62 
furnace. For instance, if a chimney of one foot high produce an 
“"y~"" effect of 1, it will require the height to be 4 feet to pro- 
duce twice, and one of 9 feet to produce three times 
the effect, and so on, increasing in the same ratio. 
In reverberating furnaces, which are heated by the 
flame of pit coal, the maximum is much higher than in 
the melting furnace, which is heated with coak. This 
arises from the flame in the former heating the interior 
of the chimney. The melting furnace should have its 
‘chimney not Jess than 30 feet. The reverberatory fur- 
nace may with good effect be made much higher. 
The chimney of a furnace should be perfectly dis- 
tinct from every other, nor can it have any opening in 
its side without sustaining an injury proportionate to its 
size; but its effect will be less, as its height above 
the fire is greater. 
Sound philosophy and experience will ever discard 
the practice of attempting to make one furnace perform 
two operations at the same time. 
Having given some account of the principles of fur- 
naces, we shall now describe ‘several at present used in 
the arts, and in the laboratory.. ‘Plate CCLXII. Fig. 
1, is a section and side elevation of a melting furnace. 
B is the body of the furnace, containing a crucible upon 
its stand, The use of the stand is to raise the crucible 
above the grate g, so as to allow its bottom to receive 
the greatest heat of the fire. A is the ash-pit opening 
through the outer wall, or into a cellar below. This 
serves to prevent the cold air from annoying the opera- 
tor. D is the damper, which when shut covers the 
under side of the grate. K is the cover, which is either 
formed by putting two fire bricks in an iron ring, or 
by moulding’ fire clay into proper form, ‘and burning 
it afterwards. C is the chimney. ° Fig. 2. is a plan of 
the same furnace. 
Figures.3, and 4, are a section and plan of a furnace 
for heating a sand-bath. A is the ash-pit, B the bed 
of the furnace, d the door for fuel, g the grate, W a wall, 
or one large fire-brick placed between the grate and 
the chimney, leaving no way for the smoke to pass but 
through the neck 2. It then descends on the other 
side, and passes through the flue F into the chimney C. 
p.is a plate of cast metal, formed of two plates ribbeting 
into each other, by which it is less liable to break by 
the heat than if the plate was in one. This plate covers 
the whole ef the top of the furnace, so as not to allow 
the escape of smoke. II is a frame of cast-iron lying 
loosely upon the plate, with as little touching surface 
as possible. Within this frame a wrought iron rim S 
is placed, for the purpose of enveloping the sand which 
constitutes the sand-bath. There are rims of different 
depths, according to the size of the vessels to be placed 
in the sand. 
Figs. 5, 6, and 7, ave two sections and a plan ofa re- 
verberatory furnace. A isthe ash-pit, B the fire place, 
‘g the grate; F, in the plan Fig. 7, isthe opening for 
the introduction of fuel, which is pit-coal. The flame 
plays along the hearth H, and passes into the chimney 
C. O is an opening for the introduction of the sub- 
stances to be entered or melted, which are placed upon 
the hearth. If the substance is to. be melted, it runs 
down to the opening T, where it is taken out. D.is 
the damper for regulating the fire. This furnace is 
amore particularly adapted for melting than for calci- 
ning, on account of its inclining hearth, and the open- 
ing at T. The construction is a little varied for the 
latter purpose. The hearth is nearly horizontal, and there 
is generally but one opening, which is in the middle. 
Pigs. 8 and 9, are two sections of an enamelling fur- 
Melting 
furnace. 
Puats 
GOLXIEL 
Figs. 1, 2. 
Furnace 
for heating 
a sand- 
bath. 
Figs. 3. 4, 
Reverbera- 
tory fur- 
nace, 
PLATE 
CCLXIL. 
