﻿Haast, 
  — 
  On 
  the 
  Geological 
  Structure 
  of 
  Banks 
  Peninsula, 
  601 
  

  

  tliese 
  two 
  European 
  volcanic 
  mountains, 
  will 
  be 
  found 
  to 
  possess 
  tlieir 
  

   systems 
  of 
  dykes 
  developed 
  in 
  the 
  same 
  manner. 
  During 
  a 
  number 
  of 
  

   years, 
  it 
  has 
  been 
  well 
  ascertained 
  by 
  me 
  that 
  the 
  dykes 
  radiating 
  from 
  the 
  

   several 
  centres 
  of 
  eruption 
  situated 
  not 
  far 
  from 
  each 
  other, 
  continue 
  in 
  

   many 
  instances 
  without 
  notable 
  interruption 
  from 
  the 
  former 
  mouth 
  of 
  the 
  

   crater 
  to 
  the 
  outer 
  slopes 
  of 
  the 
  caldera, 
  where 
  they 
  disappear 
  below 
  the 
  

   sea, 
  or 
  under 
  the 
  deposits 
  now 
  forming 
  the 
  Canterbury 
  plains. 
  Very 
  often 
  

   the 
  principal 
  dykes 
  rise 
  nearly 
  2,000 
  feet 
  above 
  the 
  sea 
  level. 
  They 
  are 
  

   well 
  visible 
  from 
  the 
  harbour 
  to 
  the 
  summit 
  of 
  the 
  rim 
  of 
  the 
  caldera 
  wall, 
  

   above 
  which, 
  in 
  some 
  instances, 
  they 
  stand 
  prominently 
  as 
  a 
  wall, 
  often 
  six 
  

   or 
  eight 
  feet 
  high. 
  Where 
  proper 
  measurements 
  of 
  the 
  same 
  dyke 
  can 
  be 
  

   obtained 
  for 
  a 
  long 
  distance, 
  it 
  has 
  been 
  found 
  that 
  generally, 
  as 
  it 
  advances 
  

   towards 
  the 
  outer 
  circle, 
  it 
  diminishes 
  in 
  breadth; 
  however, 
  in 
  other 
  

   instances 
  this 
  is 
  not 
  the 
  case, 
  as 
  repeatedly 
  I 
  have 
  found 
  some 
  which, 
  after 
  

   narrowing 
  on 
  their 
  outward 
  course, 
  considerably 
  enlarge 
  again 
  before 
  

   reaching 
  the 
  foot 
  of 
  the 
  caldera. 
  Thus 
  to 
  give 
  a 
  few 
  examples, 
  the 
  large 
  

   dyke 
  of 
  trachyte, 
  which 
  is 
  crossed 
  in 
  the 
  railway 
  tunnel, 
  about 
  29 
  chains 
  

   from 
  the 
  Heathcote 
  end, 
  is 
  first 
  seen 
  west 
  of 
  the 
  town 
  of 
  Lyttelton, 
  near 
  

   Naval 
  Point, 
  where 
  it 
  is 
  nearly 
  40 
  feet 
  thick. 
  On 
  the 
  summit 
  of 
  the 
  

   caldera 
  wall, 
  not 
  far 
  from 
  the 
  top 
  of 
  the 
  Bridlepath, 
  it 
  has 
  narrowed 
  to 
  23 
  

   feet 
  9 
  inches, 
  after 
  which 
  it 
  gradually 
  gains 
  in 
  proportion, 
  so 
  that 
  in 
  Thomp- 
  

   son's 
  quarry 
  it 
  has 
  enlarged 
  to 
  26 
  feet, 
  a 
  breadth 
  which 
  it 
  still 
  has 
  in 
  the 
  

   tunnel. 
  A 
  mile 
  beyond 
  the 
  quarry 
  the 
  spur 
  along 
  which 
  its 
  course 
  can 
  be 
  

   followed 
  runs 
  out 
  in 
  the 
  Heathcote 
  valley, 
  where 
  it 
  disappears 
  below 
  the 
  

   Loess. 
  

  

  Two 
  remarkable 
  dykes, 
  reaching 
  the 
  summit 
  of 
  Dyke 
  Hill, 
  about 
  2,000 
  

   feet 
  high, 
  west-south-west 
  of 
  Castle-hill, 
  are 
  very 
  conspicuous. 
  They 
  both 
  

   project 
  boldly 
  from 
  the 
  mountain, 
  with 
  a 
  space 
  of 
  35 
  feet 
  between 
  them. 
  

   The 
  eastern 
  one 
  is 
  18 
  feet, 
  and 
  the 
  western 
  12 
  feet 
  broad. 
  Two 
  similar 
  

   dykes 
  exist 
  on 
  the 
  opposite 
  side, 
  and 
  run 
  up 
  the 
  caldera 
  wall 
  behind 
  Eau- 
  

   paki. 
  To 
  mention 
  a 
  few 
  others, 
  there 
  are 
  some 
  important 
  dykes 
  south 
  of 
  

   Dyer's 
  Pass, 
  which, 
  after 
  crossing 
  Manson's 
  Peninsula, 
  are 
  again 
  met 
  with 
  at 
  

   Ohinitahi 
  (Governor's 
  Bay), 
  and 
  of 
  which 
  several, 
  after 
  ascending 
  to 
  the 
  very 
  

   summit 
  of 
  the 
  caldera, 
  reach 
  to 
  the 
  foot 
  of 
  the 
  peninsula 
  near 
  Cashmere, 
  

   being 
  extensively 
  quarried 
  in 
  different 
  localities 
  along 
  then- 
  course. 
  These 
  

   dykes, 
  like 
  many 
  others 
  which 
  cross 
  the 
  caldera 
  wall 
  towards 
  the 
  Canter- 
  

   bury 
  plains, 
  mostly 
  all 
  radiate 
  from 
  a 
  point 
  lying 
  in 
  the 
  centre 
  of 
  the 
  bay, 
  

   formed 
  by 
  Manson's 
  Peninsula 
  on 
  the 
  one 
  side, 
  and 
  Potts' 
  Peninsula 
  on 
  the 
  

   other, 
  both 
  of 
  which 
  consist 
  of 
  quartziferous 
  porphyries, 
  and 
  between 
  which 
  

   this 
  newer 
  focus 
  has 
  been 
  formed 
  after 
  the 
  greatest 
  portion 
  of 
  the 
  caldera 
  

   wall 
  had 
  already 
  been 
  built 
  up. 
  There 
  is 
  also 
  the 
  large 
  dyke 
  which 
  crosses 
  

  

  