﻿38 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  of 
  underinining 
  or 
  washing 
  out 
  the 
  ends 
  of 
  the 
  dam, 
  it 
  is 
  best 
  not 
  to 
  

   undertake 
  to 
  raise 
  a 
  great 
  head 
  in 
  this 
  way. 
  With 
  any 
  bottom 
  except 
  

   one 
  of 
  solid 
  ledge 
  there 
  is 
  always 
  great 
  danger, 
  and 
  to 
  guard 
  against 
  

   it 
  when 
  the 
  dam 
  is 
  more 
  than 
  2 
  feet 
  high 
  may 
  be 
  very 
  troublesome. 
  If 
  

   there 
  is 
  a 
  scarcity 
  of 
  water, 
  or 
  if 
  it 
  is 
  desirable, 
  for 
  aerating 
  or 
  other 
  

   purposes, 
  to 
  secure 
  a 
  considerable 
  fall, 
  it 
  is 
  better 
  to 
  construct 
  the 
  dam 
  

   at 
  some 
  distance 
  above 
  the 
  hatching-house, 
  on 
  higher 
  ground, 
  where 
  a 
  

   vfery 
  low 
  dam 
  will 
  suffice 
  to 
  turn 
  the 
  water 
  into 
  a 
  conduit 
  which 
  will 
  

   lead 
  it 
  into 
  the 
  hatching 
  house 
  at 
  the 
  desired 
  height. 
  

  

  A 
  square 
  conduit 
  made 
  of 
  boards 
  or 
  planks, 
  carefully 
  jointed 
  and 
  

   nailed, 
  is 
  in 
  nearly 
  all 
  cases 
  perfectly 
  satisfactory, 
  and 
  for 
  an 
  ordinary 
  

   establishment 
  a 
  very 
  small 
  one 
  will 
  suffice. 
  

  

  The 
  volume 
  of 
  water 
  that 
  will 
  flow 
  through 
  a 
  pipe 
  of 
  a 
  given 
  form 
  

   depends 
  upon 
  its 
  size 
  and 
  the 
  inclination 
  at 
  which 
  it 
  is 
  laid. 
  A 
  straight 
  

   cylindrical 
  pipe, 
  1 
  inch 
  in 
  diameter, 
  inclined 
  1 
  foot 
  in 
  10, 
  conveys 
  about 
  

   11 
  gallons 
  of 
  water 
  per 
  minute. 
  The 
  same 
  pipe, 
  with 
  an 
  inclination 
  

   of 
  1 
  in 
  20, 
  conveys 
  8 
  gallons 
  per 
  minute; 
  with 
  an 
  inclination 
  of 
  1 
  in 
  

   100, 
  it 
  conveys 
  3i 
  gallons 
  per 
  minute; 
  with 
  an 
  inclination 
  of 
  1 
  in 
  1,000, 
  

   it 
  conveys 
  1 
  gallon 
  per 
  minute. 
  A 
  2-inch 
  pipe 
  conveys 
  about 
  5^ 
  times 
  

   as 
  much 
  water 
  as 
  an 
  inch 
  pipe; 
  a 
  3-inch 
  pipe 
  nearly 
  15 
  times 
  as 
  much. 
  

   A 
  1-inch 
  pipe, 
  with 
  an 
  inclination 
  of 
  1 
  in 
  1,000, 
  conveys 
  water 
  enough 
  

   for 
  hatching 
  25,000 
  eggs; 
  with 
  an 
  inclination 
  of 
  1 
  in 
  50, 
  enough 
  for 
  

   100,000 
  eggs; 
  with 
  an 
  inclination 
  of 
  1 
  in 
  20, 
  enough 
  for 
  nearly 
  200,000 
  

   eggs. 
  A 
  square 
  conduit 
  conveys 
  one-quarter 
  more 
  water 
  than 
  a 
  cylin- 
  

   drical 
  pipe 
  of 
  the 
  same 
  diameter. 
  If 
  there 
  are 
  any 
  angles 
  or 
  abrupt 
  

   bends 
  in 
  the 
  pipe, 
  its 
  capacity 
  will 
  be 
  considerably 
  reduced. 
  It 
  should 
  

   be 
  remembered 
  that 
  if 
  the 
  water 
  completely 
  fills 
  the 
  aqueduct 
  it 
  is 
  

   entirely 
  shut 
  out 
  from 
  contact 
  with 
  the 
  air 
  during 
  its 
  passage, 
  whereas 
  

   if 
  the 
  pii)e 
  is 
  larger 
  than 
  the 
  water 
  can 
  fill, 
  the 
  remainder 
  of 
  the 
  space 
  

   will 
  be 
  occupied 
  by 
  air, 
  of 
  which 
  the 
  water, 
  rushing 
  down 
  the 
  incline, 
  

   will 
  absorb 
  a 
  considerable 
  volume 
  and 
  be 
  greatly 
  improved. 
  It 
  is 
  

   therefore 
  much 
  better 
  to 
  make 
  the 
  conduit 
  twice 
  or 
  thrice 
  the 
  size 
  

   demanded 
  by 
  the 
  required 
  volume 
  of 
  water. 
  If 
  the 
  bottom 
  and 
  sides 
  

   are 
  rough, 
  so 
  as 
  to 
  break 
  up 
  the 
  water, 
  so 
  much 
  the 
  better, 
  and 
  the 
  

   wider 
  the 
  conduit 
  is 
  the 
  more 
  surface 
  does 
  the 
  water 
  present 
  to 
  the 
  air. 
  

  

  AERATION. 
  

  

  The 
  water 
  which 
  fishes 
  breathe 
  is 
  but 
  the 
  medium 
  for 
  the 
  conveyance 
  

   of 
  air, 
  which 
  is 
  the 
  real 
  vivifying 
  agent, 
  without 
  which 
  fish 
  and 
  eggs 
  

   will 
  die, 
  and 
  with 
  a 
  scanty 
  supply 
  of 
  which 
  the 
  proper 
  development 
  of 
  

   the 
  growing 
  embryo 
  is 
  impossible. 
  Water 
  readily 
  absorbs 
  air 
  when- 
  

   ever 
  it 
  comes 
  in 
  contact 
  with 
  it, 
  and 
  the 
  more 
  intimate 
  and 
  the 
  longer 
  

   continued 
  the 
  contact 
  the 
  greater 
  the 
  volume 
  it 
  will 
  absorb. 
  The 
  ample 
  

   aeration 
  of 
  the 
  water 
  to 
  be 
  used 
  in 
  the 
  hatching-house 
  has 
  already 
  been 
  

   mentioned 
  as 
  a 
  desideratum 
  of 
  the 
  first 
  importance, 
  and 
  some 
  of 
  the 
  

   devices 
  by 
  which 
  it 
  is 
  to 
  be 
  secured 
  have 
  been 
  alluded 
  to. 
  

  

  Water 
  from 
  either 
  a 
  brook 
  or 
  a 
  river 
  that 
  has 
  been 
  torn 
  into 
  froth 
  by 
  

  

  