﻿316 
  REV. 
  E. 
  BAEON 
  ON 
  THE 
  

  

  arundinacea, 
  &c), 
  a 
  species 
  of 
  Indigofera, 
  and 
  an 
  orchid. 
  On 
  its 
  

   top 
  is 
  an 
  unbreached 
  funnel-shaped 
  crater, 
  which 
  measures, 
  from 
  

   the 
  highest 
  point 
  of 
  its 
  rim, 
  243 
  feet 
  in 
  depth. 
  Contiguous 
  with 
  

   Kasige, 
  and 
  adjoining 
  its 
  south 
  side, 
  though 
  not 
  so 
  high, 
  there 
  is 
  

   another 
  volcano, 
  Ambohimalala, 
  and 
  many 
  others 
  are 
  to 
  be 
  seen 
  

   near 
  by. 
  

  

  One 
  thing 
  with 
  regard 
  to 
  these 
  volcanic 
  piles 
  soon 
  strikes 
  the 
  

   observer, 
  which 
  is, 
  that 
  they 
  are 
  frequently 
  higher 
  on 
  one 
  side 
  of 
  

   the 
  crater 
  than 
  on 
  the 
  other. 
  The 
  higher 
  side 
  varies 
  from 
  north 
  to 
  

   north-west 
  and 
  west. 
  This 
  is 
  accounted 
  for 
  by 
  the 
  direction 
  of 
  the 
  

   wind 
  during 
  the 
  eruption, 
  causing 
  the 
  ejected 
  fragments 
  to 
  accu- 
  

   mulate 
  on 
  the 
  leeward 
  side 
  of 
  the 
  vent. 
  Now 
  we 
  know 
  that 
  the 
  

   south-east 
  trades 
  blow 
  during 
  the 
  greater 
  part 
  of 
  the 
  year 
  in 
  Mada- 
  

   gascar, 
  hence 
  the 
  unequal 
  development 
  of 
  the 
  sides 
  of 
  the 
  cones. 
  

   The 
  same 
  thing 
  may 
  also 
  be 
  observed 
  in 
  the 
  volcanic 
  piles 
  in 
  the 
  

   neighbourhood 
  of 
  Betafo. 
  

  

  A 
  very 
  large 
  number 
  of 
  the 
  cones 
  have 
  breached 
  craters, 
  whence 
  

   lava 
  has 
  flowed 
  in 
  numerous 
  streams 
  and 
  flooded 
  the 
  plains 
  around. 
  

   These 
  streams 
  and 
  floods 
  consist, 
  in 
  most 
  instances, 
  I 
  believe, 
  of 
  

   black 
  basaltic 
  lava 
  ; 
  a 
  sheet 
  of 
  this 
  lava, 
  the 
  mingled 
  streams 
  of 
  

   which 
  have 
  flowed 
  from 
  Ambohimalala 
  and 
  some 
  other 
  vents, 
  has 
  

   covered 
  the 
  plain 
  at 
  the 
  foot 
  of 
  Kasige 
  to 
  such 
  an 
  extent 
  as 
  almost 
  

   to 
  surround 
  the 
  mountain. 
  Similar 
  sheets 
  are 
  to 
  be 
  seen 
  in 
  other 
  

   parts 
  of 
  the 
  district, 
  but 
  they 
  are 
  so 
  much 
  alike, 
  that 
  a 
  description 
  

   of 
  one 
  will 
  suffice 
  for 
  all. 
  Amboditaimamo 
  (or 
  Ambohitritaimamo 
  ?) 
  

   is 
  a 
  small 
  volcano 
  at 
  the 
  south-west 
  end 
  of 
  Ifanja 
  marsh, 
  and 
  at 
  the 
  

   northern 
  confines 
  of 
  the 
  volcanic 
  district. 
  It 
  possesses 
  a 
  breached 
  

   crater 
  turned 
  towards 
  the 
  east. 
  From 
  this 
  has 
  issued 
  a 
  stream 
  of 
  

   lava 
  which, 
  following 
  the 
  direction 
  of 
  the 
  lowest 
  level 
  of 
  the 
  ground, 
  

   has 
  swept 
  through 
  a 
  small 
  valley, 
  round 
  the 
  northern 
  end 
  of 
  the 
  

   mountain, 
  and 
  spread 
  out 
  at 
  its 
  west 
  foot. 
  This 
  sheet 
  of 
  lava, 
  

   which 
  is 
  excessively 
  rough 
  on 
  the 
  surface, 
  occupies 
  but 
  a 
  small 
  area 
  

   of 
  some 
  two 
  or 
  three 
  square 
  miles. 
  It 
  has 
  been 
  arrested 
  in 
  its 
  flow 
  

   in 
  front 
  by 
  the 
  form 
  of 
  the 
  ground. 
  It 
  is 
  cut 
  through 
  in 
  one 
  part 
  

   by 
  a 
  stream 
  (Ikotombolo) 
  which, 
  in 
  some 
  places, 
  has 
  worn 
  a 
  channel 
  

   to 
  the 
  depth 
  of 
  80 
  or 
  90 
  feet. 
  Its 
  surface, 
  which 
  is 
  slightly 
  cellular, 
  

   is 
  covered 
  by 
  hundreds 
  of 
  mammiform 
  hillocks, 
  which 
  must 
  have 
  

   been 
  formed 
  during 
  the 
  cooling 
  of 
  the 
  liquid 
  mass. 
  The 
  hillocks 
  are 
  

   mostly 
  from 
  20 
  to 
  30 
  feet 
  high, 
  and 
  apparently 
  are 
  heaped 
  up 
  masses 
  

   of 
  lava, 
  and 
  not 
  hollow 
  blisters. 
  The 
  lava 
  itself 
  is 
  black, 
  heavy, 
  

   and 
  compact, 
  being 
  porphyritic 
  with 
  somewhat 
  large 
  crystals 
  of 
  

   augite. 
  As 
  yet 
  it 
  is 
  scarcely 
  decomposed 
  sufficiently 
  to 
  form 
  

   much 
  of 
  a 
  soil, 
  though 
  grass 
  and 
  a 
  few 
  other 
  plants 
  grow 
  on 
  it 
  

   abundantly. 
  

  

  A 
  little 
  to 
  the 
  south 
  of 
  Amboditaimamo 
  there 
  is 
  another 
  volcano, 
  

   known 
  by 
  the 
  name 
  of 
  Andrarivahy. 
  It 
  is 
  situated 
  on 
  the 
  summit 
  

   of 
  a 
  ridge 
  of 
  hills 
  — 
  astride 
  of 
  it, 
  so 
  to 
  speak 
  — 
  and 
  from 
  its 
  crater 
  

   there 
  has 
  been 
  an 
  outflow 
  of 
  what 
  must 
  have 
  been 
  very 
  viscid 
  lava 
  ; 
  

   for 
  though 
  the 
  sides 
  of 
  the 
  volcano 
  and 
  the 
  ridge 
  of 
  hills 
  form 
  an 
  

   angle 
  of 
  from 
  30 
  to 
  40 
  degrees, 
  the 
  ejected 
  matter 
  has 
  set 
  or 
  " 
  gut- 
  

  

  