A^ugi?srtfT?95fm'}      The  Commerce  in  Vegetable  Oils.  417 
The  quantity  of  oil  yielded  varies,  not  only  in  different  species, 
but  according  to  climate  and  culture.  Roughly  it  may  be  assumed 
that  oily  nuts  yield  half  their  weight ;  colza  seed  two-fifths ;  hemp 
seed  one- fourth,  and  linseed  from  one-fourth  to  one-fifth. 
Some  oils  are  employed  for  food,  others  are  burned  in  lamps  ; 
some  form  the  basis  of  soap,  or  are  used  as  lubricants,  not  to  men- 
tion their  employment  in  painting,  in  perfumes  and  many  other 
economic  purposes. 
In  the  manufacture  of  woollens  from  10  to  15  per  cent,  of  oil  is 
required.  For  the  finer  kinds  of  wool,  olive  and  ground-nut  oils 
are  used,  while  for  the  coarser  kinds  rape  is  employed. 
The  largest  source  of  vegetable  oils  is  the  small  seeds  of  plants, 
and  some  of  them  are  used  for  food.  The  seed  of  the  cotton  plant, 
gingilie,  mustard,  linseed  and  rape  seed  may  be  quoted  as  illustra- 
tions of  those  products,  and  oils  of  a  very  fine  quality  are  procur- 
able from  them.  The  seeds  of  the  common  cucumber  and  those  of 
other  cucurbita  may  be  especially  cited  as  yielding  an  edible  oil  of 
delicious  and  delicate  taste,  and  that  of  the  large  cucumber,  grown 
on  the  slave  coast,  far  exceeds  in  flavor  the  finest  olive  oil. 
Seed  oil  is  more  commonly  eaten  in  India  and  other  hot  countries 
than  in  England.  The  seeds  of  the  safflower  and  the  sesamum  oils 
may  be  added  to  the  list,  as  representing  Indian  oils,  which  are  used 
in  cooking  grain  and  other  vegetables ;  whilst  in  the  gloomy  forests 
of  Central  Africa  and  in  the  great  mangrove  swamps,  where  the 
cassava,  plantain  and  yam  are  the  chief  foods,  palm  oil  and  vege- 
table fats  are  almost  necessaries  of  life. 
In  a  work  which  I  helped  Dr.  Edward  Smith  to  bring  out  some 
years  ago,  ft  On  Foods,"  he  observes  :  "  There  can  be  no  doubt  that 
we  have  in  this  product  of  seeds  of  plants,  which  seem  otherwise  to 
be  useless,  a  great  storehouse  of  most  valuable  nutritive  material ; 
and  if  we  know  but  little  of  many  of  them  in  this  climate,  it  is 
because  we  have  the  olive  oil  at  hand,  and  are  bountifully  supplied 
with  many  kinds  of  animal  fats.  It  is,  however,  probable  that  the 
cheapness  of  some  of  these  vegetable  oils,  in  addition  to  the  deli- 
cacy of  their  flavor,  will,  ere  long,  force  themselves  into  notice  and 
obtain  a  place  among  our  foods." 
In  China  there  are  a  number  of  edible  oils  used  which  do  not 
appear  in  English  commerce,  and  they  have  even  some  mode  of 
purifying  castor  oil  to  remove  its  drastic  properties.    The  enormous 
