﻿302 
  LT.-GEN. 
  0. 
  A. 
  MCMAHOS 
  & 
  CAPT. 
  A. 
  JE. 
  MCMAHON 
  [Aug. 
  1 
  89 
  7, 
  

  

  substance 
  of 
  any 
  of 
  the 
  minerals 
  remains, 
  all 
  having 
  been 
  converted 
  

   into 
  iron 
  oxide 
  and 
  serpentine. 
  

  

  Pieces 
  of 
  the 
  rock 
  ground 
  down 
  to 
  fine 
  powder 
  were 
  digested 
  in 
  

   hot 
  hydrochloric 
  acid, 
  and 
  yielded 
  a 
  large 
  amount 
  of 
  iron, 
  a 
  con- 
  

   siderable 
  amount 
  of 
  magnesia, 
  an 
  appreciable 
  amount 
  of 
  alumina, 
  

   and 
  a 
  little 
  lime. 
  The 
  residue 
  consisted 
  of 
  quartz 
  with 
  mineral 
  

   matter 
  caught 
  up 
  in 
  it. 
  This 
  was 
  treated 
  with 
  hydrofluoric 
  and 
  

   sulphuric 
  acid, 
  and 
  it 
  yielded 
  a 
  little 
  iron, 
  a 
  little 
  lime, 
  and 
  a 
  good 
  

   deal 
  of 
  magnesia. 
  The 
  residue 
  untouched 
  by 
  the 
  hydrofluoric 
  and 
  

   sulphuric 
  acids 
  consisted 
  of 
  iron 
  that 
  dissolved 
  in 
  hot 
  nitrohydro- 
  

   chloric 
  acid. 
  

  

  The 
  rock 
  does 
  not 
  attract 
  the 
  magnet, 
  showing 
  how 
  much 
  limo- 
  

   nite 
  preponderates 
  over 
  magnetite. 
  

  

  Pumice. 
  

  

  No. 
  1423. 
  From 
  Amir 
  Chah. 
  

   „ 
  1433. 
  

  

  These 
  are 
  samples 
  of 
  the 
  pumice 
  sprinkled 
  in 
  abundance 
  all 
  over 
  

   the 
  country 
  around 
  Amir 
  Chah. 
  

  

  No. 
  1423 
  is 
  a 
  highly 
  vesicular 
  lava. 
  The 
  remains 
  of 
  felspars 
  are 
  

   abundant 
  in 
  the 
  slice, 
  but 
  they 
  are 
  all 
  so 
  highly 
  altered 
  that 
  they 
  

   remain 
  dark 
  between 
  crossed 
  nicols. 
  The 
  slice 
  contains 
  flecks 
  

   of 
  calcite 
  here 
  and 
  there, 
  and 
  some 
  leucoxene-pseudomorphs 
  after 
  

   ilmenite. 
  

  

  No. 
  1433 
  is 
  also 
  a 
  highly 
  vesicular 
  lava, 
  and 
  is 
  composed 
  of 
  a 
  

   colourless 
  glass, 
  drawn 
  into 
  fibres 
  and 
  full 
  of 
  air 
  or 
  gas-bubbles 
  

   round 
  the 
  vesicles. 
  The 
  slice 
  contains 
  some 
  fibres 
  of 
  mica, 
  one 
  

   or 
  two 
  fragments 
  of 
  hornblende, 
  one 
  or 
  two 
  felspars 
  with 
  straight 
  

   extinction, 
  and 
  some 
  small 
  flakes 
  of 
  quartz, 
  evidently 
  extraneous 
  

   fragments. 
  It 
  is 
  dotted 
  over 
  with 
  granules 
  of 
  calcite, 
  and 
  the 
  hand- 
  

   specimen 
  effervesces 
  strongly 
  with 
  an 
  acid. 
  

  

  Volcanic 
  Ash-beds. 
  

  

  No. 
  1418. 
  From 
  the 
  west 
  side 
  of 
  the 
  great 
  fault. 
  Sarlat 
  Range. 
  

  

  „ 
  1427. 
  „ 
  Gazi-Chah 
  hills. 
  

  

  „ 
  1428. 
  

  

  „ 
  1439. 
  „ 
  Shibian 
  Kotal. 
  

  

  „ 
  1440. 
  

  

  „ 
  1441. 
  

  

  ,, 
  1445. 
  ,, 
  Gargarok. 
  

  

  „ 
  1450. 
  ,, 
  west 
  side 
  of 
  the 
  great 
  fault. 
  

  

  „ 
  1465. 
  ,, 
  natural 
  monolith, 
  Neza-i-Sultan. 
  

  

  The 
  above 
  specimens 
  of 
  volcanic 
  ash 
  do 
  not 
  require 
  separate 
  

   description. 
  They 
  are 
  all 
  fine-grained, 
  almost 
  compact-looking 
  

   rocks, 
  varying 
  in 
  colour 
  from 
  purple- 
  grey 
  to 
  greenish 
  grey. 
  They 
  

   are 
  composed 
  of 
  fragments 
  of 
  various 
  kinds 
  of 
  lavas 
  of 
  the 
  inter- 
  

   mediate 
  class, 
  fragments 
  of 
  limestones 
  and 
  crystals 
  of 
  felspar. 
  

   These 
  ashes 
  have 
  been 
  much 
  altered 
  by 
  aqueous 
  agencies, 
  and 
  

  

  