134 TECHNOLOGY. 
other, which, however, permit the flame to pass through. 6, the openings 
from which the ore is withdrawn as it is roasted; g, inclined iron plates, 
over which the iron is withdrawn from the furnace. The ore to be roasted 
is supplied from above, at the top of the stack. fare openings in the ash- 
pit, to supply draught and for the withdrawal of ashes. 
fig. 8 a is a vertical and jig. 8b a horizontal section of a furnace for 
roasting iron ore; @ is the shaft, lined with fire-proof stone ; 6 is the grate. 
The roasted ore is withdrawn at the openings, ¢, into the spaces, e, and thence 
to the arched chambers, 7; d is the ash-pit. The operation in this furnace 
is continual, the material being constantly supplied at top, and withdrawn 
below as it is roasted. 
Pl. 27, figs. 9a and 96 are sections of an ellipsoidal furnace for roasting 
iron ore; 6’ are three fire doors ; below each grate is an ash-pit, d; ¢ are 
openings for withdrawing the ore. 
All stack furnaces used for the purpose of smelting metals, and which 
require a high heat, are furnished with a blowing apparatus ; they may be 
divided into blast furnaces and blue ovens. 
Fig. 10 a@ is a vertical section and jig. 106 a horizontal section of an iron 
blast furnace; a is the shaft; } the boshes; ¢ the crucible; cand p are the 
tuyeres, of which there may be one, two, or three; ¢ is the hearth-pit, where 
the melted iron collects; gis the dam-stone, which closes the hearth-pit, 
except at a single point, which is closed with clay, through which an. open- 
ing is made to let off the melted iron; / the timpstone, which is protected 
by the timp-plate, imbedded in fire-clay. The upper portion of the stack 
is seen at 10a, above jig. 7. his the fauld-plate, over which the cinder is 
run out; a is the working side, B the back, c and p the blast sides of the 
furnace. At jig. 20 are seen the tuyere chambers. Every part of the wall 
exposed to a strong heat is constructed of fire-proof stone. 
Pl. 28, jigs. 1a,16, are sections of a blast furnace, through the dam- 
stone and hearth, upon a large scale. The stones a rest upon a layer of sand, 
, and form the hearth ; beneath the sand is an iron plate, 0, and beneath 
the plate is the air passage, q ; the cheek stones, 6, the back stone, c, and 
the dam-stone, @, form the walls of the hearth-pit ; fis the timp-iron, g the 
timp-plate, ¢ the timp-stone ; A and ¢@ are the tuyere stones, £ & iron plates 
to support the wall above; // are the wall stones between the timp-stone 
and boshes, m the openings for the tuyeres. PU. 27, jig. 19, is an interior 
view of a blast furnace house in the department Aveyron. /%ig. 12 isa 
so-called blwe oven, which is worked with a closed breast, and has an open- 
ing below to let off the iron and cinders; @ is the shaft, 6 arched openings 
through which enter the blast tubes ; ¢ is an opening which, when the furnace 
is in operation, is walled up as high at the tap hole. When the furnace is 
started the breast is closed, with the exception of a hole at the bottom to 
let out the iron, and a hole six or eight inches above the first through which 
the cinder flows out; it is filled to the top with coal and iron, the supply of 
which is renewed as the charges sink. This furnace is kept in continuous 
blast for three, six, or nine months. 
Pl. 27, figs. 13 a, 13 6, and 13 ¢, represent a crucible furnace with closed 
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