﻿164 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  6. 
  Linguoid 
  current-ripples. 
  1G 
  

  

  A 
  peculiar 
  form 
  of 
  current-ripples, 
  resulting 
  from 
  a 
  

   transformation 
  of 
  the 
  common 
  type, 
  was 
  described 
  by 
  

   Blasius 
  (1910). 
  In 
  Ms 
  experiments, 
  each 
  current-ripple, 
  

   regular 
  at 
  first, 
  was 
  broken 
  up 
  into 
  a 
  series 
  of 
  alternating 
  

   small 
  "sandbanks" 
  and 
  hollows. 
  

  

  Each 
  "sandbank" 
  has 
  the 
  shape 
  of 
  a 
  tongue 
  or 
  

   shingle 
  with 
  a 
  notch 
  somewhere 
  near 
  the 
  center. 
  The 
  

   "tongues" 
  of 
  one 
  row 
  lie 
  opposite 
  the 
  lines 
  of 
  contact 
  

   of 
  those 
  of 
  the 
  preceding 
  and 
  following 
  rows. 
  The 
  points 
  

   of 
  deepest 
  excavation 
  are 
  not 
  located 
  right 
  behind 
  the 
  

   highest 
  crest 
  of 
  each 
  tongue, 
  but 
  opposite 
  the 
  line 
  of 
  con- 
  

   tact 
  of 
  two 
  adjoining 
  ones. 
  Upstream 
  of 
  each 
  such 
  deep 
  

   hollow, 
  in 
  the 
  angle 
  between 
  the 
  sides 
  of 
  two 
  adjoining 
  

   tongues, 
  is 
  found 
  a 
  flat 
  triangular 
  area, 
  which 
  in 
  height 
  

   stands 
  half 
  way 
  between 
  the 
  top 
  of 
  the 
  crest 
  and 
  the 
  

   bottom 
  of 
  the 
  hollow. 
  The 
  actual 
  form 
  of 
  the 
  ripples 
  as 
  

   seen 
  in 
  nature 
  is 
  much 
  more 
  irregular 
  and 
  often 
  deviates 
  

   widely 
  from 
  this 
  ideal 
  form 
  (cf. 
  fig. 
  2). 
  For 
  this 
  form 
  

   of 
  current-ripples 
  I 
  suggest 
  the 
  name 
  linguoid 
  (current-) 
  

   ripples. 
  

  

  The 
  essential 
  feature 
  of 
  these 
  linguoid 
  ripples 
  is 
  the 
  

   fact 
  that 
  they 
  present 
  a 
  complication 
  of 
  the 
  flow 
  lines 
  in 
  

   the 
  horizontal 
  in 
  addition 
  to 
  that 
  of 
  the 
  vertical 
  plane. 
  

   Fig. 
  1 
  represents 
  Blasius' 
  ideal 
  map 
  reconstruction 
  of 
  

   such 
  ripples 
  in 
  contour 
  lines 
  with 
  the 
  corresponding 
  flow- 
  

   lines, 
  which 
  are 
  characteristically 
  sinuous. 
  Blasius 
  

   interprets 
  the 
  transformation 
  of 
  the 
  straight 
  flow-lines 
  

   into 
  this 
  pattern 
  of 
  sinuous 
  lines 
  as 
  a 
  direct 
  analogy 
  to 
  

   the 
  well-known 
  law, 
  17 
  according 
  to 
  which 
  water 
  laden 
  with 
  

   sediment 
  and 
  flowing 
  in 
  a 
  straight 
  channel, 
  will 
  soon 
  

   change 
  its 
  straight 
  direction 
  of 
  flow 
  and 
  the 
  uniform 
  

   transportation 
  into 
  a 
  sinous 
  line 
  of 
  flow 
  with 
  erosion 
  on 
  

   the 
  outer 
  and 
  deposition 
  on 
  the 
  inner 
  sides 
  of 
  the 
  curves 
  

   on 
  alternating 
  sides 
  of 
  the 
  channel. 
  

  

  With 
  the 
  scanty 
  data 
  at 
  hand 
  it 
  is 
  impossible 
  to 
  define 
  

   the 
  conditions 
  that 
  lead 
  to 
  this 
  transformation 
  of 
  cur- 
  

   rent-ripples. 
  Linguoid 
  ripples 
  seem, 
  however, 
  confined 
  

   to 
  sandbanks 
  and 
  shores 
  of 
  rivers 
  and 
  tidal 
  flats, 
  where 
  

   the 
  water-level 
  underwent 
  a 
  rapid 
  change 
  leading 
  to 
  com- 
  

   plete 
  exposure. 
  In 
  such 
  situations 
  they 
  are 
  very 
  com- 
  

   mon. 
  

  

  Good 
  illustrations 
  : 
  Kindle, 
  1917, 
  pi. 
  16, 
  17, 
  33 
  (fossil). 
  

   27 
  Handbuch 
  d. 
  Ingen. 
  Wiss., 
  pt. 
  3, 
  vol. 
  1, 
  p. 
  350. 
  

  

  