500 
MANUFACTURE  OF  VEGETABLE  OILS. 
tity  of  oil  oozes,  and  this,  being  considered  purer  than  that 
which  is  obtained  by  expression,  is  conveyed  to  a  cistern  set 
apart  for  the  purpose.  The  paste  is  next  put  into  a  jacketed 
kettle, — that  is,  one  surrounded  by  a  hollow  chamber,  into  which 
steam  is  injected  for  the  purpose  of  heating  it.  Within  this 
kettle  is  an  agitator  or  stirrer,  so  that  all  the  paste  is  in  turn 
brought  to  the  heated  surface  and  raised  to  an  even  temperature. 
Having  remained  in  the  kettle  six  minutes,  it  is  collected  in 
woollen  bags,  about  eighteen  inches  long  and  six  inches  wide ; 
each  bag  is  placed  between  four  layers  of  press  hairs  (a  kind  of 
horse-hair  mat),  and  eight  of  them  being  thus  prepared,  they 
are  ranged  in  two  perpendicular  rows  between  four  grooved 
shelves  of  a  hydraulic  press.  The  pumps,  worked  by  the  steam- 
engine,  are  set  in  motion,  and  a  pressure  of  400  tons  is  speedily 
realized.  The  oil,  being  expressed,  runs  into  an  underground 
tank  ;  the  bags  are  then  withdrawn,  and  on  being  removed,  the 
residue  presents  itself  in  the  form  of  what  is  known  as  linseed 
cake.  These  cakes  are  placed  in  a  rack  to  cool,  when  they 
become  so  hard  as  not  to  be  easily  broken ;  they  are  then 
orderly  stacked,  and  from  time  to  time  sent  away  in  wagons  or 
barges  to  supply  the  cattle-food  market,  for  which  purpose  the 
cake  is  in  great  request. 
A  quarter  of  linseed,  which  only  undergoes  one  pressure, 
yields  an  average  of  120  lbs.  of  oil  and  35  cakes  of  nutritious 
food,  each  weighing  8  lbs.,  or  an  aggregate  of  two  hundred- 
weight and  a  half.  Rape  seed,  which  is  twice  ground  and 
pressed,  yields  per  quarter  from  88  lbs.  to  90  lbs.  of  oil  at  the 
first,  and  from  60  lbs.  to  70  lbs.  at  the  second  pressure.  Of 
these  two  kinds  of  oil-producing  seeds  upwards  of  600,000 
quarters  are  annually  imported,  and  this  mill  alone  works  up 
35,000  quarters  per  annum.  Calcutta,  Bombay,  and  Kurrachee 
are  the  great  emporia  for  the  seeds ;  and  it  is  a  remarkable  fact 
that,  whereas  the  last-named  place,  when  it  fell  into  the  hands 
of  the  British  in  1839,  consisted  of  only  about  fifty  wretched 
huts,  inhabited  by  fishermen,  it  is  now  a  thriving  port,  and  one 
of  the  principal  outlets  for  the  oil-producing  seeds  of  India. 
After  the  oil  has  remained  a  few  days  in  the  receiving  cistern, 
the  parenchymatous  matter  subsides ;  it  is  then  pumped  into 
vats  for  a  second  settling,  after  which  it  is  barrelled  and  con- 
