﻿262 
  

  

  Backer 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  appears 
  very 
  doubtful, 
  as 
  was 
  pointed 
  out 
  in 
  Part 
  I 
  

   (March 
  No.), 
  whether 
  ripples 
  of 
  this 
  size 
  can 
  form 
  at 
  all 
  

   through 
  the 
  action 
  of 
  waves 
  alone. 
  All 
  experimental 
  

   and 
  observational 
  evidence 
  seems 
  to 
  speak 
  against 
  it. 
  

  

  In 
  the 
  course 
  of 
  a 
  discussion 
  the 
  objection 
  was 
  raised 
  

   that 
  a 
  current 
  should 
  be 
  expected 
  to 
  "cut 
  through 
  the 
  

  

  Fig. 
  13. 
  

  

  Fig. 
  13. 
  Para-ripples 
  on 
  limestone 
  in 
  the 
  Bichmond 
  group, 
  Blue 
  Bank 
  

   Creek, 
  above 
  Goddard, 
  Fleming 
  Co., 
  Ky. 
  (See 
  table 
  VI.) 
  

  

  Note 
  that 
  the 
  para-ripples 
  cover 
  undulations 
  of 
  a 
  higher 
  order 
  of 
  

   magnitude, 
  four 
  of 
  which 
  are 
  seen 
  in 
  the 
  figure 
  (Nos. 
  1-4). 
  The 
  hammer 
  

   rests 
  on 
  the 
  second 
  one. 
  

  

  rippled 
  layer 
  into 
  the 
  underlying 
  sediment" 
  in 
  places, 
  

   while 
  no 
  such 
  case 
  is 
  known 
  at 
  present. 
  This 
  should 
  be 
  

   indeed 
  the 
  case 
  if 
  there 
  existed 
  local 
  differences 
  in 
  veloc- 
  

   ity 
  or 
  depth 
  of 
  the 
  current. 
  We 
  have, 
  however, 
  in 
  Part 
  

   I 
  endeavored 
  to 
  show 
  that 
  the 
  establishment 
  of 
  ripples 
  

   at 
  the 
  contact 
  of 
  sediment 
  and 
  water 
  serves 
  the 
  very 
  pur- 
  

   pose 
  to 
  eliminate 
  any 
  such 
  irregular, 
  local 
  differences 
  and 
  

   to 
  replace 
  them 
  by 
  a 
  uniform 
  system 
  of 
  flow-lines. 
  

  

  These 
  large 
  current-ripples 
  agree 
  in 
  most 
  points 
  with 
  

  

  