78 SS. S. Haldeman on the Construction of Blast-furnaces 
Pe b pata represent a transverse section of the stack, if the 
left hal re symmetrical with the right. In this case the temp 
ma de open space in front of it, would be filled with stone 
es of the hearth, and e would repres sent the place, of 
for th 
e iron. 
~ The bosh BB, fig. 2, (shaded _vertically,) resembles a large 
funnel, except that its termination at H, fig. 1, 2, is squ 
built of fire bricks, except its inWer portion in front, Cini. ah 
consequence of the open temp arch (m), a large stone (7) called 
sconsh’n, is laid across the front portion of the hearth. ‘The 
a of the bosh is seen to be at a higher angle than when 
charcoal is used; but it may vary considerably without affecting 
the result. When in blast a few mouths, the bosh increases in 
steepness from the abrasion of its surface, and the hearth partakes 
of this enlargement; so that instead of ‘being a parallelogram, it 
assames an oval form. The enlargement of the hearth continues 
until its walls become so thin, that the radiation of the heat will 
prevent the inner portion from melting away any further; and in 
case the temperature diminishes, the inside will be protected by 
a coating of slag. ave known a furnace to be in successful 
action, when the hearth had been so much enlarged as to have 
the middle portion of the inmost back sow (s, fig. 2) melted 
away, permitting the blast to escape until the aperture was closed 
with tenacious clay. In this case the under surface of the sow 
was in contact with a brick wall usually built beneath, as an ad- 
ditional barrier to the escape of the heat. 
Towards the head of the furnace, there are diiee, equidistant 
apertures ( f, fig. 2) to admit the waste flame, first under the boil- 
ers, then through a return flue in them-into the hot oven, which 
is ia phd 1 in part upon the top of the stack posteriorly and later- 
ally. When a separate ale is Peg be: the oven is placed 
pom the front side of ee the flame passes into it by a 
aperture 
Pie boilers are: in thie lee three in “number, twenty-six feet 
long; forty-five inches in diameter, with a return flue eighteen 
nches in diameter. They are represented at w 2, in fig. 3, where 
pn course of the flame is a 
outlet of the flues in the stack, an 
pape upon the top, atd the chins vor around ates seiritpl- 
-The engine is placed upon the ground on this side, the 
