﻿32 
  () 
  EEV. 
  E. 
  EAEON 
  OX 
  THE 
  

  

  The 
  whole 
  series 
  of 
  sedimentary 
  strata 
  above 
  mentioned 
  are 
  re- 
  

   markably 
  horizontal, 
  bavins: 
  perhaps 
  generally 
  only 
  a 
  dip 
  of 
  a 
  few 
  

   degrees 
  seawards 
  ; 
  consequently 
  it 
  is 
  impossible 
  to 
  say 
  upon 
  what 
  

   beda 
  they 
  arc 
  superimposed, 
  except 
  that 
  at 
  their 
  eastern 
  boundary 
  

   they 
  lie 
  unconformably 
  on 
  the 
  gneiss. 
  Probably, 
  however, 
  future 
  

   investigation 
  may 
  be 
  able 
  to 
  discover 
  the 
  underlying 
  strata 
  — 
  that 
  

   is, 
  the 
  strata 
  (if 
  there 
  are 
  such) 
  lying 
  between 
  the 
  Jurassic 
  and 
  the 
  

   crystalline 
  rocks. 
  

  

  From 
  what 
  I 
  have 
  observed, 
  the 
  sandstone, 
  clay, 
  and 
  limestone 
  

   are 
  arranged 
  more 
  or 
  less 
  in 
  horizontal 
  sequence 
  from 
  east 
  to 
  west 
  ; 
  

   that 
  is 
  to 
  say, 
  the 
  sandstone 
  chiefly 
  occupies 
  the 
  territory 
  adjoining 
  

   the 
  crystalline 
  rocks 
  (being 
  a 
  sandstone-grit 
  at 
  the 
  junction), 
  the 
  

   limestone 
  forms 
  the 
  western 
  zone, 
  and 
  the 
  clay 
  and 
  shales 
  are 
  in- 
  

   termediate. 
  Of 
  course 
  this 
  rule 
  may 
  not 
  hold 
  good 
  in 
  every 
  locality 
  ; 
  

   but 
  if 
  this 
  be 
  the 
  general 
  sequence 
  of 
  the 
  rocks, 
  which 
  undoubtedly 
  

   it 
  is, 
  it 
  becomes 
  evident 
  that 
  their 
  component 
  materials 
  have 
  been 
  

   derived 
  from 
  the 
  elevated 
  crystalline 
  rocks 
  of 
  the 
  interior, 
  and 
  that 
  

   therefore 
  these 
  latter 
  formed 
  part, 
  if 
  not 
  the 
  whole, 
  of 
  the 
  island 
  

   previous 
  to 
  Jurassic 
  times. 
  

  

  It 
  may 
  be 
  worthy 
  of 
  mention 
  that 
  on 
  the 
  western 
  bank 
  of 
  the 
  

   River 
  Betsiboka 
  *, 
  a 
  few 
  miles 
  to 
  the 
  south 
  of 
  Mahabo 
  (near 
  Maro- 
  

   hala), 
  there 
  is 
  an 
  outcrop 
  of 
  basalt 
  with 
  numerous 
  agates. 
  

  

  In 
  my 
  journey 
  to 
  the 
  north-west 
  of 
  the 
  island 
  in 
  1886 
  I 
  came 
  

   across 
  some 
  remarkable 
  rocks 
  which 
  deserve 
  notice. 
  As 
  I 
  had 
  not 
  

   time 
  sufficient 
  properly 
  to 
  examine 
  them 
  or 
  their 
  surroundings, 
  I 
  

   can 
  only 
  give 
  the 
  data 
  as 
  I 
  observed 
  them 
  from 
  a 
  hurried 
  inspection 
  

   of 
  them, 
  hoping 
  that 
  they 
  may 
  receive 
  the 
  careful 
  attention 
  of 
  some 
  

   future 
  traveller. 
  The 
  rocks 
  in 
  question, 
  which 
  are 
  crystalline, 
  are 
  

   located 
  about 
  a 
  mile 
  and 
  a 
  half 
  to 
  the 
  north 
  of 
  Mahitsihazo 
  (on 
  the 
  

   road 
  between 
  Andranosamonta 
  and 
  Ankaramy) 
  in 
  about 
  48° 
  5' 
  E. 
  

   long, 
  and 
  14° 
  22' 
  S. 
  lat. 
  One 
  of 
  the 
  rocks 
  is 
  on 
  the 
  road 
  near 
  

   the 
  summit 
  of 
  an 
  ascent 
  ; 
  it 
  is 
  most 
  curiously, 
  though 
  irregularly, 
  

   guttered 
  with 
  canoe-like 
  channels, 
  some 
  of 
  which 
  are 
  fully 
  a 
  yard 
  

   in 
  depth. 
  It 
  is 
  as 
  though 
  it 
  had 
  been 
  turned 
  in 
  a 
  lathe, 
  with 
  

   ridges 
  and 
  prominences 
  left 
  between 
  the 
  parts 
  gouged 
  out, 
  which 
  

   parts, 
  however, 
  are 
  not 
  continuous 
  round 
  the 
  stone. 
  In 
  the 
  valley 
  

   immediately 
  to 
  the 
  south 
  there 
  is 
  another 
  of 
  these 
  curious 
  rocks, 
  

   and 
  to 
  the 
  north 
  there 
  are 
  several 
  others, 
  all 
  of 
  which 
  are 
  guttered 
  

   in 
  the 
  same 
  way. 
  They 
  do 
  not 
  seem 
  to 
  be 
  protrusions 
  from 
  below, 
  

   nor 
  to 
  belong 
  to 
  rocks 
  disintegrated 
  in 
  situ, 
  and 
  there 
  arc 
  no 
  hills 
  

   in 
  the 
  immediate 
  neighbourhood 
  from 
  which 
  they 
  could 
  have 
  fallen, 
  

   nor, 
  indeed, 
  is 
  there 
  to 
  be 
  found, 
  so 
  far 
  as 
  I 
  know, 
  any 
  similar 
  rock 
  

   in 
  the 
  surrounding 
  district. 
  The 
  gutters, 
  in 
  all 
  that 
  I 
  saw, 
  run 
  in 
  

   a 
  direction 
  round 
  the 
  rocks 
  north 
  and 
  south, 
  and 
  the 
  rooks 
  them- 
  

   selves 
  seem 
  to 
  observe 
  the 
  same 
  direction 
  in 
  their 
  distribution. 
  I 
  

   examined 
  the 
  rock 
  upon 
  which 
  one 
  of 
  them 
  was 
  superimposed, 
  and 
  

   found 
  it 
  to 
  consist 
  of 
  sand 
  and 
  clay. 
  I 
  would 
  also 
  point 
  out 
  for 
  

  

  * 
  While 
  speaking 
  of 
  the 
  Betsiboka, 
  I 
  may 
  say 
  thai 
  within 
  the 
  Inst 
  few 
  years 
  

   M 
  has 
  shifted 
  its 
  bed 
  al 
  Amparihibe. 
  Formerly 
  it 
  ran 
  on 
  the 
  west 
  side 
  of 
  the 
  

   village 
  ; 
  now 
  its 
  course 
  is 
  about 
  a 
  mile 
  to 
  the 
  east. 
  

  

  