﻿Yerrill 
  — 
  JVotes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  331 
  

  

  tion 
  of 
  the 
  "red 
  soil," 
  as 
  a 
  decomposition 
  product, 
  or 
  insoluble 
  

   residue 
  left 
  after 
  the 
  solution 
  of 
  the 
  limestone, 
  be 
  able 
  to 
  esti- 
  

   mate 
  approximately 
  the 
  total 
  age 
  of 
  the 
  dry 
  land 
  of 
  the 
  Ber- 
  

   mudas. 
  At 
  present 
  we 
  can 
  only 
  say 
  that 
  this 
  process 
  of 
  

   accumulation 
  of 
  the 
  red 
  soil 
  is 
  an 
  extremely 
  slow 
  one. 
  It 
  

   probably 
  requires 
  the 
  destruction 
  of 
  at 
  least 
  200 
  feet 
  of 
  lime- 
  

   stone 
  to 
  form 
  one 
  foot 
  of 
  soil. 
  Probably 
  the 
  amount 
  of 
  this 
  

   native 
  soil 
  on 
  the 
  island, 
  if 
  evenly 
  distributed 
  over 
  the 
  surface, 
  

   would 
  amount 
  to 
  at 
  least 
  two 
  feet. 
  Though 
  there 
  are 
  large 
  

   tracts 
  where 
  the 
  average 
  depth 
  of 
  soil 
  is 
  not 
  over 
  six 
  inches, 
  

   and 
  also 
  tracts 
  of 
  nearly 
  bare 
  rock, 
  there 
  are 
  depressions 
  and 
  

   valleys 
  between 
  the 
  hills 
  where 
  it 
  is 
  many 
  feet 
  deep. 
  This 
  

   light 
  soil 
  is 
  easily 
  washed 
  from 
  the 
  hillsides 
  into 
  the 
  valleys 
  

   by 
  the 
  heavy 
  rains, 
  unless 
  it 
  be 
  closely 
  covered 
  by 
  grass 
  or 
  

   some 
  other 
  vegetation. 
  On 
  the 
  contrary, 
  as 
  there 
  are 
  no 
  

   brooks 
  or 
  streams 
  of 
  fresh 
  water, 
  comparatively 
  little 
  of 
  it 
  is 
  

   carried 
  into 
  the 
  sea 
  and 
  wasted. 
  * 
  Hence 
  it 
  follows 
  that 
  unless 
  

   these 
  limestones 
  disintegrate 
  with 
  unusual 
  rapidity, 
  it 
  must 
  

   have 
  taken 
  a 
  very 
  long 
  period 
  to 
  form 
  even 
  one 
  foot 
  of 
  soil. 
  

   Some 
  data 
  that 
  I 
  obtained 
  by 
  examining 
  the 
  ruins 
  of 
  the 
  old 
  

   stone 
  forts 
  on 
  Castle 
  Island 
  and 
  others, 
  built 
  before 
  1620, 
  

   show 
  an 
  unexpectedly 
  slow 
  rate 
  of 
  disintegration 
  of 
  the 
  ordi- 
  

   nary 
  limestone 
  used 
  in 
  the 
  walls 
  and 
  buildings. 
  This 
  was 
  con- 
  

   firmed 
  by 
  observations 
  made 
  at 
  other 
  places. 
  These 
  data 
  

   would 
  make 
  the 
  average 
  rate 
  of 
  subserial 
  disintegration 
  for 
  the 
  

   harder 
  seolian 
  limestones 
  to 
  be 
  less 
  than 
  an 
  inch 
  in 
  a 
  century. 
  

   This 
  would 
  require 
  210,000 
  years 
  for 
  the 
  destruction 
  of 
  the 
  

   200 
  feet 
  of 
  limestone 
  necessary 
  to 
  form 
  one 
  foot 
  of 
  soil. 
  

  

  But 
  there 
  are, 
  in 
  many 
  places, 
  areas 
  of 
  much 
  softer 
  limestones 
  

   which 
  decay 
  far 
  more 
  rapidly 
  and 
  furnish 
  soil 
  much 
  more 
  

   freely. 
  Such 
  tracts 
  of 
  soft 
  limestones 
  have, 
  by 
  their 
  decay 
  

   and 
  solution, 
  given 
  origin, 
  in 
  many 
  cases, 
  to 
  the 
  sinks, 
  ponds, 
  

   marshes, 
  and 
  caverns 
  that 
  abound 
  on 
  the 
  larger 
  islands. 
  But 
  

   many 
  of 
  the 
  softer 
  limestones 
  when 
  exposed 
  to 
  the 
  air, 
  as 
  in 
  

   the 
  road 
  cuttings, 
  become, 
  in 
  a 
  few 
  months, 
  very 
  much 
  harder 
  

   and 
  resistant 
  to 
  decay. 
  It 
  is 
  rare 
  to 
  find 
  in 
  the 
  extensive 
  road- 
  

   cuts 
  any 
  great 
  portion 
  of 
  the 
  nearly 
  perpendicular 
  side-walls 
  

   that 
  have 
  fallen 
  away 
  by 
  decay. 
  

  

  My 
  observations, 
  therefore, 
  on 
  this 
  point, 
  though 
  not 
  very 
  

   satisfactory 
  and 
  far 
  too 
  few 
  in 
  number, 
  point 
  to 
  a 
  great 
  

   antiquity 
  for 
  the 
  Bermuda 
  limestones, 
  f 
  though 
  recent 
  in 
  a 
  

  

  * 
  This 
  was 
  probably 
  not 
  the 
  case 
  in 
  the 
  time 
  of 
  the 
  Greater 
  Bermuda, 
  for 
  tor- 
  

   rents 
  and 
  large 
  subterranean 
  streams 
  probabl} 
  r 
  existed 
  then, 
  owing 
  to 
  the 
  larger 
  

   expanse 
  of 
  high 
  land. 
  

  

  + 
  Doubtless 
  investigations 
  carefully 
  made 
  as 
  to 
  the 
  rate 
  of 
  excavation 
  of 
  the 
  

   caverus 
  by 
  solution 
  of 
  the 
  rock, 
  and 
  of 
  the 
  rate 
  of 
  formation 
  of 
  stalactites, 
  would 
  

   show 
  the 
  same 
  thing, 
  for 
  some 
  of 
  the 
  Bermuda 
  caverns, 
  now 
  partly 
  filled 
  with 
  

   sea 
  water, 
  are 
  of 
  considerable 
  extent 
  and 
  depth, 
  with 
  large 
  stalactites 
  that 
  extend 
  

  

  