Let us  next    inquire what    are the qualities   which   enter   into    what    we  call    a   good
memory. The merchant    or  politician  will    say,    "Ability    to  remember    well    people's
faces   and names"; the teacher of  history,    "The    ability to  recall  readily dates   and
events";     the     teacher     of  mathematics,    "The    power   to  recall  mathematical
formulæ";   the hotel   waiter, "The    ability to  keep    in  mind    half-a-dozen    orders  at  a
time";  the manager  of a   corporation,     "The   ability to   recall all the  necessary
details connected   with    the running of  the concern."   While   these   answers are very
divergent,  yet they    may all be  true    for the particular  person  testifying; for out of
them    all there   emerges this    common  truth,  that    the best    memory  is  the one which
best    serves  its possessor.  That    is, one's   memory  not only    must    be  ready   and
exact,  but must    produce the right   kind    of  material;   it  must    bring   to  us  what    we
need     in  our     thinking.   A   very    easy    corollary   at  once    grows   out     of  this    fact;
namely, that    in  order   to  have    the memory  return  to  us  the right   kind    of  matter,
we  must    store   it  with    the right   kind    of  images  and ideas,  for the memory  cannot
give    back    to  us  anything    which   we  have    not first   given   into    its keeping.
A   Good    Memory  Selects Its Material.—The   best    memory  is  not necessarily
the one which   impartially repeats the largest number  of  facts   of  past    experience.
Everyone    has many    experiences which   he  never   needs   to  have    reproduced  in
memory; useful  enough  they    may have    been    at  the time,   but wholly  useless and
irrelevant  later.  They    have    served  their   purpose,    and should  henceforth  slumber
in  oblivion.   They    would   be  but so  much    rubbish and lumber  if  they    could   be
recalled.   Everyone    has surely  met that    particular  type    of  bore    whose   memory  is
so  faithful    to  details that    no  incident    in  the story   he  tells,  no  matter  however
trivial,    is  ever    omitted in  the recounting. His associations    work    in  such    a   tireless
round   of  minute  succession, without ever    being   able    to  take    a   jump    or  a   short
cut,    that    he  is  powerless   to  separate    the wheat   from    the chaff;  so  he  dumps   the
whole   indiscriminate  mass    into    our long-suffering  ears.
Dr.  Carpenter   tells   of  a   member  of  Parliament  who     could   repeat  long    legal
documents   and acts    of  Parliament  after   one reading.    When    he  was congratulated
on  his remarkable  gift,   he  replied that,   instead of  being   an  advantage   to  him,    it
was often   a   source  of  great   inconvenience,  because when    he  wished  to  recollect
anything    in  a   document    he  had read,   he  could   do  it  only    by  repeating   the whole
from    the beginning   up  to  the point   which   he  wished  to  recall. Maudsley    says    that
the kind    of  memory  which   enables a   person  "to read    a   photographic    copy    of
former  impressions with    his mind's  eye is  not,    indeed, commonly    associated  with
high    intellectual    power," and gives   as  a   reason  that    such    a   mind    is  hindered    by
the  very    wealth  of  material    furnished   by  the     memory  from    discerning  the
