﻿AND 
  BANDED 
  CRYSTALLINE 
  ROCKS 
  OF 
  THE 
  LIZARD. 
  539 
  

  

  the 
  foliation 
  of 
  the 
  granite 
  been 
  produced 
  by 
  pressure 
  after 
  it 
  had 
  

   completely 
  cooled, 
  the 
  diorite 
  and 
  the 
  gabbro 
  could 
  not 
  possibly 
  have 
  

   escaped 
  putting 
  on 
  a 
  foliated 
  structure. 
  If 
  the 
  thin 
  veins 
  of 
  granite 
  

   yielded, 
  why 
  not 
  the 
  diorite 
  between 
  them? 
  

  

  At 
  Holestrow, 
  and 
  north-west 
  of 
  Pentreath 
  Beach, 
  the 
  rocks 
  that 
  

   crop 
  up 
  on 
  the 
  sea-shore 
  are, 
  I 
  think, 
  as 
  suggested 
  by 
  Messrs. 
  Fox 
  and 
  

   Somervail 
  in 
  their 
  paper 
  read 
  before 
  the 
  British 
  Association 
  in 
  1887, 
  

   a 
  part 
  of 
  the 
  " 
  granulitic 
  "' 
  group. 
  They 
  certainly 
  resemble 
  the 
  

   rocks 
  of 
  this 
  group 
  very 
  closely 
  and 
  they 
  occur 
  here, 
  and 
  further 
  on 
  

   near 
  the 
  Lion 
  rock, 
  in 
  their 
  normal 
  position 
  * 
  next 
  the 
  serpentine 
  — 
  

   facts 
  that 
  cannot 
  be 
  alleged 
  of 
  the 
  dykes 
  of 
  intrusive 
  rocks 
  in 
  ser- 
  

   pentine 
  at 
  North 
  Pentreath, 
  which 
  are 
  also 
  claimed 
  by 
  Mr. 
  Somervail 
  

   as 
  a 
  portion 
  of 
  this 
  group. 
  At 
  North 
  Pentreath, 
  where 
  the 
  serpentine 
  

   cliffs 
  touch 
  the 
  shingle 
  of 
  the 
  beach, 
  at 
  the 
  east 
  side 
  of 
  the 
  chine, 
  

   the 
  serpentine 
  is 
  cut 
  through 
  by 
  several 
  veins 
  of 
  intrusive 
  diorite, 
  

   which 
  pierce 
  it 
  in 
  various 
  directions, 
  but, 
  at 
  least, 
  one 
  of 
  which 
  strikes 
  

   up 
  the 
  hill. 
  These 
  veins 
  are 
  cut 
  across 
  by 
  a 
  strong 
  vein 
  of 
  granite 
  

   (here 
  very 
  felspathic), 
  which 
  after 
  running 
  a 
  course 
  approximately 
  

   parallel 
  to 
  the 
  sea-shore 
  also 
  turns 
  upwards 
  towards 
  the 
  main 
  dyke 
  

   of 
  granite 
  described 
  by 
  Prof. 
  Bonney 
  in 
  his 
  first 
  paper 
  f 
  . 
  These 
  

   veins 
  of 
  granite 
  and 
  diorite 
  do 
  not 
  intermingle. 
  Higher 
  up, 
  where 
  

   the 
  granite 
  appears 
  in 
  force, 
  it 
  contains 
  at 
  least 
  one 
  included 
  block 
  

   of 
  diorite 
  — 
  a 
  block 
  so 
  sharply 
  angular 
  that 
  its 
  character 
  can 
  hardly 
  

   be 
  mistaken. 
  A 
  little 
  above 
  this 
  there 
  is 
  a 
  mass 
  of 
  diorite, 
  one 
  side 
  

   of 
  which 
  is 
  buried 
  under 
  grass, 
  of 
  which 
  it 
  is 
  difficult 
  to 
  say 
  whether 
  

   it 
  is 
  a 
  collection 
  of 
  transported 
  blocks, 
  or 
  whether 
  the 
  granite 
  in 
  its 
  

   upward 
  course 
  impinged 
  against 
  the 
  side 
  of 
  a 
  dyke 
  of 
  diorite. 
  

   Whichever 
  be 
  the 
  true 
  explanation, 
  one 
  point 
  is 
  perfectly 
  clear, 
  

   namely, 
  that 
  the 
  granite 
  is 
  younger 
  than 
  the 
  diorite, 
  for 
  the 
  latter 
  

   is 
  penetrated 
  by 
  very 
  numerous 
  tongues 
  and 
  veins 
  of 
  the 
  former. 
  

   At 
  this 
  point 
  the 
  granite 
  disappears, 
  but 
  the 
  diorite 
  reappears 
  further 
  

   up 
  the 
  hill-side 
  as 
  a 
  thickish 
  vein 
  in 
  serpentine. 
  

  

  The 
  space 
  that 
  intervenes 
  between 
  these 
  dykes 
  of 
  intrusive 
  rocks 
  

   and 
  the 
  outcrops 
  of 
  the 
  " 
  granulitic 
  " 
  group 
  is 
  covered 
  by 
  shingle 
  and 
  

   boulders, 
  and 
  no 
  direct 
  connexion 
  is 
  to 
  be 
  made 
  out 
  between 
  them. 
  

   These 
  dykes 
  do 
  not 
  resemble 
  the 
  " 
  granulitic 
  " 
  group, 
  as 
  they 
  are 
  not 
  

   banded. 
  We 
  have 
  at 
  North 
  Pentreath 
  simply 
  an 
  example 
  of 
  what 
  

   I 
  have 
  very 
  often 
  seen 
  in 
  the 
  Himalayas, 
  namely, 
  of 
  granite 
  following 
  

   the 
  course 
  of 
  a 
  dyke 
  of 
  eruptive 
  diorite 
  for 
  a 
  short 
  distance. 
  

  

  At 
  Kennack 
  Cove 
  the 
  facts 
  are 
  very 
  similar 
  to 
  those 
  of 
  North 
  Pen- 
  

   treath. 
  In 
  the 
  illustration 
  given 
  below 
  (fig. 
  12) 
  I 
  have 
  depicted 
  two 
  

   dykes 
  of 
  diorite 
  (D 
  1 
  , 
  D 
  2 
  ) 
  and 
  two 
  dykes 
  of 
  granite 
  (G 
  1 
  , 
  G 
  2 
  ) 
  intrusive 
  

   in 
  serpentine. 
  The 
  sketch 
  represents 
  diagrammatically 
  a 
  section 
  of 
  

   the 
  serpentine 
  cliffs 
  on 
  the 
  sea-shore 
  at 
  the 
  west 
  end 
  of 
  the 
  cove. 
  

   G 
  1 
  is 
  about 
  ten 
  yards 
  distant 
  from 
  G 
  2 
  at 
  the 
  base 
  of 
  the 
  cliff. 
  Could 
  

   we 
  trace 
  the 
  course 
  of 
  the 
  diorite-dykes 
  (D 
  1 
  , 
  J) 
  2 
  ) 
  downwards 
  we 
  should 
  

   probably 
  find 
  that 
  they 
  constituted 
  the 
  two 
  bifurcations 
  of 
  one 
  

  

  * 
  I 
  do 
  not 
  mean 
  by 
  this 
  expression 
  to 
  indicate 
  their 
  geological 
  sequence, 
  only 
  

   tnat 
  in 
  the 
  field 
  they 
  are 
  commonly 
  found 
  next 
  the 
  serpentine, 
  

   t 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  xxxiii. 
  p. 
  887. 
  

  

  