﻿ACADEMY 
  OF 
  SCIENCES. 
  295 
  

  

  The 
  trunk 
  dock 
  connecting 
  the 
  outer 
  end 
  of 
  the 
  trunk 
  with 
  the 
  river 
  should 
  

   be 
  wider 
  than 
  the 
  sluice-box, 
  so 
  as 
  to 
  allow 
  the 
  free 
  egress 
  of 
  the 
  water, 
  and 
  

   should 
  also 
  be 
  deeper 
  than 
  low 
  tide. 
  

  

  The 
  flood-gates 
  now 
  being 
  in 
  place, 
  we 
  can 
  proceed 
  to 
  build 
  the 
  

  

  Levee. 
  — 
  The 
  materials 
  of 
  which 
  the 
  embankment 
  is 
  to 
  be 
  constructed 
  will 
  

   govern 
  in 
  a 
  great 
  measure 
  the 
  other 
  requisites 
  to 
  be 
  attended 
  to 
  in 
  its 
  forma- 
  

   tion. 
  

  

  These 
  materials 
  differ 
  essentially 
  on 
  the 
  San 
  Joaquin 
  and 
  Sacramento 
  Rivers 
  

   in 
  different 
  localities. 
  On 
  the 
  San 
  Joaquin, 
  we 
  generally 
  find 
  a 
  sod 
  or 
  turf 
  of 
  a 
  

   peaty 
  formation, 
  which 
  shrinks 
  when 
  dry 
  about 
  one-third, 
  becomes 
  very 
  light, 
  

   and 
  can 
  either 
  be 
  burnt 
  up 
  or 
  floated 
  away 
  ; 
  while 
  on 
  the 
  Sacramento 
  it 
  is 
  com- 
  

   posed 
  of 
  two 
  kinds. 
  In 
  some 
  places 
  the 
  turf 
  has 
  a 
  sedimentary 
  deposit 
  of 
  clay, 
  

   which 
  makes 
  it 
  firmer, 
  heavier, 
  and 
  not 
  so 
  liable 
  to 
  burn. 
  In 
  other 
  places, 
  the 
  

   banks 
  of 
  the 
  river 
  are 
  sandy, 
  which 
  is 
  the 
  most 
  difBcult 
  material 
  to 
  manage, 
  

   and 
  the 
  least 
  to 
  be 
  depended 
  on 
  ; 
  it 
  melts 
  away 
  like 
  sugar 
  in 
  water. 
  

  

  The 
  first 
  consideration 
  is 
  to 
  determine 
  the 
  height 
  of 
  the 
  levee 
  to 
  keep 
  out 
  the 
  

   ordinary 
  summer 
  freshets, 
  but 
  it 
  will 
  not 
  answer 
  to 
  have 
  the 
  levee 
  of 
  the 
  same 
  

   level, 
  for 
  in 
  certain 
  places 
  it 
  will 
  be 
  found 
  necessary 
  to 
  raise 
  it 
  ; 
  for 
  instance, 
  I 
  

   examined 
  the 
  water 
  marks 
  of 
  the 
  flood 
  of 
  '71 
  and 
  '72 
  on 
  trees 
  about 
  a 
  mile 
  

   apart 
  on 
  the 
  same 
  island, 
  where 
  the 
  bank 
  was 
  apparently 
  the 
  same 
  height 
  above 
  

   ordinary 
  tide, 
  and 
  found 
  a 
  difference 
  of 
  six 
  to 
  eight 
  inches, 
  which 
  was 
  caused 
  

   by 
  the 
  confluence 
  of 
  two 
  currents 
  backing 
  the 
  water 
  above. 
  

  

  Having 
  determined 
  the 
  height 
  that 
  you 
  wish 
  to 
  construct 
  your 
  levee, 
  add 
  at 
  

   least 
  one-fifth 
  for 
  shrinkage, 
  and 
  build 
  it 
  the 
  proper 
  height 
  at 
  once. 
  

  

  The 
  distance 
  from 
  the 
  ditch 
  to 
  the 
  inner 
  slope 
  of 
  the 
  levee 
  should 
  be 
  at 
  least 
  

   twelve 
  or 
  fifteen 
  feet, 
  and 
  from 
  the 
  outer 
  margin 
  to 
  the 
  river 
  not 
  less 
  than 
  

   thirty 
  feet, 
  and 
  in 
  some 
  cases 
  more 
  ; 
  but 
  it 
  will 
  depend 
  a 
  great 
  deal 
  on 
  the 
  for- 
  

   mation 
  of 
  the 
  bank, 
  exposure 
  to 
  currents 
  and 
  winds. 
  

  

  The 
  inner 
  slope 
  should 
  be 
  1)^ 
  to 
  1 
  ; 
  and 
  the 
  outer 
  slope 
  not 
  less 
  than 
  3 
  to 
  1 
  ; 
  

   or 
  follow 
  nature 
  as 
  far 
  as 
  possible, 
  as 
  the 
  downward 
  pressure 
  of 
  the 
  water 
  will 
  

   assist 
  to 
  keep 
  the 
  levee 
  in 
  place, 
  and 
  the 
  broader 
  the 
  base 
  will 
  enable 
  it 
  to 
  re- 
  

   sist 
  the 
  inward 
  pressure, 
  which, 
  with 
  a 
  flood 
  of 
  five 
  feet 
  on 
  the 
  levee, 
  will 
  equal 
  

   453^ 
  tons 
  on 
  every 
  hundred 
  feet 
  in 
  length, 
  without 
  allowing 
  for 
  the 
  force 
  of 
  the 
  

   current 
  or 
  wind. 
  

  

  While 
  the 
  levee 
  is 
  yet 
  wet, 
  sow 
  mesquit 
  or 
  bermuda 
  grass 
  seeds 
  on 
  it, 
  either 
  

   of 
  which 
  will 
  form 
  a 
  good 
  sod 
  to 
  protect 
  and 
  bind 
  the 
  levee 
  together 
  and 
  pre- 
  

   vent 
  it 
  from 
  cracking 
  ; 
  also, 
  would 
  form 
  a 
  good 
  pasture 
  for 
  a 
  few 
  sheep 
  or 
  

   Angora 
  goats. 
  

  

  Care 
  should 
  be 
  exercised 
  in 
  running 
  ditches 
  into 
  the 
  interior 
  ; 
  first, 
  the 
  ground 
  

   should 
  be 
  examined 
  that 
  you 
  do 
  not 
  cut 
  through 
  float 
  land, 
  second, 
  to 
  ascertain 
  

   the 
  level 
  ; 
  for 
  I 
  have 
  known 
  a 
  contract 
  let 
  to 
  Chinamen 
  to 
  dig 
  a 
  ditch 
  three 
  feet 
  

   deep, 
  aud 
  when 
  completed 
  the 
  water 
  ran 
  back 
  and 
  flooded 
  the 
  low 
  land. 
  Unless 
  

   your 
  levees 
  and 
  flood 
  gates 
  are 
  properly 
  constructed 
  it 
  is 
  only 
  a 
  waste 
  of 
  money 
  

   to 
  attempt 
  reclamation. 
  

  

  I 
  would 
  strongly 
  urge 
  the 
  attention 
  of 
  the 
  farmers 
  in 
  our 
  swamp 
  lands 
  to 
  

  

  