﻿OF 
  THE 
  ARABIAN 
  DESERT. 
  Ill 
  

  

  where 
  the 
  same, 
  since 
  the 
  intermittent 
  parallel 
  ridges 
  before 
  referred 
  

   to 
  are 
  comparatively 
  shallow, 
  while 
  their 
  depth 
  bears 
  a 
  constant 
  

   relation 
  to 
  their 
  width. 
  The 
  highest 
  sand 
  ridge 
  by 
  the 
  Haj 
  road 
  is 
  

   estimated 
  at 
  barely 
  eighty 
  feet, 
  while 
  others 
  are 
  bnt 
  twenty 
  feet 
  in 
  

   depth 
  ; 
  on 
  the 
  other 
  hand 
  the 
  continuous 
  Nefud 
  between 
  Jof 
  and 
  

   Hail 
  has 
  a 
  depth 
  of 
  at 
  least 
  two 
  hundred 
  feet. 
  Mr. 
  Blunt 
  suggests 
  

   that 
  these 
  intermediate 
  ridges 
  may 
  possibly 
  throw 
  some 
  light 
  upon 
  

   the 
  original 
  formation 
  of 
  the 
  mass. 
  It 
  would 
  appear, 
  he 
  thinks, 
  as 
  

   if 
  the 
  wind 
  acting 
  upon 
  the 
  sand 
  first 
  drove 
  it 
  into 
  lines, 
  and 
  these 
  

   growing 
  broader 
  and 
  deeper 
  at 
  last 
  filled 
  up 
  the 
  intervening 
  spaces 
  

   and 
  formed 
  themselves 
  into 
  a 
  continuous 
  desert*. 
  

  

  Although 
  the 
  Nefud 
  has 
  been 
  described 
  as 
  a 
  totally 
  barren 
  waste, 
  

   recent 
  travellers 
  state 
  that 
  it 
  is 
  everywhere, 
  excepting 
  on 
  the 
  highest 
  

   summits 
  of 
  the 
  sand 
  hills, 
  thickly 
  sprinkled 
  with 
  brushwood, 
  garda- 
  

   trees, 
  and 
  tufts 
  of 
  grass, 
  the 
  " 
  fuljes 
  " 
  being 
  especially 
  well 
  clothed 
  

   with 
  vegetation. 
  

  

  From 
  this 
  circumstance, 
  from 
  the 
  fact 
  that 
  sticks, 
  stones, 
  and 
  

   other 
  objects 
  left 
  upon 
  the 
  surface 
  remain 
  for 
  many 
  years 
  uncovered, 
  

   and 
  that 
  in 
  crossing 
  the 
  desert 
  the 
  same 
  landmarks 
  are 
  constantly 
  

   made 
  use 
  of, 
  Mr. 
  Blunt 
  concludes 
  that 
  at 
  the 
  present 
  time 
  these 
  

   sands 
  are 
  not 
  subjected 
  to 
  any 
  material 
  change 
  of 
  position 
  from 
  

   changes 
  in 
  the 
  direction 
  of 
  the 
  winds. 
  He 
  is 
  moreover 
  of 
  opinion 
  

   that 
  although 
  wind 
  has 
  at 
  some 
  time 
  unquestionably 
  caused 
  the 
  

   formation 
  of 
  the 
  Nefiid, 
  it 
  now 
  represents 
  a 
  state 
  of 
  comparative 
  

   repose, 
  as 
  the 
  winds 
  which 
  formerly 
  heaped 
  up 
  these 
  immense 
  masses 
  

   of 
  sand 
  were 
  more 
  violent 
  than 
  those 
  which 
  now 
  prevail. 
  

  

  A 
  specimen 
  of 
  Nefud 
  sand 
  taken 
  between 
  Jof 
  and 
  Hail, 
  for 
  which 
  

   I 
  am 
  indebted 
  to 
  the 
  kindness 
  of 
  Lady 
  Anne 
  Blunt, 
  was 
  found 
  to 
  be 
  

   composed 
  of 
  well-rounded 
  distinctly 
  red 
  grains, 
  varying 
  in 
  size 
  from 
  

   TQ 
  ^° 
  tu 
  °f 
  an 
  i 
  nca 
  a 
  l° 
  n 
  g 
  their 
  greatest 
  diameter. 
  Some 
  few 
  of 
  

   these 
  grains 
  have 
  evidently 
  been 
  broken, 
  and 
  the 
  resulting 
  sharp 
  

   edges 
  have 
  again 
  become 
  partially 
  rounded. 
  

  

  By 
  treatment 
  with 
  hydrochloric 
  acid 
  this 
  sand 
  becomes 
  colourless 
  ; 
  

   and 
  on 
  estimating 
  the 
  ferric 
  oxide 
  thus 
  removed 
  from 
  a 
  given 
  weight, 
  

   it 
  was 
  found 
  to 
  amount 
  to 
  '21 
  per 
  cent., 
  or 
  a 
  little 
  more 
  than 
  -^-jj 
  

   of 
  the 
  total 
  weight 
  of 
  the 
  material 
  operated 
  upon. 
  In 
  addition 
  to 
  

   ferric 
  oxide 
  a 
  small 
  quantity 
  of 
  alumina 
  was 
  removed 
  by 
  the 
  acid. 
  

  

  It 
  is 
  consequently 
  evident 
  that 
  the 
  superficial 
  coating 
  of 
  oxide 
  of 
  

   iron 
  must 
  have 
  been 
  formed 
  subsequently 
  to 
  the 
  period 
  at 
  which 
  the 
  

   rounding 
  of 
  the 
  siliceous 
  grains 
  had 
  been 
  completed. 
  

  

  In 
  order 
  to 
  ascertain 
  to 
  what 
  extent 
  this 
  covering 
  of 
  ferric 
  oxide 
  

   could 
  have 
  resulted 
  from 
  the 
  external 
  decomposition 
  and 
  oxidation 
  

   of 
  the 
  materials 
  constituting 
  the 
  grains 
  themselves, 
  an 
  analysis 
  was 
  

   made 
  of 
  the 
  dried 
  sand 
  remaining 
  after 
  the 
  attack 
  by 
  hydrochloric 
  

   acid. 
  This 
  analysis 
  afforded 
  the 
  following 
  results 
  : 
  — 
  

  

  * 
  Op. 
  tit. 
  vol 
  ii. 
  Appendix, 
  p. 
  24, 
  

  

  