Inductive  Epochs;  Preludes;  Sequels. — In  our
history,  it  is  the  progress  of  knowledge  only  which
we  have  to  attend  to.  This  is  the  main  action  of
our  drama ;  and  all  the  events  which  do  not  bear
upon  this,  though  they  may  relate  to  the  cultiva-
tion and  the  cultivators  of  philosophy,  are  not  a
necessary  part  of  our  theme.  Our  narrative  will
therefore  consist  mainly  of  successive  steps  of  gene-
ralization, such  as  have  just  been  mentioned.  But
among  these,  we  shall  find  some  of  eminent  and
decisive  importance,  which  have  more  peculiarly
influenced  the  fortunes  of  physical  philosophy,  and
to  which  we  may  consider  the  rest  as  subordinate
and  auxiliary.  These  primary  movements,  when
the  Inductive  process,  by  which  science  is  formed,
has  been  exercised  in  a  more  energetic  and  power-
ful manner,  may  be  distinguished  as  the  Inductive
Epochs  of  scientific  history;  and  they  deserve  our
more  express  and  pointed  notice.  They  are,  for  the
most  part,  marked  by  the  great  discoveries  and  the
great  philosophical  names  which  all  civilized  na-


INTRODUCTION.  1 3

tions  have  agreed  in  admiring.  But,  when  we
examine  more  clearly  the  history  of  such  disco-
veries, we  find  that  these  epochs  have  not  occurred
suddenly  and  without  preparation.  They  have  been
preceded  by  a  period,  which  we  may  call  their
Prelude,  during  which  the  ideas  and  facts  on  which
they  turned  were  called  into  action; — were  gra-
dually evolved  into  clearness  and  connexion,  per-
manency and  certainty;  till  at  last  the  discovery
which  marks  the  Epoch,  seized  and  fixed  for  ever
the  truth  which  had  till  then  been  obscurely  and
doubtfully  discerned.  And  again,  when  this  step
has  been  made  by  the  principal  discoverers,  there
may  generally  be  observed  another  period,  which
we  may  call  the  Sequel  of  the  Epoch,  during  which
the  discovery  has  acquired  a  more  perfect  certainty
and  a  more  complete  developement  among  the
leaders  of  the  advance;  has  been  diffused  to  the
wider  throng  of  the  secondary  cultivators  of  such
knowledge,  and  traced  into  its  distant  consequences.
