﻿17 
  2 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  ties 
  above 
  the 
  third 
  critical 
  point. 
  Such 
  observations 
  

   made 
  in 
  clear 
  water 
  offer 
  no 
  evidence 
  at 
  all 
  as 
  to 
  the 
  con- 
  

   ditions 
  existing 
  with 
  high 
  velocities. 
  

  

  5. 
  Wave-length 
  and 
  amplitude. 
  — 
  Table 
  4 
  gives 
  a 
  num- 
  

   ber 
  of 
  measurements 
  of 
  wave-length 
  and 
  amplitude 
  of 
  

   progressive 
  sand-waves. 
  

  

  Hider 
  states 
  that 
  wave-length, 
  amplitude, 
  and 
  rate 
  of 
  

   motion 
  of 
  the 
  sand- 
  waves 
  are 
  dependent 
  upon 
  " 
  their 
  

   location 
  with 
  reference 
  to 
  their 
  distance 
  from 
  the 
  thread 
  

   of 
  the 
  main 
  current, 
  being 
  greatest 
  at 
  high 
  water 
  

   and 
  decreasing 
  in 
  height 
  and 
  size 
  as 
  a 
  lower 
  stage 
  is 
  

   reached." 
  24 
  In 
  other 
  words: 
  Wave-length 
  and 
  ampli- 
  

   tude 
  change 
  with 
  the 
  velocity 
  of 
  the 
  current, 
  and 
  in 
  the 
  

   same 
  sense. 
  The 
  reversibility 
  of 
  the 
  process 
  is 
  due 
  to 
  

   the 
  fact 
  that 
  every 
  pronounced 
  change 
  of 
  the 
  stage 
  of 
  the 
  

   river 
  destroys 
  the 
  existing 
  set 
  of 
  sand-waves 
  and 
  gives 
  

   rise 
  to 
  new 
  ones. 
  At 
  a 
  rapid 
  change 
  from 
  a 
  lower 
  to 
  a 
  

   higher 
  stage, 
  much 
  of 
  the 
  sediment 
  making 
  up 
  the 
  waves 
  

   is 
  thrown 
  into 
  suspension 
  obliterating 
  the 
  original 
  wave 
  

   form, 
  while 
  "if 
  the 
  fall 
  in 
  stage 
  is 
  rapid 
  and 
  long-con- 
  

   tinued, 
  the 
  waves, 
  which 
  appeared 
  at 
  the 
  higher 
  stage, 
  

   become 
  covered 
  up 
  and 
  a 
  new 
  series 
  of 
  waves 
  of 
  similar 
  

   dimensions 
  corresponding 
  to 
  the 
  lower 
  stage 
  and 
  the 
  

   decreased 
  velocity 
  of 
  the 
  current 
  are 
  formed" 
  (Hider, 
  p. 
  

   2195). 
  

  

  The 
  wave-length 
  increases 
  very 
  much 
  faster 
  than 
  the 
  

   velocity. 
  This 
  fact 
  and 
  its 
  probable 
  causes 
  are 
  discussed 
  

   onpp/177 
  ff. 
  

  

  C. 
  Large 
  Ripples 
  exposed 
  after 
  high 
  water 
  along 
  Rivers 
  and 
  on 
  

  

  Tidal 
  flats. 
  

   1. 
  Along 
  rivers. 
  

  

  After 
  high 
  water 
  the 
  sandbars 
  in 
  all 
  rivers 
  and 
  creeks 
  

   exhibit 
  large 
  ripples 
  in 
  great 
  variety. 
  

  

  1. 
  Ground 
  plan. 
  — 
  In 
  ground 
  plan 
  their 
  crests 
  are 
  

   1 
  ' 
  smooth 
  curves 
  which 
  are 
  frequently 
  parallel 
  for 
  several 
  

   waves 
  in 
  succession" 
  (Ockerson 
  p. 
  2571), 
  trending 
  at 
  

   righl 
  angles 
  to 
  the 
  Gurrent. 
  

  

  All 
  I 
  have 
  seen 
  showed 
  a 
  tendency 
  to 
  break 
  up 
  along 
  

   the 
  strike 
  into 
  a 
  number 
  of 
  more 
  or 
  less 
  curved 
  crescent- 
  

   shaped 
  parts, 
  separated 
  by 
  a 
  short 
  distance 
  of 
  smooth 
  

   sand. 
  In 
  general, 
  the 
  larger 
  the 
  sand-wave 
  is, 
  the 
  more 
  

   uniform 
  is 
  it 
  in 
  its 
  entire 
  length. 
  

  

  u 
  lUd., 
  p. 
  2196; 
  Johnson, 
  1879, 
  p. 
  1966. 
  

  

  