﻿370 
  MISS 
  C. 
  A. 
  KAISIN 
  ON 
  THE 
  PETEOLOGT 
  [Aug. 
  1 
  89 
  7, 
  

  

  plagioclase, 
  some 
  of 
  (?)felsite. 
  Minute 
  flakes 
  of 
  white 
  mica 
  are 
  

   scattered 
  within 
  or 
  around 
  the 
  fragments, 
  or 
  form 
  wavy 
  patches, 
  

   the 
  silvery 
  scales 
  being 
  seen 
  macroscopically. 
  

  

  This 
  specimen, 
  brought 
  from 
  the 
  area 
  of 
  ' 
  crystalline 
  ' 
  rocks, 
  has 
  

   more 
  affinity 
  with 
  those 
  of 
  the 
  c 
  schistose 
  ' 
  region, 
  and 
  resembles 
  

   certain 
  squeezed 
  muddy 
  limestones 
  of 
  the 
  Alps, 
  which 
  probably 
  are 
  

   Jurassic 
  in 
  age. 
  

  

  (ix) 
  (?) 
  Phyllites. 
  

  

  (21* 
  22: 
  Wadi 
  Om 
  Nabadi. 
  From 
  the 
  'Schistose' 
  area.) 
  

   These 
  two 
  specimens 
  are 
  schistose 
  rocks 
  with 
  silvery-sheen 
  sur- 
  

   faces, 
  somewhat 
  iron-stained, 
  partly 
  in 
  connexion 
  with 
  rusty 
  cubic 
  

   crystals. 
  — 
  Mlcrosc. 
  The 
  fine-grained 
  clear 
  mosaic 
  is 
  crowded 
  with 
  

   pale 
  green 
  micaceous 
  (?) 
  microliths, 
  often 
  orientated, 
  and 
  sometimes 
  

   matted 
  along 
  wavy 
  lines. 
  In 
  21* 
  one 
  rather 
  large 
  crystal, 
  now 
  

   limonite, 
  has 
  a 
  border 
  of 
  coarsely 
  crystalline 
  quartz, 
  almost 
  cubic 
  

   in 
  outline. 
  Fine-grained 
  quartz-veins 
  traverse 
  the 
  slide. 
  It 
  is 
  not 
  

   easy 
  to 
  decide 
  whether 
  these 
  two 
  specimens 
  are 
  crushed, 
  some- 
  

   what 
  gritty 
  phyllites, 
  or 
  much-cleaved 
  schist, 
  like 
  certain 
  Alpine 
  

   Tocks. 
  Although 
  in 
  the 
  slice 
  from 
  22 
  a 
  crystalline 
  character 
  seems 
  

   slightly 
  more 
  evident, 
  the 
  rocks 
  which 
  have 
  been 
  crushed 
  were 
  more 
  

   probably 
  not 
  true 
  schists. 
  The 
  two 
  specimens 
  might 
  well 
  come 
  

   from 
  the 
  same 
  rock, 
  and 
  scarcely 
  represent 
  even 
  different 
  bands. 
  

  

  A 
  quantity 
  of 
  cubes 
  of 
  a 
  rich 
  brown 
  colour 
  were 
  collected 
  on 
  the 
  

   hill 
  of 
  Kageritbar, 
  where 
  it 
  was 
  crossed 
  by 
  Capt. 
  Lyons's 
  route. 
  The 
  

   mineral 
  is 
  limonite, 
  but 
  is 
  no 
  doubt 
  a 
  pseudomorph. 
  The 
  crystals 
  

   are 
  generally 
  from 
  5 
  to 
  | 
  inch 
  across, 
  and 
  they 
  were 
  probably 
  

   formed 
  in 
  situ, 
  since 
  in 
  an 
  accompanying 
  fragment 
  of 
  rock 
  are 
  

   similar 
  cubes, 
  but 
  much 
  smaller 
  (about 
  ^ 
  inch). 
  These 
  crystals 
  

   often 
  have 
  closely-fitting 
  quartz, 
  which 
  builds 
  up 
  a 
  regular 
  partially 
  

   cubic 
  form, 
  as 
  if 
  it 
  were 
  a 
  vein-like 
  growth 
  similar 
  to 
  that 
  described 
  

   in 
  slide 
  21,* 
  and 
  at 
  one 
  part 
  like 
  ' 
  faser-quartz.' 
  The 
  loose 
  cubes 
  

   often 
  exhibit 
  associated 
  quartz. 
  Thus 
  it 
  seems 
  as 
  if 
  the 
  formation 
  

   of 
  the 
  cubes 
  may 
  have 
  induced 
  crystallization 
  and 
  deposition 
  of 
  silica 
  

   around 
  them. 
  In 
  the 
  slice 
  of 
  this 
  rock, 
  micaceous 
  microliths 
  are 
  

   not 
  recognizable, 
  but 
  the 
  fine 
  granular 
  mosaic 
  of 
  the 
  groundmass 
  

   seems 
  to 
  be 
  similar 
  to 
  that 
  in 
  the 
  preceding 
  specimens, 
  although 
  

   here 
  it 
  is 
  very 
  much 
  masked 
  by 
  patchy 
  limonite. 
  By 
  the 
  kindness 
  

   of 
  Prof. 
  Bonney, 
  I 
  have 
  looked 
  for 
  comparison 
  at 
  slides 
  of 
  the 
  Ober- 
  

   mittweida 
  rocks, 
  1 
  which 
  exhibit 
  a 
  micromineralogical 
  change 
  far 
  

   more 
  marked, 
  but 
  apparently 
  of 
  the 
  same 
  type. 
  

  

  (x) 
  Vein-quartz. 
  

  

  (8, 
  12 
  : 
  Abu 
  Sinaiyat.) 
  Two 
  specimens 
  from 
  the 
  Southern 
  area 
  

   are 
  hard, 
  compact, 
  sand-worn 
  rock, 
  speckled 
  with 
  minute 
  metallic 
  

   grains, 
  and 
  weathering 
  brown. 
  They 
  have 
  a 
  brecciated 
  look, 
  the 
  

   fragments, 
  black 
  in 
  colour, 
  tinged 
  violet 
  in 
  places, 
  being 
  separated 
  

   by 
  whitish 
  veins 
  of 
  composite 
  quartz, 
  larger 
  in 
  12. 
  — 
  Microsc. 
  

   Fragments 
  of 
  the 
  original 
  vein-quartz 
  are 
  large, 
  irregular, 
  but 
  

  

  1 
  See 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xliv. 
  (1888) 
  p. 
  25. 
  

  

  