236 Iron, 
w th little loss. The height of this may be seen in the 
vertical section, fig. 2. G. 
HH, the charging doors, by which the metal is intro- 
d acid in the shape and state of pig-iron, lumps, scraps, \ 
Sic. &c e The iron generally occupies the furnace across 
to I, called the back wall, and is never meant to approach 
the bridge nearer than the dotted line, lest the metal in melt- 
ing should run back into the grates, in place of descending 
into the general reservoir or cavity below. The comers or 
notches, /z, A, A, A, receive a stout cast-iron frame lined with 
flre-bricks. This is hung by means of a chain and pul- 
ley, and can be raised and depressed at pleasure. This 
frame is, properly speaking, the charging- door, and is al- 
ways carefully made air-tight by means of moistened 
sand. 
KK, the flues or openings by which the flame enters 
the chimney. These are 15 inches by 10. On main-i 
taining these openings of a proportionate size to the other 
parts depend in a great measure the powers and oeconomy 
of the furnace. 
LL, lading doors, by which ladles are introduced, ini 
the case of small furnaces, to lift out the metal and distrii 
bute it to the various moulds. 
M M M M, binding bolts to limit within proper bounds 
;the expansion which takes place in the building when the 
furnace is highly heated. 
Fig. 2. vertical section of one of the furnaces, and its 
appropriate stalk or chimney. 
E, the grates. 
F, the teasing-hole. 
G, the bridge. 
H, the charging door. 
K, the flue or opening into the chimney, 
L, the lading door. 
MM, the binder or binding bolt. 
