GLEANINGS — MISCELLANEOUS. 
501 
has  two  openings,  one  below  for  the  ingress  of  the  refrigerating 
water,  and  one  above  for  the  escape  of  the  heated  water.  The 
upper  space  has  two  openings,  one  central  and  vertical  and 
one  lateral  and  inclined,  for  the  ingress  of  the  vapor,  so  as  to 
accommodate  a  vertical  or  inclined  tube  connecting  it  with  the 
still  or  boiler.  The  lower  apartment  has  one  lateral  opening 
for  the  escape  of  the  condensed  vapor. 
It  will  be  perceived  that  this  instrument  is  really  a  compound 
Liebig's  condenser,  and,  if  a  constant  and  sufficient  current  of 
cool  water  circulates  through  it,  that  its  condensing  power  is 
very  effective,  and  readily  serves  a  fifteen  gallon  still.  By 
making  the  lower  chamber  separate,  so  as  to  slip  over  the  cen- 
tral one  at  the  lower  diaphragm,  it  may  be  removed  at  will,  and 
the  tubes  cleaned  with  a  swab,  after  operations  with  odorous 
liquids. — (Pharm.  Journ.) 
The  Artificial  Production  of  Ice. — M.  Carre  has  recently 
communicated  to  the  French  Academy  a  means  of  producing 
low  temperatures  upon  a  large  scale,  which  are  simple  and  not 
very  expensive,  depending  on  the  rapid  evaporation  of  liqui- 
fied ammoniacal  gas.  The  apparatus  consists  of  two  or- 
dinary cylindrical  boilers,  one  having  four  times  the  capacity 
of  the  other,  the  larger  one  being  three-fourths  filled  with  the 
strongest  solution  of  ammonia.  The  two  boilers  are  connected 
by  a  tube  provided  with  a  stopcock.  Before  closing  the  appa- 
ratus the  whole  of  the  air  is  driven  out.  Heat  is  then  applied 
to  the  larger  vessel  until  the  solution  acquires  the  temperature 
of  130^  to  140°,  the  cock  being  open.  Under  these  circum- 
stances the  ammoniacal  gas,  disengaged  from  the  solution,  having 
no  means  of  escape,  condenses  in  the  small  boiler  in  a  liquid 
form  under  the  great  pressure.  When  it  ceases  to  increase,  the 
cock  is  closed  and  the  large  boiler  cooled.  The  apparatus  then 
contains  liquid  ammonia  in  one  vessel  and  cold  water  with  a 
vacuum  above  in  the  other.  The  small  boiler  is  surrounded 
with  cold  water  and  the  tap  opened,  when  the  rapid  evaporation 
of  the  condensed  gas  abstracts  so  much  heat  from  the  water 
through  the  boiler  as  to  freeze  the  water  surrounding  it.  The 
ice  thus  formed  is  then  removed  and  the  operation  repeated.  It 
is  necessary  that  the  apparatus  be  absolutely  tight  and  capable 
