﻿GEOLOGY 
  OF 
  MADAGASCAR. 
  325 
  

  

  enormous 
  denudation 
  to 
  which 
  the 
  country 
  has 
  been 
  subjected. 
  It 
  

   is 
  composed 
  of 
  horizontal 
  bands 
  of 
  sandstone 
  weathered 
  in 
  such 
  a 
  

   way 
  as 
  to 
  make 
  it 
  somewhat 
  resemble 
  a 
  vast 
  cathedral. 
  

  

  Beds 
  of 
  clay 
  and 
  shale 
  are 
  also 
  common, 
  many 
  of 
  which 
  abound 
  

   in 
  Belemnites 
  of 
  various 
  species. 
  They 
  contain 
  also, 
  in 
  many 
  places, 
  

   large 
  and 
  numerous 
  crystals 
  of 
  selenite. 
  At 
  the 
  mountain 
  of 
  Tsiton- 
  

   droina, 
  near 
  Amberobe, 
  cylindrical 
  pieces 
  of 
  iron 
  pyrites 
  with 
  a 
  

   radiate 
  structure 
  may 
  also 
  be 
  found. 
  These, 
  as 
  well 
  as 
  species 
  of 
  

   Belemnites, 
  are 
  used 
  by 
  the 
  natives 
  as 
  rifle-balls, 
  and 
  are 
  known 
  as 
  

   balahara 
  or 
  balanjiriJca. 
  In 
  some 
  places, 
  too, 
  in 
  the 
  clay 
  (between 
  

   Ankaraobato 
  and 
  Ankoala, 
  for 
  instance), 
  large 
  concretionary 
  nodules 
  

   of 
  a 
  calcareous 
  nature 
  are 
  abundant 
  ; 
  and 
  to 
  the 
  north 
  of 
  Andrano- 
  

   samonta 
  there 
  are 
  numerous 
  septaria, 
  the 
  polygonal 
  spaces 
  being 
  

   filled 
  with 
  calcite. 
  

  

  Extensive 
  beds 
  of 
  limestone, 
  which, 
  as 
  a 
  rule, 
  are 
  abundantly 
  

   fossiliferous, 
  also 
  exist 
  in 
  the 
  north-west 
  of 
  the 
  island. 
  The 
  lime- 
  

   stone 
  varies 
  much 
  in 
  texture, 
  composition, 
  and 
  colour 
  ; 
  for 
  instance, 
  

   to 
  the 
  west 
  of 
  Ankaramy 
  it 
  is 
  a 
  black 
  compact 
  rock, 
  and 
  contains 
  

   zinc-blende 
  ; 
  in 
  other 
  places 
  it 
  is 
  whitish 
  and 
  of 
  close 
  texture, 
  or 
  

   whitish 
  and 
  of 
  friable 
  texture. 
  At 
  Mojanga 
  the 
  rock 
  is 
  a 
  greyish 
  

   more 
  or 
  less 
  compact 
  dolomite. 
  The 
  limestone, 
  in 
  many 
  places, 
  

   presents 
  a 
  weathered 
  surface 
  of 
  sharp-pointed 
  and 
  sharp-edged 
  pro- 
  

   jections, 
  which 
  render 
  it 
  dangerous 
  or 
  impossible 
  to 
  walk 
  on. 
  In 
  

   some 
  localities, 
  where 
  exposed 
  to 
  the 
  sea 
  waves, 
  it 
  has 
  the 
  appearance 
  

   of 
  rude 
  masonry. 
  At 
  Ambodimadiro, 
  not 
  far 
  from 
  jNosibe, 
  the 
  rock, 
  

   a 
  good 
  section 
  of 
  which 
  is 
  exposed 
  on 
  the 
  sea 
  coast, 
  is 
  probably 
  a 
  

   kind 
  of 
  limestone-shale 
  which 
  easily 
  breaks 
  up 
  into 
  small 
  rhomboidal 
  

   fragments 
  in 
  the 
  direction 
  of 
  its 
  vertical 
  joints, 
  which 
  run 
  about 
  

   30° 
  from 
  a 
  right 
  angle 
  one 
  to 
  the 
  other. 
  It 
  contains 
  numerous 
  

   centipede- 
  shaped 
  markings 
  of 
  what 
  are 
  probably 
  tracks 
  or 
  burrows 
  

   of 
  some 
  animal, 
  possibly 
  worms. 
  The 
  rock 
  is 
  here 
  also 
  invaded 
  by 
  

   numerous 
  dykes 
  of 
  amygdaloidal 
  basalt 
  *. 
  

  

  Near 
  Ambalanjanakomby, 
  to 
  the 
  north-west 
  of 
  Antongodrahoja, 
  

   there 
  is 
  a 
  deposit 
  of 
  lignite 
  containing 
  a 
  large 
  proportion 
  of 
  iron 
  

   pyrites 
  (or 
  marcasite 
  ?). 
  

  

  Coal 
  has 
  also 
  been 
  found 
  in 
  the 
  north-west 
  of 
  the 
  island. 
  M. 
  

   Guillemin, 
  a 
  French 
  engineer 
  sent 
  out 
  by 
  the 
  Company 
  of 
  Mada- 
  

   gascar, 
  reports 
  that 
  five 
  coal-fields 
  have 
  been 
  found, 
  the 
  coal 
  from 
  

   which 
  he 
  speaks 
  of 
  as 
  houille 
  seche, 
  houille 
  grasse, 
  and 
  houille 
  a 
  gaz. 
  

   The 
  five 
  outcrops 
  of 
  Bavatoby, 
  and 
  two 
  others 
  found 
  in 
  Ampasindava 
  

   Bay, 
  yield 
  coal 
  in 
  small 
  quantity 
  near 
  the 
  surface, 
  but 
  are 
  ex- 
  

   tremely 
  rich 
  at 
  greater 
  depths. 
  The 
  following 
  is 
  an 
  analysis 
  of 
  

   the 
  coal 
  from 
  Ambavatoby 
  : 
  — 
  

  

  Volatile 
  matter 
  15*80 
  

  

  Carbon 
  70*87 
  

  

  Ash 
  13-33 
  

  

  100-00 
  

   * 
  Described 
  by 
  Dr. 
  Hatch, 
  p. 
  352. 
  

  

  