﻿144 
  ME. 
  A, 
  STBAHAN 
  ON 
  GLACIAL 
  PHENOMENA 
  OE 
  [May 
  1 
  897, 
  

  

  at 
  times 
  be 
  traced 
  to 
  its 
  source 
  among 
  the 
  older 
  rocks 
  ; 
  thirdly, 
  

   that 
  deposition 
  was 
  not 
  only 
  unequal 
  but 
  alternated 
  with 
  erosion, 
  

   leading 
  to 
  fragments 
  of 
  one 
  bed 
  being 
  included 
  as 
  pebbles 
  in 
  another 
  ; 
  

   fourthly, 
  that 
  they 
  rarely 
  contain 
  marine 
  organisms, 
  or 
  such 
  strata 
  

   as 
  usually 
  compose 
  marine 
  formations, 
  while 
  on 
  the 
  other 
  hand 
  

   drifted 
  plant-remains 
  are 
  not 
  uncommon 
  ; 
  fifthly, 
  that 
  such 
  lime- 
  

   stones 
  as 
  occur 
  consist, 
  when 
  unaltered, 
  of 
  amorphous 
  carbonate 
  of 
  

   lime 
  and 
  not 
  of 
  organic 
  remains 
  ; 
  while, 
  lastly, 
  there 
  is 
  common 
  to 
  

   all 
  a 
  tendency 
  to 
  a 
  red 
  colour. 
  All 
  these 
  characteristics 
  may 
  be 
  

   taken 
  as 
  indicating 
  the 
  proximity 
  of 
  large 
  land-areas, 
  and 
  it 
  is 
  in 
  

   rocks 
  of 
  this 
  type, 
  if 
  anywhere, 
  that 
  evidence 
  of 
  the 
  existence 
  of 
  

   land-ice 
  might 
  be 
  expected 
  to 
  be 
  preserved. 
  

  

  "We 
  are 
  here 
  reminded 
  that 
  ice-action 
  was 
  called 
  in 
  so 
  long 
  ago 
  

   as 
  1855 
  by 
  Ramsay 
  l 
  to 
  account 
  for 
  certain 
  characters 
  in 
  the 
  Old 
  

   Red 
  Sandstone 
  and 
  the 
  Permian, 
  and 
  though 
  the 
  evidence 
  on 
  which 
  

   he 
  relied 
  has 
  since 
  been 
  proved 
  by 
  Mr. 
  Wickham 
  King 
  to 
  have 
  

   been 
  insufficient, 
  the 
  idea 
  has 
  been 
  revived 
  of 
  late 
  years 
  by 
  Mr. 
  

   Oldham. 
  More 
  recently 
  Dr. 
  Hicks 
  found 
  evidence 
  of 
  glacial 
  action 
  

   in 
  the 
  Cambrian 
  rocks 
  of 
  Wales, 
  not 
  only 
  in 
  the 
  presence 
  of 
  large 
  

   boulders, 
  but 
  in 
  the 
  enormous 
  thickness 
  of 
  beds 
  devoid 
  of 
  marine 
  

   life, 
  2 
  and 
  points 
  out 
  that 
  ' 
  at 
  no 
  time 
  since, 
  unless 
  in 
  the 
  Glacial 
  

   period, 
  does 
  there 
  seem 
  to 
  have 
  been 
  so 
  much 
  land 
  in 
  the 
  higher 
  

   latitudes, 
  and 
  it 
  is, 
  therefore, 
  reasonable 
  to 
  suppose 
  that 
  in 
  the 
  

   earlier 
  stages 
  at 
  least 
  of 
  the 
  epoch 
  the 
  climate 
  was 
  one 
  of 
  great 
  cold 
  ' 
  

   (op. 
  cit. 
  p. 
  252). 
  It 
  is 
  especially 
  noteworthy 
  that 
  the 
  Gaisa 
  Beds 
  

   appear 
  to 
  be 
  approximately 
  of 
  the 
  same 
  age 
  as 
  the 
  rocks 
  referred 
  

   to 
  by 
  Dr. 
  Hicks. 
  

  

  In 
  the 
  formations 
  in 
  other 
  parts 
  of 
  the 
  world 
  in 
  which 
  glacial 
  

   phenomena 
  occur 
  we 
  find 
  a 
  repetition 
  of 
  the 
  same 
  general 
  charac- 
  

   teristics. 
  Most 
  of 
  those 
  described 
  consist 
  of 
  sandstones, 
  mudstones, 
  

   and 
  conglomerates 
  of 
  great 
  thickness, 
  and 
  showing, 
  in 
  the 
  inter- 
  

   spersal 
  of 
  great 
  erratics, 
  evidence 
  of 
  the 
  prolonged 
  action 
  of 
  ice, 
  

   though 
  in 
  some 
  cases 
  striated 
  pavements 
  and 
  deposits 
  of 
  the 
  type 
  of 
  

   Boulder 
  Clay 
  have 
  also 
  been 
  observed. 
  They, 
  therefore, 
  differ 
  

   from 
  the 
  Gaisa 
  Beds, 
  which 
  at 
  present 
  are 
  known 
  to 
  contain 
  only 
  

   an 
  occasional 
  glacial 
  episode, 
  during 
  which 
  there 
  seems 
  to 
  have 
  been 
  

   a 
  sudden 
  and 
  possibly 
  brief 
  invasion 
  of 
  the 
  water 
  by 
  land-ice, 
  though 
  

   the 
  sediments 
  above 
  and 
  below 
  contain 
  no 
  erratics 
  or 
  any 
  other 
  hint 
  

   of 
  glacial 
  action. 
  But 
  both 
  to 
  the 
  Gaisa 
  and 
  the 
  other 
  formations 
  

   there 
  seems 
  to 
  be 
  common 
  a 
  general 
  absence 
  of 
  marine 
  organisms 
  or 
  

   of 
  strata 
  of 
  open-sea 
  origin. 
  They 
  rarely 
  contain 
  any 
  fossils 
  save 
  

   plant-remains, 
  and 
  in 
  this 
  and 
  other 
  respects 
  approximate 
  to 
  the 
  

   same 
  type 
  as 
  the 
  great 
  continental 
  formations 
  alluded 
  to 
  above. 
  

  

  Evidence 
  of 
  glacial 
  action 
  in 
  such 
  formations 
  has 
  been 
  discovered 
  

   in 
  Australia 
  by 
  Selwyn, 
  3 
  in 
  Tasmania, 
  in 
  India 
  by 
  Dr. 
  Blanford, 
  in 
  

  

  1 
  Quart. 
  Joum. 
  Geo!. 
  Soc. 
  vol. 
  xi. 
  (1855) 
  p. 
  185. 
  See 
  also 
  R. 
  D. 
  Oldham, 
  

   ibid. 
  vol. 
  1. 
  (1894) 
  p. 
  463. 
  

  

  2 
  Geol. 
  Mag. 
  1876, 
  p. 
  157 
  ; 
  ibid. 
  1880, 
  p. 
  488. 
  

  

  3 
  The 
  latest 
  account 
  of 
  these 
  glacial 
  beds, 
  together 
  with 
  references 
  to 
  the 
  

   previous 
  literature, 
  will 
  be 
  found 
  in 
  a 
  paper 
  by 
  Prof. 
  Edgeworth 
  David, 
  Quart. 
  

   Journ. 
  Geol. 
  Soc. 
  vol. 
  lii. 
  (1896) 
  p. 
  289. 
  

  

  