiently wide al its IJwcr
eod to a!lmit the funnel of the aperture at the top of the
dome. This conical tube is to be applied to the dome
whcn the fire is require,j to be extremely aaive : it ta·
pm gradually froOl its bafe up\vards, and breaks off as
if truncateJ at top, where it !hould be about two ioches
wide.
l:l~fides the apertures already mentioned as necetl'ary
lo a rel'crberating furo,ce, there mufl alfo be many o·
ther fmaller hales made io iu a!h·hole, fire'place, labo.
ratory, and dJmc, whicli mufl all be fa contrivcd as tO
be e.fily opcned and Ihut with f!opples of emh: thefe
holcs are the regiflm of lhc furnace, and ferve to regu·
late the ,aivily of the 6fe accordiog tO the principies
befare laiddown
Wheo the aaion of the fire is required to be exa'aly
uniformand very briOc, it is necetrary 10 flap carefully
with moifl earth all the little chinks in the junélure of the
dome \Vith the furoace, betweeo lhe oeck of thc retar!
and the circular hale through which it patres, and \Vhich
it never filIs exaal~, and laOly the hales which receive
the iron ban that fuflain the retort.
1t is proFer tO have in a laboratory feveral reverbera.
ling furnaces of diferent magnit~des; becaufe th¿y mu!!
be proportioned to the fize of the retom employed. The
reton oughl 10 611 the furnace, fo as tO lcave only
Ihe diflance of an ineh belweeo il aod the iofide of Ihe
{urnace.
Yel ",heo Ihe relor! is 10 be expofed 10 • Ola!! violenl
fue, and efpecially when it is required thal the heal .!hall
.a with equal force 00 alI paru of the furnace, and as
i1rongly on its vault as 00 iu bottom, a gre"er diflance
muObe lefl between the retar! and the infide of Ihe
{urnace.: for theo Ihe furoace may be 6lIed with coals,
even to the upper par! of the dome. If moreover fome
piem of wood be put into the ath·hole, Ihe cooical ca·
Dal fi tted 00 to Ihe fuooel of the dome, aod all the a·
pertures of Ihe furoace exaaly clofed, excepl Ihe ath·
hale a~d the chimney, the greatefl heat will Ihen be
exciled that this fumace cao produce.
The furnace oow defcribed may alfo be employed in
many olher chemical operation,. lf the dome be laid a·
fide, an alembic may very well be placed .herein: bUI
.hen the fpace, which will be Ifft betweeo the body of
Ihe . Iemhic and the top of the upper part of the furoace,
muf! be carefully filled up wilh Windfor·loam moiOened ;
for without that precaution the heat would fooo reach
Ihe wy he.d, which ought to be kept ., cool as poflible,
in order tO promote the coodenfatioo of the vapOUT!.
On tbi. octafion therefore il will be proper to leave no
hale. open in the 6re.place, bUI the lateral ones; oC
NC No. 34. ;
s T R y, J (3
wh ich alfo Ihofe over again!! Ihe receiYCf mufl be flop.
pedo
A pot or broad·brimmed earlhen pan may be placed
over this furnace, aod bciog fa fitted 10 il as to clofe th.
upper part thereof accuratcly, aod filled with {and, may
ferve fur a fand·heat to di(lill with.
The bars dcfigoed to fupport difliJling vetrcls being tao
ken OUt, a crucible may !!and therein, and many opera.
tiotts be performed that do not requi~e Ihe utmo!! violeoce
of breo lo a word, this furnace is ooeof the mun como
modious that can be, aod more exteofively ufeful tban
aoy other.
The meltiog furnace is defigoed for applyine the greateil
force of heat to Ihe moil fi xed bodies, fuch as nletals
and emhs. It is oever emplo)'ed io di!!illing: it is of
no ufe but for cal¿ination and fufionj anu confequeouy
oeed not admil aoy vell't1s but crucibles.
The alb·hole of this furnace dif ers (rom that of the
remberating furoace ooly io Ihis, that it OlU!! be high.
er, in arder to raife !he 6re.place tO a level with the
artifl's haod; becaufe io thal all the operations of this
furnace are performed. The ath·bole therefore mufl be
about three foot high : and thi, height procures it more·
over lhe advantage of a good draught of air. For the
fame rearon, and in coofequeoce of the priociples we
laid down, it thould be fo built that ill w(dlh letreniog
iofenfibly from the bOltom tO the tOP, it may he oar·
rower where it opeos ioto tbe 6re·place tbao ¡ny where
below.
The ath·hole is terminated al iu upper eod, like that
of the reverberating furnace, by a grate which ferves fo¡
tbe botwtU of the fire·place, and ought to be very fub·
llantial that il may rcfifl the violeoce of the fire. The
inCIde of this furoace j, commooly ao elliptic curve;
becaufe il is demonflrated by m.thematiciaos, that furo
faces having that curvature reflea the rays of tite fuo, or
of 6re, io fuch a maooer, Ihal, meetiog iDa point or a
line, they produce there a violeot heat . Burto anfwer
this purpofe, Ihofe furfaces mu(l be finely ; ao
advantage hatdly procure.ble to the interoal furface of
this furoace, ••hieh can be made of oothiog but eQrth :
befides, if it were poflible to give it a polith, the ,'iolcor
aaion of the 6re thal mu!! be employed io thi, furoace
would prefently dellroyit, Yet theellipticál figure mufr
not be eotirelydifregarJed : for, if care be takeo to keep
the iOtCrnal furface of the furoace as fmooth'as poffible,
it will cert.,ioly reflea the heat pretty flroogly, aod col·
lel! il about the center.
The 6re'plaee of Ihis furoaee ought to have but fotll
apenures.
Fir!!, that of the lower grate, which tommuoicm,
with tbe alb·hole.
Secoodly, a door io iu fore.fide, through whirh m~y
be introduced coals, crucibles, and tongs for maoaging
them: tltis aperture !hould be made to Ibut exaa ly wit~
a plate of iron, having its iofide coated with omh, aod
turning 00 two hioges fixed tOthe furnace.
Thirdly, over this door a hole Oantiog downwards too
wards the place wherethecrucibleis tO nand. Theufe of
this hole js to give the operator ao opportunity 01' ell'
t 2 F amioinll