the  product.  Boyd  v.  McAlpine,  3  McLean,  427  ;  Wilson  v.  Sher-
man, 1  Blatchf.  536,

The  jurisdiction  of  the  circuit  courts  sitting  in  equity  over  con-
troversies under  the  patent  laws  is  not  merely  a  jurisdiction  ancil-
lary to  courts  of  law,  but  a  substantive  jurisdiction  conferred  by
direct  grant  from  Congress.  Blank  u.  Manufacturing  Co.,  3  Wall.
Jr.  196  ;  Saunders  v.  Logan,  2  Pittsb.  241  ;  Jenkins  v.  Greenwald,
1  Bond,  126  ;  2  Fish.  Pat.  Gas.  37.
History  of  equity  jurisdiction  and  of  the  statutes  conferring  it
on  the  circuit  courts,  in  patent  cases,  explained  ;  with  special  refer-
ence to  the  question  whether  an  injunction  suit  begun  after  expira-
tion of  a  patent  can  be  maintained,  even  for  the  purpose  of  com-
pelling an  accounting.  Root  v.  Railway  Co.,  105  U.  S.  189.  See
also  post,  note  249.
An  accounting  may  be  decreed,  in  a  proper  case,  notwithstand-
ing no  right  to  a  discovery  or  an  injunction  or  other  distinct  head
of  equitable  relief  is  shown  ;  as,  where  the  patent  expired  pending
the  suit,  leaving  nothipg  in  litigation  but  the  right  to  an  account.
Blank  v.  Manufacturing  Co.,  3  Wall.  Jr.  196.  To  same  effect,
Gottfried  v.  Moerlein,  14  Fed.  Pep'r,  170  ;  Burdell  v.  Corn-
stock,  15  Md.  Eep'r,  395.
A  single  infringement  will  not  warrant  a  suit  for  an  injunction;
there  being  no  threat  to  continue  infringing  ;  the  remedy  is  by  suit
for  damages.     Smith  v.  Sands,  20  PepW,  326.
