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are ; Ihe nc~rer 10 il' honom, or f'''lher end. Ihe cnpcls
are pbcro, Ihe more will Ihe mattcrs Iher~in conlaioed
bc alrell~d wilh h~:tt .
Bcfides Ihe opcmions 10 b~ performetl by tI:c cupel,
Ihis fnrn¡ce is I'cry uCcf"I, ao,1 cl'en oecdr.lry, for n\.lny
themic~1 eXl'erim(·nts; fuch, for innance, as Ihofc re·
1, ling 10 fundry "ilrific.llions ~nd ellamclling. As il is
pr~ny 10IV, Ihe bdl IVay is lO place il, when il is 10 be
pfed, on a baCe of brick'IVork Ihal Olay raife il to a le"el
wilh Ihe0FeralOr's hand .
A rnacé is exmding nfeful for all opemions
thal require only a mooerale, bUI long conlinued degree
of hca!. The fnrn~ee for working wilh a lamp heat is
very fi mple: il confills only of a hollowe)'linder, froO!
fifleento ei~hleen inche~ high, and fil'e or fix in di,meter,
ha"ing at its bottoman aperlure large enough for a lamp
10 be i'olroduced and wilhdrawll wilh cafe. The lamp
mul! have Ihree or four wicks, 10 Ihe end Ihal by lighl'
ing more or f, wer of Ihem a greater or Icfs degree of
bc.\t may be produced. The body of Ihe furnace mufl
morearer have feveral fmall ho!es in il, in order 10 fup.
I'lyIhe Oame of Ihe I"mp ",ilhair enough 10 keepil alil'e.
On Ihe 10p of tI:is furn ace rbnc!s a bafon fi l'e or fix
Ulches derl', whieh onghl 10 filllhe cal'ily of Ihe crlin.
der exa~ly, an,\ 10 be fupported al irs circumference by
a rim which may enlire\y corer and clofe the furnage:
T he u!r of this baCon is to contain Ihe fand through
",hich the Jamp·hm is ufually conveyed.
BcC,des this, Ihere mufl beakind of cover or dome' made
oc. the fame malerial wilh Ihe furnace, and of Ihe fame
diamelcr with the filnd·b"h, withoUl any other opening
~han a hole, nearly circular, cut in its lower extrcmilY.
This dome is a fOrl of reverberalOry, whieh ferves 10
confine the heat and direll it lotvuds the bouy of the re·
.I,UII; for it is ufed only ",hen fomelhing is to be di
Hilled in a veOel of Ihis fathion; and Ihen Ihe hole al
iu bOllomfmes for a paO'age to Ihe nCék of Ihe retort.
1"his dome fhould have an ear or handle, (or the coove·
nieocy of putting il 00 and laking il oll' wi.h eafe.
o¡ Lu/u .
CHE MICAL , errel" efpecially fu ch as are made of
glafs, and the earlhen verrds commonly called flone·
ware, are very fubjell to break when expofed 10 fudden
hm or cold; whence it comes Ihat Ihey oflen crack when
Ihey begio 10 heat, and alfo wheo beiog vcry hOl they
happen10 be cooled, eilher by frefh coals Ihrown inlo
Ihe furnace, or by Ihe accefs o( cold airo Time is no
vlay to prevenl Ihe former of Ihefe aceioents, but by
taking Ihe pains 10 warm your Vtrrel veryOowly, and by
almofl infenfible degrees. The fecond may be avoided
hy cO~ling the body o( the verre! wilh a pafle or IUle,
which being dried will defend it againfl the attacks of
cold.
