3 1

Chap. 3. Furnaces. ^ ^

In furnaces whofe chimney is fixed, fiic depends

procured on another principle. As t !^liv elv palling through andwholly upon the quantity of an ' * . mo ft vehement

animating the burning fuel, it is_ " by mo reor lefs clofmg

lire mav be fuppreffedor rcftraineci a - p _< ' t j 0 r the chim-either the afh-pit door by which the air is . >■ ^ m0 rc or lefs

ney by which it paffes eff", and that t .c ^ ^ moveable

raifed a^ain, by more or lefs opening t10 1 chimney, af-

plate, or r'eg I st**, in any convenient p r of the c y ^

fords commodious means of varying the width ot P bconfequently of regulating the heat.

r= , L„r tViefe wind furnaces •, one,

There are two general Kinds ot tne t ^ e f ur nace;

with the chimney on the top, over r ,/ ^'Ahe mouth clear,the other with the chimney on one hde, ■* • contrn &ed to

In the firft, either the uppet pa» of the '«, f „ ^

fuch an aperture, that the chimney may > 1 - n , T ■, like aperturewith an arched dome, or with a flat plate « ^ P infnle

in the middle. As in this ditpofuion of the chimney,^ _ n

of the furnace cannot be come at from » . , j n fp e £ling

the fide, a little above the grate, for fupplymg tuel > *the matter in the fire, 8cc. _ , rruc ible, or melt-

For performing fusions in this furnac , with a flip

ing veffel, is placed immediately among an d the grate, toof brick, or fome other like fupport, betwe ftriking on its

keep the cold air, which enters underneath, frombottom. , • for aiftillatiort

When defigned as a reverbekai oti , 1 • g are placed

in long necks or coated giafs retorts, w u f e nec t comesacrofs, above the fire, for fupporting ^ V^ e , This aperture

out at an aperture made for that purpoie 11. t y door

fiiould be made in the fide oppolite to ^ at in _ the receiver,above-mentioned, or at lead fo remote ro,m 1 , f urnaC e, mayfitted on the neck of the diftilling veil el wi 1 ^ f ire or

not lie in the operator's way when he wants to uir

throw in frefh fuel. ,„: ra tes bv an aperture

r lhe other kind of wind furnace comm ■ in'nioe of its own,in its back part near the top, either with an U P"» 1 ^ fe b11 ot i ie ror with the chimney of the room ; m w nc 1 ' re mou th ofpaflages into the chimney muft be doled up- nna ilv covered

the furnace ferves for a door, which may -e 0 mn (V commonlywith a plate or tile. Of this kind is the furnace\)fed for fufion in a crucible.

Tins laft conftruaion, by leaving the or evapo-

clear, affords the conveniency of letting irK Vll - hartfhom- '-it 1rating pan, a copper ftill, an iron pot for dv ,1 • » * - rQ;l