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  XV. 
  Proceedings 
  of 
  Learned 
  Societies. 
  

  

  GEOLOGICAL 
  SOCIETY. 
  

  

  [Continued 
  from 
  vol. 
  xv. 
  p. 
  580.] 
  

  

  March 
  4th, 
  1908.— 
  Prof. 
  W. 
  J. 
  Sollas, 
  Sc.D., 
  LL.D., 
  F.R.S., 
  

  

  President, 
  in 
  the 
  Chair. 
  

  

  ^HE 
  following 
  communications 
  were 
  read 
  : 
  — 
  

  

  1. 
  'On 
  Metriorhynchus 
  brachyrhynclius, 
  Deslong., 
  from 
  the 
  

   Oxford 
  Clay 
  near 
  Peterborough.' 
  By 
  E. 
  Thurlow 
  Leeds, 
  B.A. 
  

  

  2. 
  ' 
  The 
  High-Level 
  Platforms 
  of 
  Bodmin 
  Moor, 
  and 
  their 
  

   Relation 
  to 
  the 
  Deposits 
  of 
  Stream-Tin 
  and 
  Wolfram.' 
  By 
  George 
  

   Barrow, 
  F.G.S. 
  

  

  In 
  this 
  area 
  there 
  are 
  three 
  platforms 
  : 
  — 
  one, 
  which 
  is 
  marine 
  

   and 
  of 
  Pliocene 
  age, 
  terminating 
  in 
  a 
  steep 
  slope 
  at 
  430 
  feet 
  above 
  

   the 
  sea 
  ; 
  a 
  second, 
  at 
  a 
  height 
  of 
  750 
  feet, 
  seen 
  about 
  Camelford 
  

   and 
  at 
  the 
  foot 
  of 
  Delabole 
  Hill 
  ; 
  and 
  a 
  third, 
  a 
  little 
  under 
  1000 
  feet, 
  

   first 
  recognized 
  on 
  Davidstow 
  Moor. 
  The 
  valleys 
  cutting 
  the 
  lowest 
  

   platform 
  are 
  found 
  to 
  have 
  been 
  much 
  deepened 
  since 
  the 
  uplift 
  of 
  

   the 
  platform 
  to 
  its 
  present 
  level 
  ; 
  but 
  the 
  features 
  thus 
  caused 
  

   gradually 
  die 
  out 
  in 
  the 
  higher 
  part 
  of 
  the 
  valleys, 
  disappearing 
  

   in 
  the 
  Biver 
  Camel 
  about 
  22 
  miles 
  from 
  the 
  sea. 
  At 
  the 
  higher 
  

   parts 
  of 
  all 
  these 
  platforms, 
  marshes 
  are 
  frequently 
  found. 
  

  

  The 
  superficial 
  deposits 
  which 
  bear 
  tin 
  above 
  the 
  750-foot 
  

   platform 
  differ 
  markedly 
  at 
  times 
  from 
  those 
  below 
  it, 
  as 
  here 
  

   ancient 
  wash 
  is 
  preserved 
  — 
  possibly 
  protected, 
  by 
  a 
  snowfield 
  or 
  by 
  

   being 
  frozen, 
  from 
  the 
  denudation 
  which 
  has 
  destroyed 
  them 
  below 
  

   this 
  level. 
  These 
  deposits 
  are 
  not 
  so 
  concentrated 
  as 
  the 
  stream- 
  

   sorted 
  material 
  below, 
  but 
  they 
  have 
  been 
  frequently 
  worked 
  

   in 
  past 
  times 
  until 
  the 
  industry 
  languished, 
  in 
  consequence 
  of 
  the 
  

   difficulty 
  or 
  impossibility 
  of 
  separating 
  the 
  wolfram 
  contained 
  in 
  

   the 
  enriched 
  portion 
  of 
  these 
  deposits 
  from 
  the 
  tin-ore. 
  This 
  

   difficulty 
  having 
  been 
  overcome, 
  and 
  the 
  wolfram 
  being 
  even 
  more 
  

   valuable 
  than 
  the 
  tin-ore, 
  the 
  industry 
  is 
  now 
  reviving. 
  The 
  

   veins 
  from 
  which 
  the 
  wolfram 
  is 
  derived 
  have 
  been 
  found 
  close 
  

   to 
  the 
  points 
  where 
  the 
  ' 
  wash 
  ' 
  is 
  enriched 
  by 
  their 
  denudation. 
  

   The 
  method 
  of 
  working 
  is 
  described, 
  and 
  it 
  is 
  shown 
  that 
  the 
  

   success 
  of 
  it 
  depends 
  to 
  some 
  extent 
  on 
  the 
  slope 
  of 
  the 
  granite- 
  

   floor 
  on 
  which 
  the 
  detritus 
  rests 
  ; 
  otherwise 
  the 
  deposit 
  becomes 
  

   water-logged, 
  and 
  the 
  method 
  of 
  separation 
  adopted 
  is 
  expensive 
  to 
  

   carry 
  out. 
  

  

  On 
  Bodmin 
  Moor, 
  the 
  larger 
  marshes 
  have 
  a 
  floor 
  of 
  kaolinized 
  

   granite; 
  but 
  there 
  is 
  a 
  difficulty 
  in 
  working 
  it 
  at 
  many 
  points, 
  in 
  

   consequence 
  of 
  the 
  water-logging 
  by 
  peaty 
  water. 
  This 
  difficulty 
  

   docs 
  not 
  exist 
  at 
  Btannon 
  Marsh, 
  which 
  has 
  sloping 
  Bides 
  

   instead 
  of 
  a 
  flat 
  base, 
  the 
  cycle 
  of 
  denudation 
  in 
  this 
  case 
  being 
  

   incomplete. 
  

  

  