1000000030

Thirdly.

a'nd' I~OIy,

it is a trtllh demonnrated in hy.

draulics, tlw thevelocity of a gil'enquantity of any flutd,

dmrmined to 80w in auy dtreétion whatefer, is fo much

Ihe greater, the narrolVer the

ch~nnel

is to which that

fluid is confin:J; ami conCequendy that the velocity

a Huid will be

incre~Ced

by making it run frolD a wider

through a nlrrow<r p,{fage.

TheCe

prin~iples

being enablinle.d, i: is eaCy tO apply

them to the con(lruétion of Curnaces. Firn, if

fire be

J.:indled in the

fire'pl~ce

furn~ce,

\Vhich is open on

al) fides, it burns omly as if it

WeJe

in the open airo

has ",ith Ihe Currounding air a free communication; fo

that freíb air is cootinually adrr.itted

facilitJte the en–

lire combu(lion of Ihe

inft~mmablc

maners elllployed as

fuel. But there being nothing to determine that air to

paCs witb rapidily through the fire in this caCe, it does

nÓl al all auglllenl Ihe aétivilY thereof, but Culfers it 10

walle away

~uieuy.

Secondly,

the alh·hole or .dome of a furnace in

",hich a fire is burning be íbut quite clore. then there is

longer a!ly free communication between the air and

the fi re: if the anl·hole be íbut, the air is debarred from

h4\'iog free acceCs 10 the fire; if the dome be (lopt, the

tgtefs

the air rarefied by the fire is preveoled; and

cUIlCequeotly the fi re mu(l in either caCe burn veryCaintly

and Oowly, gradually die away, and al la!1 go quite OUI.

Thirdly, lf all Ihe openings

the furnace be wholly

cMed. it is evideot tbat the fire will be very quickly ex–

linguilhed.

Founhly,

onlyIhe laleral openings

Ihe

fire-pl~ce

be: fuUI, leaving the aíb-hole and upper part

Ihe fur–

Dlce open; il is plaio Ihat Ihe air eotering by the aíb·

hole ,viII oece{farily be determioed tOgo out at 10p, and

Ih>! conrequeotly a current of air \ViII be formed, which

will paes through tbe 6re, aod make it buro briOtly aod

vigoroufly.

.Fifully,

both the aíb·hole and the upper (lory of the

furnace be of Come leoglh, and form canals either cylio·

dric ur prirmatic, theo the air beiog kept io the fame di·

reétino through a longer Cpace, the courre of in /lream

will be both flronger and beuer delerrnined, aod conCe–

queotly rbe

6r~

will be more animated by il.

Sixthly, and lanIy, if the aíb bole aod the upper part

of the furnace.

in(le~d

of being cylindric or prifmaric

car,als,

h~ve

the form of truncmd cones or pyramids,

lbnding on their bafes, and fo ordered thal rhe upper

opening oí rhe aíb·bole adjoining to the 6re·place may

be wider than the baCe of the Cuperior cone or pyramid;

then !he (lream of air, being forced 10 paC, incell'antly

from a larger channel through a fmaller, mufl be con·

fiderably accelermd, and procure to the fire the greal–

e(l aétivity whicb it cao receive (rolD tbe make o( a furo

nace.

The mate,ials finen for 'buildiog furnam are,

nric~I,

joined together witb poners clay lOixed with

fand, and moi/lened with water.

Ponen clay mingled

with ror'herds. moinened wirhwater, and baked iD a vi–

oleot fire_ 3. lron; of which all furnaces may be

made ; with this precautioo, thar the iofide be provided

witb a great mioy promincot poiol!, as fa(\enings for a

.coal of eanh,

itb which tbe

umIDaI

paru of !he furoate

mu(l necell'¿rily be comed 10 defeod il from Ihe

a~ioo

the fire.

The re"erberating furnace is one

Ibofe Ihal are

moll employed io cltemi(lry : it is proper for di(lillatiool

by rhe retort, aod íbould be coo(lruéted in the follolVin,

manner.

Firll, The ufe o( Ihe anl-hole .being. as. was raid, 10

give

p~ll'~ge

ro the air, and 10 receive the aíbes, no bad

confequence can attend il! beiog made pretty high:

may have from twelve 10tweoty or twemy.four ioches iD

heighth, lts apenure íbould be wide enough 10 admil

billets of wood when a grear fi re is 10 be made.

Secondly, Tite aíb·hole mu(l be lerminated at il! up.

per

p~n

by an iron grate, the bars of wbich íboold be

very Cubllantial, that they may refi(l Ihe aétioo of the

fire: this grate is the bOllom of Ihe 6re.place, and de·

tlined to fuppon the coals. In Ihe lateral pan of the

fire-plm, and oearly about the fame height with the

grm , there Ihould be

hole of fuch a fize

th~t

it m:,y

eafi ly admit charcoal, as well

little longs and Ihovell

for man.ging the 6re. This aperture or mouth of the

fire.place íbould be perpendicularly over the mouth of Ihe

anl·hole.

Thirdly, flom fix to eight or len inches high above

the grm, over the afu·hole. linle apenures mull b.

IlUde in the

w~lIs

of the fumace. of eight or teo lines in

diameter, an inch froOl o'oe another,

a~d

thoCe in one

fide mu/l

diametrically oppofite to thofe io the other.

The ufe of thefe holes is tOreceive bars of iron for the

relon 10 re!\ on; which íbould be, as was

f~id,

al cliff.,.

reot heights, in order 10 ,ccommodate rerOrtl of dif- _

ferent fizes. At the upper exuemity of this part 01 the

fumace, which reaches from the iron bars to the IOP,

the heighth whereof fllould be Comewhat lefs rhan Ihe

width of the furnace, mu/l be CUt a Cemi-circular apero

ture for the neck o( the reton to come through. This

hole mu(l by no means be over the doors of the fire–

place aod alh·hole; for then. as it gll'es pa{fage to Ihe

neck of the retOrl, it mun of courfe be oppoGte 10 the

receiver, aod in that cafe Ihe recelver itrelf would (land

over

ag~inll

thoCe IWO apertures; which would be al–

tended with this double inconvenience, that Ihe receiver

would not ooly grow.veryhot, but greatly embarrafs the

operator, whofe free accers tO the fi re.place aod alb·hole

would be thereby ob!\ruéted.

is prorer dlerc(ore,

Ihal the Cemi·circular cut we m fpeakiog of be fo placed,

lhat, wheo the greatefl ballons are :uled tO the mon,

l!tey IDay leate ao open palfage 10 Ihe 6re-place or

afh–

bole.

FounhlYr in order com in the laboratory of Ihe re–

. erberating fumace, tbere mu!\ be a roo( made (or it iD

Ihe (orm of a cupola, or concave hemiCphere, having the

fame diameter as the (urnace. This dome íbould have

a Cemi-circular CUt io its rim aofwering 10 that ahove:

direlled to be made in the upper extremity of- the fur–

nace, fo that, whcn adjuned tO each otber, Ihe IWO t9-

gether may form a circular hole for Ihe neck of Ihe

Je-

10r! to pafs lhrough. Al the 10p of this dome Ihere

mu!\ alfo be a circular hole of rhree or four inches dia–

meler, carrying a!horl tapering funoel of the fame dla–

meter,

and

tbue incbes higb, wbich wiJl fme for a

chimoey