﻿XOVIl 
  

  

  surface 
  below 
  the 
  water 
  level 
  — 
  the 
  purpose 
  being 
  to 
  in- 
  

   sure 
  them 
  against 
  being 
  clogged 
  by 
  the 
  piling 
  up 
  of 
  

   successive 
  layers 
  of 
  drift, 
  which 
  otherwise 
  would 
  inevi- 
  

   tably 
  be 
  occasioned 
  by 
  the 
  gradual 
  rise 
  of 
  the 
  water 
  

   consequent 
  upon 
  its 
  obstructed 
  flow. 
  The 
  arrangement 
  

   suggested 
  will 
  always 
  afford 
  a 
  free 
  exit 
  to 
  the 
  water 
  

   beneath 
  the 
  mass 
  of 
  accumulated 
  floating 
  rubbish. 
  

  

  The 
  general 
  details 
  of 
  outlet, 
  A, 
  are 
  clearly 
  indica- 
  

   ted 
  in 
  the 
  views 
  given. 
  The 
  screens 
  .<^. 
  .v. 
  s. 
  — 
  as 
  well 
  

   as 
  those 
  of 
  the 
  ' 
  'overflow'' 
  — 
  are 
  disposed 
  in 
  a 
  suita- 
  

   ble 
  frame 
  work, 
  and 
  should 
  slide 
  easily 
  in 
  tlieir 
  re- 
  

   spective 
  grooves, 
  so 
  that 
  they 
  may 
  be 
  readily 
  removed, 
  

   cleaned 
  and 
  replaced. 
  An 
  additional 
  set 
  of 
  such 
  grooves 
  

   are 
  provided 
  at 
  this 
  outlet, 
  as 
  will 
  be 
  seen 
  by 
  reference 
  

   to 
  the 
  plate 
  ; 
  and 
  these 
  latter, 
  which 
  are 
  innermost 
  in 
  

   point 
  of 
  position, 
  are 
  furnished, 
  instead 
  of 
  screens, 
  withi 
  

   solid 
  planks 
  g. 
  g. 
  g. 
  — 
  the 
  edges 
  of 
  which 
  are 
  neatly 
  fltted 
  

   to 
  each 
  other, 
  so 
  as 
  to 
  render 
  their 
  joints 
  water 
  tight, 
  or 
  

   as 
  nearly 
  so 
  as 
  possible. 
  The 
  upper 
  edge 
  of 
  each 
  plank, 
  

   again 
  is 
  provided 
  with 
  staples 
  or 
  eyes—;/, 
  f. 
  f. 
  — 
  through 
  

   which 
  the 
  hook, 
  Ji, 
  may 
  be 
  readily 
  passed 
  in 
  order 
  to 
  lift 
  

   the 
  plank 
  from 
  the 
  frame. 
  When 
  the 
  planks 
  are 
  in 
  posi- 
  

   tion 
  these 
  eyes 
  are 
  received 
  into 
  corresponding 
  slots, 
  n. 
  n., 
  

   in 
  the 
  lower 
  edge 
  of 
  the 
  planks 
  immediately 
  above 
  them, 
  

   so 
  as 
  to 
  allow 
  the 
  planks 
  to 
  flt 
  closely 
  together. 
  

  

  The 
  purpose 
  of 
  this 
  fourth, 
  and 
  solid, 
  screen 
  is 
  to 
  ena- 
  

   ble 
  the 
  culturist 
  to 
  lower 
  the 
  water 
  in 
  the 
  pond, 
  whenever 
  

   it 
  becomes 
  necessary 
  to 
  do 
  so, 
  by 
  drawing 
  it 
  from 
  either 
  

   the 
  surface 
  or 
  the 
  bottom, 
  as 
  may 
  be 
  deemed 
  most 
  advis- 
  

   able. 
  To 
  draw 
  it 
  from 
  the 
  surface 
  only, 
  it 
  will 
  simply 
  

   be 
  necessary 
  to 
  open 
  the 
  valve 
  c 
  ; 
  and 
  to 
  remove 
  the 
  

   planks 
  in 
  succession, 
  as 
  the 
  water 
  subsides. 
  While 
  to 
  

   draw 
  from 
  the 
  bottom 
  will 
  require 
  all 
  the 
  planks 
  to 
  be 
  

   first 
  removed 
  ; 
  and 
  the 
  valve 
  to 
  be 
  opened 
  when 
  this 
  has 
  

   been 
  done. 
  

  

  In 
  addition 
  to 
  the 
  valve 
  c, 
  the 
  drain-pipe, 
  P, 
  may 
  be 
  

   provided, 
  at 
  m.^ 
  with 
  a 
  clog 
  or 
  strainer, 
  to 
  guard 
  it 
  

  

  