﻿Related 
  Sedimentary 
  Surface 
  Forms. 
  267 
  

  

  storm. 
  In 
  Midbay, 
  at 
  a 
  depth 
  of 
  over 
  12 
  meters, 
  where 
  

   the 
  bottom 
  usually 
  is 
  a 
  soft 
  muddy 
  sand 
  that 
  clogs 
  the 
  

   dredge 
  in 
  a 
  few 
  minutes, 
  he 
  found 
  the 
  ground 
  hard, 
  pro- 
  

   ducing 
  "not 
  a 
  single 
  shell 
  or 
  a 
  particle 
  of 
  the 
  usual 
  

   muddy 
  sand. 
  " 
  Four 
  weeks 
  after 
  the 
  storm 
  "the 
  ground 
  

   was 
  still 
  very 
  hard, 
  both 
  the 
  dredge 
  and 
  a 
  fishing-lead 
  

   tied 
  to 
  a 
  line 
  bumping 
  along 
  as 
  though 
  over 
  ridges." 
  

   Over 
  six 
  weeks 
  after 
  the 
  gale 
  the 
  same 
  spot 
  had 
  returned 
  

   to 
  its 
  normal 
  state. 
  

  

  Similarly, 
  Cornish 
  (p. 
  175) 
  found 
  Pegwell 
  Bay 
  (Kent) 
  

   in 
  which 
  ordinarily 
  the 
  tide 
  never 
  produces 
  anything 
  but 
  

   small 
  current-ripples, 
  covered 
  with 
  large 
  tidal 
  ripples 
  

   after 
  a 
  heavy 
  gale 
  blowing 
  into 
  the 
  bay. 
  

  

  These 
  observations 
  indicate 
  that 
  the 
  drift 
  produced 
  by 
  

   periods 
  of 
  storms 
  may 
  so 
  strengthen 
  the 
  tidal 
  current 
  as 
  

   to 
  produce 
  large 
  current-ripples. 
  This 
  I 
  suggest 
  as 
  the 
  

   probable 
  origin 
  of 
  our 
  large 
  Eden 
  and 
  Richmond 
  ripples. 
  

  

  The 
  ripples 
  observed 
  by 
  Hunt 
  formed 
  at 
  a 
  depth 
  of 
  

   over 
  12 
  meters 
  with 
  a 
  tide 
  of 
  over 
  2 
  meters. 
  In 
  open 
  

   waters 
  the 
  range 
  of 
  the 
  tides 
  and 
  the 
  velocity 
  of 
  the 
  

   resulting 
  currents 
  would 
  be 
  much 
  smaller 
  than 
  in 
  the 
  

   channel. 
  With 
  gales 
  of 
  similar 
  strength, 
  therefore, 
  

   the 
  same 
  mechanical 
  effect 
  of 
  the 
  currents 
  would 
  be 
  possi- 
  

   ble 
  only 
  at 
  a 
  much 
  smaller 
  depth 
  of 
  water. 
  Allowing, 
  

   however, 
  for 
  extreme 
  conditions, 
  we 
  may 
  safely 
  say 
  that 
  

   our 
  Ordovician 
  ripples 
  probably 
  were 
  formed 
  in 
  water 
  

   less 
  than 
  25 
  meters 
  deep 
  rather 
  than 
  more. 
  The 
  Persian 
  

   Gulf 
  offers 
  an 
  interesting 
  analogy. 
  "With 
  an 
  area 
  of 
  about 
  

   90,000 
  square 
  miles, 
  it 
  has 
  a 
  mean 
  depth 
  of 
  but 
  25 
  

   meters. 
  64 
  The 
  tidal 
  range 
  along 
  all 
  its 
  shores 
  is 
  more 
  

   than 
  2 
  meters. 
  65 
  

  

  We 
  may 
  summarize 
  the 
  geographic 
  conditions 
  inferred 
  

   from 
  the 
  large 
  current-ripples 
  of 
  the 
  Upper 
  Ordovician 
  

   of 
  the 
  Cincinnati 
  Anticline 
  as 
  follows 
  : 
  

  

  1. 
  A 
  sea 
  having 
  sufficient 
  connection 
  with 
  the 
  open 
  

   ocean 
  to 
  allow 
  relatively 
  high 
  tides. 
  

  

  2. 
  Sufficient 
  area 
  to 
  permit 
  the 
  formation 
  of 
  strong 
  

   wind-drifts 
  in 
  most 
  directions 
  during 
  periods 
  of 
  storms. 
  

  

  3. 
  A 
  depth 
  small 
  enough 
  to 
  admit 
  of 
  a 
  strong 
  action 
  

   on 
  the 
  bottom 
  sediments 
  by 
  wind-drift 
  and 
  tidal 
  current 
  

   combined, 
  probably 
  25 
  meters 
  or 
  less 
  on 
  the 
  average. 
  

  

  4. 
  Atmospheric 
  conditions 
  providing 
  for 
  the 
  occur- 
  

   rence 
  of 
  storms, 
  blowing 
  from 
  all 
  points 
  of 
  the 
  compass, 
  

  

  G4 
  Supan, 
  A., 
  Grimdziige 
  der 
  physischen 
  Erdkunde, 
  1911, 
  p. 
  260. 
  

   ^Berghaus, 
  Atlas 
  der 
  Hydrographie, 
  1891, 
  pi. 
  XX. 
  

  

  