﻿332 
  Verrill 
  — 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Bermudas. 
  

  

  geological 
  sense. 
  It 
  would, 
  in 
  fact, 
  appear 
  that 
  the 
  age 
  of 
  the 
  

   older 
  or 
  greater 
  Bermuda 
  must 
  be 
  as 
  great 
  as 
  the 
  Glacial 
  

   Period 
  at 
  least. 
  

  

  Littoral 
  Erosion. 
  Figs. 
  2, 
  3, 
  7. 
  

  

  The 
  same 
  result 
  was 
  arrived 
  at 
  from 
  a 
  study 
  of 
  the 
  rate 
  of 
  

   erosion 
  by 
  the 
  waves, 
  as 
  shown 
  on 
  the 
  masonry 
  of 
  the 
  cause- 
  

   way 
  leading 
  to 
  St. 
  George 
  and 
  in 
  other 
  places. 
  This 
  rate 
  of 
  

   erosion 
  was 
  found 
  to 
  be 
  unexpectedly 
  slow, 
  under 
  ordinary 
  

   conditions, 
  owing 
  to 
  the 
  absence 
  of 
  ice 
  and 
  frost, 
  and 
  because 
  

   there 
  are 
  no 
  deposits 
  of 
  hard 
  sand, 
  gravel, 
  and 
  pebbles 
  on 
  the 
  

   shores, 
  which 
  the 
  storm 
  waves 
  might 
  pick 
  up 
  and 
  use 
  as 
  tools 
  

   of 
  destruction, 
  by 
  dashing 
  them 
  against 
  the 
  bases 
  of 
  the 
  cliffs 
  

   and 
  against 
  each 
  other, 
  as 
  they 
  do 
  on 
  our 
  rocky 
  coasts.* 
  It 
  is 
  

   only 
  during 
  the 
  severe 
  storms 
  and 
  hurricanes, 
  which 
  occasion- 
  

   ally 
  occur, 
  that 
  much 
  erosion 
  is 
  accomplished. 
  

  

  Most 
  observers, 
  seeing 
  the 
  evidence 
  of 
  great 
  erosion 
  on 
  all 
  

   sides, 
  and 
  considering 
  the 
  softness 
  of 
  the 
  rocks, 
  have 
  naturally 
  

   supposed 
  that 
  the 
  erosion 
  has 
  taken 
  place 
  far 
  more 
  rapidly 
  than 
  

   is 
  the 
  case. 
  

  

  The 
  causeway 
  between 
  the 
  main 
  island 
  and 
  St. 
  George's 
  was 
  

   completed 
  in 
  1871. 
  It 
  was 
  about 
  a 
  mile 
  long, 
  and 
  well 
  built 
  

   of 
  native 
  limestone 
  blocks 
  of 
  large 
  size. 
  It 
  was 
  wide 
  enough 
  

   for 
  two 
  or 
  three 
  carriages 
  abreast. 
  It 
  included 
  an 
  iron 
  draw- 
  

   bridge 
  and 
  several 
  smaller 
  bridges 
  under 
  which 
  were 
  strong 
  

   tidal 
  currents, 
  flowing 
  in 
  and 
  out 
  of 
  Castle 
  Harbor. 
  It 
  was 
  so 
  

   situated 
  in 
  the 
  passage 
  between 
  the 
  islands 
  that 
  it 
  was 
  partly 
  

   sheltered, 
  and 
  ordinarily 
  it 
  would 
  not 
  be 
  exposed 
  to 
  the 
  full 
  

   violence 
  of 
  storms. 
  By 
  an 
  examination 
  of 
  the 
  masonry 
  of 
  this 
  

   causeway 
  at 
  several 
  places 
  I 
  found 
  that 
  during 
  the 
  27 
  years 
  

   that 
  it 
  had 
  been 
  built 
  the 
  erosion 
  by 
  the 
  sea 
  rarely 
  amounted 
  

   to 
  an 
  inch 
  in 
  depth, 
  where 
  most 
  active, 
  and 
  the 
  average 
  erosion 
  

   was 
  less 
  than 
  half 
  an 
  inch, 
  between 
  tides 
  ; 
  most 
  of 
  this, 
  also, 
  

   had 
  evidently 
  been 
  effected 
  within 
  the 
  first 
  few 
  years 
  after 
  its 
  

  

  far 
  below 
  the 
  surface 
  of 
  the 
  sea 
  water. 
  It 
  is 
  said 
  that 
  the 
  salt 
  water 
  is 
  40 
  feet 
  

   deep 
  in 
  some 
  of 
  the 
  partly 
  submerged 
  caves. 
  The 
  sinks 
  and 
  ponds, 
  that 
  are 
  

   believed 
  to 
  be 
  due 
  to 
  the 
  falling 
  in 
  of 
  the 
  roofs 
  of 
  large 
  caverns, 
  also 
  give 
  evidence 
  

   of 
  a 
  very 
  long 
  period 
  of 
  disintegration 
  that 
  must 
  have 
  preceded 
  the 
  great 
  subsi- 
  

   dence, 
  for 
  such 
  caverns 
  must 
  have 
  been 
  excavated 
  while 
  above 
  the 
  sea-level. 
  

  

  * 
  On 
  the 
  coast 
  of 
  Maine 
  and 
  at 
  Grand 
  Menan 
  Island, 
  Bay 
  of 
  Fundy, 
  the 
  frost- 
  

   every 
  year 
  throws 
  down 
  from 
  the 
  high 
  basaltic 
  cliffs 
  vast 
  quantities 
  of 
  angular 
  

   blocks 
  of 
  hard 
  trap 
  rock, 
  large 
  and 
  small. 
  These 
  are 
  tossed 
  about, 
  smashed 
  

   together, 
  and 
  dashed 
  against 
  the 
  base 
  of 
  the 
  cliffs, 
  rolling 
  up 
  and 
  down 
  the 
  slope 
  

   of 
  the 
  beach 
  with 
  every 
  storm- 
  wave, 
  with 
  a 
  thunderous 
  noise, 
  audible 
  for 
  many 
  

   miles, 
  so 
  that 
  in 
  a 
  few 
  months 
  they 
  become 
  round 
  paving 
  stones 
  and 
  small 
  pebbles. 
  

   The 
  smoothing 
  of 
  their 
  surfaces 
  is 
  aided 
  by 
  the 
  coarse 
  gravel 
  and 
  sand 
  mixed 
  

   with 
  them. 
  

  

  Nothing 
  of 
  this 
  kind 
  can 
  occur 
  at 
  Bermuda, 
  where 
  the 
  fragments 
  of 
  soft 
  lime- 
  

   stone 
  are 
  quickly 
  crushed 
  and 
  broken 
  by 
  the 
  waves 
  until 
  nothing 
  is 
  left 
  but 
  soft 
  

   calcareous 
  sand 
  and 
  mud, 
  with 
  very 
  little 
  erosive 
  power. 
  

  

  