Blast  Furnace  and  its  Accessories.
An  English  blast  furnace  of  the  old  type  (Fig.  42)  was  a
very  massive  structure  of  stonework  or  brickwork,  usually
circular  in  form  in  the  interior,
which  consisted  of  a  shaft
approaching  in  sectional  eleva-
tion to  that  of  two  truncated
cones  joined  at  their  bases  ;  the
upper  and  more  acute  one  being
termed  the  "  body,"  which  was
surmounted  by  a  chimney  con-
taining one  or  more  openings  for
the  purpose  of  charging ;  the
lower  cone  forming  the  "boshes."
This  lower  cone  was  sometimes  _
continued  to  the  ground  level,
but  more  often  the  furnace  was
enlarged,  forming  the  "hearth,"

in  which  the  molten  iron  collected,  three  sides  being  con-
tinued to  the  bottom,  and  the  other  left  open  for  means  of
access.  The  hearth  was  supported  on  a  mass  of  masonry,
with  channels  for  the  escape  of  moisture.  The  foundations
were  traversed  by  arched  galleries  in  order  to  keep  the  whole
building  dry.  One  of  the  objects  in  the  construction  was
to  keep  the  heat  as  much  as  possible  in  that  part  where  it
was  required,  and  to  diminish  loss  of  heat  by  radiation.
The  interior  was  lined  with  firebrick,  and  the  outer  part


Fig.  42.
142


PRINCIPLES  OF  METALLURGY.
was  built  of  rough  sandstone  or  ordinary  brickwork,  the  two
layers  being  separated  by  a  space  filled  with  sand  or  slag.
The  dimensions  varied  in  England  from  9  to  20  feet  in
diameter,  and  30  to  45  feet  in  height.
