﻿MARINE 
  DEIFTS 
  IN 
  NORTH. 
  WALES. 
  

  

  193 
  

  

  4. 
  North-central 
  Wales. 
  — 
  At 
  levels 
  above 
  1000 
  feet 
  on 
  the 
  moun- 
  

   tain-slopes 
  or 
  plateaux 
  bordering 
  the 
  valley 
  of 
  the 
  Dee, 
  between 
  

   Llangollen 
  and 
  Bala, 
  I 
  have 
  not 
  yet 
  seen 
  any 
  deposits 
  consisting 
  of 
  

   well-rounded 
  gravel 
  and 
  stratified 
  sand. 
  The 
  occurrence, 
  however, 
  of 
  

   such 
  deposits 
  on 
  watersheds 
  nearly, 
  if 
  not 
  quite, 
  600 
  feet 
  above 
  the 
  

   sea, 
  would 
  appear 
  to 
  show 
  that 
  the 
  sea 
  at 
  one 
  time 
  must 
  have 
  been 
  

   present 
  in 
  the 
  Dee 
  valley. 
  Mr. 
  Euddy 
  (who 
  is 
  intimately 
  acquainted 
  

   with 
  the 
  area 
  between 
  Corwen 
  and 
  Bala) 
  informs 
  me 
  that 
  there 
  are 
  

   several 
  extensive 
  dome-shaped 
  deposits 
  of 
  regularly 
  stratified 
  gravel 
  

   and 
  sand 
  at 
  an 
  elevation 
  of 
  about 
  700 
  feet, 
  and 
  that 
  on 
  the 
  east 
  side 
  

   of 
  the 
  great 
  Arenig 
  mountain 
  there 
  is 
  a 
  remarkable 
  deposit 
  of 
  small 
  

   rounded 
  pebbles 
  and 
  sand 
  at 
  an 
  elevation 
  of 
  not 
  less 
  than 
  1000 
  feet 
  

   above 
  the 
  sea. 
  

  

  Causes 
  of 
  Driftless 
  Areas. 
  — 
  With 
  regard 
  to 
  the 
  areas 
  S. 
  and 
  N". 
  of 
  

   Pont 
  Fadog, 
  1ST. 
  and 
  N.W. 
  of 
  Minera, 
  and 
  the 
  Moelfre-uchaf 
  and 
  

   Frithog 
  areas, 
  two 
  theories 
  might 
  be 
  proposed 
  as 
  an 
  explanation, 
  

   (1) 
  the 
  occupation 
  of 
  the 
  areas 
  by 
  land-ice, 
  which 
  blocked 
  out 
  the 
  

   sea, 
  and 
  (2) 
  the 
  non-exposure 
  of 
  the 
  areas 
  to 
  tempestuous 
  seas, 
  or 
  seas 
  

   capable 
  of 
  rounding 
  stones 
  within 
  the 
  period 
  during 
  which 
  the 
  land 
  

   stood 
  at 
  the 
  required 
  level. 
  The 
  advocates 
  of 
  land-ice 
  might 
  appeal 
  

   to 
  ice-capped 
  islands 
  surrounded 
  by 
  deep 
  water 
  (such 
  as 
  those 
  in 
  

   the 
  Franz 
  Josef 
  Land 
  group) 
  as 
  modern 
  " 
  analogues 
  " 
  of 
  what 
  may 
  

   possibly 
  have 
  been 
  the 
  condition 
  of 
  Moelfre-uchaf 
  and 
  other 
  Welsh 
  

   mountains 
  during 
  some 
  part 
  of 
  the 
  glacial 
  period. 
  With 
  regard 
  to 
  

   North- 
  central 
  Wales, 
  the 
  comparatively 
  land-locked 
  position 
  of 
  the 
  

   district 
  may 
  have 
  prevented 
  it 
  from 
  being 
  much 
  exposed 
  to 
  tempes- 
  

   tuous 
  seas, 
  or 
  land-ice 
  may 
  have 
  capped 
  the 
  mountains 
  down 
  to 
  the 
  

   level 
  of 
  the 
  lower 
  boundary 
  of 
  the 
  marine 
  drifts 
  of 
  the 
  outer 
  slopes, 
  

   while 
  the 
  sea 
  may 
  have 
  found 
  its 
  way 
  up 
  what 
  is 
  now 
  the 
  valley 
  of 
  

   the 
  Dee, 
  but 
  then 
  a 
  fiord, 
  so 
  as 
  to 
  accumulate 
  the 
  gravel 
  and 
  sand 
  

   above 
  noticed. 
  In 
  connexion 
  with 
  this 
  subject 
  it 
  may 
  be 
  remarked 
  

   that 
  the 
  interior 
  of 
  the 
  southern 
  part 
  of 
  the 
  Penine 
  Hills 
  is 
  almost 
  

   entirely 
  free 
  from 
  rounded 
  gravel 
  and 
  sand. 
  Mr. 
  John 
  Aitken 
  (if 
  I 
  

   understand 
  him 
  correctly) 
  believes 
  that 
  there 
  the 
  sea 
  was 
  blocked 
  

   out 
  by 
  snow 
  and 
  ice. 
  Both 
  areas 
  (the 
  north 
  Welsh 
  central 
  and 
  

   the 
  southern 
  Penine) 
  likewise 
  agree 
  in 
  being 
  almost 
  entirely 
  free 
  

   from 
  erratic 
  stones 
  *. 
  

  

  VI. 
  Boulders 
  and 
  Drifts 
  on 
  Moel 
  Wnion. 
  

  

  My 
  first 
  search 
  for 
  erratic 
  stones 
  on 
  this 
  mountain 
  (which 
  is 
  

   situated 
  near 
  Aber, 
  North 
  Wales) 
  was 
  unsuccessful 
  ; 
  but 
  during 
  

   two 
  ascents 
  in 
  last 
  August 
  and 
  September 
  (1881), 
  I 
  found 
  five 
  

   specimens 
  of 
  granite, 
  including 
  a 
  small 
  boulder 
  and 
  a 
  pebble, 
  a 
  short 
  

   distance 
  below 
  the 
  summit, 
  and 
  three 
  boulders 
  in 
  the 
  cairn, 
  on 
  the 
  

   summit, 
  the 
  height 
  of 
  which 
  is 
  1905 
  feet 
  above 
  the 
  sea-level. 
  To 
  

   make 
  sure 
  that 
  the 
  latter 
  had 
  not 
  been 
  carried 
  up 
  hill 
  (a 
  circum- 
  

  

  * 
  I 
  lately 
  found 
  a 
  rounded 
  chalk-flint 
  on 
  the 
  N.W. 
  side 
  of 
  Bala 
  lake 
  ; 
  and 
  

   Professor 
  Green, 
  many 
  years 
  ago, 
  informed 
  me 
  that 
  he 
  had 
  found 
  granite 
  in 
  

   the 
  Wye 
  valley, 
  near 
  Buxton 
  ; 
  and 
  I 
  once 
  saw 
  a 
  small 
  granite 
  boulder 
  in 
  Cas- 
  

   tleton, 
  which 
  had 
  been 
  dug 
  up 
  from 
  a 
  considerable 
  depth 
  in 
  the 
  churchyard. 
  

  

  