﻿332 
  T. 
  F. 
  JAMIESON 
  ON 
  THE 
  LAST 
  STAGE 
  OF 
  

  

  the 
  freshwater 
  drift 
  of 
  the 
  Western 
  States, 
  where 
  we 
  can 
  scarcely 
  

   suppose 
  the 
  sea 
  to 
  have 
  operated. 
  

  

  As 
  the 
  later 
  glaciers 
  in 
  Britain 
  and 
  Ireland 
  in 
  many 
  cases 
  must 
  

   have 
  moved 
  over 
  sand 
  and 
  gravel 
  previously 
  accumulated 
  hy 
  the 
  sea, 
  

   it 
  is 
  evident 
  that 
  their 
  marginal 
  deposits 
  would 
  he 
  influenced 
  hythis 
  

   circumstance 
  ; 
  for 
  the 
  gravel 
  and 
  pehhles 
  in 
  front 
  of 
  them 
  might 
  

   have 
  been 
  originally 
  waterworn 
  by 
  the 
  waves, 
  and 
  some 
  marine 
  

   shells 
  might 
  thus 
  be 
  occasionally 
  found 
  in 
  them. 
  The 
  occurrence 
  of 
  

   such 
  remains 
  in 
  a 
  few 
  Eskers 
  I 
  wc^ld 
  therefore 
  consider 
  to 
  be 
  no 
  

   material 
  objection 
  to 
  my 
  mode 
  of 
  accounting 
  for 
  them. 
  In 
  reference 
  

   to 
  the 
  waterworn 
  and 
  pebbly 
  character 
  which 
  many 
  of 
  these 
  glacial 
  

   accumulations 
  present, 
  it 
  may 
  be 
  useful 
  to 
  bear 
  in 
  mind 
  that 
  deposits 
  

   of 
  similar 
  materials 
  are 
  common 
  in 
  frwrtzeiidnd, 
  and 
  that 
  even 
  the 
  

   famous 
  blocks 
  of 
  Monthey 
  lie 
  amongst 
  stratified 
  sand 
  and 
  gravel. 
  

  

  § 
  7. 
  Gravel 
  Terraces. 
  

  

  The 
  terraced 
  banks 
  of 
  sand 
  and 
  gravel 
  that 
  occur 
  along 
  the 
  sides 
  of 
  

   our 
  Scottish 
  rivers 
  seem 
  to 
  me 
  to 
  have 
  been 
  formed 
  during 
  the 
  close 
  of 
  

   the 
  glacial 
  period. 
  Some 
  geologists 
  have 
  attributed 
  them 
  to 
  marine 
  

   action, 
  and 
  have 
  considered 
  them 
  to 
  be 
  ancient 
  sea-margins. 
  I 
  

   myself, 
  at 
  one 
  time, 
  endeavoured 
  to 
  account 
  for 
  many 
  of 
  these 
  gravel 
  

   accumulations 
  by 
  the 
  off-rushing 
  action 
  of 
  the 
  sea 
  during 
  movements 
  

   of 
  upheaval 
  at 
  the 
  time 
  the 
  land 
  was 
  gradually 
  emerging 
  from 
  the 
  

   sea 
  of 
  the 
  glacial 
  period, 
  which 
  we 
  know 
  covered 
  much 
  of 
  Great 
  

   Britain. 
  But 
  I 
  have 
  become 
  convinced 
  that 
  this 
  explanation 
  is 
  not 
  

   the 
  right 
  one, 
  and 
  I 
  now 
  incline 
  to 
  think 
  they 
  are 
  almost 
  all 
  fresh- 
  

   water 
  and 
  glacial 
  deposits. 
  

  

  Not 
  a 
  single 
  marine 
  fossil 
  has 
  been 
  found 
  in 
  them. 
  Not 
  a 
  trace 
  

   of 
  old 
  estuary 
  mud 
  occurs 
  along 
  the 
  higher 
  reaches 
  of 
  our 
  rivers 
  in 
  

   connexion 
  with 
  them. 
  Now 
  it 
  seems 
  to 
  me 
  that 
  if 
  the 
  sea 
  had 
  

   occupied 
  a 
  valley 
  after 
  the 
  glaciers 
  finally 
  left 
  it 
  we 
  ought 
  to 
  find 
  some 
  

   marine 
  fossils 
  and 
  estuary 
  beds 
  here 
  and 
  there 
  along 
  the 
  valley. 
  The 
  

   absence 
  of 
  all 
  organic 
  remains, 
  terrestrial 
  as 
  well 
  as 
  marine, 
  in 
  these 
  

   terraces 
  and 
  valley- 
  gravels, 
  agrees 
  better 
  with 
  the 
  supposition 
  that 
  

   Scotland 
  was 
  at 
  the 
  time 
  covered 
  with 
  snow 
  and 
  ice. 
  Moreover 
  

   these 
  river-terraces 
  are 
  not 
  horizontal, 
  as 
  they 
  ought 
  to 
  be 
  if 
  they 
  

   were 
  sea-margins 
  ; 
  for 
  as 
  a 
  rule 
  they 
  slope 
  seawards, 
  like 
  the 
  bed 
  

   of 
  the 
  present 
  rivers 
  *. 
  They 
  occasionally 
  contain 
  large 
  heavy 
  

   boulders, 
  3 
  to 
  4 
  feet 
  in 
  diameter 
  or 
  more, 
  and 
  are 
  associated 
  with 
  

   elongated 
  mounds 
  and 
  confused 
  hillocks 
  of 
  coarse 
  gravel 
  of 
  a 
  more 
  

   morainic 
  character. 
  I 
  am 
  of 
  opinion, 
  as 
  I 
  have 
  expressed 
  in 
  former 
  

   papers, 
  that 
  these 
  deposits 
  have 
  been 
  for 
  the 
  most 
  part 
  accumulated 
  

   during 
  the 
  gradual 
  retreat 
  and 
  melting 
  of 
  the 
  later 
  glaciers. 
  That 
  

   such 
  terraces 
  and 
  mounds 
  can 
  be 
  formed 
  without 
  the 
  presence 
  of 
  the 
  

   sea 
  is 
  very 
  well 
  shown 
  by 
  the 
  similar 
  deposits 
  that 
  occur 
  in 
  the 
  

   valleys 
  of 
  the 
  Pyrenees, 
  the 
  Himalaya, 
  and 
  other 
  mountain-chains 
  in 
  

  

  * 
  Eor 
  a 
  good 
  account 
  of 
  some 
  Scottish 
  terraces, 
  see 
  a 
  paper 
  on 
  the 
  Old 
  River- 
  

   terraces 
  of 
  the 
  Earn 
  and 
  Teith, 
  by 
  the 
  Rev. 
  Thos. 
  Brown. 
  Trans, 
  of 
  Royal 
  

   Society 
  of 
  Edinburgh, 
  vol. 
  xxvi., 
  1870. 
  

  

  