Conceding  the  principle  established  in  the  two  cases  just  decided
to  be  that  the  fact  that  books  published  at  stated  intervals  and  in
consecutive  numbers  do  not  thereby  become  periodicals,  even  though
in  other  respects  they  conform  to  the  requirements  of  Act  March  3,
18T9,  c.  180,  §  14,  20  Stat.  359  (U.  S.  Comp.  St.  1901,  p.  2647),
cases  may  still  arise  where  the  classification  of  a  certain  publication
may  be  one  of  doubt.  Such  is  this  case.  But  we  think  that,  although
the  question  is  largely  one  of  law,  determined  by  a  comparison  of
the  exhibit  with  the  statute,  there  is  some  discretion  left  in  the
Postmaster  General  with  respect  to  the  classification  of  such  pub-
lications as  mail  matter,  and  that  the  exercise  of  such  discretion
ought  not  to  be  interfered  with  unless  the  court  be  clearly  of  opinion
that  it  was  wrong.  The  Postmaster  General  is  charged  with  the
duty  of  examining  these  publications   and  of  determining  to  which


GG4  RELIEF   AGAINST   ADMINISTRATIVE    ACTION.  (Part    2

class  of  mail  matter  they  properly  belong;  and  we  think  his  decision
should  not  be  made  the  subject  of  judicial  investigation  in  every  case
where  one  of  the  parties  thereto  is  dissatisfied.  The  consequence  of
a  dift'erent  rule  would  be  that  the  court  might  be  flooded  by  appeals
of  this  kind  to  review  the  decision  of  the  Postmaster  General  in  every
individual  instance.  In  the  case  of  American  School  of  Magnetic
Healing  v.  McAnnulty,  187  U.  S.  94,  104,  23  Sup.  Ct.  33,  47  L.  Ed.
