﻿MANUAL 
  OF 
  FISH-CULTURE. 
  

  

  41 
  

  

  of 
  the* 
  lateral 
  compartments, 
  and 
  filters 
  tlironoh 
  the 
  gravel 
  into 
  the 
  

   opposite, 
  compartment, 
  from 
  Avhich 
  it 
  is 
  taken 
  by 
  a 
  plank 
  aqueduct, 
  6 
  

   by 
  6 
  inches, 
  to 
  the 
  hatchery. 
  Under 
  the 
  conditions 
  described, 
  and 
  with 
  

   a 
  fall 
  of 
  about 
  1 
  foot 
  from 
  supply 
  to 
  discharge, 
  this 
  filter 
  discharges 
  

   over 
  300 
  gallons 
  of 
  water 
  per 
  minute 
  into 
  the 
  aqueduct 
  — 
  water 
  not 
  abso- 
  

   lutely 
  pure, 
  but 
  suflBcieutly 
  free 
  from 
  coarse 
  dirt 
  for 
  the 
  purpose. 
  In 
  

   many 
  cases, 
  where 
  small 
  quantities 
  of 
  water 
  are 
  used, 
  it 
  is 
  customary 
  to 
  

   filter 
  through 
  flannel 
  screens 
  in 
  the 
  hatchery, 
  and 
  such 
  filters 
  do 
  very 
  

   good 
  service. 
  They 
  can 
  be 
  introduced 
  into 
  the 
  egg-troughs, 
  or 
  by 
  

   running 
  them 
  lengthwise 
  of 
  a 
  trough 
  a 
  very 
  large 
  volume 
  of 
  water 
  can 
  

   be 
  filtered. 
  

  

  Gravel 
  Filter. 
  

  

  /(, 
  a. 
  .single 
  long 
  compartment 
  for 
  filtered 
  water. 
  

   i,j, 
  racks 
  to 
  bold 
  gravel 
  in 
  place. 
  

   i 
  is 
  in 
  5 
  sections, 
  movable, 
  and 
  can 
  be 
  taken 
  out 
  

   wben 
  gravel 
  is 
  to 
  be 
  renewed. 
  

   k, 
  I, 
  sluices 
  near 
  liottom 
  for 
  cleaning 
  out. 
  

   m, 
  wasteway. 
  

   /i, 
  aqueduct 
  to 
  batcbery. 
  

  

  a, 
  conduit 
  from 
  brook. 
  

  

  b, 
  gate, 
  swinging 
  on 
  ])ivot 
  at 
  c, 
  to 
  cbange 
  

  

  direction 
  of 
  water. 
  

   d, 
  direct 
  brancb 
  of 
  conduit. 
  

  

  c, 
  reverse 
  brancb 
  of 
  conduit. 
  

   /,/, 
  *'<■•! 
  * 
  single 
  long 
  compartment 
  for 
  unfiltered 
  

  

  water. 
  

   (j,g,etc., 
  compartments 
  occupied 
  by 
  gravel. 
  

  

  A 
  form 
  of 
  filter 
  that 
  has 
  given 
  good 
  satisfaction 
  at 
  the 
  Craig 
  Brook 
  

   station 
  through 
  five 
  years 
  of 
  service 
  consists 
  in 
  a 
  series 
  of 
  graduated 
  

   wire 
  screens, 
  through 
  which 
  the 
  water 
  passes 
  upward, 
  first 
  through 
  

   the 
  coarser, 
  and 
  then 
  through 
  the 
  finer 
  screens, 
  with 
  provision 
  for 
  the 
  

   reversal 
  of 
  the 
  current 
  for 
  cleaning 
  purposes. 
  By 
  reference 
  to 
  the 
  

   above 
  plan 
  and 
  section, 
  it 
  will 
  be 
  seen 
  that 
  the 
  water 
  is 
  brought 
  to 
  

   the 
  filter 
  through 
  a 
  plank 
  conduit, 
  and 
  is 
  admitted 
  to 
  the 
  filter 
  through 
  

   either 
  of 
  two 
  gates 
  that 
  swing 
  on 
  hinges, 
  one 
  for 
  the 
  direct 
  flow 
  and 
  

   the 
  other 
  for 
  the 
  reversal. 
  The 
  direct 
  flow 
  is 
  first 
  into 
  a 
  receiving 
  

   chamber, 
  which 
  extends 
  under 
  the 
  screens, 
  then 
  upward 
  through 
  the 
  

   whole 
  series 
  and 
  out 
  at 
  the 
  top, 
  overflowing 
  into 
  a 
  catch-trough, 
  from 
  

   which 
  it 
  is 
  distributed 
  as 
  desired. 
  In 
  cleansing, 
  the 
  supply 
  gate 
  is 
  

   closed 
  and 
  the 
  other 
  one 
  opened, 
  and 
  at 
  the 
  same 
  time 
  the 
  sluice-gate 
  

   at 
  the 
  bottom 
  is 
  opened 
  ; 
  the 
  water 
  then 
  flows 
  in 
  full 
  volume 
  upon 
  the 
  

   screens 
  and 
  down 
  through 
  them, 
  carrying 
  all 
  the 
  intercepted 
  debris 
  

   into 
  the 
  lower 
  chamber 
  and 
  out 
  through 
  the 
  sluice-gate. 
  

  

  