﻿Haast, 
  — 
  On 
  the 
  Geological 
  Structure 
  of 
  Banh 
  Peninsula. 
  507 
  

  

  sliowing 
  some 
  remarkable 
  irregularity, 
  is 
  the 
  one 
  in 
  wliich 
  tlie 
  so-called 
  

   Ellis 
  Quarry 
  is 
  situated. 
  Tins 
  dyke, 
  wlncli 
  strikes 
  nearly 
  east 
  and 
  west, 
  

   goes 
  out 
  about 
  400 
  feet 
  below 
  the 
  summit, 
  where 
  a 
  saddle 
  intersects 
  the 
  

   spur. 
  Shortly 
  above 
  its 
  lower 
  termination 
  it 
  sends 
  off 
  a 
  smaller 
  branch 
  in 
  

   a 
  sonth-west 
  direction, 
  also 
  ceasing 
  after 
  a 
  short 
  course. 
  Whilst 
  the 
  main 
  

   dyke 
  does 
  not 
  appear 
  any 
  more 
  above 
  the 
  surface, 
  the 
  smaller 
  south-western 
  

   branch 
  crops 
  up 
  again 
  on 
  the 
  other 
  side 
  of 
  the 
  depression, 
  now 
  gradually 
  

   changing 
  its 
  direction, 
  so 
  that, 
  in 
  its 
  lower 
  course, 
  about 
  300 
  feet 
  above 
  the 
  

   plains, 
  it 
  crosses 
  the 
  spur 
  in 
  a 
  south-east 
  and 
  north-west 
  direction. 
  The 
  

   whole 
  system 
  of 
  dykes 
  in 
  the 
  Lyttelton 
  caldera 
  wall 
  is 
  thus 
  very 
  different 
  

   from 
  the 
  dykes 
  of 
  Mount 
  Somma, 
  of 
  which, 
  in 
  his 
  paper, 
  Mr, 
  E, 
  Mallet 
  

   gives 
  us 
  such 
  a 
  lucid 
  and 
  suggestive 
  account, 
  and 
  of 
  which 
  many 
  are 
  

   fractured, 
  displaced, 
  and 
  crushed, 
  and 
  have 
  at 
  the 
  same 
  time 
  a 
  wedge- 
  

   shaped 
  form. 
  We 
  can, 
  therefore, 
  assume 
  that 
  the 
  fissures 
  and 
  dykes 
  in 
  the 
  

   Lyttelton 
  caldera 
  were 
  only 
  formed 
  after 
  the 
  latter 
  had 
  been 
  so 
  thoroughly 
  

   consolidated 
  that, 
  after 
  the 
  formation 
  of 
  the 
  fissures 
  and 
  their 
  filling 
  up 
  by 
  

   the 
  principal 
  dykes, 
  no 
  more 
  changes 
  of 
  any 
  importance 
  took 
  place 
  in 
  them 
  ; 
  

   and 
  that, 
  moreover, 
  the 
  forces 
  by 
  which 
  the 
  walls 
  of 
  the 
  volcano 
  were 
  

   starred 
  from 
  top 
  to 
  bottom, 
  must 
  have 
  been 
  far 
  deeper-seated 
  and 
  more 
  

   effective 
  than 
  the 
  agencies 
  by 
  which 
  Mount 
  Somma 
  was 
  rent. 
  

  

  In 
  conclusion, 
  I 
  wish 
  to 
  lay 
  before 
  you 
  a 
  few 
  notes 
  on 
  the 
  geological 
  

   features 
  of 
  the 
  Lyttelton 
  and 
  Christchurch 
  railway 
  tunnel, 
  of 
  which 
  I 
  made 
  

   a 
  careful 
  survey 
  during 
  a 
  number 
  of 
  years, 
  as 
  the 
  work 
  of 
  the 
  miner 
  

   advanced. 
  I 
  watched 
  this 
  interesting 
  and 
  instructive 
  work 
  with 
  great 
  

   attention, 
  this 
  being 
  the 
  first 
  time 
  that 
  a 
  caldera 
  wall 
  of 
  a 
  large 
  extinct 
  

   volcano 
  was 
  to 
  be 
  pierced 
  through, 
  I 
  prepared 
  at 
  the 
  time 
  a 
  section 
  on 
  a 
  

   scale 
  of 
  liu. 
  to 
  20ft., 
  which 
  I 
  have 
  great 
  pleasure 
  in 
  laying 
  before 
  you, 
  . 
  

  

  The 
  direction 
  of 
  the 
  tunnel 
  is 
  N, 
  14° 
  W, 
  The 
  first 
  trial 
  shaft 
  was 
  

   commenced 
  in 
  January, 
  1860, 
  and 
  the 
  permanent 
  works 
  under 
  contract 
  

   with 
  Messrs, 
  Holmes 
  and 
  Co., 
  began 
  in 
  July, 
  1861, 
  The 
  tunnel 
  was 
  laid 
  

   out, 
  and 
  its 
  execution 
  solely 
  superintended 
  by 
  Mr. 
  Edward 
  Dobson, 
  C.E., 
  

   Provincial 
  Engineer. 
  It 
  was 
  brought 
  to 
  a 
  successful 
  termination 
  on 
  May 
  

   25, 
  1866, 
  when 
  both 
  adits 
  met 
  near 
  the 
  centre. 
  The 
  opening 
  for 
  railway 
  

   traffic 
  took 
  place 
  on 
  December 
  9, 
  1867. 
  The 
  total 
  length 
  of 
  the 
  tunnel 
  is 
  

   8,598 
  feet, 
  and 
  if 
  we 
  deduct 
  from 
  this 
  365 
  feet 
  on 
  the 
  northern 
  or 
  outer 
  

   side, 
  and 
  105 
  feet 
  on 
  the 
  southern 
  or 
  inner 
  side, 
  formed 
  by 
  slope 
  deposits 
  

   and 
  loess, 
  there 
  remains 
  8,128 
  feet 
  of 
  rock 
  of 
  volcanic 
  origin, 
  of 
  which 
  the 
  

   caldera 
  wall 
  has 
  been 
  built 
  up. 
  Classifying 
  the 
  rocks 
  according 
  to 
  their 
  

   lithological 
  character, 
  we 
  find 
  that 
  the 
  crater 
  above 
  the 
  present 
  waterline 
  

   consists 
  of 
  — 
  

  

  61 
  lava-streams, 
  having 
  the 
  character 
  of 
  a 
  stony 
  compact 
  or 
  por- 
  

   phyritic 
  basalt. 
  

  

  