CHAPTER  V.
OF  THE  FOUNDATIONS  OF  WALLS  AND  TOWERS.
WHEN  we  are  satisfied  with  the  spot  fixed  on  for  the  site
of  the  city,  as  well  in  respect  of  the  goodness  of  the  air  as
of  the  abundant  supply  of  provisions  for  the  support  of  the
population,  the  communications  by  good  roads,  and  river
or  sea  navigation  for  the  transport  of  merchandise,  we
should  take  into  consideration  the  method  of  constructing
the  walls  and  towers  of  the  city.  Their  foundations  should
be  carried  down  to  a  solid  bottom,  if  such  can  be  found,
and  should  be  built  thereon  of  such  thickness  as  may  be  necessary -
  for  the  proper  support  of  that  part  of  the  wall  which
stands  above  the  natural  level  of  the  ground.  They  should
be  of  the  soundest  workmanship  and  materials,  and  of
greater  thickness  than  the  walls  above.  From  the  exterior -
  face  of  the  wall  towers  must  be  projected,  from  which
an  approaching  enemy  may  be  annoyed  by  weapons,  from
the  embrasures  of  those  towers,  right  and  left.  An  easy
approach  to  the  walls  must  be  provided  against:  indeed
they  should  be  surrounded  by  uneven  ground,  and  the
roads  leading  to  the  gates  should  be  winding  and  turn
to  the  left  from  the  gates.  By  this  arrangement,  the
right  sides  of  the  attacking  troops,  which  are  not  covered
by  their  shields,  will  be  open  to  the  weapons  of  the  besieged. -
  The  plan  of  a  city  should  not  be  square,  nor
formed  with  acute  angles,  but  polygonal;  so  that  the
motions  of  the  enemy  may  be  open  to  observation.  A
city  whose  plan  is  acute-angled,  is  with  difficulty  defended; -
  for  such  a  form  protects  the  attacker  more  than