﻿40 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  communication 
  with 
  the 
  water 
  beneath 
  the 
  tray, 
  though 
  of 
  course 
  the 
  

   circulation 
  of 
  the 
  water 
  through 
  the 
  tray 
  is 
  not 
  perfect. 
  It 
  is 
  not, 
  

   therefore, 
  deemed 
  necessary 
  to 
  introduce 
  any 
  considerable 
  devices 
  for 
  

   filtering 
  water 
  which 
  is 
  naturally 
  very 
  pure, 
  like 
  lake 
  and 
  spring 
  water 
  

   when 
  not 
  subject 
  to 
  intermixture 
  with 
  surface 
  water 
  during 
  rains; 
  but 
  

   where 
  it 
  is 
  necessary 
  to 
  use 
  water 
  subject 
  to 
  constant 
  or 
  occasional 
  

   turbidness 
  some 
  method 
  of 
  filtering 
  is 
  indispensable. 
  

  

  In 
  the 
  majority 
  of 
  cases 
  at 
  least 
  a 
  portion 
  of 
  the 
  water 
  supply 
  is 
  

   obtained 
  from 
  an 
  open 
  brook, 
  lake, 
  or 
  pond, 
  and 
  measures 
  must 
  be 
  taken 
  

   to 
  get 
  rid 
  of 
  the 
  leaves 
  and 
  other 
  coarse 
  rubbish 
  brought 
  down 
  by 
  the 
  

   stream 
  or 
  conduit. 
  A 
  great 
  deal 
  of 
  such 
  material 
  is 
  encountered 
  in 
  a 
  

   stream 
  at 
  all 
  seasons, 
  but 
  during 
  fall 
  and 
  early 
  winter 
  it 
  is 
  especially 
  

   abundant, 
  and 
  to 
  secure 
  entire 
  safety 
  from 
  a 
  stoppage 
  of 
  the 
  water, 
  and 
  

   consequent 
  loss, 
  a 
  screen 
  on 
  a 
  generous 
  scale 
  must 
  be 
  provided. 
  

  

  A 
  description 
  of 
  the 
  means 
  adopted 
  at 
  this 
  station 
  for 
  providing 
  a 
  

   temporary 
  extra 
  water 
  service 
  of 
  several 
  hundred 
  gallons 
  per 
  minute, 
  

   taken 
  from 
  Craig 
  Brook, 
  will 
  serve 
  as 
  an 
  illustration 
  : 
  A 
  tank 
  or 
  vat, 
  

   12 
  feet 
  square 
  and 
  about 
  2 
  feet 
  deep, 
  is 
  built 
  in 
  the 
  bed 
  of 
  the 
  brook 
  

   with 
  a 
  tight 
  dam 
  of 
  stones, 
  gravel, 
  loam, 
  and 
  leaves 
  (these 
  to 
  stop 
  

   small 
  leaks) 
  running 
  ashore 
  on 
  either 
  side, 
  so 
  that 
  the 
  entire 
  volume 
  of 
  

   the 
  brook 
  passes 
  over 
  the 
  tank. 
  The 
  bottom 
  and 
  sides 
  are 
  tight 
  and 
  

   strong, 
  and 
  both 
  bottom 
  and 
  top 
  are 
  inclined 
  about 
  6 
  inches 
  down 
  the 
  

   stream. 
  The 
  cover 
  is 
  of 
  spruce 
  lumber 
  sawed 
  1^ 
  inches 
  square, 
  and 
  

   nailed 
  on 
  in 
  the 
  direction 
  of 
  the 
  current, 
  with 
  interstices 
  open 
  half 
  an 
  

   inch; 
  when 
  in 
  operation 
  the 
  water 
  fills 
  the 
  tank 
  and 
  runs 
  over 
  the 
  lower 
  

   edge, 
  which 
  is 
  raised 
  enough 
  to 
  maintain 
  a 
  depth 
  of 
  several 
  inches 
  over 
  

   nearly 
  the 
  whole 
  tank. 
  All 
  leaves 
  and 
  other 
  materials 
  floating 
  near 
  the 
  

   surface 
  of 
  the 
  water 
  are 
  carried 
  over, 
  together 
  with 
  most 
  rubbish 
  which 
  

   floats 
  deep. 
  At 
  one 
  of 
  the 
  lower 
  corners 
  of 
  the 
  tank, 
  near 
  the 
  bottom, 
  

   is 
  a 
  gate 
  about 
  15 
  inches 
  square, 
  which 
  is 
  hung 
  by 
  hinges 
  on 
  its 
  upper 
  

   side. 
  It 
  opens 
  inward, 
  and 
  is 
  closed 
  tightly 
  by 
  the 
  pressure 
  of 
  the 
  

   water 
  ; 
  but 
  it 
  can 
  be 
  easily 
  opened 
  by 
  pushing 
  with 
  a 
  pole 
  from 
  without, 
  

   and 
  then 
  serves 
  as 
  a 
  floodgate, 
  whereby 
  the 
  tank 
  may 
  be 
  thoroughly 
  

   cleaned 
  out. 
  

  

  At 
  the 
  other 
  lower 
  corner 
  is 
  a 
  conduit, 
  G 
  by 
  9 
  inches, 
  which 
  takes 
  

   from 
  this 
  "leaf-screen" 
  a 
  supply 
  of 
  water 
  not 
  entirely 
  free 
  from 
  rubbish, 
  

   but 
  so 
  nearly 
  so 
  that 
  a 
  filter 
  of 
  moderate 
  capacity 
  can 
  cope 
  with 
  what 
  

   remains. 
  A 
  very 
  useful 
  adjunct 
  would 
  be 
  a 
  second 
  horizontal 
  screen 
  

   of 
  similar 
  construction, 
  through 
  which 
  the 
  water 
  that 
  has 
  passed 
  down- 
  

   w^ard 
  through 
  the 
  first 
  screen, 
  as 
  described, 
  should 
  next 
  pass 
  upward 
  

   through 
  the 
  second; 
  the 
  first 
  screen 
  would 
  remove 
  floating 
  debris, 
  the 
  

   second 
  such 
  as 
  is 
  heavier 
  than 
  water. 
  

  

  The 
  filter, 
  situated 
  about 
  70 
  feet 
  from 
  the 
  leaf-screen, 
  consists 
  of 
  a 
  

   wooden 
  flume, 
  12 
  feet 
  long 
  and 
  4 
  feet 
  deep, 
  divided 
  lengthwise 
  into 
  three 
  

   compartments, 
  of 
  which 
  the 
  central 
  contains 
  fine 
  gravel 
  held 
  in 
  place 
  

   by 
  a 
  rack 
  on 
  either 
  hand, 
  of 
  which 
  the 
  interstices 
  are 
  ^ 
  inch 
  wide 
  and 
  

   IJ 
  inches 
  apart. 
  The 
  water 
  from 
  the 
  leaf-screen 
  is 
  introduced 
  into 
  one 
  

  

  