NEW  METHOD  OF  HEATING  STONEWARE  VESSELS,  ETC.  468 
from.  The  mode  of  procedure  in  vogue  before  Pasteur's  inves- 
tigation of  the  subject  was  to  examine  the  eggs.  Pasteur  re- 
marks, that  the  culture  of  the  silkworm  ought  to  become  a  pro- 
fitable industry  in  many  of  the  colonies  of  Great  Britain.— 
Pharm.  Journ.^  Lond.,  July  16,  1870. 
NEW  METHOD  OF  HEATING  STONEWARE  VESSELS,  AND 
OF  OBTAINING  EEGULATED  HIGH  TEMPERATURES. 
In  conducting  chemical  and  pharmaceutical  operations  for 
manufacturing  purposes,  it  is  generally  necessary  to  effect  evap- 
oration and  distillation  in  stoneware  vessels  ;  but  great  difficulty 
has  been  hitherto  experienced  in  obtaining  a  sufficiently  high 
temperature  without  cracking  or  breaking  the  pan  employed. 
The  use  of  a  naked  fire  inevitably  causes  a  fracture  ;  and  a  sand 
bath  offers  too  great  an  obstruction  to  the  passage  of  the  heat. 
With  a  steam-jacket,  it  is  impossible  even  to  raise  water  to  the 
boiling  point,  unless,  indeed,  such  a  pressure  of  steam  be  ap- 
plied as  to  cause  a  very  dangerous  strain  on  the  flanges  of  the 
vessel. 
A  new  method  of  applying  heat,  however,  has  been  patented 
by  Mr.  J.  A.  Coffey,  the  pharmaceutical  engineer,  and  is  now 
introduced  by  Messrs.  Doulton  k  Watts,  for  working  stoneware 
pans  and  stills,  by  which  any  temperature  ranging  from  100°  to 
700°  F.  can  be  safely  and  easily  obtained. 
Mr.  Coffey's  principle  is  to  cause  heavy  paraffin  oil  to  circu- 
late, first  through  a  coil  of  pipes  in  a  furnace,  and  then  through 
the  jackets  of  the  pans.  The  oil  is  carefully  selected  for  the 
purpose,  from  the  heaviest  of  the  petroleum  or  paraffin  products. 
It  moves  by  its  own  convection.  Heated  in  a  close  coil  of  pipe 
by  a  coke  fire,  it  rises  into  an  air-tight  tank,  from  which  it 
passes,  through  pipes,  to  the  jackets  of  the  different  vessels  to 
be  heated,  returning,  after  it  has  done  its  work,  to  the  lowest 
part  of  the  furnace  coil ;  a  continuous  circulation  is  thus  main- 
tained, similar  to  that  which  occurs  in  a  hot-water  apparatus  for 
warming  buildings.  After  leaving  the  tank,  the  oil  passes 
through  a  pyrometer,  by  which  its  temperature  is  indicated,  and, 
by  means  of  dampers,  &c.,  to  the  fire,  this  can  be  regulated  to 
any  required  point.  The  heating  medium  is  turned  on  or  off 
the  jackets  by  taps,  in  the  same  manner  as  steam ;  and,  as  the 
