But  a  sale  of  the  thing  patented  to  an  agent  of  the  patentee,
employed  by  him  to   make  the  purchase,  and  on  account  of  the


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MEASURE  OF    DAMAGES.  355

patentee,  is  not  an  act  from  wliicli  damage  will  be  presumed,  as  it
must  be  supposed  to  have  been  done  for  the  patentee's  benefit,  or  at
least  not  to  have  been  to  his  loss.  Such  a  sale,  however,  accompanied
by  other  circumstances,  may  warrant  a  jury  in  finding  an  infringe-
ment by  sales  to  others  than  the  patentee.     lb.
The  general  principle  is,  that  the  plaintiff  is  entitled  to  recover
a  fair  and  adequate  compensation  for  the  loss  or  injury  he  has  sus-
tained by  the  infringement.  Taylor  v.  Carpenter,  2  Woodh.  &  M.
1  ;  10  i.  Rep'r,  35 ;  Hall  v.  Wiles,  2  Blatchf.  194  ;  Pitts  v.  Hall,
Id.  229  ;  McCormick  v.  Seymour,  2  Blatchf:.  240  ;  Buck  v.  Her-
mance,  1  Blatchf.  398  ;  Kneass  v.  Schuylkill  Bank,  4  Wash.  9  ;
Parker  v.  Hulme,  1  Fish.  Pat.  Gas.  44  ;  7  West.  L.  J.  428.
When  a  user  of  a  machine  in  violation  of  a  patent  is  proved,  the-
value  of  the  use  of  such  a  machine  during  the  time  of  the  illegal
user  is  the  measure  of  damage.  Whittemore  v.  Cutter,  1  Qall.
478.
It  is  difficult  to  establish  any  general  rule  as  to  damages.  The
better  course  is  not  to  lay  down  any  particular  rule  of  damages,  but
to  leave  the  jury  at  large  to  estimate  the  actual  damages  according
to  the  circumstances  of  each  particular  case.  Earle  v.  Sawyer,  4
Mas.  1,  14.
