﻿16 
  WATER-POWER 
  DEVELOPMENT 
  IN 
  THE 
  MISSISSIPPI. 
  

  

  waters 
  above. 
  The 
  tail-race 
  will 
  always 
  be 
  comparatively 
  free 
  from 
  

   drift 
  or 
  ice, 
  which 
  must 
  be 
  screened 
  out 
  above 
  for 
  protection 
  of 
  the 
  

   turbines. 
  It 
  will 
  not 
  be 
  strictly 
  free 
  of 
  drift 
  below 
  the 
  power 
  house 
  

   on 
  account 
  of 
  there 
  being 
  in 
  the 
  lower 
  end 
  of 
  the 
  power 
  house 
  a 
  

   small 
  spillway, 
  or 
  chute, 
  through 
  which 
  drift 
  that 
  has 
  entered 
  the 
  

   head-bay 
  may 
  be 
  shunted 
  to 
  the 
  tail-race 
  below. 
  Close 
  to 
  this 
  chute 
  

   but 
  just 
  without 
  the 
  west 
  power-house 
  wall, 
  is 
  another 
  small 
  spill- 
  

   way 
  for 
  shunting 
  the 
  drift 
  which 
  may 
  collect 
  in 
  the 
  region 
  of 
  the 
  

   lock. 
  

  

  THE 
  LOCK. 
  

  

  The 
  lock 
  was 
  an 
  essential 
  requirement 
  of 
  the 
  Government 
  in 
  

   order 
  to 
  provide 
  for 
  the 
  necessities 
  of 
  navigation. 
  It 
  is 
  of 
  pax'ticular 
  

   interest 
  also 
  since 
  it 
  is 
  the 
  only 
  passageway 
  by 
  which 
  it 
  is 
  supposed 
  

   fish 
  may 
  pass 
  from 
  the 
  lower 
  river 
  to 
  the 
  upper. 
  The 
  lock, 
  built 
  by 
  

   the 
  proprietors 
  of 
  the 
  dam 
  and 
  deeded 
  to 
  the 
  Government, 
  is 
  located 
  

   below 
  the 
  power 
  house 
  and 
  inshore 
  from 
  it, 
  the 
  upper 
  eastern 
  corner 
  

   of 
  the 
  lock 
  being 
  connected 
  with 
  the 
  lower 
  western 
  corner 
  of 
  the 
  

   power 
  house 
  by 
  a 
  short 
  section 
  of 
  dam 
  provided 
  with 
  narrow 
  spill- 
  

   ways, 
  as 
  before 
  mentioned. 
  (PL 
  i.) 
  The 
  lock 
  is 
  110 
  feet 
  wide 
  and 
  

   400 
  feet 
  long 
  inside 
  and 
  has 
  a 
  maximum 
  lift 
  of 
  40 
  feet. 
  The 
  time 
  

   required 
  for 
  locking 
  a 
  boat 
  tlirough 
  is 
  about 
  15 
  minutes. 
  For 
  such 
  

   a 
  great 
  hft 
  in 
  so 
  large 
  a 
  lock 
  to 
  be 
  accomplished 
  in 
  so 
  short 
  a 
  time 
  

   requires 
  a 
  most 
  eflScient 
  and 
  special 
  arrangement 
  for 
  filling 
  and 
  

   emptying 
  the 
  lock. 
  

  

  The 
  bottom 
  of 
  the 
  lock 
  (which 
  is 
  8 
  feet 
  below 
  the 
  water 
  level 
  at 
  

   the 
  lowest 
  stage 
  of 
  the 
  river) 
  is 
  a 
  gridiron 
  of 
  culverts, 
  the 
  mains 
  

   being 
  under 
  the 
  bottom 
  of 
  the 
  walls 
  running 
  lengthwise 
  of 
  the 
  lock, 
  

   and 
  the 
  crossbars 
  of 
  the 
  gridiron 
  being 
  culverts 
  crossing 
  the 
  lock 
  

   floor 
  at 
  intervals. 
  The 
  largest 
  of 
  these 
  culverts 
  are 
  13 
  feet 
  in 
  diameter 
  

   and 
  the 
  smallest 
  are 
  6 
  feet 
  in 
  diameter. 
  The 
  culverts 
  are 
  cast 
  of 
  

   concrete 
  around 
  steel 
  lining. 
  The 
  angles 
  in 
  them 
  are 
  so 
  sharp 
  

   and 
  the 
  water 
  pressure 
  and 
  velocity 
  wiU 
  be 
  so 
  great 
  that 
  the 
  friction 
  

   of 
  the 
  water 
  against 
  the 
  concrete 
  would 
  wear 
  the 
  latter 
  if 
  it 
  were 
  

   not 
  protected 
  with 
  steel. 
  The 
  outlet 
  ends 
  of 
  the 
  culverts 
  discharge 
  

   on 
  the 
  side 
  of 
  the 
  lock 
  at 
  right 
  angles 
  to 
  the 
  course 
  of 
  the 
  river. 
  

  

  By 
  adjustment 
  of 
  a 
  series 
  of 
  valves 
  the 
  water 
  in 
  the 
  lock 
  is 
  permitted 
  

   to 
  run 
  out 
  into 
  the 
  river 
  through 
  the 
  culverts. 
  After 
  the 
  boat 
  has 
  

   entered 
  and 
  the 
  gates 
  are 
  closed, 
  the 
  culvert 
  valves 
  of 
  the 
  iiUing 
  

   system 
  will 
  be 
  opened, 
  the 
  water 
  from 
  the 
  higher 
  level 
  of 
  the 
  fore 
  

   bay 
  will 
  rush 
  through 
  the 
  culverts 
  entering 
  the 
  lock 
  chambers 
  tlu-ough 
  

   fifty-seven 
  3-foot 
  culvert 
  openings 
  until 
  the 
  level 
  within 
  the 
  lock 
  is 
  

   the 
  same 
  as 
  that 
  of 
  the 
  fore 
  bay, 
  the 
  boat 
  being 
  lifted 
  40 
  feet 
  

   vertically 
  within 
  a 
  few 
  minutes. 
  (PI. 
  vi.) 
  As 
  soon 
  as 
  the 
  upper 
  

   gate 
  is 
  submerged 
  the 
  boat 
  may 
  pass 
  out 
  and 
  continue 
  its 
  course 
  

   through 
  the 
  deep 
  water 
  of 
  the 
  bay 
  and 
  lake. 
  In 
  leaving 
  the 
  lock 
  

  

  