﻿OF 
  THE 
  ARABIAN 
  DESERT. 
  113 
  

  

  grains 
  was 
  their 
  completely 
  rounded 
  character, 
  and 
  the 
  fact 
  that 
  

   the 
  iron 
  was 
  chiefly 
  present 
  on 
  the 
  outside. 
  There 
  is 
  generally 
  

   more 
  iron 
  oxide 
  on 
  the 
  grains 
  of 
  the 
  millet-seed 
  sandstones 
  of 
  the 
  

   Trias 
  than 
  on 
  the 
  desert 
  sand. 
  If 
  Prof. 
  Seeley 
  s 
  suggestion 
  were 
  to 
  

   be 
  adopted 
  we 
  must 
  suppose 
  that 
  each 
  grain 
  of 
  the 
  sand 
  was 
  origi- 
  

   nally 
  twice 
  as 
  large 
  as 
  at 
  present. 
  The 
  only 
  cases 
  in 
  which 
  he 
  had 
  

   found 
  the 
  smallest 
  grains 
  of 
  a 
  sand 
  rounded 
  were 
  in 
  wind-blown 
  

   sands. 
  He 
  pointed 
  out 
  that 
  it 
  would 
  require 
  the 
  solution 
  of 
  

   enormous 
  quantities 
  of 
  limestone 
  to 
  produce 
  the 
  thick 
  beds 
  of 
  crys- 
  

   talline 
  sandstone 
  which 
  had 
  been 
  referred 
  to, 
  

  

  