﻿222 
  CHANGES 
  OF 
  LEVEL 
  IN 
  THE 
  BEEMTTDA 
  ISLANDS. 
  [May 
  1 
  897, 
  

  

  17. 
  Changes 
  of 
  Level 
  in 
  the 
  Bekmtjda 
  Islands. 
  By 
  Prof. 
  

   Ealph 
  S. 
  Tare, 
  of 
  Cornell 
  University. 
  (Communicated 
  by 
  

   the 
  Secretary. 
  Read 
  January 
  6th, 
  1897.) 
  

  

  [Abstract.] 
  

  

  The 
  Author 
  gives 
  a 
  summary 
  of 
  previous 
  writings 
  bearing 
  upon 
  

   the 
  geology 
  of 
  the 
  Bermudas 
  ; 
  but 
  his 
  own 
  researches 
  point 
  to 
  

   a 
  rather 
  more 
  complicated 
  series 
  of 
  changes 
  than 
  those 
  which 
  have 
  

   been 
  inferred 
  by 
  other 
  writers. 
  The 
  formation 
  of 
  the 
  ' 
  base-rock 
  ' 
  

   or 
  ' 
  beach-rock 
  ' 
  occurred 
  at 
  some 
  period 
  which 
  cannot 
  be 
  accurately 
  

   ascertained 
  at 
  present, 
  owing 
  to 
  the 
  fragmentary 
  nature 
  of 
  the 
  

   included 
  fossils. 
  It 
  may 
  have 
  been 
  formed 
  in 
  Pleistocene 
  or 
  even 
  

   late 
  Tertiary 
  times. 
  After 
  its 
  formation 
  it 
  was 
  converted 
  into 
  a 
  

   dense 
  limestone 
  and 
  then 
  eroded, 
  probably 
  by 
  subaerial 
  agents, 
  and 
  

   finally 
  attacked 
  by 
  the 
  waves 
  at 
  an 
  elevation 
  of 
  at 
  least 
  15 
  feet 
  

   above 
  present 
  sea-level 
  ; 
  during 
  this 
  stage 
  it 
  was 
  covered 
  by 
  beach- 
  

   deposits 
  of 
  pebbles 
  and 
  shells, 
  which 
  were 
  accumulated 
  in 
  a 
  period 
  

   so 
  recent 
  that 
  the 
  contained 
  fossils 
  are 
  of 
  the 
  same 
  species 
  as 
  the 
  

   organisms 
  living 
  in 
  the 
  neighbouring 
  sea. 
  Then 
  followed 
  an 
  

   uplift, 
  during 
  which 
  land-shells 
  lived 
  on 
  the 
  beach 
  -deposits 
  ; 
  but 
  

   these 
  were 
  soon 
  covered 
  by 
  blown 
  sand 
  — 
  the 
  principal 
  accumulations 
  

   of 
  the 
  islands, 
  and 
  the 
  outline 
  of 
  the 
  islands 
  was 
  perfected 
  by 
  the 
  

   action 
  of 
  the 
  winds. 
  This 
  was 
  done 
  at 
  an 
  elevation 
  which 
  was 
  at 
  

   one 
  time 
  certainly 
  as 
  much 
  as 
  40 
  or 
  50 
  feet 
  above 
  present 
  sea- 
  

   level. 
  The 
  author 
  adduces 
  evidence 
  of 
  a 
  depression 
  since 
  this 
  

   accumulation, 
  causing 
  land 
  to 
  disappear 
  and 
  the 
  outline 
  of 
  the 
  area 
  

   to 
  become 
  very 
  irregular 
  ; 
  and 
  he 
  proves 
  that 
  these 
  changes 
  cannot 
  

   be 
  accounted 
  for 
  solely 
  by 
  erosion, 
  as 
  some 
  have 
  maintained. 
  There 
  

   are 
  indications 
  that 
  the 
  land 
  is 
  at 
  present 
  quiescent. 
  It 
  appears, 
  

   then, 
  that 
  most 
  of 
  the 
  work 
  of 
  construction 
  of 
  the 
  Bermudas 
  has 
  

   been 
  done 
  in 
  recent 
  times. 
  

  

  Discussion. 
  

  

  Dr. 
  J. 
  W. 
  Gregory 
  thought 
  it 
  appropriate 
  for 
  the 
  paper 
  to 
  be 
  

   sent 
  to 
  this 
  Society, 
  as 
  one 
  of 
  the 
  earliest 
  fossil- 
  collections 
  from 
  

   Bermuda 
  was 
  in 
  the 
  Society's 
  Museum, 
  and 
  as 
  the 
  geological 
  

   structure 
  of 
  the 
  islands 
  had 
  been 
  described 
  in 
  the 
  Society's 
  Trans- 
  

   actions 
  by 
  Capt. 
  Nelson. 
  He 
  had 
  hoped 
  that 
  the 
  age 
  of 
  the 
  basal 
  

   rock 
  of 
  Bermuda 
  might 
  have 
  been 
  settled 
  by 
  this 
  paper, 
  as 
  this 
  

   would 
  have 
  precisely 
  limited 
  the 
  short 
  period 
  during 
  which 
  had 
  

   occurred 
  the 
  movements 
  described 
  by 
  the 
  Author. 
  

  

  Capt. 
  Stiefe 
  said 
  that, 
  having 
  given 
  some 
  attention 
  to 
  the 
  subject 
  

   while 
  at 
  the 
  Bermudas, 
  he 
  had 
  formed 
  the 
  opinion 
  that 
  recent 
  elevation 
  

   or 
  depression 
  was 
  not 
  necessar}^ 
  to 
  account 
  for 
  the 
  present 
  condition 
  

   of 
  th<5 
  islands. 
  iEolian 
  agency 
  was 
  quite 
  adequate 
  to 
  produce 
  the 
  

   present 
  state 
  of 
  things. 
  The 
  blown 
  calcareous 
  sand 
  associated 
  with 
  

   recent 
  shells 
  has 
  been 
  consolidated 
  into 
  a 
  very 
  porous 
  limestone, 
  

   apparently 
  by 
  pluvial 
  and 
  chemical 
  action. 
  

  

  