﻿300 
  CAPT. 
  H, 
  G. 
  LYONS 
  ON 
  THE 
  {Aug. 
  1 
  89 
  7, 
  

  

  27. 
  Note 
  on 
  a 
  Portion 
  of 
  the 
  Nubian 
  Desert 
  south-east 
  of 
  

   Korosko 
  : 
  I. 
  Field 
  Geology. 
  By 
  Capt. 
  H. 
  G. 
  Lyons, 
  R.E., 
  

   F.G.S. 
  II. 
  Petrology. 
  By 
  Miss 
  C. 
  A. 
  Raisin, 
  B.Sc. 
  (Com- 
  

   municated 
  by 
  Prof. 
  T. 
  G. 
  Bonney, 
  D.Sc, 
  LL.IX, 
  F.R.S., 
  V.P.G.S.) 
  

   III. 
  Water 
  Analyses. 
  By 
  Miss 
  E. 
  Aston, 
  B.Sc. 
  {Idem.) 
  

   (Head 
  April 
  28th, 
  1897.) 
  

  

  [Plate 
  XXVI— 
  "Map.] 
  

  

  I. 
  Field 
  Geology. 
  

  

  In 
  the 
  month 
  of 
  December, 
  1894, 
  while 
  on 
  a 
  military 
  patrol 
  in 
  the 
  

   Nubian 
  Desert 
  to 
  the 
  south 
  and 
  east 
  of 
  Korosko, 
  I 
  was 
  able 
  to 
  

   examine 
  a 
  portion 
  of 
  this 
  area 
  which 
  has 
  not 
  previously 
  been 
  

   described. 
  Linant 
  de 
  Bellefonds, 
  in 
  his 
  ' 
  L'Etbaye/ 
  and 
  Col. 
  Colston, 
  

   of 
  the 
  Egyptian 
  General 
  Staff, 
  have 
  given 
  short 
  accounts 
  of 
  the 
  

   rocks 
  met 
  with 
  on 
  the 
  Korosko-Abu 
  Hamed 
  caravan-road, 
  while 
  

   the 
  traveller 
  Burckhardt 
  l 
  in 
  1814 
  passed 
  by 
  Bir 
  Ongat, 
  and 
  then 
  

   rather 
  to 
  the 
  east 
  of 
  the 
  area 
  now 
  described, 
  along 
  the 
  Berber 
  road. 
  

   From 
  these 
  different 
  accounts 
  it 
  seemed 
  that 
  the 
  Nubian 
  Sandstone 
  

   of 
  this 
  part 
  reached 
  as 
  far 
  east 
  as 
  long. 
  33° 
  E. 
  of 
  Greenwich, 
  but 
  

   the 
  topography 
  of 
  all 
  this 
  part 
  was 
  very 
  inaccurate, 
  and 
  the 
  object 
  

   of 
  the 
  patrol 
  was 
  to 
  correct 
  this. 
  Surveying 
  and 
  marching 
  from 
  

   22 
  to 
  25 
  miles 
  a 
  day 
  gave 
  little 
  time 
  for 
  geological 
  investigation, 
  

   and 
  all 
  that 
  was 
  possible 
  was 
  to 
  indicate 
  the 
  boundary-line 
  between 
  

   the 
  Nubian 
  Sandstone 
  and 
  the 
  crystalline 
  rocks, 
  and 
  to 
  form 
  a 
  small 
  

   collection 
  of 
  specimens 
  from 
  the 
  latter. 
  

  

  A 
  set 
  of 
  microscope-slides 
  has 
  been 
  prepared 
  from 
  33 
  of 
  these 
  and 
  

   submitted 
  to 
  Prof. 
  Bonney, 
  F.R.S., 
  under 
  whose 
  supervision 
  they 
  

   have 
  been 
  described 
  by 
  Miss 
  C. 
  A. 
  Raisin, 
  B.Sc, 
  at 
  University 
  College, 
  

   London. 
  In 
  the 
  sketch-map 
  attached 
  to 
  this 
  paper 
  (PI. 
  XXVI) 
  no 
  

   attempt 
  has 
  been 
  made 
  to 
  distinguish 
  the 
  minor 
  varieties 
  of 
  rocks 
  

   which 
  occur 
  in 
  this 
  district; 
  but 
  the 
  Nubian 
  Sandstone, 
  and 
  the 
  

   crystalline 
  rocks 
  respectively, 
  have 
  been 
  indicated, 
  as 
  well 
  as 
  one 
  or 
  

   two 
  areas 
  where 
  schistose 
  rocks 
  are 
  especially 
  developed. 
  

  

  (1) 
  General 
  Description. 
  

  

  Between 
  Korosko 
  and 
  Siala 
  the 
  Nile 
  runs 
  through 
  a 
  comparatively 
  

   narrow 
  channel 
  excavated 
  in 
  the 
  Nubian 
  Sandstone, 
  which 
  here 
  on 
  

   the 
  eastern 
  bank 
  forms 
  cliffs 
  some 
  200 
  feet 
  in 
  height 
  descending 
  to 
  

   the 
  water's 
  edge, 
  while 
  on 
  the 
  western 
  bank 
  the 
  sandstone 
  desert, 
  

   with 
  its 
  patches 
  of 
  drift 
  quartz-sand, 
  rises 
  more 
  gradually 
  and 
  does 
  

   not 
  attain 
  to 
  the 
  height 
  of 
  the 
  eastern 
  plateau. 
  

  

  Cultivation 
  is 
  restricted 
  to 
  small 
  patches 
  and 
  strips 
  ; 
  while 
  in 
  

   places 
  the 
  foot-track 
  passes 
  through 
  the 
  hills, 
  since 
  there 
  is 
  no 
  room 
  

  

  1 
  ' 
  Travels 
  in 
  Nubia.' 
  

  

  