The  ship  then  is  in  the  lowest  lock,  one  pair  of
gates  closed  tightly  behind  her.    Another  pair  con-


2i8         PANAMA  AND  THE  CANAL

fronts  her  holding  back  the  water  in  the  lock  above,
which  if  filled,  will  be  just  28}^  feet  above  the
surface  of  that  on  which  she  floats.  But  the  water
about  her  is  now  slowly  rising.  Another  set  of
electric  motors  concealed  in  the  concrete  wall  have
set  in  motion  the  valves  in  the  floor  of  the  lock,
and  the  water  is  flowing  in  from  the  tunnels,  raising
the  ship  and  at  the  same  time  lowering  the  water  in
the  lock  above.  When  the  vessel's  keel  is  higher  than
the  sill  of  the  lock  above  the  upper  gates  swing  slowly
back  and  fold  in  flat  with  the  wall.  The  ship  is
now  in  a  chamber  2000  feet  long  filled  to  a  level.
The  locomotives  pull  her  forward  a  thousand  feet
or  so.  Again  great  gates  close  behind  her.  Again
the  water  rises  slowly  about  her  lifting  her  with  it.
The  first  process  is  repeated  and  she  enters  the
third  lock.  By  the  time  she  has  been  drawn  out
into  the  lake  and  the  locomotives  have  cast  her  off,
more  than  100  electric  motors  with  a  horse  power
ranging  from  7}^  to  50  each  will  have  contributed
to  her  progress.  Altogether  over  1000  individual
motors  will  be  required  for  the  different  locks.
Indeed  the  whole  interior  of  those  massive  lock
walls  is  penetrated  by  Hghted  galleries  strung  with
insulated  wires  bearing  a  death-dealing  current.  Men
will  be  stationed  at  the  various  machinery  rooms,
but  the  whole  line  of  machinery  will  be  operated
from  a  central  operating  tower  on  the  lock  above.
