﻿190 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  3. 
  The 
  formation 
  of 
  oscillation 
  ripples. 
  

  

  A 
  comparison 
  of 
  pages 
  157 
  ff\ 
  and 
  188 
  f 
  . 
  of 
  this 
  paper 
  

   shows 
  the 
  perfect 
  identity 
  of 
  all 
  factors 
  entering 
  into 
  the 
  

   formation 
  of 
  oscillation- 
  and 
  current-ripples, 
  so 
  far 
  as 
  

   observed 
  in 
  nature 
  and 
  experiment. 
  We 
  are, 
  therefore, 
  

   justified 
  in 
  considering 
  the 
  oscillation-ripple 
  as 
  nothing 
  

   but 
  a 
  modification 
  of 
  the 
  current-ripple 
  resulting 
  from 
  

   the 
  reversal 
  of 
  the 
  current. 
  For 
  every 
  half 
  oscillation 
  

   the 
  relation 
  between 
  sediment 
  and 
  current 
  is 
  that 
  exist- 
  

   ing 
  in 
  current-ripples. 
  The 
  reversal 
  of 
  the 
  current 
  com- 
  

   plicates 
  the 
  process, 
  but 
  it 
  does 
  not 
  change 
  its 
  nature. 
  

  

  IV. 
  Complex 
  Ripple 
  Patterns. 
  

  

  Once 
  formed, 
  all 
  ripples 
  may 
  be 
  subject 
  to 
  tranforma- 
  

   tion, 
  in 
  the 
  course 
  of 
  which 
  one 
  type 
  may 
  be 
  changed 
  into 
  

   another 
  or 
  entirely 
  new 
  compound 
  patterns 
  produced. 
  

  

  1. 
  Transformation 
  of 
  one 
  type 
  into 
  another. 
  

   Meta-ripples 
  may 
  be 
  reshaped 
  by 
  waves 
  acting 
  in 
  the 
  

  

  same 
  direction 
  as 
  the 
  preceding 
  current; 
  their 
  surface 
  

   material 
  is 
  assorted 
  and 
  a 
  sharp 
  crest 
  49 
  placed 
  in 
  the 
  

   center 
  of 
  the 
  originally 
  broad, 
  round 
  ridges. 
  If 
  small 
  

   current 
  and 
  oscillation-ripples 
  are 
  in 
  this 
  way 
  trans- 
  

   formed 
  one 
  into 
  the 
  other, 
  there 
  is 
  nothing 
  to 
  indicate 
  the 
  

   change. 
  Oscillation-ripples 
  are 
  extremely 
  sensitive 
  even 
  

   to 
  very 
  gentle 
  current 
  action, 
  as 
  shown 
  by 
  Kindle 
  's 
  obser- 
  

   vations 
  (1917, 
  p. 
  31). 
  

  

  2. 
  Oscillation 
  cross-ripples. 
  

  

  A 
  special 
  form 
  of 
  compound 
  rippling, 
  to 
  which 
  the 
  term 
  

   "interference-ripples" 
  or 
  "cross-ripples" 
  should 
  be 
  

   limited, 
  consists 
  of 
  polygonal, 
  usually 
  more 
  or 
  less 
  

   irregular 
  pits, 
  arranged 
  side 
  by 
  side 
  like 
  stones 
  in 
  a 
  

   mosaic. 
  50 
  Two 
  fundamental 
  types 
  can 
  be 
  distinguished, 
  

   the 
  " 
  rectangular' 
  ' 
  and 
  the 
  "hexagonal" 
  type, 
  which 
  

   usually 
  occur 
  together 
  and 
  rarely 
  show 
  their 
  pure 
  form. 
  

   Both 
  consist 
  of 
  parallel 
  ridges 
  connected 
  by 
  crossbars. 
  

   In 
  the 
  hexagonal 
  type 
  the 
  crests 
  of 
  the 
  parallel 
  ridges 
  

   zigzag, 
  forming 
  obtuse 
  angles 
  which 
  in 
  adjoining 
  crests 
  

   face 
  in 
  opposite 
  directions 
  with 
  crossbars 
  connecting 
  the 
  

  

  40 
  Analogous 
  to 
  that 
  shown 
  on 
  a 
  sand 
  ridge 
  of 
  different 
  origin 
  on 
  the 
  beach 
  

   of 
  Lake 
  Ontario 
  in 
  fig. 
  10, 
  pi. 
  5, 
  American 
  Geologist 
  (Fairchild, 
  1901). 
  

   60 
  Kindle, 
  1914; 
  1917, 
  pp. 
  34-36. 
  

  

  