﻿DR. 
  A. 
  DUNLOP 
  ON 
  THE 
  JERSEY 
  BRICK-CLAY. 
  119 
  

  

  The 
  clay, 
  which 
  occurs 
  in 
  patches 
  here 
  and 
  there 
  all 
  over 
  the 
  island, 
  

   and 
  sometimes 
  spreads 
  over 
  extensive 
  areas, 
  is 
  found 
  on 
  all 
  the 
  

   rocks, 
  and 
  covers 
  the 
  raised 
  beaches. 
  The 
  highest 
  mentioned, 
  

   which 
  is 
  on 
  the 
  top 
  of 
  the 
  cliff 
  at 
  the 
  South 
  Hill 
  Port, 
  is 
  filled 
  up 
  

   with 
  it. 
  It 
  is 
  thickly 
  and 
  widely 
  spread 
  over 
  the 
  highest 
  parts 
  of 
  

   the 
  island, 
  and 
  at 
  one 
  or 
  two 
  points 
  it 
  is 
  used 
  for 
  brick-making. 
  

   Mr. 
  Copp, 
  one 
  of 
  the 
  principal 
  brick-makers, 
  states 
  that 
  where 
  he 
  

   works 
  he 
  gets 
  a 
  depth 
  of 
  from 
  ten 
  to 
  thirty 
  feet, 
  and 
  that 
  a 
  little 
  to 
  

   the 
  north 
  of 
  his 
  works 
  a 
  well 
  was 
  sunk 
  through 
  fifty 
  feet 
  of 
  the 
  

   clay. 
  It 
  also 
  attains 
  great 
  thickness 
  in 
  many 
  parts 
  of 
  the 
  lower 
  

   ground, 
  where 
  the 
  original 
  deposit 
  has 
  been 
  added 
  to 
  by 
  rain 
  -wash. 
  

   Under 
  the 
  town 
  of 
  iSt. 
  Helier 
  it 
  overlies 
  a 
  blue 
  clay, 
  which 
  varies 
  

   in 
  thickness 
  from 
  one 
  to 
  thirty 
  feet. 
  Mr. 
  Green 
  gives 
  the 
  following 
  

   section 
  found 
  in 
  sinking 
  a 
  well 
  in 
  the 
  town 
  : 
  — 
  

  

  Yellow 
  sandy 
  clay 
  15 
  feet. 
  

  

  Lavge 
  angular 
  gravel 
  15 
  inches. 
  

  

  Stiff 
  blue 
  clay 
  27 
  feet. 
  

  

  Blue 
  sand 
  with 
  somewhat 
  rounded 
  pebbly 
  rock 
  . 
  A 
  few 
  inches. 
  

  

  It 
  seems, 
  on 
  the 
  whole, 
  to 
  cover 
  a 
  greater 
  and 
  more 
  continuous 
  

   area 
  in 
  the 
  north 
  and 
  centre 
  of 
  the 
  island, 
  the 
  highest 
  parts, 
  while 
  

   there 
  is 
  little 
  to 
  be 
  seen 
  over 
  most 
  of 
  the 
  south-western 
  corner. 
  

   The 
  same 
  clay 
  is 
  found 
  on 
  the 
  opposite 
  coast 
  of 
  Normandy 
  and 
  in 
  

   the 
  other 
  Channel 
  Islands, 
  but 
  I 
  have 
  not 
  examined 
  it 
  in 
  these 
  

   localities. 
  

  

  Prom 
  the 
  fact 
  that 
  the 
  same 
  clay 
  is 
  found 
  over 
  different 
  rocks, 
  

   from 
  the 
  fact 
  of 
  its 
  covering 
  the 
  raised 
  beaches 
  and 
  lying 
  over 
  the 
  

   blue 
  clay, 
  as 
  well 
  as 
  from 
  the 
  position 
  in 
  which 
  many 
  of 
  the 
  stones 
  

   it 
  contains 
  lie 
  in 
  it, 
  it 
  seems 
  improbable 
  that 
  it 
  can 
  be 
  the 
  result 
  of 
  

   disintegration 
  in 
  situ. 
  Besides, 
  the 
  fine 
  yellow 
  sandy 
  clay, 
  though 
  

   it 
  might 
  be 
  the 
  product 
  of 
  the 
  disintegration 
  of 
  the 
  clay-shale, 
  which 
  

   is 
  often 
  arenaceous, 
  or 
  of 
  the 
  felsitic 
  rocks, 
  has 
  little 
  resemblance 
  

   to 
  disintegrated 
  granite, 
  on 
  which, 
  indeed, 
  it 
  may 
  sometimes 
  be 
  seen 
  

   lying. 
  It 
  seems 
  to 
  me 
  most 
  probable 
  that 
  it 
  is 
  a 
  fluviatile 
  deposit, 
  

   laid 
  down 
  during, 
  or 
  at 
  the 
  close 
  of, 
  the 
  glacial 
  period, 
  when 
  the 
  

   rivers, 
  flooded 
  in 
  summer 
  time 
  by 
  the 
  melting 
  glaciers, 
  spread 
  

   over 
  large 
  tracts 
  of 
  country 
  the 
  muddy 
  debris 
  with 
  which 
  they 
  were 
  

   highly 
  charged. 
  At 
  that 
  time 
  the 
  Channel 
  Islands 
  were 
  united 
  

   to 
  the 
  mainland, 
  and 
  in 
  all 
  probability 
  the 
  clay 
  was 
  deposited 
  at 
  the 
  

   same 
  time 
  as, 
  and, 
  in 
  fact, 
  forms 
  part 
  of 
  one 
  of 
  the 
  brick-earths 
  of 
  

   Northern 
  France. 
  

  

  There 
  is, 
  however, 
  another 
  view 
  that 
  might 
  be 
  taken 
  ; 
  such 
  a 
  clay 
  

   could 
  be 
  produced 
  by 
  the 
  decomposition 
  of 
  the 
  clay-shale, 
  of 
  the 
  

   ielspathic 
  porphyries, 
  and 
  of 
  the 
  rhyolite 
  ; 
  some 
  sections 
  seem 
  to 
  

   show 
  this 
  going 
  on, 
  and 
  the 
  clay 
  is, 
  I 
  think, 
  more 
  developed 
  over 
  

   those 
  rocks. 
  

  

  Perhaps, 
  then, 
  the 
  long-continued 
  subaerial 
  decomposition 
  of 
  those 
  

   rocks 
  may 
  have 
  produced 
  the 
  material 
  which 
  has 
  been 
  washed 
  away 
  

   and 
  spread 
  out 
  by 
  the 
  action 
  of 
  water. 
  If 
  this 
  were 
  the 
  case, 
  

   however, 
  the 
  moving 
  force 
  must 
  have 
  been 
  a 
  greater 
  and 
  more 
  

   extensive 
  flow 
  than 
  that 
  of 
  ordimary 
  rain-wash. 
  For 
  example, 
  La 
  

  

  