﻿188 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  At 
  present 
  practically 
  no 
  data 
  comparing 
  amplitude 
  of 
  

   water 
  waves 
  and 
  wave-length 
  of 
  ripples 
  are 
  available. 
  

   A 
  collection 
  of 
  such 
  data 
  would 
  represent 
  a 
  distinct 
  con- 
  

   tribution 
  to 
  the 
  study 
  of 
  ripples. 
  4S 
  Merely 
  to 
  compare 
  

   water-waves 
  and 
  ripples 
  observed 
  at 
  the 
  same 
  time, 
  

   would, 
  however, 
  be 
  insufficient 
  according 
  to 
  Forel's 
  

   experiences 
  mentioned 
  above. 
  The 
  sand 
  should 
  be 
  

   smoothed 
  out 
  first 
  over 
  a. 
  considerable 
  area 
  and 
  the 
  

   formation 
  of 
  ripples 
  by 
  the 
  waves 
  should 
  be 
  observed. 
  

  

  (c.) 
  Forel's 
  experiments 
  and 
  observations 
  have 
  shown 
  

   conclusively 
  that 
  the 
  wave-length 
  diminishes 
  with 
  increas- 
  

   ing 
  depth 
  of 
  water. 
  The 
  most 
  beautiful 
  example 
  of 
  this 
  

   relation 
  is 
  offered 
  by 
  the 
  ripples 
  of 
  coral 
  sand 
  and 
  basalt 
  

   grains 
  off 
  the 
  island 
  of 
  Bourbon 
  in 
  the 
  Indian 
  Ocean 
  

   observed 
  by 
  Siau 
  (cf. 
  p. 
  184). 
  At 
  the 
  inlet 
  of 
  the 
  

   barrier 
  reef 
  he 
  observed 
  ripples 
  measuring 
  30-50 
  cm. 
  

   from 
  crest 
  to 
  crest. 
  Down 
  to 
  a 
  depth 
  of 
  20 
  m. 
  at 
  least, 
  

   the 
  black 
  troughs 
  and 
  white 
  crests 
  could 
  be 
  distinguished 
  

   with 
  slowly 
  decreasing 
  wave-length. 
  By 
  means 
  of 
  the 
  

   sound 
  the 
  existence 
  of 
  these 
  ripples 
  was 
  shown 
  down 
  to 
  

   a 
  depth 
  of 
  188 
  m. 
  The 
  wave-length 
  had 
  decreased 
  so 
  

   much 
  that 
  both 
  crest 
  and 
  hollow 
  were 
  found 
  impressed 
  

   on 
  the 
  grease-covered 
  bottom 
  of 
  the 
  sound. 
  

  

  This 
  decrease 
  is, 
  of 
  course, 
  due 
  to 
  the 
  reduction 
  of 
  cur- 
  

   rent-velocity 
  with 
  increasing 
  depth, 
  and 
  therefore 
  in 
  

   reality 
  nothing 
  but 
  a 
  special 
  case 
  of 
  (b.). 
  

  

  It 
  should 
  be 
  noted, 
  however, 
  that 
  with 
  relatively 
  strong 
  

   waves 
  "for 
  moderate 
  depths 
  the 
  size 
  of 
  ripples 
  is 
  not 
  

   very 
  sensitive 
  to 
  variation 
  of 
  water 
  depth,' 
  ' 
  as 
  observed 
  

   by 
  Gilbert 
  on 
  the 
  bed 
  of 
  Lake 
  Ontario 
  (1899, 
  p. 
  138). 
  

  

  In 
  a 
  series 
  of 
  observations 
  (1917, 
  p. 
  26) 
  made 
  along 
  

   the 
  shore 
  of 
  Lake 
  Ontario, 
  near 
  Wellington, 
  Ontario, 
  

   Kindle 
  found 
  a 
  regular 
  increase 
  of 
  the 
  wave-length 
  with 
  

   depth. 
  He 
  found 
  in 
  water 
  : 
  

  

  Les 
  

  

  >s 
  than 
  

  

  % 
  ft. 
  

  

  deep 
  ripples 
  

  

  1-2 
  in. 
  

  

  long 
  

  

  in 
  

  

  water 
  

  

  1% 
  " 
  

  

  i 
  i 
  

  

  i 
  i 
  

  

  2-4 
  " 
  

  

  c 
  1 
  

  

  < 
  i 
  

  

  i 
  i 
  

  

  21/2 
  " 
  

  

  < 
  1 
  

  

  ( 
  i 
  

  

  3i/ 
  2 
  -4 
  " 
  

  

  1 
  i 
  

  

  1 
  1 
  

  

  i 
  i 
  

  

  10 
  " 
  

  

  1 
  1 
  

  

  i 
  i 
  

  

  4-6 
  " 
  

  

  c 
  ( 
  

  

  i 
  c 
  

  

  1 
  1 
  

  

  11 
  " 
  

  

  t 
  c 
  

  

  i 
  c 
  

  

  41/2 
  " 
  

  

  a 
  

  

  i 
  ( 
  

  

  1 
  1 
  

  

  20 
  " 
  

  

  t 
  i 
  

  

  1 
  1 
  

  

  ^5 
  " 
  

  

  a 
  

  

  ^ 
  The 
  only 
  observation 
  of 
  this 
  kind 
  that 
  has 
  come 
  to 
  my 
  notice 
  is 
  that 
  by 
  

   Stuchlik, 
  which 
  shows 
  the 
  wave-length 
  of 
  the 
  ripple 
  equalling 
  one 
  half 
  of 
  

   the 
  amplitude 
  of 
  the 
  wave 
  under 
  the 
  conditions 
  given 
  in 
  Table 
  V. 
  Cf. 
  

   Gilbert's 
  statement 
  (1899, 
  p. 
  138) 
  "that 
  at 
  the 
  most 
  the 
  ripple-marks 
  are 
  

   only 
  half 
  as 
  broad 
  as 
  the 
  waves 
  rolling 
  above 
  them 
  are 
  high. 
  " 
  

  

  