﻿246 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  deep. 
  They 
  might, 
  of 
  course, 
  have 
  formed 
  just 
  as 
  well 
  

   at 
  a 
  depth 
  of 
  100 
  meters 
  or 
  more. 
  12 
  

  

  The 
  range 
  of 
  depth 
  at 
  which 
  ripples 
  may 
  form 
  is, 
  on 
  

   the 
  other 
  hand, 
  limited 
  for 
  the 
  largest 
  ripples, 
  as 
  the 
  

   minimum 
  depth 
  is 
  rather 
  great 
  and 
  the 
  maximum 
  small. 
  

   From 
  the 
  scanty 
  data 
  in 
  table 
  V 
  the 
  former 
  seems 
  to 
  

   measure 
  a 
  few 
  meters, 
  while 
  the 
  maximum 
  depth 
  is 
  most 
  

   likely 
  to 
  lie 
  within 
  the 
  littoral 
  region 
  or 
  the 
  upper 
  40-50 
  m. 
  

   of 
  the 
  neritic 
  zone 
  of 
  the 
  oceans. 
  

  

  (b) 
  Owing 
  to 
  the 
  fact 
  that 
  the 
  largest 
  ripples 
  possible 
  

   in 
  one 
  locality 
  have 
  by 
  far 
  the 
  best 
  chance 
  to 
  be 
  preserved, 
  

   a 
  gradual 
  decrease 
  in 
  the 
  average 
  wave-length 
  of 
  ripples 
  

   of 
  a 
  sedimentary 
  series 
  should 
  be 
  expected 
  in 
  the 
  direc- 
  

   tion 
  towards 
  deeper 
  water. 
  The 
  absence 
  of 
  such 
  a 
  

   decrease 
  over 
  great 
  distance 
  offers 
  a 
  valuable 
  evidence 
  

   of 
  uniformity 
  of 
  depth. 
  

  

  (c) 
  The 
  depth 
  to 
  which 
  the 
  action 
  of 
  waves 
  is 
  felt, 
  that 
  

   is, 
  the 
  depth 
  of 
  the 
  wave-base, 
  depends 
  on 
  their 
  size, 
  and 
  

   this, 
  in 
  turn, 
  is 
  determined 
  largely 
  by 
  the 
  fetch 
  of 
  the 
  

   wind. 
  For 
  each 
  given 
  diameter 
  of 
  a 
  body 
  of 
  water 
  

   there 
  exists, 
  therefore, 
  a 
  maximum 
  depth 
  to 
  which 
  wave 
  

   action 
  may 
  extend. 
  For 
  the 
  ratio 
  of 
  depth 
  to 
  ividth 
  of 
  

   the 
  basin, 
  measured 
  along 
  any 
  line, 
  the 
  term 
  "form 
  

   ratio" 
  14 
  might 
  be 
  used. 
  For 
  each 
  basin 
  there 
  exists 
  a 
  

   minimum 
  and 
  a 
  maximum 
  form 
  ratio, 
  measured 
  along 
  the 
  

   shortest 
  and 
  the 
  longest 
  diameter. 
  If 
  the 
  latter 
  rises 
  

   above 
  a 
  certain 
  value, 
  which 
  is 
  different 
  for 
  different 
  

   widths, 
  a 
  part 
  of 
  the 
  bottom 
  will 
  never 
  be 
  touched 
  by 
  the 
  

   wave 
  action. 
  15 
  

  

  On 
  the 
  other 
  hand, 
  if 
  the 
  area 
  of 
  a 
  bay, 
  lagoon 
  or 
  lake 
  

   is 
  known 
  to 
  have 
  been 
  small, 
  the 
  possible 
  range 
  of 
  the 
  

   depth 
  at 
  which 
  the 
  largest 
  ripples 
  found 
  in 
  its 
  sediments 
  

   may 
  have 
  formed, 
  is 
  reduced 
  considerably. 
  

  

  Along 
  the 
  shores 
  of 
  the 
  small, 
  shallow 
  ponds 
  of 
  our 
  

   parks, 
  on 
  which 
  but 
  small 
  waves 
  can 
  form, 
  ripples 
  are 
  

  

  12 
  The 
  same 
  is 
  true, 
  for 
  instance, 
  of 
  small 
  ripples 
  observed 
  in 
  cannel 
  

   coal 
  (Upper 
  Stinson 
  coal) 
  in 
  Kentucky; 
  cf. 
  White 
  and 
  Thiessen, 
  The 
  

   origin 
  of 
  coal, 
  Bureau 
  of 
  Mines, 
  Bull. 
  38, 
  p. 
  42, 
  1913. 
  

  

  13 
  Note 
  omitted. 
  

  

  14 
  This 
  term 
  is 
  used 
  by 
  Gilbert 
  (1914, 
  p. 
  36) 
  for 
  the 
  ratio 
  of 
  the 
  depth 
  

   of 
  stream 
  to 
  the 
  width 
  of 
  channel. 
  

  

  15 
  Systematic 
  observations 
  on 
  the 
  vertical 
  distribution 
  of 
  oscillation- 
  

   ripples 
  on 
  carefully 
  selected 
  portions 
  of 
  the 
  bottoms 
  of 
  various 
  water 
  

   bodies, 
  might 
  yield 
  valuable 
  data 
  concerning 
  the 
  depth 
  of 
  wave-action, 
  

   especially 
  if 
  combined 
  with 
  extended 
  measurements 
  of 
  the 
  waves 
  themselves. 
  

   The 
  photographic 
  camera 
  could 
  probably 
  be 
  adapted 
  to 
  this 
  purpose 
  and 
  

   lateral 
  illumination 
  be 
  used 
  to 
  distinguish 
  oscillation-ripples. 
  

  

  