﻿170 
  Bucher 
  — 
  Origin 
  of 
  Ripples, 
  and 
  

  

  at 
  high 
  water 
  to 
  be 
  a 
  regular 
  gravel 
  stream 
  saturated 
  

   with 
  water, 
  being 
  in 
  motion 
  down 
  to 
  a 
  depth 
  of 
  over 
  3 
  m. 
  22 
  

  

  There 
  seems 
  to 
  be, 
  therefore, 
  the 
  same 
  gradation 
  of 
  

   motion 
  downward 
  from 
  the 
  surface 
  of 
  the 
  sediment 
  which 
  

   Gilbert 
  observed 
  in 
  his 
  "anti-dunes." 
  It 
  appears 
  

   highly 
  probable 
  that 
  it 
  is 
  connected 
  with 
  the 
  same 
  man- 
  

   ner 
  of 
  flow, 
  i. 
  e., 
  absence 
  of 
  vortices 
  and 
  parallelism 
  

   between 
  flow-lines 
  and 
  surface 
  of 
  the 
  sediment. 
  

  

  4. 
  Traveling. 
  — 
  The 
  large 
  sand-waves 
  of 
  rivers 
  travel 
  

   down-stream. 
  "The 
  heavier 
  material 
  23 
  finds 
  its 
  way 
  

   down-stream 
  by 
  being 
  pushed 
  or 
  rolled 
  up 
  the 
  flat 
  ante- 
  

   rior 
  slope 
  of 
  the 
  wave 
  by 
  the 
  action 
  of 
  the 
  current 
  and 
  

   dropped 
  over 
  the 
  crest 
  of 
  the 
  wave 
  where 
  it 
  remains 
  until 
  

   the 
  wave 
  has 
  progressed 
  far 
  enough 
  down- 
  stream 
  to 
  leave 
  

   it 
  again 
  exposed 
  to 
  the 
  action 
  of 
  the 
  current." 
  But 
  the 
  

   amount 
  of 
  material 
  transported 
  near 
  the 
  bottom 
  "as 
  

   measured 
  by 
  the 
  progression 
  of 
  the 
  waves, 
  as 
  shown 
  on 
  

   a 
  profile, 
  it 
  is 
  believed 
  represents 
  but 
  a 
  small 
  amount 
  of 
  

   the 
  material 
  actually 
  in 
  motion 
  along 
  the 
  bottom" 
  (ib., 
  

   p. 
  2199). 
  

  

  At 
  low 
  stages 
  of 
  the 
  river, 
  with 
  small 
  velocity 
  of 
  the 
  

   water, 
  such 
  sand-waves 
  can 
  be 
  seen 
  to 
  progress 
  slowly 
  

   after 
  the 
  manner 
  of 
  wind-dunes 
  or 
  current-ripples, 
  as 
  

   was 
  for 
  instance 
  described 
  by 
  Partiot. 
  He 
  refers 
  to 
  

   the 
  lee-side 
  of 
  such 
  sand-waves 
  as 
  the 
  "talus" 
  unto 
  

   which 
  the 
  sand 
  is 
  dropped 
  from 
  the 
  crest, 
  with 
  an 
  

   inclination 
  of 
  about 
  45 
  degrees, 
  in 
  strong 
  contrast 
  to 
  the 
  

   gentle 
  up-stream 
  side 
  (1871, 
  p. 
  270). 
  

  

  This 
  form, 
  however, 
  is 
  no 
  sand-wave 
  at 
  all 
  in 
  the 
  sense 
  

   in 
  which 
  the 
  term 
  is 
  used 
  here, 
  but 
  a 
  subaqueous 
  dune 
  

   and 
  is 
  obviously 
  the 
  result 
  of 
  a 
  transformation 
  of 
  a 
  sand- 
  

   wave. 
  That 
  this 
  dune-form 
  is 
  not 
  stable 
  at 
  higher 
  

   velocities 
  was 
  observed 
  by 
  Partiot 
  himself. 
  With 
  

   increasing 
  velocity 
  he 
  saw 
  the 
  sediment 
  carried 
  beyond 
  

   the 
  talus 
  on 
  the 
  lee-side 
  ; 
  the 
  crest 
  rapidly 
  was 
  reduced, 
  

   the 
  advance 
  was 
  greatly 
  retarded 
  or 
  the 
  "dune" 
  

   remained 
  stationary. 
  If 
  the 
  velocity 
  of 
  the 
  water 
  was 
  

   not 
  diminished 
  in 
  due 
  time, 
  the 
  "dune" 
  often 
  dis- 
  

   appeared 
  entirely. 
  

  

  This 
  shows 
  conclusively 
  that 
  the 
  dune-form 
  and, 
  prob- 
  

   ably, 
  the 
  dune 
  mode 
  of 
  progression 
  do 
  not 
  exist 
  at 
  veloci- 
  

  

  22 
  Pestalozzi, 
  Die 
  Geschiebsbewegung 
  und 
  das 
  natuerliche 
  Gefaelle 
  der 
  

   Gebirgsfluesse, 
  Prog, 
  eidgenoess. 
  polytechn. 
  Schule, 
  1878-1879, 
  Zurich, 
  p. 
  

   vi. 
  Quoted 
  from 
  Penck, 
  Morphologic 
  der 
  Erdoberflaeche, 
  1894, 
  vol. 
  1, 
  

   p. 
  284. 
  

  

  23 
  Coarse 
  sand, 
  gravel 
  and 
  small 
  bowlders, 
  Hider, 
  1883, 
  p. 
  2198. 
  

  

  