Figs. 5, 6, 
y 
FURNACE. 
nace. A is the ash-pit, g the grate, B the body-furnace,. 
where the fuel is contained ; M is the muffle, an earthen t 
vessel, more plainly seen in Plate CXLIII. Fig. 9. -It ‘= 
contains the substances to be operated upon, and is for ‘ 
the purpose of defending them from smoke or flame, and Enamel 
admitting a supply of fresh air; K is the cover, T the tpg 
throat, and C the chimney. This furnace is also em- oc.x7 
ployed for assaying metals by cupellation. » oe) Figs. 8, 
Figs. 10, 11, and 12, contain a view and section of a yuiie 
muffle furnace, for producing very intense heats. The nace. 
body of the furnace, shewn at AA, is in the form Figs. 10 
of an oblong coffer, swelling out in the middle. The 1); 1% 
grate is shewn at C, standing over the ash-pit F. The 
hole for the muffle is seen at E ; and the. 2, or Up- 
er part of the furnace, is seen’ at BB, mee Be: 
i door D, for the teal 3 of. introducing fuel. 
This furnace was employed by Pott, and afterwards by 
D’Arcet, in their experiments on the habitudes of earths 
and stones, when ex to a violent and long con- 
tinued heat. Figs. 13, 14, 15, 16. represent fire-tongs 
for various purposes, 
A description of Dr Black’s portable wirid furnace 
will be found in our article on Cuemistry, vol. vi. 
p- 189, and a perspective view and section of it in Plate 
CXLII. Fig. 7. ands. 
A description of Mr Arthur Aikin’s portable blast 
furnace is given in the article CurmistRy, p. 160, and 
a perspective view and section of it.in Plate CXLIE.. 
Figs.10,11, 12, and 13. 
Farther information on this subject will be found in 
our articles GrAss-makine, Inon, Srove, and in several 
other articles where furnaces are>adapted to particular 
purposes in the arts. See also Lewis’ Philosophical 
Commerce of Arts; Aikin’s Dictionary of Chemisiry, 
vol. ii.; Miche on Reverberatory Furnaces, in Rozier’s 
Journal, vol. xxxii. p. 385. | Perceval’s Chamber Lam 
Furnace, in the 2epertory of Aris, vol. iii, p. 29 ; pi 
in the Transactions of the Royal Irish Academy, vol. iv. 
p. 91; Watt’s Patent Furnaces, in’ the Repertory of 
Arts, vol. iv. p. 226; Mr Edward Howard’s Improyed 
Air Furnace is describéd, in Tilloch’s Philosophical 
Magazine, vol. v. Pp 190—193, and represented. in 
plate iv. of that work ; Raley’s Patent Furnaces, in the 
Repertory of Aris, vol. x. p. 155 ; Accum’s Improved 
Universal Furnace of Dr Black, is described in his Sys- 
tem of Practical, Chemistry, vol. ii. p. 357, and in 
Nicholson’s Journal; 8vo. vol. vi. p. 273; Curaudau’s 
New Evaporating Furnace is described in the Annales. 
de Chimie, No. 149. An. xii. and in Nicholson’s Jour- 
nal, 8vo. vol. ix. p. 204—207; and Lucas’s.furnace for 
cast-iron cutlery, in Patke’s Chemical Essays, vol. iv. 
Ess. 15. A furnace for decomposing the sulphate of bary- . 
tes, is described in the same work, vol. ii. Ess. 5. (c..s.) - 
FURNEAUX’s Istanps. The great continent of New 
Holland is separated from.Van Diemen’s Land on the 
south, which was during centuries believed to be an inte-. 
gral part of it, by a considerable expanse of water lately 
discovered, called Bass Strait; and numerous islands, 
some towards the centre of the strait, and some on the ree 
spective coasts are interposed between the two territories. _ 
These have been classed. into groups-by successive na- 
vigators, though with little regard to order, and with- 
out any decided analogies, One of the principal and» 
most comprehensive is Furneaux’s Islands, divided by 
Bank’s Strait 12.or 15 miles in width from the north- 
east extremity of Van Diemen’s Land, stretching from. 
about 40° 22" to 41° 27’ of South Latitude, and situated, 
with respect. to the centre of the group, ‘in about 148° 
of East Longitude, , 
far 
