﻿1864.] 
  MAW 
  BOULDER-CLAY. 
  451 
  

  

  nite 
  dejDosit, 
  read 
  before 
  the 
  Royal 
  Society 
  in 
  1862, 
  Betula 
  nana, 
  

   SalLv 
  cinerea, 
  and 
  other 
  Alpine 
  Salices 
  indigenous 
  to 
  a 
  much 
  colder 
  

   temperature 
  than 
  the 
  present 
  climate 
  of 
  Devonshire, 
  are 
  stated 
  to 
  

   have 
  been 
  found 
  at 
  the 
  bottom 
  of 
  the 
  drift 
  covering 
  Bovey 
  Chase, 
  

   implying 
  the 
  probability 
  of 
  its 
  deposition 
  during 
  some 
  part 
  of 
  the 
  

   Glacial 
  epoch. 
  I 
  notice 
  the 
  fact 
  as 
  suggesting 
  the 
  possibility 
  of 
  

   the 
  shell-less 
  shingle 
  of 
  Fremington, 
  and 
  its 
  overlying 
  clay, 
  being 
  

   alike 
  referable 
  to 
  it. 
  If 
  the 
  Fremington 
  clay 
  is 
  a 
  representative 
  of 
  

   the 
  boulder-clay 
  formation, 
  the 
  scarcity 
  of 
  boulders 
  in 
  it 
  becomes 
  an 
  

   interesting 
  fact, 
  as 
  being 
  correlative 
  with 
  the 
  comparative 
  absence 
  

   of 
  erratic 
  blocks 
  throughout 
  Devonshire, 
  and 
  would 
  lessen 
  its 
  im- 
  

   portance 
  as 
  implying 
  the 
  non-submergence 
  of 
  this 
  part 
  of 
  the 
  country 
  

   during 
  the 
  Glacial 
  period. 
  

  

  In 
  connexion 
  with 
  this 
  subject, 
  I 
  would 
  notice 
  the 
  occurrence 
  at 
  

   Petroclistow, 
  near 
  the 
  centre 
  of 
  the 
  county, 
  of 
  an 
  isolated 
  bed 
  of 
  

   gravel, 
  composed 
  almost 
  entirely 
  of 
  the 
  detritus 
  of 
  Dartmoor 
  Gra- 
  

   nite, 
  twelve 
  miles 
  from 
  the 
  nearest 
  granite 
  in 
  situ. 
  

  

  From 
  its 
  situation, 
  it 
  is 
  impossible 
  that 
  it 
  can 
  be 
  a 
  mere 
  alluvial 
  de- 
  

   posit 
  brought 
  down 
  from 
  Dartmoor 
  by 
  any 
  existing 
  or 
  ancient 
  river- 
  

   valley. 
  I 
  have 
  carefully 
  examined 
  the 
  country 
  between 
  Dartmoor 
  

   and 
  Petroclistow, 
  and 
  could 
  not 
  find 
  a 
  trace 
  of 
  the 
  deposit 
  in 
  any 
  of 
  

   the 
  intervening 
  valleys, 
  the 
  alluvium 
  of 
  which 
  is 
  of 
  a 
  different 
  cha- 
  

   racter, 
  being 
  composed 
  of 
  the 
  detritus 
  of 
  the 
  adjacent 
  Carboniferous 
  

   beds. 
  

  

  The 
  Oakment 
  is 
  the 
  only 
  river 
  that 
  runs 
  from 
  south 
  to 
  north, 
  or 
  

   that 
  could 
  have 
  brought 
  detritus 
  from 
  the 
  direction 
  of 
  Dartmoor 
  ; 
  

   but 
  the 
  form 
  of 
  the 
  ground 
  denies 
  the 
  possibility 
  of 
  its 
  ever 
  having 
  

   flowed 
  over 
  the 
  site 
  of 
  the 
  Petroclistow 
  gravel-bed, 
  situated 
  in 
  an 
  

   independent 
  close 
  valley, 
  the 
  drainage 
  of 
  which 
  falls 
  into 
  the 
  valley 
  

   of 
  the 
  Torridge 
  ; 
  and 
  it 
  is 
  also 
  separated 
  from 
  Dartmoor 
  by 
  uncon- 
  

   nected 
  valleys 
  and 
  several 
  high 
  parallel 
  ridges 
  of 
  early 
  formations, 
  

   running 
  at 
  right 
  angles 
  to 
  it. 
  It 
  therefore 
  seems 
  probable 
  that 
  the 
  

   deposit 
  of 
  gravel 
  can 
  only 
  be 
  accounted 
  for 
  by 
  an 
  amount 
  of 
  sub- 
  

   mergence 
  covering 
  the 
  whole 
  of 
  these 
  ridges, 
  and 
  that 
  since 
  its 
  de- 
  

   position 
  a 
  great 
  amount 
  of 
  denudation 
  must 
  have 
  taken 
  place 
  to 
  

   remove 
  all 
  trace 
  of 
  the 
  trail 
  or 
  connecting 
  link 
  between 
  it 
  and 
  Dart- 
  

   moor, 
  the 
  evident 
  source 
  of 
  its 
  derivation. 
  The 
  granite 
  -gravel 
  of 
  the 
  

   Petroclistow 
  valley 
  closely 
  resembles 
  that 
  covering 
  the 
  Bovey 
  Tracy 
  

   deposit, 
  which, 
  as 
  before 
  noticed, 
  is 
  possibly 
  assignable 
  to 
  the 
  Glacial 
  

   epoch. 
  

  

  I 
  refer 
  to 
  these 
  facts 
  in 
  connexion 
  with 
  the 
  Fremington 
  deposit, 
  

   from 
  the 
  probability 
  of 
  their 
  all 
  bearing 
  on 
  the 
  question 
  of 
  the 
  sub- 
  

   mergence 
  of 
  Devonshire 
  during 
  the 
  Glacial 
  period, 
  and 
  as 
  being 
  

   worthy 
  of 
  fuller 
  investigation 
  by 
  those 
  who 
  may 
  have 
  opportunities 
  of 
  

   comparing 
  them 
  with 
  glacial 
  deposits 
  in 
  other 
  parts 
  of 
  the 
  country. 
  

  

  