﻿338 
  Yerrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  

  

  ever, 
  there 
  is 
  no 
  evidence 
  of 
  any 
  volcanic 
  activity 
  in 
  this 
  region 
  

   during 
  several 
  geological 
  periods 
  and 
  therefore 
  this 
  considera- 
  

   tion 
  may 
  have 
  no 
  importance.' 
  54 
  ' 
  In 
  regard 
  to 
  the 
  probable 
  cor- 
  

   relation, 
  I 
  differ 
  materially 
  from 
  Professor 
  Rice, 
  for 
  I 
  consider- 
  

   that 
  the 
  period 
  of 
  greatest 
  elevation 
  was 
  coincident 
  with 
  the 
  

   great 
  continental 
  elevation 
  of 
  the 
  Glacial 
  Period, 
  that 
  affected 
  

   the 
  northern 
  parts 
  of 
  America 
  and 
  Europe 
  and 
  doubtless, 
  also, 
  

   the 
  intervening 
  bed 
  of 
  the 
  North 
  Atlantic. 
  As 
  Bermuda 
  is 
  

   only 
  about 
  TOO 
  miles 
  south 
  of 
  Nova 
  Scotia, 
  where 
  the 
  eleva- 
  

   tion 
  was 
  very 
  great, 
  it 
  is 
  natural 
  that 
  the 
  same 
  movement, 
  in 
  

   less 
  degree, 
  should 
  have 
  affected 
  Bermuda. 
  The 
  same 
  corre- 
  

   spondence 
  in 
  the 
  periods 
  of 
  Post-glacial 
  subsidence 
  and 
  reeleva- 
  

   tion 
  would 
  be 
  expected 
  to 
  have 
  occurred. 
  So 
  far 
  as 
  I 
  could 
  obtain 
  

   data 
  to 
  indicate 
  the 
  duration 
  of 
  present 
  and 
  past 
  conditions 
  of 
  

   erosion, 
  they 
  confirm 
  this 
  view. 
  No 
  doubt 
  it 
  would 
  be 
  possible 
  

   for 
  a 
  resident 
  geologist 
  to 
  obtain 
  much 
  more 
  complete 
  evidence 
  

   as 
  to 
  the 
  rate 
  of 
  erosion 
  of 
  the 
  Bermuda 
  cliffs 
  than 
  I 
  could 
  

   obtain 
  by 
  a 
  very 
  brief 
  study 
  of 
  the 
  subject, 
  but 
  my 
  results 
  

   may 
  be 
  of 
  some 
  value 
  in 
  the 
  absence 
  of 
  something 
  better. 
  

  

  Changes 
  in 
  Climate. 
  

  

  That 
  the 
  climate 
  of 
  Bermuda 
  was 
  warmer 
  during 
  the 
  Glacial 
  

   Period 
  than 
  at 
  present 
  is 
  inferred 
  because 
  the 
  great 
  elevation 
  

   of 
  the 
  northern 
  parts 
  of 
  Europe 
  and 
  America, 
  together 
  with 
  

   the 
  whole 
  bottom 
  of 
  the 
  intervening 
  North 
  Atlantic, 
  that 
  

   occurred 
  at 
  that 
  time 
  and 
  the 
  southward 
  extension 
  of 
  the 
  shore 
  

   ice 
  of 
  boreal 
  regions, 
  would 
  have 
  diminished 
  the 
  flow 
  of 
  the 
  

   Gulf 
  Stream 
  into 
  the 
  Arctic 
  regions 
  and 
  confined 
  it 
  more 
  to 
  

   the 
  central 
  parts 
  of 
  the 
  North 
  Atlantic. 
  This 
  is 
  confirmed, 
  

   also, 
  by 
  the 
  existence 
  of 
  large 
  West 
  Indian 
  shells, 
  as 
  fossils, 
  in 
  

   deposits 
  that 
  are 
  probably 
  of 
  glacial 
  age, 
  on 
  the 
  coast 
  of 
  North 
  

   Carolina, 
  far 
  north 
  of 
  their 
  present 
  range, 
  and 
  north 
  of 
  the 
  

   latitude 
  of 
  Bermuda. 
  So, 
  also, 
  a 
  large 
  living 
  West 
  Indian 
  

   shell 
  (Livona 
  pica) 
  is 
  a 
  common 
  fossil 
  in 
  the 
  Bermuda 
  lime- 
  

   stone, 
  although 
  it 
  no 
  longer 
  lives 
  north 
  of 
  the 
  Bahamas, 
  so 
  

   far 
  as 
  known. 
  Its 
  shells 
  were 
  doubtless 
  carried 
  inland 
  by 
  the 
  

   large 
  land 
  hermit-crabs 
  (Cenobita 
  diogenes).\ 
  These 
  crabs 
  still 
  

   continue 
  to 
  occupy 
  the 
  same 
  shells, 
  for 
  the 
  fossil 
  shells 
  weather 
  

   out 
  of 
  the 
  soft 
  limestones 
  ail 
  over 
  the 
  islands 
  and 
  are 
  quickly 
  

   selected 
  hy 
  the 
  crabs 
  for 
  protection. 
  (Fig. 
  12.) 
  In 
  the 
  older 
  

   limestone 
  a 
  large 
  fossil 
  land 
  shell 
  {Poecilozonites 
  Nelsoni), 
  

   peculiar 
  to 
  the 
  islands 
  and 
  now 
  extinct, 
  is 
  often 
  abundant, 
  

  

  * 
  Earthquakes 
  are 
  rare 
  in 
  Bermuda. 
  I 
  have 
  found 
  but 
  two 
  mentioned 
  : 
  one 
  

   June 
  25, 
  1664 
  ; 
  one 
  Feb. 
  19, 
  1801, 
  neither 
  of 
  which 
  did 
  much 
  damage. 
  

  

  \ 
  In 
  the 
  Yale 
  Museum 
  there 
  is 
  a 
  fossil 
  crab 
  of 
  this 
  species 
  found 
  in 
  the 
  Ber- 
  

   muda 
  limestone 
  many 
  years 
  ago 
  by 
  J. 
  Matthew 
  Jones. 
  

  

  