ON  A  PROCESS  OF  FRACTIONAL  CONDENSATION.  459 
a  sheet-iron  apron,  DD,  folded  above.  This  is  for  security  against 
fire  in  case  of  accident,  either  to  the  retort  or  hot  bath  of  oil. 
As  arranged,  the  contents  of  either  or  both  of  these  could  run 
out  and  burn  without  danger  to  the  operator  or  the  premises,  as 
the  brick-work  in  front  would  prevent  the  liquid  from  spreading 
beyond  the  fire-place,  and  the  dropping  of  the  sheet-iron  apron 
would  cause  an  additional  draft,  and  thus  insure  the  passage  of 
the  flames  into  the  chimney.  Instead  of  placing  the  apparatus 
in  a  fire-place,  where  that  is  not  convenient,  equal  security 
against  accidents  may  be  attained  by  the  use  of  my  safety  heat- 
ing lamp,*  fig.  1,  to  heat  the  retort,  and  safety-furnace,  p, 
containing  a  Bensen's  burner,  for  heating  the  bath.  The  bot- 
tom of  this  furnace,  and  also  a  large  part  of  the  sides,  is  formed 
of  wire  gauze,  such  as  described  for  the  safety-lamp. f  The 
gauze  upon  the  battom  need  not  be  permanently  attached  to  the 
furnace,  but  may  simply  be  laid  upon  an  opening  cut  in  the  stool 
or  board  on  which  the  furnace  is  to  be  placed  ;  if  the  furnace 
be  then  set  upon  it,  taking  care  that  the  joint  shall  be  tight 
around  the  edge,  nothing  more  will  be  required.  A  strip  of 
vulcanized  caoutchouc,  about  an  eighth  of  an  inch  in  thickness, 
is  riveted  around  the  edge  of  the  opening  for  the  door ;  against 
this  the  door  tightly  closes,  so  that  no  ignition  can  take  place 
through  the  cracks  which  would  otherwise  remain  under  the 
edges  of  the  door. 
For  an  apparatus  to  stand  upon  the  table,  the  safety -lamp  and 
furnace  are  especially  desirable.  I  have  also  used  them  for  the 
larger  apparatus,  placed  upon  the  floor  of  the  laboratory.  As 
a  practical  test  of  the  security  which  they  afford,  I  may  relate 
an  incident  which  happened  to  myself.  I  had  left  the  laboratory 
for  a  short  time,  with  such  an  apparatus  in  full  operation  ;  the 
retort  containing  nearly  a  quart  of  light  petroleum  boiling  below 
100°  C.  Having  been  detained  longer  than  I  expected,  on  re- 
turning I  found  the  laboratory  filled  with  the  vapors  of  hydro- 
carbons ;  and,  on  approaching  the  retort,  found  that  the  caout- 
chouc joint,  connecting  the  retort  with  the  elevated  worm,  had 
failed,  and  that  the  larger  portion  of  the  liquid  had  distilled  into 
*  American  Journal  of  Science  and  Arts,  May,  1862  [2;]  xxxiii,  275. 
f  Loc.  cit.  See  Amer.  Jour.  Pharm.  xxxiv.  217. 
