﻿330 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  80CIETY. 
  [Apr. 
  13, 
  

  

  In 
  the 
  upper 
  third 
  of 
  this 
  white 
  chalk, 
  cut 
  through 
  by 
  the 
  fissure, 
  

   is 
  a 
  pale 
  mottled 
  layer, 
  about 
  15 
  to 
  18 
  inches 
  thick. 
  Thus 
  there 
  is 
  

   a 
  layer 
  of 
  red 
  chalk 
  fairly 
  enclosed 
  in 
  the 
  white 
  chalk 
  ; 
  it 
  is 
  not 
  to 
  be 
  

   traced 
  very 
  far, 
  but, 
  curiously 
  enough, 
  to 
  about 
  an 
  equal 
  distance 
  on 
  

   each 
  side 
  of 
  the 
  fissure. 
  

  

  Where 
  the 
  Huns'ton 
  Eock 
  leaves 
  the 
  cliff, 
  it 
  may 
  be 
  seen 
  that 
  

   the 
  reconstructed 
  chalk, 
  although 
  broken 
  up, 
  has 
  never 
  been 
  re- 
  

   moved 
  from 
  its 
  original 
  site 
  ; 
  for 
  the 
  Red 
  Rock 
  is 
  similarly 
  broken, 
  

   and 
  is 
  still 
  in 
  its 
  natural 
  position. 
  Thus, 
  at 
  the 
  top 
  of 
  the 
  incline 
  

   there 
  has 
  been, 
  ever 
  since 
  the 
  middle 
  of 
  the 
  Drift-period, 
  and 
  per- 
  

   haps 
  earlier, 
  a 
  large 
  surface 
  of 
  the 
  Red 
  Limestone 
  exposed 
  to 
  the 
  

   action 
  of 
  weather 
  and 
  rain. 
  Its 
  carbonate 
  of 
  lime 
  would 
  be 
  dis- 
  

   solved 
  and 
  carried 
  away, 
  but 
  the 
  alumina 
  could 
  only 
  be 
  carried 
  

   down 
  the 
  incline 
  with 
  the 
  iron 
  and 
  manganese. 
  This 
  drainage- 
  

   material 
  would 
  be 
  engulfed 
  by 
  any 
  fissures, 
  and, 
  the 
  chalk 
  acting 
  

   as 
  a 
  filter, 
  much 
  of 
  the 
  insoluble 
  matter 
  would 
  be 
  precipitated 
  at 
  the 
  

   top, 
  and 
  the 
  remainder 
  carried 
  down. 
  The 
  author 
  supposes 
  the 
  cir- 
  

   cumstance 
  of 
  the 
  Red 
  Rock 
  never 
  having 
  been 
  hollowed 
  out 
  under 
  

   one 
  of 
  these 
  cracks 
  to 
  be 
  owing 
  to 
  the 
  thin 
  film 
  of 
  iron 
  deposited 
  on 
  its 
  

   top. 
  The 
  sand, 
  too, 
  may 
  have 
  had 
  the 
  same 
  origin 
  as 
  the 
  red 
  

   matter 
  ; 
  for 
  it 
  has 
  quite 
  the 
  character 
  of 
  the 
  sandy 
  particles 
  abounding 
  

   in 
  bed 
  No. 
  3, 
  and 
  may 
  have 
  been 
  carried 
  down 
  the 
  cracks 
  by 
  heavy 
  

   rains, 
  or 
  by 
  the 
  sea 
  or 
  tidal 
  waters 
  when 
  the 
  land 
  was 
  lower. 
  

  

  As 
  so 
  many 
  of 
  these 
  cracks 
  are 
  visible 
  along 
  the 
  cliff, 
  the 
  number 
  

   that 
  would 
  be 
  visible 
  on 
  a 
  large 
  horizontal 
  surface 
  would 
  probably 
  

   be 
  great 
  ; 
  and 
  the 
  waters 
  draining 
  down 
  them 
  must 
  have 
  made 
  

   channels 
  to 
  flow 
  in, 
  since 
  the 
  deposited 
  iron 
  and 
  alumina 
  would 
  have 
  

   made 
  the 
  floor 
  comparatively 
  impervious 
  ; 
  hence 
  the 
  waters 
  would 
  

   still 
  be 
  excavating 
  channels 
  reaching 
  up 
  into 
  the 
  sponge-rock. 
  

   Many 
  figures 
  might 
  be 
  given, 
  showing 
  that 
  the 
  nest-like 
  enlarge- 
  

   ments 
  are 
  in 
  immediate 
  connexion 
  with 
  the 
  bases 
  of 
  cracks 
  ; 
  so 
  

   the 
  nest 
  may 
  indicate 
  numerous 
  other 
  fissures 
  which 
  are 
  not 
  seen. 
  

  

  It 
  has 
  been 
  supposed 
  that 
  the 
  colour 
  of 
  the 
  Huns'ton 
  Rock 
  might 
  

   be 
  owing 
  to 
  this 
  layer 
  of 
  red 
  matter 
  just 
  described, 
  which 
  ap- 
  

   pears 
  to 
  have 
  been 
  introduced 
  under 
  the 
  sponge-rock 
  at 
  a 
  very 
  

   recent 
  period. 
  But 
  it 
  nowhere 
  affects 
  the 
  colour 
  of 
  the 
  chalk 
  in 
  

   which 
  it 
  is 
  contained. 
  Though 
  it 
  is 
  singular 
  that 
  the 
  fissure 
  in 
  fig. 
  2 
  

   passes 
  through 
  the 
  subordinate 
  band 
  of 
  red 
  chalk, 
  capillary 
  absorp- 
  

   tion 
  could 
  scarcely 
  have 
  tinted 
  the 
  thin 
  band 
  with 
  a 
  substance 
  

   which 
  it 
  is 
  almost 
  impossible 
  could 
  have 
  permeated 
  its 
  mass. 
  Here 
  

   too, 
  as 
  in 
  the 
  Red 
  Rock, 
  the 
  tinge 
  is 
  probably 
  due 
  to 
  decomposed 
  

   glauconite. 
  

  

  What 
  in 
  the 
  whole 
  section 
  is 
  most 
  remarkable 
  is 
  the 
  physical 
  

   resemblance 
  between 
  the 
  sponge-stratum 
  and 
  bed 
  No. 
  1 
  of 
  the 
  Red 
  

   Rock, 
  on 
  the 
  one 
  hand, 
  and 
  between 
  many 
  parts 
  of 
  bed 
  JNo. 
  3 
  and 
  

   the 
  Carstone 
  on 
  the 
  other 
  ; 
  so 
  that 
  there 
  is 
  something 
  very 
  like 
  a 
  

   gradual 
  passage 
  from 
  the 
  Carstone 
  up 
  to 
  the 
  chalk 
  ; 
  and 
  the 
  natural 
  

   inference 
  is 
  that 
  there 
  is 
  no 
  break 
  in 
  time. 
  If 
  it 
  were 
  also 
  inferred 
  

   that 
  the 
  Carstone 
  represents 
  the 
  Shanklin 
  sands, 
  then 
  it 
  would 
  follow 
  

   that 
  part 
  of 
  the 
  Red 
  Rock 
  replaces 
  the 
  Gault. 
  

  

  