﻿Related 
  Sedimentary 
  Surface 
  Forms. 
  195 
  

  

  of 
  the 
  current 
  is 
  sufficiently 
  weak 
  and 
  only 
  of 
  very 
  short 
  

   duration. 
  As 
  there 
  is 
  no 
  oscillation 
  of 
  the 
  current, 
  there 
  

   is 
  no 
  reason 
  for 
  a 
  transformation 
  into 
  the 
  hexagonal 
  

   pattern, 
  and 
  the 
  two 
  sets 
  of 
  ripples 
  may 
  be 
  found 
  inter- 
  

   secting 
  at 
  any 
  angle. 
  (Rectangular 
  and 
  diagonal 
  pat- 
  

   terns.) 
  Menzel 
  54 
  observed 
  the 
  formation 
  of 
  cross-ripples 
  

   of 
  this 
  type 
  by 
  a 
  single 
  wave 
  on 
  the 
  sloping 
  beach 
  of 
  the 
  

   summer 
  resort 
  Gross-Moellen 
  on 
  the 
  Baltic. 
  A 
  wave 
  of 
  

   translation, 
  rushing 
  up 
  the 
  slope 
  in 
  an 
  oblique 
  direction, 
  

   produced 
  relatively 
  large 
  current-ripples, 
  while 
  the 
  

   water, 
  in 
  flowing 
  back 
  down 
  the 
  slope, 
  gave 
  rise 
  to 
  a 
  

   large 
  number 
  of 
  smaller 
  ripples 
  which 
  intersected 
  with 
  

   the 
  first 
  ones 
  at 
  angles 
  ranging 
  from 
  ninety 
  down 
  to 
  few 
  

   degrees. 
  

  

  It 
  seems 
  doubtful 
  if 
  there 
  is 
  any 
  other 
  current 
  suffi- 
  

   ciently 
  weak 
  and 
  of 
  short 
  duration 
  to 
  produce 
  this 
  effect, 
  

   unless 
  it 
  is 
  a 
  very 
  weak 
  wind-drift. 
  55 
  

  

  4. 
  Compound 
  ripples.™ 
  

  

  A 
  great 
  variety 
  of 
  forms 
  of 
  complex 
  rippling 
  owe 
  their 
  

   origin 
  to 
  the 
  simultaneous 
  interference 
  of 
  wave-oscilla- 
  

   tion 
  with 
  current 
  action. 
  All 
  seem 
  to 
  be 
  characterized 
  

   by 
  a 
  systematic 
  breaking 
  or 
  offsetting 
  of 
  the 
  crests 
  of 
  

   the 
  current-ripples. 
  A 
  systematic 
  discussion 
  of 
  these 
  

   forms, 
  to 
  which 
  the 
  term 
  "compound 
  ripples" 
  might 
  

   well 
  be 
  applied, 
  is 
  impossible 
  at 
  the 
  present 
  time, 
  since 
  

   practically 
  no 
  observations 
  are 
  available 
  of 
  the 
  factors 
  

   entering 
  into 
  their 
  formation, 
  or 
  even 
  of 
  the 
  forms 
  them- 
  

   selves. 
  

  

  V. 
  Eolian 
  Ripples 
  and 
  Dunes. 
  

  

  ^ 
  Although 
  this 
  paper 
  deals 
  primarily 
  with 
  subaqueous 
  

   ripples, 
  a 
  discussion 
  of 
  the 
  principles 
  underlying 
  their 
  

   formation 
  would 
  be 
  very 
  unsatisfactory 
  if 
  it 
  were 
  not 
  put 
  

   on 
  a 
  broader 
  basis. 
  In 
  extending 
  the 
  discussion 
  to 
  eolian 
  

   ripples 
  and 
  dunes, 
  I 
  limit 
  myself 
  to 
  the 
  presentation 
  of 
  

   such 
  facts 
  as 
  have 
  a 
  direct 
  bearing 
  on 
  the 
  question 
  to 
  

  

  "Menzel, 
  H., 
  Monatsber. 
  Zs. 
  Deutsch. 
  Geol. 
  Ges., 
  vol. 
  61, 
  p. 
  69-70 
  (1 
  

   figure), 
  1909; 
  see 
  also: 
  Dammer, 
  B., 
  ibid., 
  p. 
  66-69; 
  Schucht, 
  F., 
  p. 
  217- 
  

   218; 
  Menzel, 
  H., 
  ibid., 
  p. 
  427-430; 
  Strasser, 
  E., 
  Bericht. 
  42, 
  Vers. 
  Oberr- 
  

   hein. 
  Geol. 
  Ver., 
  1909, 
  p. 
  124 
  ff. 
  

  

  55 
  The 
  specimen 
  from 
  the 
  Berea 
  s.s., 
  Berea, 
  Ohio, 
  figured 
  on 
  pi. 
  26 
  of 
  

   Kindle, 
  1917, 
  probably 
  should 
  be 
  explained 
  this 
  way. 
  (Note 
  especially 
  the 
  

   rounding 
  of 
  the 
  crests 
  of 
  the 
  symmetrical 
  ripples.) 
  

  

  56 
  For 
  illustrations, 
  see 
  Kindle, 
  1917, 
  pi. 
  14, 
  15, 
  28, 
  29. 
  See 
  also 
  p. 
  174, 
  

   the 
  effect 
  of 
  a 
  gale 
  on 
  tidal 
  meta-ripples. 
  

  

  