﻿600 
  Transactions. 
  — 
  Geology, 
  

  

  Returning 
  to 
  tlie 
  orifice 
  or 
  orifices 
  from 
  which 
  the 
  material 
  for 
  the 
  for« 
  

   mation 
  of 
  the 
  caldera 
  wall 
  was 
  ejected, 
  and 
  to 
  which 
  also 
  the 
  numerous 
  dykes, 
  

   mostly 
  having 
  a 
  vertical 
  position, 
  intersecting 
  it, 
  can 
  he 
  traced, 
  it 
  appears 
  

   that 
  the 
  principal 
  focus 
  of 
  eruption 
  was 
  situated 
  a 
  little 
  to 
  the 
  south-west 
  of 
  

   Quail 
  Island, 
  as 
  the 
  greatest 
  portion 
  of 
  the 
  dykes 
  radiate 
  from 
  here, 
  and 
  

   the 
  eastern 
  and 
  southern 
  sides 
  of 
  Quail 
  Island, 
  and 
  the 
  shores 
  near 
  

   Charteris 
  Bay, 
  are 
  formed 
  of 
  tufaceous 
  agglomeratic 
  and 
  hrecciated 
  heds, 
  in 
  

   which 
  a 
  number 
  of 
  angular 
  blocks 
  of 
  rock 
  are 
  enclosed, 
  having 
  all 
  a 
  very 
  

   bleached 
  appearance. 
  

  

  It 
  would 
  go 
  beyond 
  the 
  limits 
  of 
  this 
  address 
  were 
  I 
  to 
  follow 
  the 
  further 
  

   genetic 
  history 
  of 
  Banks 
  Peninsula 
  in 
  all 
  its 
  details. 
  I 
  can, 
  therefore, 
  only 
  

   indicate 
  here 
  in 
  a 
  few 
  words 
  how 
  the 
  whole, 
  in 
  course 
  of 
  time, 
  has 
  been 
  

   built 
  up. 
  Simultaneously 
  with, 
  or 
  shortly 
  after, 
  the 
  Lyttelton 
  caldera, 
  the 
  

   Little 
  Eiver 
  caldera, 
  of 
  which 
  only 
  a 
  small 
  portion 
  remains, 
  was 
  formed 
  in 
  

   the 
  same 
  manner. 
  The 
  formation 
  of 
  the 
  largest 
  of 
  the 
  whole 
  series, 
  the 
  

   Akaroa 
  caldera, 
  is 
  next 
  in 
  age, 
  which, 
  with 
  the 
  exception 
  of 
  a 
  small 
  portion 
  

   of 
  its 
  northern 
  rim, 
  is 
  perfectly 
  well 
  preserved. 
  After 
  their 
  formation, 
  new 
  

   eruptions, 
  and 
  of 
  a 
  different 
  form, 
  took 
  place 
  south 
  of 
  the 
  Lyttelton 
  caldera 
  

   and 
  north 
  of 
  the 
  Little 
  Eiver 
  and 
  Akaroa 
  calderas, 
  during 
  which 
  the 
  highest 
  

   portion 
  of 
  Banks 
  Peninsula 
  was 
  built 
  up 
  — 
  Mount 
  Herbert, 
  3,050 
  ; 
  Castle- 
  

   hill, 
  2,900 
  ; 
  and 
  Mount 
  Sinclair, 
  2,800 
  feet 
  ; 
  only 
  portions 
  of 
  the 
  craters 
  of 
  

   these 
  younger 
  systems 
  are 
  still 
  preserved, 
  but 
  easily 
  recognized 
  when 
  

   standing 
  on 
  the 
  summits 
  of 
  these 
  mountains. 
  The 
  southernmost 
  portion 
  

   of 
  the 
  Lyttelton 
  caldera 
  was 
  partly 
  destroyed 
  or 
  covered 
  by 
  lava-streams 
  

   belonging 
  to 
  the 
  Mount 
  Herbert 
  system, 
  also 
  of 
  a 
  basic 
  (basaltic) 
  nature, 
  of 
  

   which 
  a 
  whole 
  series 
  flowed 
  into 
  it, 
  now 
  forming 
  the 
  huge 
  spurs 
  descending 
  

   from 
  the 
  summit 
  of 
  Mount 
  Herbert 
  into 
  the 
  harbour 
  between 
  Charteris 
  

   and 
  Khodes 
  Bays. 
  The 
  last 
  eruption, 
  of 
  a 
  submarine 
  character, 
  took 
  

   place 
  in 
  the 
  centre 
  of 
  the 
  Lyttelton 
  caldera, 
  by 
  which 
  Quail 
  Island 
  was 
  

   formed. 
  

  

  I 
  shall 
  now 
  proceed 
  to 
  offer 
  you 
  some 
  observations 
  on 
  the 
  system 
  of 
  

   dykes, 
  which 
  are 
  so 
  well 
  developed 
  in 
  the 
  Lyttelton 
  caldera. 
  The 
  most 
  strik- 
  

   ing 
  facts 
  in 
  connection 
  with 
  the 
  system 
  of 
  dykes 
  of 
  the 
  caldera, 
  and 
  to 
  

   which 
  I 
  have 
  devoted 
  considerable 
  attention, 
  are 
  their 
  size, 
  longitudinal 
  extent, 
  

   and 
  constancy 
  in 
  direction. 
  From 
  the 
  researches 
  of 
  numerous 
  observers, 
  

   it 
  has 
  been 
  proved 
  that 
  all 
  the 
  dykes 
  of 
  Mount 
  Vesuvius 
  and 
  Mount 
  Etna 
  

   do 
  not 
  extend 
  much 
  beyond 
  the 
  centres 
  of 
  eruption, 
  so 
  that 
  they 
  advance 
  

   only 
  a 
  short 
  distance, 
  and, 
  rapidly 
  thinning 
  out, 
  soon 
  disappear, 
  a 
  fact 
  

   which 
  my 
  own 
  observations 
  along 
  the 
  crater 
  walls 
  of 
  both 
  mountains 
  have 
  

   amply 
  confirmed. 
  However, 
  I 
  have 
  no 
  doubt 
  that 
  other 
  volcanoes 
  similar 
  

   in 
  construction 
  to 
  Banks 
  Peninsula, 
  and 
  differing 
  as 
  considerably 
  from 
  

  

  