can  he  study  with  profit  the  works  of  Ctesibius,  Archimedes, -
  and  many  other  authors  who  have  written  on  the
subject.  Music  assists  him  in  the  use  of  harmonic  and
mathematical  proportion.  It  is,  moreover,  absolutely
necessary  in  adjusting  the  force  of  the  balistæe,  catapultæe,
and  scorpions,  in  whose  frames  are  holes  for  the  passage

of  the  homotona,  which  are  strained  by  gut-ropes  attached -
  to  windlasses  worked  by  hand-spikes.  Unless
these  ropes  are  equally  extended,  which  only  a  nice  ear  can
discover  by  their  sound  when  struck,  the  bent  arms  of
the  engine  do  not  give  an  equal  impetus  when  disengaged, -
  and  the  strings,  therefore,  not  being  in  equal

states  of  tension,  prevent  the  direct  flight  of  the  weapon.
So  the  vessels  called  ixela  by  the  Greeks,  which  are
placed  in  certain  recesses  under  the  seats  of  theatres,
are  fixed  and  arranged  with  a  due  regard  to  the  laws  of
harmony  and  physics,  their  tones  being  fourths,  fifths,
and  octaves  ;  so  that  when  the  voice  of  the  actor  is  in
unison  with  the  pitch  of  these  instruments,  its  power  is

increased  and  mellowed  by  impinging  thereon.  He  would,
moreover,  be  at  a  loss  in  constructing  hydraulic  and
other  engines,  if  ignorant  of  music.  Skill  in  physic
enables  him  to  ascertain  the  salubrity  of  different  tracts
of  country,  and  to  determine  the  variation  of  climates,
which  the  Greeks  call  Miuara:  for  the  air  and  water  of
different  situations,  being  matters  of  the  highest  importance,

  no  building  will  be  healthy  without  attention  to
those  points.  Law  should  be  an  object  of  his  study,
especially  those  parts  of  it  which  relate  to  party-walls,  to
the  free  course  and  discharge  of  the  eaves'  waters,  the

regulations  of  sesspools  and  sewage,  and  those  relating
to  window  lights.  The  laws  of  sewage  require  his  particular -
  attention,  that  he  may  prevent  his  employers
being  involved  in  law-suits  when  the  building  is  finished.
Contracts,  also,  for  the  execution  of  the  works,  should
be  drawn  with  care  and  precision  :  because,  when  without -
  legal  flaws,  neither  party  will  be  able  to  take  advan¬