454         ON  A  PROCESS  OF  FRACTIONAL  CONDENSATION. 
perature  of  which  is  regulated  by  means  of  a  separate  lamp,  b, 
fig.  2,  or  by  a  safety-furnace,  p,  as  shown  in  fig.  1.  The  bath 
may  be  of  oil  or  water,  or  of  metal  for  very  high  temperatures, 
as  the  case  may  require,  and  is  furnished  with  a  thermometer,  t. 
That  this  bath  may  be  equally  adapted  for  the  separation  of 
liquids  boiling  below  the  common  temperature,  an  empty  vessel, 
c,  figs.  1  and  2,  is  permanently  secured  in  the  interior  of  the 
bath  by  means  of  straps  of  metal  across  the  top,  to  serve  as  a 
convenient  receptacle  for  ice  or  iced  water,  by  means  of  which  a 
low  temperature  may  be  steadily  maintained.  The  interior  ves- 
sel also  serves  a  good  purpose  in  economizing  time,  and  fuel  in 
heating  the  bath,  as  it  diminishes  the  quantity  of  oil  required  to 
cover  the  worm.  It  is  made  to  extend  to  within  about  three 
inches  of  the  bottom  of  the  bath,  and  large  enough  to  fill  the 
greater  part  of  the  space  in  the  centre  of  the  coil.  The  bath 
ami  interior  vessel  are  both  made  of  sheet-copper,  with  joints 
