﻿318 
  Verrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  

  

  Aeolian 
  limestones, 
  with 
  strata 
  dipping 
  irregularly 
  in 
  all 
  

   directions 
  and 
  often 
  at 
  high 
  angles, 
  so 
  that 
  they 
  wear 
  away 
  on 
  

   the 
  coast 
  into 
  very 
  rough 
  and 
  rugged 
  forms. 
  Where 
  these 
  

   rocks, 
  along 
  the 
  shore 
  and 
  between 
  tides, 
  are 
  exposed 
  alter- 
  

   nately 
  to 
  the 
  sun 
  and 
  to 
  the 
  action 
  of 
  salt 
  spray, 
  they 
  become 
  

   deeply 
  pitted 
  and 
  honeycombed, 
  and 
  often 
  very 
  jagged, 
  while 
  

   the 
  surface 
  and 
  a 
  layer 
  beneath 
  become 
  very 
  hard 
  and 
  solid 
  

   by 
  the 
  infiltration 
  and 
  deposition 
  of 
  calcium 
  carbonate. 
  In 
  

   this 
  condition 
  these 
  rocks 
  often 
  give 
  a 
  ringing 
  sound, 
  when 
  

   struck 
  with 
  a 
  hammer, 
  and 
  are 
  resistant 
  to 
  erosion. 
  (Figs. 
  2, 
  3.) 
  

  

  My 
  attention 
  was 
  directed 
  more 
  particularly 
  towards 
  the 
  

   determination 
  of 
  the 
  precise 
  nature 
  and 
  mode 
  of 
  formation 
  of 
  

   the 
  white 
  calcareous 
  mud 
  and 
  sand 
  on 
  the 
  bottom 
  of 
  the 
  bays 
  

   and 
  lagoons, 
  and 
  of 
  the 
  beaches, 
  and 
  its 
  probable 
  rate 
  of 
  

   formation 
  ; 
  to 
  the 
  probable 
  rate 
  and 
  mode 
  of 
  erosion 
  of 
  the 
  

   cliffs 
  and 
  reefs 
  ; 
  to 
  the 
  rate 
  of 
  subaerial 
  erosion 
  and 
  formation 
  

   of 
  the 
  " 
  red 
  clay 
  " 
  soil 
  ; 
  to 
  the 
  evidence 
  of 
  former 
  elevation 
  

   and 
  subsidence 
  of 
  the 
  land 
  and 
  its 
  extent 
  ; 
  and 
  to 
  the 
  possibility 
  

   of 
  connecting 
  such 
  changes 
  with 
  corresponding 
  changes 
  on 
  the 
  

   American 
  coast 
  in 
  the 
  Glacial 
  and 
  Post-glacial 
  periods. 
  

  

  My 
  general 
  conclusions 
  may 
  be 
  summarized 
  as 
  follows 
  : 
  

  

  1. 
  The 
  present 
  Bermuda 
  Islands 
  are 
  a 
  small 
  remnant 
  of 
  a 
  

   very 
  much 
  larger 
  island 
  which 
  formerly 
  occupied 
  the 
  same 
  

   position, 
  and 
  which 
  we 
  may 
  call 
  the 
  Greater 
  Bermuda. 
  This 
  

   Greater 
  Bermuda 
  covered 
  an 
  area 
  of 
  about 
  300 
  to 
  400 
  square 
  

   miles 
  ; 
  was 
  elliptical 
  in 
  outline, 
  about 
  28 
  miles 
  long 
  and 
  15 
  

   wide, 
  and 
  the 
  highest 
  land 
  must 
  have 
  been 
  at 
  least 
  375 
  feet 
  

   above 
  the 
  sea. 
  It 
  had 
  large 
  areas 
  of 
  sand 
  beaches 
  and 
  flats, 
  

   bare 
  at 
  low 
  tide. 
  The 
  existing 
  islands 
  contain 
  only 
  about 
  20 
  

   square 
  miles 
  (12,378 
  acres), 
  and 
  the 
  highest 
  hill 
  is 
  268 
  feet. 
  

   (See 
  map, 
  fig. 
  1.) 
  

  

  2. 
  A 
  subsidence 
  of 
  at 
  least 
  80 
  to 
  100 
  feet 
  took 
  place 
  at 
  a 
  

   period 
  comparatively 
  recent 
  (geologically 
  speaking), 
  by 
  which 
  

   the 
  Greater 
  Bermuda 
  was 
  depressed 
  below 
  the 
  level 
  of 
  the 
  sea, 
  

   for 
  the 
  most 
  part, 
  converting 
  what 
  were 
  lowlands 
  into 
  sounds 
  

   and 
  bays, 
  and 
  changing 
  the 
  shore 
  cliffs 
  of 
  the 
  Greater 
  Bermuda 
  

   into 
  a 
  series 
  of 
  islands 
  and 
  reefs, 
  corresponding 
  to 
  the 
  present 
  

   outlying 
  reefs, 
  most 
  of 
  which 
  now, 
  after 
  a 
  long 
  period 
  of 
  

   erosion, 
  hardly 
  rise 
  above 
  the 
  sea-level. 
  The 
  submerged 
  reefs, 
  

   as 
  shown 
  by 
  the 
  excavations 
  for 
  the 
  dry 
  dock, 
  are 
  composed 
  

   of 
  the 
  sand-drifted 
  rock 
  to 
  the 
  depth 
  of 
  at 
  least 
  50 
  feet 
  below 
  

   the 
  present 
  sea-level. 
  This 
  observation 
  shows 
  that 
  the 
  amount 
  

   of 
  sinking 
  has 
  been 
  at 
  least 
  50 
  feet. 
  Other 
  facts, 
  referred 
  to 
  

   below, 
  show 
  that 
  it 
  must 
  have 
  been 
  at 
  least 
  80 
  to 
  100 
  feet.* 
  

  

  3. 
  The 
  Greater 
  Bermuda, 
  as 
  well 
  as 
  the 
  present 
  Bermudas, 
  

   and 
  also 
  the 
  submerged 
  reefs 
  and 
  islands, 
  so 
  far 
  as 
  visible 
  or 
  

  

  *Por 
  a 
  discussion 
  of 
  this 
  (see 
  pp. 
  324-327). 
  

  

  