SUPPLY  AND  DEMAND  79
expenses,  apart  from  his  own  remuneration,
would  vary  with  the  variation  in  the  extent
of  his  firm’s  operations.  The  firm,  suppose,
produces  boots  of  one  sort.  If  it  turned  out
very  few  pairs  a  year  the  expenses  of  production ­
  would  certainly  be  high,  because  for  a
tiny  output  very  little  machinery  could  be
used  and  very  little  division  of  labour  could  be
introduced.  Successive  enlargements  of  output ­
  by  equal  increments  would,  therefore,
entail  additions  to  the  total  expenses  of
production  which  for  a  time  would  become
continuously  less  and  less.  These  additions
to  the  total  expenses  of  a  business  (involved
in  its  expansion)  may  be  called  the  marginal
expenses  of  a  business;  which  are  to  be
distinguished  from  marginal  expenses,  socalled,
  meaning  the  expenses  per  unit  of
output  of  the  marginal  firm.
Let  us  have  figures  to  prevent  any  misapprehension. ­
  Say  1000  pairs  of  boots  a
year  are  manufactured  and  that  the  aggregate
expenses,  including  interest  on  capital,  wages,
cost  of  material,  and  everything  with  the
exception  of  the  employer’s  earnings  for  himself, ­
  amount  to  £1000.  Let  the  size  of  the
business  increase  so  that  the  output  becomes
1001  pairs  of  boots,  and  let  the  addition  to
the  total  expense  be  15s.  This  may  be  called