﻿196 
  HIGH-LEVEL 
  MARINE 
  DELFTS 
  IN 
  NOETH 
  AVALES. 
  

  

  DISCUSSION. 
  

  

  Prof. 
  Hughes 
  thought 
  that 
  the 
  drifts 
  of 
  Derwen 
  and 
  Moel 
  Uchaf 
  

   were 
  to 
  be 
  distinguished 
  from 
  those 
  of 
  the 
  Minera 
  region. 
  The 
  

   former 
  were 
  in 
  the 
  Bala 
  lake-trough 
  ; 
  and 
  striations 
  showed 
  that 
  

   there 
  were 
  local 
  peculiarities 
  in 
  the 
  glacial 
  phenomena. 
  He 
  

   thought 
  that 
  the 
  terraces 
  mentioned 
  by 
  the 
  author 
  were 
  connected 
  

   with 
  a 
  ponding 
  back 
  of 
  the 
  Clwyd. 
  The 
  marine 
  drift 
  ran 
  up 
  the 
  

   Elwy 
  valley 
  far 
  from 
  the 
  sea. 
  The 
  Minera 
  drifts 
  were 
  obviously 
  

   a 
  coast-deposit. 
  The 
  shells 
  in 
  these 
  beds 
  could 
  not 
  have 
  existed 
  

   when 
  land-ice 
  came 
  down 
  to 
  the 
  sea 
  from 
  the 
  great 
  mountain 
  

   districts. 
  Flints 
  were 
  always 
  present, 
  iron-stained, 
  as 
  if 
  derived 
  

   from 
  flint-gravel. 
  He 
  thought 
  it 
  would 
  be 
  worth 
  calculating 
  the 
  

   percentage 
  of 
  flints 
  in 
  the 
  gravels, 
  tracing 
  them 
  from 
  this 
  district 
  

   to 
  E. 
  and 
  N.E. 
  He 
  regarded 
  these 
  deposits 
  as 
  postglacial, 
  and 
  

   thought 
  there 
  was 
  a 
  period 
  of 
  great 
  ice-extension, 
  then 
  of 
  a 
  melting- 
  

   back 
  of 
  the 
  local 
  ice 
  during 
  submergence, 
  and 
  that 
  these 
  Minera 
  

   drifts 
  were 
  the 
  result 
  of 
  the 
  winnowing 
  of 
  the 
  Boulder-clay. 
  

  

  