REVERBERATORY,  OR  AIR  FURNACE.
327
The  floor  of  this  oven  is  made  considerably  hollow  in  the  middle,
and  the  matters  to  be  treated  are  laid  there.  Opposite  to  the  entry
into  this  oven  from  the  fire-place,  is  another  opening  into  the  chimney
or  vent.  The  effect  of  this  construction  is  plain.  The  tall  vent  occasions ¬
  a  current  of  air  through  the  whole  furnace,  from  the  aſh-pit
door  to  the  top  of  the  chimney.  This  blows  up  the  fire,  and  this,  by
heating  the  air,  increases  the  current,  and  the  fire  soon  becomes  furious. ¬
  A  volume  of  flame  rises  from  the  raw  fuel  ;  this  is  hurried  into
the  lateral  passage  mixed  with  air;  and  the  form  of  that  passage  causes
the  stream  of  flame  to  dart  violently  down  on  the  materials  lying  in
the  bed  of  the  laboratory  (so  is  the  oven  generally  named).  The  low
roof  of  this  place,  and  some  inequalities  artfully  made  in  it  on  purpose,
confine  the  stream  of  flame  to  the  subject,  and,  by  tossing  it  into  violent ¬
  eddies  on  its  furface,  mixes  the  air  most  intimately  with  every
part  of  the  flame,  and  thus  completely  consumes  the  whole  combustible ¬
  matter  of  the  fuel,  so  that,  in  a  good  reverberatory,  not  a  particle
of  flame  gets  as  far  as  the  bottom  of  the  vent.  In  the  Journal  de
Pbyfique,  1776,  there  is  a  description  of  a  Reverberatory  Furnace,
which  seems  very  ingeniously  fitted  for  a  general  experimental  furnace. ¬

Thus  a  moſt  intense  heat  is  produced  on  the  matter  lying  in  the
bed  of  the  reverberatory.  There  are  openings  made  in  the  side  of  it,
juſt  where  the  matter  lies..  Here  the  workmen,  from  time  to  time,
open  the  door,  and  put  in  their  tongs  and  rakes,  and  other  instruments, ¬
  to  stir  and  manage  the  stuff  according  to  their  views.  Frequently, ¬
  too,  the  nozzle  of  a  pair  of  bellows  is  directed  on  the  surface
of  the  stuff,  to  burn  it  still  more  completely,  and,  blow  the  liquid  slag
and  the  dross  from  off  its  furface  to  the  other  side,  where  a  way  is
made  for  its  getting  out.
Another  furnace,  in  which  the  flame  of  fuel  is  employed,  is  the
GLASS  FURNACE.  The  specialities  of  this  depend  on  this  circumstance,
that  it  is  necessary  for  the  workmen  to  have  free  access  to  the  matter,