﻿530 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  the 
  top 
  of 
  the 
  pool 
  is 
  allowed 
  to 
  flow 
  into 
  the 
  head 
  of 
  the 
  irrigating 
  

   canal 
  ; 
  then 
  when 
  the 
  pool, 
  or 
  f 
  orebay, 
  is 
  partially 
  filled 
  by 
  the 
  silt 
  

   or 
  mud 
  the 
  large 
  gates 
  shown 
  at 
  the 
  right 
  of 
  the 
  picture 
  in 
  plate 
  9, 
  

   figure 
  1, 
  are 
  raised 
  and 
  the 
  mud 
  is 
  washed 
  downstream 
  in 
  a 
  few 
  

   minutes 
  ; 
  then 
  the 
  gates 
  can 
  be 
  lowered 
  and 
  the 
  mud 
  in 
  the 
  water 
  is 
  

   allowed 
  to 
  settle. 
  

  

  Another 
  engineering 
  device, 
  growing 
  out 
  of 
  the 
  necessity 
  of 
  con- 
  

   veying 
  water 
  through 
  or 
  across 
  rough 
  country, 
  is 
  illustrated 
  in 
  plate 
  

   9, 
  figure 
  2, 
  where 
  is 
  shown 
  the 
  iron 
  skeleton 
  or 
  reinforcement 
  of 
  

   concrete 
  pipes, 
  upward 
  of 
  7 
  feet 
  or 
  more 
  in 
  diameter. 
  These 
  can 
  

   be 
  built 
  across 
  depressions 
  or 
  around 
  irregular 
  hill 
  slopes, 
  and 
  when 
  

   completed 
  carry 
  large 
  volumes 
  of 
  water 
  under 
  moderate 
  pressure, 
  

   and 
  in 
  localities 
  where 
  it 
  would 
  appear 
  almost 
  impracticable 
  to 
  build 
  

   canals. 
  

  

  Another 
  kind 
  of 
  difficulty 
  which 
  has 
  given 
  great 
  concern 
  in 
  the 
  

   past, 
  but 
  which 
  has 
  been 
  overcome 
  in 
  reclamation 
  work, 
  has 
  been 
  

   the 
  development 
  of 
  a 
  machine 
  which 
  could 
  excavate 
  canals 
  in 
  soft 
  

   or 
  wet 
  ground 
  or 
  in 
  places 
  where 
  men 
  and 
  animals 
  could 
  hardly 
  

   work. 
  Such 
  machines 
  are 
  illustrated 
  in 
  plate 
  10. 
  A 
  drag-line 
  exca- 
  

   vator, 
  mounted 
  on 
  what 
  is 
  known 
  as 
  a 
  caterpillar 
  truck, 
  is 
  shown 
  in 
  

   plate 
  10, 
  figure 
  1. 
  This 
  machine 
  may 
  be 
  said 
  to 
  carry 
  its 
  own 
  rails 
  

   and 
  to 
  lay 
  these 
  down 
  and 
  pick 
  them 
  up 
  again 
  as 
  the 
  machine 
  pro- 
  

   ceeds. 
  Thus 
  it 
  can 
  move 
  through 
  wet 
  lands, 
  where 
  a 
  horse 
  would 
  

   be 
  mired, 
  and 
  can 
  dig 
  ditches 
  under 
  conditions 
  which 
  in 
  the 
  past 
  

   have 
  been 
  considered 
  almost 
  impossible. 
  

  

  Still 
  another 
  application 
  of 
  science 
  and 
  ingenuity, 
  overcoming 
  

   obstacles 
  which 
  have 
  long 
  interfered 
  with 
  reclamation 
  work, 
  is 
  shown 
  

   in 
  the 
  cleaning 
  out 
  and 
  maintaining 
  of 
  canals 
  for 
  irrigation 
  or 
  drain- 
  

   age 
  while 
  these 
  are 
  in 
  use. 
  For 
  many 
  years 
  it 
  was 
  considered 
  neces- 
  

   sary, 
  in 
  order 
  to 
  clean 
  an 
  irrigation 
  canal, 
  to 
  turn 
  out 
  the 
  water 
  and 
  

   let 
  the 
  bottom 
  of 
  the 
  ditch 
  become 
  dry, 
  so 
  that 
  horse-drawn 
  machines 
  

   could 
  be 
  used. 
  In 
  countries 
  where 
  weeds 
  and 
  aquatic 
  plants 
  grow 
  

   rapidly 
  this 
  turning 
  out 
  of 
  water 
  during 
  the 
  irrigation 
  season 
  has 
  

   resulted 
  in 
  serious 
  inconvenience 
  and 
  loss. 
  Now, 
  however, 
  the 
  prob- 
  

   lem 
  has 
  been 
  solved 
  (as 
  shown 
  by 
  pi. 
  10, 
  fig. 
  2) 
  by 
  a 
  machine 
  which 
  

   traverses 
  the 
  banks 
  of 
  the 
  canal 
  and 
  reaches 
  down, 
  digging 
  up 
  the 
  

   weeds 
  and 
  dirt, 
  depositing 
  the 
  material 
  on 
  the 
  side, 
  and 
  without 
  

   interfering 
  with 
  the 
  flow 
  of 
  the 
  water. 
  

  

  The 
  conclusion 
  of 
  the 
  matter 
  is 
  this 
  : 
  That 
  the 
  vision 
  of 
  benefits 
  to 
  

   the 
  individual 
  citizens 
  and 
  to 
  the 
  country 
  as 
  a 
  whole 
  has 
  been 
  shown 
  

   by 
  20 
  years 
  of 
  experience 
  to 
  be 
  a 
  true 
  vision. 
  The 
  ideals 
  of 
  the 
  

   advocates 
  of 
  reclamation 
  and 
  home 
  making 
  have 
  been 
  realized 
  in 
  

   part 
  ; 
  much 
  more 
  can 
  be 
  done 
  with 
  corresponding 
  benefits 
  to 
  all 
  parts 
  

   of 
  the 
  Nation 
  by 
  increasing 
  the 
  stability 
  of 
  governmental 
  and 
  busi- 
  

  

  