A  parallel-flow  wheel  some  40  inches  external  diameter
was  inserted  in  a  pit  formed  in  one  of  the  approaches  of  the
lock..  The  head  of  the  vertical  shaft  w^as  disposed  as  indicated
in  Fig.  211.     It  had  a  square  neck  which  entered  a  sort  of  hub


Fig.   211.
B  revolving  in  a  fixed  bearing.  This  arrangement  allowed
the  wheel  to  sink  b}-  the  wearing  of  the  step  without  bringing
any  strain  on  its  upper  supports.  This  hub  forms  a  part  of  the
crank,  which  revolves  with  the  wheel,  and  carries  the  crank-
pin  C .  This  crank-pin  carries  a  circular  disk  to  wliich  are
attached  the  pump-rods  cc  of  six  pumps  arranged  in  a  circle,
Avith  the  wheel-shaft  in  the  centre.  These  pumps  are  worked
by  hollow  plungers  f,  to  the  bottom  of  which  the  pump-rod  e
is  jointed,  an  arrangement  which  gives  sufficient  pla}-  to  the
pump-rod  within  the  hollow  plunger  and  dispenses  with  a  con-
necting-rod. The  crank-pin  C  is  adjustable  by  means  of  a
screw  d  giving   the   pump-plungers    a  greater   or  less  stroke


APPLIED    TO   LOCKS.
453


according  to  the  fall  available.  The  wheel  is  only  intended
to  run  while  the  lock  is  in  use,  and  the  pipes  are  provided  with
a  relief-valve,  adjusted  to  the  desired  pressure,  for  wasting  the
superfluous  water.  One  of  the  rods  c  is  rigidly  fastened  to  the
disk,  the  rest  are  jointed.  The  discernmg  reader  will  see  that
the  device  would  not  operate  if  all  the  rods  were  jointed,  neither


j'' — iV- — >!


Fig.  212.
