﻿Belated 
  Sedimentary 
  Surface 
  Forms. 
  

  

  205 
  

  

  resembling 
  in 
  shape 
  and 
  arrangement 
  the 
  rhomboidal 
  

   ripples 
  described 
  on 
  an 
  early 
  page. 
  The 
  bottom 
  of 
  each 
  

   rhomb 
  rises 
  from 
  its 
  lowest 
  point 
  in 
  one 
  acute 
  angle 
  to 
  

   its 
  crest 
  in 
  the 
  opposite 
  angle, 
  from 
  which 
  along 
  the 
  

   adjoining 
  two 
  sides 
  there 
  is 
  a 
  sudden 
  drop 
  to 
  the 
  bottom 
  

   of 
  the 
  next 
  pit. 
  The 
  gentle 
  slope 
  faces 
  upstream^ 
  the 
  

   steep 
  one 
  downstream. 
  It 
  seems, 
  as 
  though 
  the 
  combined 
  

   action 
  of 
  corrosion 
  and 
  corrasion 
  had 
  led 
  to 
  the 
  establish- 
  

   ment 
  of 
  that 
  surface 
  form, 
  which 
  we 
  infer 
  from 
  the 
  obser- 
  

   vations 
  on 
  similar 
  sand-ripples 
  to 
  offer 
  a 
  minimum 
  of 
  

   friction. 
  

  

  Fig. 
  10. 
  

  

  Fig. 
  10. 
  Specimen 
  of 
  white, 
  fine-grained 
  limestone 
  from 
  the 
  bottom 
  of 
  a 
  

   stream 
  in 
  White's 
  Cave, 
  near 
  Burkville, 
  Mo. 
  The 
  steep 
  sides 
  face 
  with 
  the 
  

   current. 
  

  

  This 
  rhomboidal 
  pattern 
  of 
  ripples 
  represents 
  a 
  nota- 
  

   ble 
  deviation 
  from 
  the 
  ordinary 
  undulating 
  contact 
  sur- 
  

   faces 
  described, 
  in 
  that 
  the 
  crestlines 
  are 
  arranged 
  

   diagonally 
  to 
  the 
  direction 
  of 
  flow 
  of 
  the 
  water. 
  Diagonal 
  

   lines 
  are 
  also 
  introduced 
  along 
  the 
  sides 
  of 
  linguoid 
  rip- 
  

   ple 
  marks, 
  although 
  in 
  quite 
  a 
  different 
  way. 
  

  

  Blasius 
  called 
  attention 
  to 
  the 
  fact 
  that 
  the 
  distribu- 
  

   tion 
  of 
  sediment 
  with 
  reference 
  to 
  any 
  thread 
  of 
  water 
  

   passing 
  over 
  the 
  sides 
  of 
  linguoid-ripples 
  is 
  the 
  same 
  as 
  

   that 
  of 
  shoals 
  in 
  river 
  channels. 
  Most 
  textbooks 
  of 
  

  

  