﻿164 
  THE 
  ZOOLOGIST. 
  

  

  picked 
  up 
  near 
  the 
  edge 
  of 
  the 
  mud, 
  and 
  live 
  Periwinkles 
  and 
  

   Mussels 
  are 
  numerous 
  about 
  the 
  stones, 
  where 
  can 
  also 
  be 
  found 
  

   a 
  few 
  small 
  specimens 
  of 
  the 
  Oyster. 
  It 
  may 
  be 
  fair 
  to 
  assume, 
  

   that 
  these 
  deposits 
  of 
  dead 
  Cockle-shells 
  point 
  to 
  there 
  having 
  

   been 
  large 
  colonies 
  of 
  the 
  same 
  mollusc, 
  in 
  such 
  positions, 
  in 
  the 
  

   bed 
  of 
  the 
  rivers, 
  and 
  that 
  their 
  dead 
  shells 
  were 
  washed 
  up 
  by 
  

   the 
  tide 
  on 
  to 
  the 
  places 
  where 
  the 
  banks 
  are 
  formed. 
  

  

  Those 
  banks 
  of 
  shells 
  and 
  sand 
  which 
  are 
  deposited 
  on 
  the 
  

   outer 
  edge 
  of 
  the 
  existing 
  saltings, 
  in 
  the 
  cases 
  where 
  the 
  saltings 
  

   they 
  are 
  on 
  present 
  a 
  high 
  perpendicular 
  edge 
  to 
  the 
  tide, 
  present 
  

   a 
  problem 
  to 
  be 
  solved 
  as 
  to 
  how 
  they 
  originally 
  got 
  there. 
  At 
  

   the 
  present 
  day 
  the 
  ordinary 
  tides 
  may 
  only 
  lap 
  over 
  the 
  perpen- 
  

   dicular 
  edge 
  on 
  to 
  the 
  level 
  of 
  the 
  marsh 
  ; 
  a 
  spring 
  tide 
  may 
  just 
  

   cover 
  the 
  salting 
  itself 
  with 
  a 
  few 
  inches 
  of 
  water, 
  while 
  a 
  spring 
  

   tide, 
  in 
  conjunction 
  with 
  a 
  strong 
  wind 
  blowing 
  up 
  the 
  river, 
  may 
  

   make 
  the 
  water 
  wash 
  the 
  top 
  of 
  the 
  lowest 
  shelly 
  beaches. 
  It 
  

   seems 
  therefore 
  almost 
  certain 
  that 
  since 
  these 
  deposits 
  were 
  

   made 
  the 
  relative 
  positions 
  of 
  land 
  and 
  water 
  have 
  been 
  altered 
  

   by 
  a 
  gradual 
  upheaval 
  of 
  the 
  land, 
  and 
  this 
  idea 
  is 
  in 
  some 
  

   measure 
  confirmed 
  by 
  the 
  fact, 
  already 
  mentioned, 
  of 
  certain 
  

   portions 
  of 
  the 
  shelly 
  beaches 
  becoming 
  rapidly 
  overgrown 
  

   with 
  vegetation. 
  I 
  venture 
  also 
  to 
  think 
  that 
  the 
  perpendicular 
  

   edges 
  of 
  these 
  saltings 
  is 
  a 
  sort 
  of 
  object-lesson 
  in 
  miniature, 
  

   showing 
  how 
  cliffs 
  are 
  formed 
  by 
  the 
  action 
  of 
  water 
  on 
  the 
  

   edge 
  of 
  gradually 
  rising 
  land. 
  A 
  more 
  difficult 
  thing 
  to 
  account 
  

   for, 
  is 
  why 
  the 
  level 
  of 
  the 
  marsh 
  inside 
  the 
  wall 
  should 
  be 
  lower 
  

   by 
  several 
  feet 
  than 
  the 
  level 
  of 
  the 
  salt-marsh 
  outside 
  the 
  wall, 
  

   this 
  being 
  certainly 
  the 
  case 
  nearly 
  everywhere. 
  

  

  The 
  wall 
  itself 
  forms 
  a 
  very 
  convenient 
  roadway 
  from 
  which 
  

   to 
  carry 
  on 
  observations, 
  as 
  from 
  its 
  top 
  can 
  be 
  commanded 
  a 
  

   complete 
  survey 
  of 
  the 
  marshland 
  on 
  the 
  one 
  hand, 
  and 
  the 
  

   mud-flats 
  or 
  estuaries 
  on 
  the 
  other 
  ; 
  and 
  it 
  also, 
  upon 
  occasions, 
  

   forms 
  a 
  useful 
  screen, 
  under 
  cover 
  of 
  which 
  birds 
  can 
  be 
  

   approached 
  nearer, 
  without 
  alarming 
  them, 
  than 
  would 
  other- 
  

   wise 
  be 
  the 
  case. 
  And 
  there 
  are 
  many 
  birds 
  which 
  become 
  

   associated 
  with 
  the 
  vicinity 
  of 
  these 
  walls, 
  though 
  not, 
  pro- 
  

   perly 
  speaking, 
  shore-birds 
  ; 
  such 
  as 
  the 
  Wheatear 
  (Saxicola 
  

   cenantlie), 
  which 
  is 
  fairly 
  common 
  in 
  the 
  eastern 
  portion 
  of 
  the 
  

   district 
  during 
  spring 
  and 
  summer, 
  a 
  few 
  pairs 
  also 
  nesting 
  in 
  

  

  