﻿Verrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  327 
  

  

  depth 
  is 
  from 
  50 
  to 
  80 
  feet 
  or 
  more.* 
  Some 
  of 
  the 
  narrow 
  

   passages 
  in 
  the 
  outer 
  reefs 
  have 
  similar 
  depths. 
  They 
  are 
  now 
  

   apparently 
  filling 
  up 
  by 
  the 
  accumulation 
  of 
  the 
  shell-sands 
  on 
  

   the 
  bottom. 
  This 
  must 
  certainly 
  be 
  the 
  case 
  in 
  Harrington 
  

   Sound 
  and 
  Great 
  Sound, 
  where 
  there 
  are 
  not 
  sufficient 
  tidal 
  

   currents 
  or 
  storm 
  waves 
  to 
  carry 
  away 
  even 
  fine 
  mud. 
  In 
  fact, 
  

   everywhere 
  over 
  the 
  bottoms 
  of 
  the 
  enclosed 
  sounds 
  the 
  

   accumulations 
  of 
  recent 
  soft 
  calcareous 
  shell-sand 
  and 
  mud 
  is 
  

   far 
  in 
  excess 
  of 
  the 
  amount 
  carried 
  away 
  mechanically 
  and 
  by 
  

   solution 
  combined. 
  Possibly 
  the 
  currents 
  may 
  be 
  sufficient, 
  in 
  

   the 
  main 
  ship 
  channel, 
  to 
  carry 
  away 
  the 
  detritus 
  and 
  prevent 
  

   filling 
  up 
  rapidly, 
  but 
  they 
  are 
  not 
  sufficient 
  to 
  effect 
  erosion 
  

   of 
  the 
  bottom. 
  

  

  Therefore 
  it 
  is 
  reasonable 
  to 
  conclude 
  that 
  all 
  such 
  depres- 
  

   sions 
  give 
  evidence 
  of 
  former 
  erosion 
  above 
  the 
  sea 
  and 
  conse- 
  

   quently 
  of 
  later 
  submergence 
  to 
  the 
  extent 
  of 
  their 
  greatest 
  

   depth 
  or 
  more. 
  

  

  These 
  sunken 
  areas, 
  within 
  the 
  outer 
  reef, 
  are 
  identical 
  in 
  

   character 
  and 
  depth 
  with 
  Harrington 
  Sound, 
  which 
  they 
  often 
  

   exceed 
  in 
  size. 
  The 
  latter 
  has 
  also 
  a 
  deep 
  subterranean 
  outlet 
  

   into 
  Castle 
  Harbor, 
  besides 
  its 
  shallow 
  outlet 
  at 
  Flat's 
  Village. 
  

   Were 
  the 
  high 
  ridges 
  around 
  Harrington 
  Sound 
  eroded 
  to 
  the 
  

   level 
  of 
  the 
  reefs, 
  it 
  would 
  agree 
  in 
  every 
  way 
  with 
  such 
  areas 
  

   as 
  II, 
  III, 
  or 
  "V, 
  except 
  that 
  it 
  is 
  rather 
  deeper. 
  

  

  The 
  bottom 
  outside 
  the 
  outer 
  reefs 
  is 
  covered 
  with 
  rough 
  

   ledges 
  or 
  broken 
  masses 
  of 
  limestone 
  to 
  the 
  depth 
  of 
  150 
  feet 
  

   or 
  more, 
  and 
  the 
  slope 
  is 
  gradual 
  to 
  300 
  feet 
  or 
  more. 
  This 
  

   zone 
  represents, 
  most 
  likely, 
  the 
  shore 
  ledges, 
  beaches, 
  and 
  

   shallow 
  waters 
  of 
  Greater 
  Bermuda. 
  If 
  so 
  this 
  zone 
  of 
  rough 
  

   bottom 
  would 
  indicate 
  a 
  submergence 
  of 
  at 
  least 
  150 
  feet, 
  

   which 
  is 
  by 
  no 
  means 
  improbable. 
  

  

  The 
  present 
  very 
  uneven 
  surfaces 
  of 
  Argus 
  and 
  Challenger 
  

   Banks 
  are 
  like 
  those 
  of 
  Bermuda, 
  and 
  indicate 
  erosion 
  when 
  

   they 
  stood 
  above 
  sea-level. 
  Some 
  considerable 
  parts 
  of 
  their 
  

   summits 
  are 
  now 
  180 
  to 
  240 
  feet 
  beneath 
  the 
  sea 
  ; 
  other 
  parts 
  

   (Argus 
  Bank) 
  are 
  only 
  8 
  feet. 
  Erosion 
  by 
  waves 
  on 
  such 
  

   sunken 
  banks 
  would 
  be 
  a 
  levelling 
  process 
  and 
  does 
  not 
  extend, 
  

   even 
  in 
  great 
  storms, 
  with 
  noticeable 
  effect, 
  more 
  than 
  120 
  

   feet 
  below 
  the 
  sea-level, 
  f 
  Hence 
  it 
  is 
  probable 
  that 
  they 
  have 
  

   subsided 
  at 
  least 
  240 
  feet 
  since 
  they 
  were 
  eroded. 
  

  

  * 
  The 
  most 
  important 
  of 
  these 
  are 
  represented 
  on 
  the 
  map 
  (Fig. 
  1) 
  by 
  the 
  

   areas 
  shaded 
  with 
  coarser 
  parallel 
  lines 
  (I-VI). 
  The 
  deep 
  narrow 
  passages 
  lead- 
  

   ing 
  out 
  from 
  these 
  and 
  sometimes 
  (as 
  at 
  X) 
  running 
  under 
  the 
  reefs, 
  are 
  num- 
  

   bered 
  VII- 
  XV. 
  

  

  f 
  George's 
  Bank 
  and 
  Nantucket 
  Shoals, 
  off 
  Cape 
  Cod, 
  maintain 
  themselves 
  in 
  

   the 
  face 
  of 
  the 
  most 
  violent 
  storms. 
  Although 
  composed 
  only 
  of 
  loose 
  sand 
  and 
  

   gravel, 
  their 
  shallowest 
  parts 
  rise 
  to 
  within 
  25 
  to 
  30 
  feet 
  of 
  the 
  sea-level. 
  This 
  

   indicates 
  that 
  the 
  abrading 
  action 
  of 
  the 
  waves 
  decreases 
  very 
  rapidly 
  even 
  at 
  

   such 
  depths. 
  

  

  