﻿1863.] 
  ADAMS 
  — 
  NILE 
  VALLEY. 
  7 
  

  

  his 
  portion 
  of 
  our 
  inquiries, 
  I 
  cannot 
  help 
  expressing 
  a 
  hope 
  that 
  

   his 
  valuable 
  researches 
  will 
  soon 
  be 
  published. 
  

  

  II. 
  Physical 
  character 
  of 
  the 
  Nile 
  Valley 
  in 
  Nubia, 
  from 
  Selsileh 
  

   to 
  the 
  Second 
  Cataract. 
  — 
  After 
  passing 
  Selsileh, 
  about 
  thirty-six 
  miles 
  

   below 
  the 
  First 
  Cataract, 
  and 
  proceeding 
  southwards, 
  the 
  physical 
  

   aspect 
  of 
  the 
  Nile 
  Yalley 
  is 
  seen 
  to 
  change 
  rapidly. 
  The 
  bed 
  of 
  the 
  

   river 
  gradually 
  narrows, 
  until 
  it 
  is 
  hemmed 
  in 
  on 
  both 
  sides 
  by 
  rocks 
  

   and 
  steep 
  banks, 
  either 
  of 
  sandstone 
  or 
  granite, 
  which 
  appear 
  as 
  bold 
  

   crags 
  and 
  rugged 
  and 
  worn 
  cliffs, 
  and, 
  as 
  you 
  approach 
  Wadi 
  Half 
  eh, 
  

   as 
  isolated 
  conical 
  hills 
  of 
  sandstone 
  ; 
  and 
  hogs' 
  backs, 
  or 
  elevated 
  

   plateaus, 
  alternate 
  with 
  wide 
  expanses 
  of 
  desert 
  covered, 
  as 
  usual, 
  

   with 
  a 
  reddish-white 
  sand. 
  

  

  1. 
  Sandstone 
  and 
  Sand-drift 
  of 
  Nubia. 
  — 
  The 
  siliceous 
  sandstone 
  of 
  

   Nubia 
  has 
  a 
  perfectly 
  parallel 
  stratification, 
  and, 
  except 
  at 
  its 
  junc- 
  

   tion 
  with 
  the 
  granitic 
  rocks, 
  very 
  few 
  traces 
  of 
  disturbance 
  are 
  ob- 
  

   servable 
  ; 
  on 
  the 
  contrary, 
  the 
  absence 
  of 
  fissures 
  and 
  rents 
  is 
  remark- 
  

   able, 
  and 
  would 
  appear, 
  in 
  conjunction 
  with 
  other 
  facts, 
  to 
  indicate 
  

   that 
  the 
  rate 
  of 
  upheaval 
  had 
  been 
  slow. 
  There 
  is 
  likewise 
  reason 
  

   to 
  suppose, 
  from 
  the 
  wear 
  and 
  tear 
  so 
  evident 
  everywhere 
  on 
  the 
  

   surface, 
  that 
  the 
  degradation 
  and 
  denudation 
  have 
  been 
  enormous, 
  

   perhaps 
  far 
  beyond 
  what 
  the 
  geologist 
  would 
  expect 
  from 
  atmo- 
  

   spheric 
  influences 
  alone 
  ; 
  the 
  sandstone 
  of 
  Nubia, 
  however, 
  crumbles 
  

   readily, 
  especially 
  the 
  grits 
  and 
  large- 
  grained 
  varieties. 
  The 
  finer 
  

   particles 
  are 
  drifted 
  about 
  by 
  the 
  wind, 
  and, 
  from 
  the 
  proximity 
  of 
  

   the 
  desert 
  to 
  the 
  river, 
  the 
  latter 
  is 
  constantly 
  receiving 
  materials 
  

   which 
  mix 
  with 
  its 
  mud, 
  and 
  form 
  soil 
  and 
  sand-banks, 
  which 
  are 
  

   ever 
  being 
  added 
  to 
  or 
  removed, 
  according 
  to 
  the 
  direction 
  and 
  force 
  

   of 
  the 
  currents. 
  The 
  physical 
  aspect 
  of 
  Nubia 
  is 
  therefore 
  under- 
  

   going 
  considerable 
  change, 
  especially 
  in 
  the 
  neighbourhood 
  of 
  the 
  

   Nile 
  ; 
  so 
  that 
  the 
  even 
  and 
  perfectly 
  horizontal 
  stratification 
  of 
  the 
  

   high 
  lands 
  is 
  continuous 
  with 
  that 
  of 
  the 
  flat- 
  topped 
  isolated 
  hills 
  in 
  

   the 
  neighbourhood, 
  showing 
  vast 
  valleys 
  of 
  denudation, 
  and 
  what 
  a 
  

   tremendous 
  scouring 
  the 
  country 
  has 
  undergone 
  at 
  one 
  time 
  or 
  other. 
  

   Although 
  a 
  great 
  portion 
  of 
  the 
  Nile-deposit 
  is 
  evidently 
  the 
  result 
  

   of 
  denudation 
  going 
  on 
  towards 
  its 
  origin, 
  the 
  vast 
  degradation 
  

   taking 
  place 
  even 
  between 
  the 
  First 
  and 
  Second 
  Cataracts 
  affords 
  

   ample 
  materials 
  for 
  the 
  formation 
  of 
  alluvial 
  and 
  arenaceous 
  deposits 
  

   along 
  its 
  course 
  northwards. 
  The 
  sandstone 
  is 
  of 
  various 
  sorts, 
  and 
  

   differs 
  in 
  consistence, 
  being 
  either 
  fine-grained* 
  and 
  of 
  divers 
  shades 
  

   of 
  colour, 
  most 
  frequently 
  of 
  a 
  light 
  yellowish 
  white, 
  or 
  a 
  gritstonef, 
  

   of 
  considerable 
  variety 
  as 
  to 
  the 
  size 
  of 
  its 
  rounded 
  pebbles, 
  which 
  

   are 
  mostly 
  composed 
  of 
  quartz 
  and 
  hornblende, 
  and 
  are 
  frequently 
  

   as 
  big 
  as 
  walnuts. 
  The 
  finer 
  particles, 
  forming 
  the 
  matrix, 
  become 
  

   the 
  sport 
  of 
  the 
  winds 
  ; 
  thus 
  the 
  plain 
  is 
  often 
  observed 
  covered 
  

   with 
  pebbles 
  or 
  angular 
  fragments 
  of 
  the 
  harder 
  portions 
  of 
  the 
  sand- 
  

   stone. 
  The 
  drifting 
  of 
  the 
  sands 
  of 
  the 
  Nubian 
  desert 
  in 
  certain 
  

   localities, 
  as 
  at 
  Faras 
  (the 
  Phtharis 
  of 
  Pliny), 
  below 
  Wadi 
  Halfeh, 
  

   and 
  for 
  some 
  distance 
  along 
  the 
  left 
  bank, 
  produces 
  remarkably 
  

   constructed 
  dunes, 
  composed 
  of 
  a 
  mixture 
  of 
  fine 
  sand 
  with 
  the 
  de- 
  

   * 
  See 
  Specimen 
  No. 
  1. 
  t 
  See 
  Specimen 
  No. 
  2. 
  

  

  