﻿244 
  THE 
  SUPERFICIAL 
  DEPOSITS 
  OP 
  CTJTCH. 
  [May 
  1 
  89 
  7, 
  

  

  Mr. 
  Lampltjgh 
  was 
  glad 
  that 
  the 
  Author 
  had 
  called 
  attention 
  to 
  

   the 
  phenomena 
  of 
  dry 
  erosion, 
  as 
  he 
  had 
  touched 
  the 
  fringe 
  of 
  an 
  

   important 
  subject 
  which 
  had 
  not 
  yet 
  received 
  its 
  due 
  recognition 
  

   from 
  the 
  geologists 
  of 
  this 
  country. 
  Over 
  vast 
  areas 
  in 
  various 
  

   parts 
  of 
  the 
  world 
  the 
  surface-drainage 
  was 
  at 
  present 
  insufficient 
  

   to 
  remove 
  the 
  detritus 
  brought 
  down 
  the 
  slopes 
  by 
  atmospheric! 
  

   agencies, 
  and 
  the 
  waste-material 
  consequently 
  accumulated 
  around 
  

   the 
  hills 
  and 
  partially 
  buried 
  them. 
  The 
  speaker 
  had 
  been 
  greatly 
  

   impressed 
  by 
  these 
  phenomena 
  in 
  Arizona, 
  where, 
  as 
  Dr. 
  Blanford 
  

   had 
  just 
  remarked 
  with 
  respect 
  to 
  another 
  region, 
  the 
  rocky 
  ground 
  

   often 
  stood 
  out 
  like 
  islands 
  above 
  the 
  vast 
  spreads 
  of 
  loose 
  material. 
  

  

  Mr. 
  Vaughan 
  Cornish 
  said 
  that 
  the 
  power 
  of 
  the 
  winds 
  in 
  the 
  

   locality 
  dealt 
  with 
  in 
  Mr. 
  Blake's 
  paper 
  was 
  undoubtedly 
  adequate 
  

   to 
  carry 
  sand 
  to 
  the 
  situations 
  described 
  ; 
  and 
  that, 
  with 
  regard 
  to 
  

   the 
  calcareous 
  nature 
  of 
  the 
  subrecent 
  concrete 
  which 
  Dr. 
  Blanford 
  

   regarded 
  as 
  a 
  difficulty, 
  the 
  blown 
  sand 
  of 
  Hale 
  in 
  Cornwall 
  might 
  

   be 
  cited 
  in 
  support 
  of 
  the 
  Author's 
  views. 
  This 
  was 
  largely 
  com- 
  

   posed 
  of 
  shell-fragments, 
  and 
  he 
  had 
  observed 
  that 
  it 
  was 
  more 
  

   mobile 
  under 
  the 
  action 
  of 
  wind 
  than 
  the 
  ordinary 
  quartz-sand 
  of 
  the 
  

   sea-shore. 
  Referring 
  to 
  the 
  boulder-beds, 
  he 
  said 
  that 
  the 
  travel 
  of 
  

   boulders 
  presented 
  some 
  curious 
  features, 
  which 
  he 
  was 
  at 
  present 
  

   examining. 
  For 
  example, 
  a 
  large 
  boulder 
  travelled 
  badly 
  on 
  fine 
  

   sand 
  because 
  the 
  sand 
  was 
  readily 
  displaced, 
  and 
  the 
  boulder 
  sank. 
  

   Conversely, 
  little 
  pebbles 
  travelled 
  with 
  difficulty 
  over 
  a 
  bed 
  of 
  

   boulders 
  because 
  they 
  were 
  caught 
  in 
  the 
  hollows, 
  and 
  with 
  diffi- 
  

   culty 
  surmounted 
  the 
  humps 
  of 
  the 
  rough 
  surface. 
  The 
  best 
  con- 
  

   dition 
  for 
  the 
  transport 
  of 
  large 
  boulders, 
  and 
  of 
  blocks 
  or 
  slabs 
  of 
  

   stone, 
  appeared 
  to 
  be 
  when 
  the 
  bed 
  was 
  composed 
  of 
  pebbles 
  large 
  

   enough 
  to 
  form 
  a 
  hard 
  floor, 
  but 
  not 
  so 
  large 
  as 
  to 
  allow 
  the 
  boulder 
  

   to 
  catch 
  in 
  the 
  pits 
  of 
  the 
  surface. 
  It 
  seemed, 
  therefore, 
  that 
  to 
  

   every 
  size 
  of 
  boulder 
  there 
  should 
  correspond 
  a 
  particular 
  size 
  of 
  

   pebbles 
  over 
  which 
  the 
  boulder 
  could 
  be 
  transported 
  with 
  the 
  

   minimum 
  effort. 
  

  

  The 
  Author, 
  in 
  replying, 
  remarked 
  that 
  the 
  infratrappean 
  grits 
  

   were, 
  in 
  his 
  view, 
  of 
  entirely 
  local 
  origin 
  and 
  not 
  to 
  be 
  compared, 
  

   except 
  in 
  point 
  of 
  time, 
  with 
  any 
  deposits 
  elsewhere 
  ; 
  while 
  the 
  

   presence 
  of 
  a 
  single 
  quartz-pebble 
  in 
  them 
  would 
  be 
  destructive 
  of 
  

   his 
  account 
  of 
  their 
  origin. 
  He 
  admitted 
  that 
  there 
  were 
  laterites 
  

   in 
  Cutch 
  of 
  Eocene 
  age. 
  Those 
  examined 
  by 
  him, 
  however, 
  which 
  

   were 
  far 
  more 
  widely 
  spread, 
  gave 
  no 
  indication 
  of 
  age, 
  but 
  were 
  

   certainly 
  neither 
  derived 
  from 
  the 
  rocks 
  on 
  which 
  they 
  rested 
  nor 
  

   produced 
  by 
  the 
  reconstruction 
  of 
  such 
  as 
  were 
  so 
  derived. 
  He 
  

   very 
  much 
  doubted 
  the 
  usual 
  statement 
  that 
  water 
  was 
  driven 
  

   on 
  to 
  the 
  Ban 
  from 
  the 
  Indus-mouth 
  by 
  the 
  monsoon. 
  He 
  had 
  

   ridden 
  over 
  part 
  of 
  it 
  towards 
  the 
  end 
  of 
  an 
  exceptionally 
  rainy 
  

   season, 
  and 
  there 
  was 
  less 
  water 
  on 
  it 
  than 
  the 
  rain 
  that 
  had 
  

   fallen. 
  Moreover, 
  the 
  strongest 
  winds 
  in 
  Cutch 
  blow 
  in 
  the 
  hot 
  

   season, 
  but 
  the 
  Ran 
  is 
  not 
  flooded 
  till 
  the 
  rain 
  has 
  fallen. 
  He 
  

   agreed 
  with 
  Mr. 
  Lamplugh 
  that 
  the 
  study 
  of 
  the 
  phenomena 
  

   of 
  denudation 
  by 
  aerial 
  agencies 
  in 
  the 
  tropics 
  was 
  a 
  new 
  experience 
  

   for 
  an 
  English 
  geologist. 
  

  

  