The finefl flufl' for coating vc!Tels is a compoC,lion of
• fat earlh, Windfor·loam, fine fand , filings of iron, or
powdercd gl,fs, and chopped COIV'S hair., mixed aod
m de into a pafle with IVattr. This lute ferves alfo 10
derend glafs verrds againfl the violence of Ihe fire, aod
10 prevent Iheir melting eafily
In almo(l all dill~lalioos it is of great confequeoce,
I s T R Y.
as ha:h been faid, that the of Ihe difl illing ven:.1
be ex.lIly joined with Ihat of Ihe recci ~er into whidl
il is introducen, in order topr.:v:nt 1!le vapours from el
fc_ping iOlo theair and fo being lofl : Alld tlris jundio~
is efl'c{leu by , of a IUle.
A f<w Oips of paper, applied round the neck of .Ihe
veOel< with common fize, will be fullicienl to keep in
fuch v:tpour! as are aqucous, or AOt very fpiriluous.
If Ihe I'apours are more acrid and more fpiriluous, re·
courfe may be liad 10 Oips 01 bladder long rleeped in wa–
t, r, which, containing a fon of nalurdl glue, clofe the
junllures of the verrels very well.
If il be required 10 confine vapou" of a fl ill more pe ·
oelraliog nature, il will be proper tO employ a lute that
quickly grows very hard; Pdrlicularly a parle made widl
quick.lime and any fOrl of jelly, whelher vegelable or
animal; f"ehas the white of anegg, HifF fize, 9'c. Thi~
is an exeeUent IUle, and not eafily penetrated. 11 is alf~
ufed 10 flop any cracks or frallures thal happen 10 glafs
ve!Tds. llllt it is nOI eapable of rcGfling the I'a pours of
mineral acid fpirils, efpecially wh( n they are (lrong,and
fmoking : For lhal purpofe il is neceff.,y 10 incorporale
Ihe olher ingrcdicnts Ihorougilly wilh fal earth foflened
",ilh W.ler ; and even Ihen il frequently happens Ihat
Ihis IUle is pcnetrated by acid ,'apouls, efpecially Ihofe
of Ihe fpi ril of fall, which of all olhers are con6neu
with Ihe gremfl difficulty.
In fuch eafes iu place may be filpplied with anolher,
which is c~lIed fat lute, becaufe it is aélually worked up
wi.h fal liquo!'s. This lute is compofed of a very finc
crmceous eanh, called lobacco·pipe tlay, mOlfleoed
wilh equal parts of the drying oil of lint·feed, and •
varnifh made of anlber and gum copal. It mufl have–
Ihe conJiaence of a lIifF pafle. When the joints of Ihe
verrels are clofed up \Vilh Ihis lute, they may, for great–
-er fecuril)', be covered over with J1ips of Iinen. fmeared
wilh thc lutemade of quick.lime and Ihe white of an
egg.
Chemical verrds are !iable to be broken in an opera·
lion by olher caufes bendes the fudden app:icalion of
heat or eold. lt frequently happens th/! the .apours oí
the matters, expofed 10 Ihe allion of fire, ruth OUI wilh
fuch impetuolilY, and are fo e1.aic, that finding no paf.
fage through the lute with which the joinls of Ihe veffel,
are clofed, Ihey burfl the v.errds Ihemfelves, fomelimes
with explofion and danger to the operalor.
To prevent Ihis inconvenience, il is ncce!Tary, that in
every receiver Ihere be afmall hole, which beine aopped
only wilh a linlelute mayeafilybe opened and fhuI again
as occafion requires. It ferves for a vent·hole 10 lel out
Ibe vapou", when the receiver begins to be toO much
crowded with Ihem Nothing but prallice can teach the
anifl when it is requifite to open Ihis vento If he hils
the prope; lime, the vapours commonly ruth out whh ta–
pidity, and a confiJerable hilliog noife; and Ihe vent
fllould be ftopped again as (oon as Ihe hilling begins tO–
grow faint. The IUle employed 10 flop this fmal! Iloie
ought always to be kepl fo dullile, Ihat by taking the6-
gure of Ihehole exallly it may enlirely flop it. Refides,
if il fhould harden upun Ihe glafs, it \Vould aick fo ,
,that il would bc very difficult to rcmove it without bre· I ••
in,