Presently  he  will  arrive  at  another  post,  with  arm  projecting
downwards  in  a  reverse  or  backward  direction,  and  marked  in
the  SEmie  terms,  but  on  the  other  or  forward  side  of  the  post
he  will  see  another  arm  in  a  horizontal  position,  indicating
that  beginning  from  that  point  the  road  is  now  horizontal  or
level,  and  so  on  at  every  place  where  the  slope  of  the  artificial
surface  or  'gradient'  changes  he  will  find  it  duly  recorded  by
the  posts  and  arms.  ITie  object  of  these  gradient  posts  is  to
inform  the  engine-driver  of  the  nature  and  degree  of  the  road
inclination  against  him  or  in  his  favour.
Horizontally,  or  in  plan,  the  construction  of  railway  earth-
works will  always  proceed  in  a  straight  line  except  at  certain
definite  places  where  two  straight  lines  will  be  joined  together
by  a  airve  or  cur\-es.  Tliere  are,  tlierefore,  two  important
matters  to  l>e  carefully  regarded  by  the  engineer  immediately
engaged  on  the  works,  \-iz.,  tlie  correct  formation  of  the  surface
'  gradients,'  and  the  accurate  tracing  and  preser^nng  the  align-


ed tyGoOglc


RAILWAYS  IN  INDIA  253

ment  of  the  various  straight  lengths  and  curves  as  exhibited  on
the  plans.  For  a  long  time  after  the  first  iatroduction  of  rail-
ways it  was  held  as  the  very  first  principle  of  construction  that
the  running  surface  should  be  everywhere  made  as  nearly  level  as
possible — original  outlay  being  held  of  secondary  consideration
as  compared  with  the  supposed  subsequent  economy  of  working.
