104  NOTICE  OF  M.  Carre's  apparatus  for  making  ice. 
apparatus.  The  stacks  of  zig-zags  connect  at  bottom  with  a 
cylindrical  vessel  called  the  collector.  When  now  the  distributing 
valve  is  partially  opened,  the  liquid  ammonia  is  forced  in  due 
proportion  into  the  zig-zag  tubes,  where  it  rapidly  expands  into 
gas  by  the  assumption  of  the  heat  necessary  for  its  vaporization 
from  the  sarrounding  brine,  which  in  its  turn  abstracts  the  heat 
of  the  water  in  the  cans  (by  virtue  of  which  only  it  can  retain  its 
fluidity),  and  thus  converts  it  into  ice  and  accomplishes  the 
chief  purpose  of  the  machine.  But  the  apparatus,  acting  con- 
tinuously, now  gathers  the  resulting  ammoniacal  gas,  redissolves 
it  in  the  weak  liquor  of  the  boiler  which  it  has  previously  ab- 
stracted and  cooled,  and  then  returns  it  to  the  boiler  to  be  again 
deprived  of  its  gas.  This  remarkable  compound  result  is  eifected 
in  this  wise :  The  ammoniacal  gas,  after  performing  its  office  of 
rendering  latent  the  sensible  heat  of  the  water,  passes  on  first  to 
the  collector,  and  from  this  through  a  cooling  tube  to  the  absorp- 
tion vase  (which  consists  of  a  cylindrical  vessel  enclosing  a  tall 
coil  of  tube,  through  which  passes  a  constant  current  of  cold 
water)"  and  there,  after  the  machine  has  been  working  some  time, 
it  meets  with  the  exhausted  ammonia  liquor,  by  which  it  is  rapidly 
absorbed,  and  which  thus  regains  its  original  strength.  The 
manner  in  which  the  weak  ammonia  liquor  reaches  the  absorption 
vase,  and  the  regenerated  liquor  ammonise  is  returned  to  the 
boiler,  all  of  which  has  to  be  effected  under  the  heavy  pressure 
of  thirteen  atmospheres,  is  as  follows  :  By  a  syphon  tube  reach- 
ing to  the  bottom  of  the  boiler  the  latter  is  connected  with  the 
double  coil  of  the  exclianger,  which  consists  of  a  tall  cylindrical 
iron  vessel,  about  twenty  inches  in  diameter.  The  lower  end  of 
the  coil  is  connected  with  the  lower  end  of  another  coil  in  a 
similar  vessel  beside  it,  called  the  complement^  the  upper  end  of 
which  coil  enters  the  absorption  vase  at  the  top,  and  descends 
nearly  to  the  bottom.  At  first  the  boiler,  exchanger,  comple- 
ment, and  absorption  vase  are  all  charged  with  strong  ammonia, 
but  as  soon  as  the  heat  under  the  boiler  has  driven  off  sufficient 
gas  to  create  strong  pressure,  the  weakened  hot  ammonia  liquor 
is  forced  into  the  coil  of  the  exchanger,  where  it  is  partially 
cooled  by  the  cold  ammonia  of  the  absorption  vase,  which  the 
pump  has  forced  into  the  cylinder  of  the  exchanger,  ready  to 
