2  The  leading  kinds  of  cupolas  have  the  same  general  proportions
which  leave  little  room  for  improvement;  by  measuring  a  large
number  of  cupolas,  before  any  type  had  become  common,  and  tabu-
lating records  of  melting,  the  writer  determined  that  proportions
exert  almost  no  influence  upon  the  melting  efficiency.  The  results
depend  rather  upon  the  skill  or  care  of  the  melter.
3  A  special  form  of  cupola  is  described  in  this  article;  but  so  far
as  details  of  construction  are  concerned,  there  are  as  many  opinions
as  there  are  designers,  and  as  good  results  are  claimed  with  other
forms.
4  It  does  not  pay  to  purchase  a  small  cupola.  A  72-inch  shell
may  be  lined  with  common  red  brick  next  to  the  shell  and  with  fire
brick  inside  to  bring  the  inside  diameter  right — say  36  inches  for  a
small  business,  to  be  increased  as  the  business  grows.  Above  the
charging  door  the  ordinary  5-inch  lining  may  be  used.
THE   LINING

5  Every  test  the  writer  has  made  has  shown  that  for  ordinary
melting  of  gray  iron  the  cheapest  stock  brick  may  be  used  to  good
advantage.
6  Square  bricks  should  be  used  wherever  possible,  and  key  or
arch  bricks  only  when  necessary  to  turn  the  circle  without  leaving
spaces  between.     A  stock  brick,  whether  square,  split,  key  or  arched,

Presented  at  the  New  York  Meeting  (December  1907)  of  The  American
Society  of  Mechanical  Engineers  and  forming  part  of  Volume  29  of  the  Transac-
tions.
