These  wires  are  arranged
in  "circuits."  For  exam-
ple, one  circuit  may  start
at  St.  Paul,  Minnesota,
and,  passing  through  a
number  of  weather  sta-
tions, end  at  the  Central
Office  at  Washington.  At
each  of  these  offices  is  an
operator  seated  at  his  in-
strument ready  to  copy
the  reports  from  other
stations,  or  to  send  his

own.  The  main  circuit  is  tapped  at  convenient
points  by  wires  or  circuits  from  either  side,  so  that
when  the  work  begins  the  messages  flow  toward  the
main  circuit  much  as  streams  converge  toward  the
main  channel  of  a  river.    Each  operator  has  a  par-


ticular time  for  placing  his  own  report  on  the  cir-
cuit, and  he  copies  all  reports  from  other  stations
passing  over  the  wire.  At  the  terminal  points  of
the  main  and  auxiliary  circuits,  reports  from  sta-
tions in  adjacent  territory  are  gathered  and  placed
on  the  wire,  so  that  at  the  end  of  an  hour  not  only
the  Central  Office  at  Washington  but  a  hundred  or
more  local  offices  are  in  possession  of  observations
taken  an  hour  before  over  a  large  territory.
Construction  of  the  weather  map.
As  soon  as  the  reports  come  from  the  wires,  they
are  passed  to  the  observers  and  the  preparation  of
the  daily  weather  map  begins.  For  this,  an  outline
map  of  the  United  States  is  used,  the  location  of
each  station  being  shown  on  the  map  by  a  circle.
