The  furnace  fronts  are  also  provided  with  ashpit
damper  and  pricker  bar-rod.  The  dampers  are  made
to  swing  on  the  pricker  bar-rod,  and  can  be  either  taken
off  altogether,  or  lifted  by  the  chain  to  suit  the  working,
either  going  easily  or  full  speed.  In  connection  with
marine  fronts,  the  ashpit  damper  shuts  tight,  as  the
wings  of  the  ashpit  are  closed  in,  and  the  damper  makes
a  good  fit,  thus  keeping  steam  from  blowing  oft'  and  con-
sequent waste.  In  all  marine  work,  the  bars  are  not
interfered  with,  the  front  and  apparatus  being  made  to
suit  those  existing.
This  appliance  is  a  very  simple  one,  cheap  to  instal,
and  to  work.  It  requires  no  more  attention  than  closing
the  fire-door,  immediately  after  firing  or  raking,  its  action
entirely  depending  on  the  ordinary  pull,  or  draught  of  the
chimney.
The  Company  guarantee  the  apparatus  to  effectively
prevent  the  emission  of  black  smoke,  and  obtain  a  mini-
mum economy  of  5  per  cent.  If  unsuccessful,  they  will
remove  the  apparatus,  without  damage  to  bjiler,  and  at
their  own  expense.
The  "Simplex  Smoke-preventing  Applianco"  (Gre-
gory and  Applegarth's  Patents). — Figs.  44  and  45  show
the  front  and  section  of  a  Lancashire  boiler ;  and  Fig.  46
the  section  of  a  Babcock  boiler  fitted  with  this  appliance.
The  principle  -on  which  this  invention  is  worked  is
that  of  a  strong  induced  air  current  applied  in  a  special
manner.  The  apparatus  can  be  readily  understood  by
referring  to  the  illustrations,  which  show  that  it  can  easily
be  applied  to  any  boiler  without  alteration  of  existing
arrangements,  being  fitted  through  the  furnace  front  into


214


SMOKE    ABATEMENT


the  furnace  above  the  fires.  Steam  is  conveyed  by  a
pipe  of  small  diameter  from  the  nearest  convenient  source
to  the  appliance.
