Character  of  Showing  Required — Motion  to  Take.  Testi-
mony as  to  Operativeness.  As  a  prerequisite  to  the  right
to  take  testimony  as  to  the  operativeness  of  an  opponent 's
device  it  is  not  necessary  that  the  mo^dng  party  make  an
absolutely  conclusive  showing  of  inoperativeness,  but  if
he  makes  out  a  prima  facie  case  of  inoperativeness
thereof,  which  does  not  extend  to  his  own,  and  it  appears
that  it  would  be  a  matter  of  great  difficulty  to  decide
the  question  of  operativeness  from  a  mere  inspection  of
the  application  and  it  can  not  be  determined  that  a  de-
cision so  arrived  at  would  be  the  same  as  would  be
reached  in  the  light  of  information  that  might  be  derived
from  witnesses  expert  in  the  art  to  which  the  invention
relates,  a  motion  for'  leave  to  take  testimony  should  be
granted.  Lowry  tO  Cowley  v.  Spoon,  12-1  0.  G.  1846
(1906)  :  Brown  v.  Stroud,  122  0.  G.  2688.
Counter  Affidavits.  While  an  opposing  party  may  at-
tack the  sufficiency  of  the  motion,  he  should  not  present
counter  affidavits.  Clement  v.  Browne  v.  Stroud,  126  0.
G.  2589  (1907).
166.  Public  Use.  It  may  not  be  possible  to  give  any
accurate  definition  of  the  term  "public  use,''  but  the
general  principles  by  which  we  may  determine  whether
or  not  a  certain  use  is  a  public  use  or  otherwise,  are
fairl}-  well  established  by  the  decisions.
