﻿322 
  Verrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  

  

  combed 
  and 
  very 
  jagged 
  and 
  rough, 
  and 
  at 
  the 
  same 
  time 
  very 
  

   hard 
  owing 
  to 
  infiltration 
  of 
  the 
  surface 
  and 
  deposition 
  of 
  cal- 
  

   cite 
  in 
  consequence 
  of 
  the 
  evaporation 
  of 
  the 
  water 
  of 
  solution. 
  

   (See 
  figs. 
  2, 
  3.) 
  

  

  12. 
  Infiltration 
  and 
  solidification 
  of 
  the 
  rocks 
  have 
  also 
  

   occurred 
  on 
  the 
  surfaces 
  of 
  vertical 
  cracks 
  and 
  along 
  subter- 
  

   ranean 
  water 
  passages, 
  causing 
  various 
  local 
  hardenings 
  of 
  the 
  

   rock 
  which 
  become 
  very 
  evident 
  during 
  denudation. 
  

  

  The 
  formation 
  of 
  detached 
  columns 
  and 
  pinnacles 
  of 
  rock 
  

   by 
  erosion, 
  and 
  especially 
  of 
  such 
  places 
  as 
  Cathedral 
  Rocks 
  

   (fig. 
  5), 
  is 
  largely 
  due 
  in 
  most 
  cases 
  to 
  the 
  previous 
  local 
  hard- 
  

   ening 
  of 
  the 
  rock 
  along 
  fissures 
  that 
  have 
  served 
  for 
  the 
  pas- 
  

   sage 
  of 
  calciferous 
  waters, 
  causing 
  the 
  hardened 
  portions 
  to 
  

   longer 
  resist 
  erosion. 
  

  

  13. 
  Subterranean 
  erosion 
  has 
  taken 
  place 
  on 
  a 
  large 
  scale, 
  giv- 
  

   ing 
  origin 
  to 
  extensive 
  caverns 
  and 
  water 
  channels. 
  (Figs. 
  5, 
  6.) 
  

   The 
  roofs 
  of 
  these 
  have 
  often 
  fallen 
  introducing 
  sinks, 
  ponds, 
  

   and 
  marshes, 
  large 
  and 
  small. 
  Probably 
  the 
  basins 
  occupied 
  

   by 
  Harrington 
  Sound, 
  Castle 
  Harbor, 
  and 
  others 
  similar 
  in 
  

   character 
  were 
  in 
  large 
  part 
  excavated 
  by 
  subterranean 
  waters 
  

   when 
  the 
  land 
  stood 
  at 
  its 
  highest 
  level.* 
  But 
  this 
  action 
  

   probably 
  does 
  not 
  occur 
  much, 
  if 
  at 
  all, 
  below 
  sea 
  level. 
  

   Therefore 
  if 
  the 
  deep 
  passages 
  among 
  the 
  reefs, 
  and 
  the 
  deeper 
  

   parts 
  of 
  the 
  sounds 
  (see 
  map 
  1, 
  areas 
  I-VI), 
  were 
  made 
  in 
  

   this 
  way, 
  it 
  would 
  have 
  required 
  a 
  former 
  elevation 
  of 
  over 
  a 
  

   hundred 
  feet 
  above 
  the 
  present 
  level. 
  (See 
  p. 
  326.) 
  

  

  14. 
  The 
  " 
  red 
  soil 
  " 
  of 
  Bermuda 
  and 
  other 
  native 
  soils 
  are 
  

   mainly 
  the 
  residue 
  left 
  after 
  the 
  destruction 
  and 
  solution 
  of 
  

   the 
  limestones. 
  Its 
  formation 
  has 
  been 
  a 
  very 
  long 
  and 
  slow 
  

   process, 
  for 
  the 
  amount 
  of 
  impurities 
  in 
  the 
  limestone 
  is 
  very 
  

   small 
  — 
  probably 
  less 
  than 
  an 
  average 
  of 
  1 
  per 
  cent. 
  Some 
  

   of 
  this 
  material 
  in 
  the 
  limestone 
  was 
  probably 
  of 
  foreign 
  

   volcanic 
  origin 
  (floating 
  pumice 
  and 
  ash 
  from 
  the 
  West 
  Indian 
  

   volcanoes 
  perhaps), 
  but 
  some 
  of 
  it 
  may 
  have 
  been 
  derived 
  indi- 
  

   rectly 
  from 
  the 
  ancient 
  Bermudian 
  volcano 
  or 
  from 
  the 
  craters 
  

   represented 
  by 
  the 
  Challenger 
  and 
  Argus 
  Banks, 
  which 
  may 
  

   have 
  remained 
  active 
  much 
  later 
  than 
  the 
  main 
  crater, 
  f 
  

  

  * 
  It 
  is 
  possible, 
  however, 
  that 
  the 
  central 
  basins 
  within 
  the 
  reefs 
  were 
  due 
  in 
  

   part 
  to 
  the 
  original 
  form, 
  of 
  the 
  volcanic 
  summit, 
  and 
  correspond 
  to 
  several 
  more 
  

   or 
  less 
  separated 
  and 
  filled 
  up 
  craters 
  of 
  the 
  ancient 
  volcano, 
  while 
  the 
  outer 
  

   reefs 
  may 
  correspond 
  to 
  a 
  certain 
  extent 
  with 
  their 
  more 
  or 
  less 
  elevated 
  margins, 
  

   which 
  may 
  have 
  been 
  first 
  occupied 
  by 
  ancient 
  coral 
  reefs 
  now 
  deeply 
  submerged. 
  

   Deep 
  borings 
  can 
  alone 
  determine 
  this 
  question. 
  

  

  f 
  This 
  refers 
  to 
  the 
  possibility 
  that 
  some 
  of 
  the 
  materials 
  of 
  the 
  older 
  seolian 
  

   limestones 
  may 
  have 
  been 
  derived 
  byrewashiog 
  from 
  preexistent 
  rocks, 
  now 
  sub- 
  

   merged, 
  which 
  may 
  have 
  contained 
  beds 
  of 
  volcanic 
  ashes 
  or 
  pumice 
  of 
  local 
  

   origin. 
  No 
  beds 
  containing 
  any 
  notable 
  amount 
  of 
  volcanic 
  ashes 
  are 
  known 
  to 
  

   exist 
  at 
  present 
  on 
  the 
  islands, 
  but 
  most 
  of 
  the 
  limestones 
  leave, 
  after 
  solution, 
  a 
  

   small 
  per 
  cent 
  of 
  grains 
  of 
  probable 
  volcanic 
  origin. 
  

  

  