﻿542 
  MAJOK-GENERAL 
  C. 
  A. 
  M'MAHON 
  ON 
  THE 
  HOBXBLENDE-SCHISTS 
  

  

  The 
  facts 
  seem 
  to 
  lead 
  naturally 
  to 
  this 
  conclusion, 
  and 
  I 
  do 
  not 
  

   see 
  how 
  it 
  can 
  be 
  avoided. 
  

  

  This 
  being 
  so, 
  the 
  further 
  inferences 
  seem 
  natural 
  that 
  the 
  eruptions 
  

   of 
  diorite 
  and 
  granite 
  in 
  the 
  cliff 
  at 
  Kennack 
  Cove 
  belong 
  to 
  the 
  

   same 
  period 
  as 
  the 
  intrusions 
  of 
  diorite 
  and 
  granite 
  into 
  the 
  rocks 
  

   on 
  the 
  Kennack 
  foreshore, 
  and 
  that 
  the 
  injection 
  of 
  the 
  dioritic 
  rocks 
  

   at 
  Kennack 
  Cove, 
  in 
  the 
  form 
  of 
  quasi- 
  banding, 
  took 
  place 
  during 
  

   the 
  same 
  period. 
  

  

  If 
  the 
  rocks 
  of 
  the 
  "granulitic" 
  group 
  at 
  Kennack 
  Cove 
  and 
  Cavouga 
  

   were 
  injected 
  with 
  granite 
  subsequent 
  to 
  the 
  intrusion 
  of 
  the 
  por- 
  

   phyritic 
  diorite, 
  the 
  same 
  conclusion 
  holds 
  good 
  for 
  those 
  on 
  the 
  

   sea-shore 
  at 
  Holestrow, 
  Pentreath, 
  and 
  under 
  Yellow 
  Cam: 
  but 
  

   the 
  question 
  remains 
  whether 
  the 
  bedded 
  " 
  granulite 
  " 
  at 
  Pen 
  

   Yoose 
  and 
  in 
  that 
  neighbourhood 
  ought 
  not 
  to 
  be 
  separated 
  from 
  

   them, 
  and 
  whether 
  both 
  series, 
  viz. 
  the 
  Pen-Yoose 
  " 
  granulites 
  " 
  

   and 
  the 
  Kennack 
  and 
  Holestrow 
  rocks 
  of 
  " 
  granulitic 
  " 
  aspect, 
  were 
  

   injected 
  with 
  granite 
  during 
  the 
  same 
  or 
  at 
  different 
  periods. 
  On 
  

   these 
  points 
  I 
  think 
  it 
  prudent 
  to 
  suspend 
  judgment 
  for 
  the 
  present. 
  

   There 
  are 
  several 
  matters 
  connected 
  with 
  these 
  questions 
  that 
  require 
  

   elucidation. 
  Faults 
  are 
  so 
  abundant 
  along 
  the 
  coast 
  of 
  the 
  Lizard 
  

   that 
  the 
  apparent 
  relation 
  of 
  the 
  " 
  granulitic 
  " 
  rocks 
  to 
  the 
  horn- 
  

   blende-schists 
  differs 
  materially 
  in 
  different 
  places. 
  

  

  One 
  more 
  exposure 
  requires 
  to 
  be 
  briefly 
  noted. 
  At 
  the 
  north 
  

   end 
  of 
  Kildown 
  Cove 
  three 
  strips 
  of 
  the 
  "granulitic" 
  group 
  are 
  to 
  

   be 
  seen 
  in 
  serpentine 
  cutting 
  across 
  the 
  root 
  of 
  the 
  Eny's 
  Head 
  

   under 
  circumstances 
  that 
  give 
  colour 
  to 
  Air. 
  SomervaiFs 
  theory 
  that 
  

   the 
  "granulitic" 
  rocks 
  have 
  intruded 
  into 
  the 
  serpentine. 
  Prof. 
  

   Bonney's 
  explanation 
  of 
  this 
  section 
  is 
  that 
  the 
  serpentine 
  is 
  intrusive 
  

   in 
  the 
  " 
  granulitic 
  " 
  group. 
  My 
  own 
  view 
  is 
  that 
  the 
  position 
  of 
  

   the 
  " 
  granulitic" 
  rocks 
  here 
  is 
  due 
  to 
  faulting. 
  The 
  more 
  westerly 
  

   of 
  the 
  three 
  strips 
  has 
  the 
  appearance 
  of 
  being 
  faulted 
  against 
  the 
  

   serpentine 
  ; 
  for 
  a 
  broad 
  dyke 
  of 
  gabbro 
  that 
  strikes 
  at 
  the 
  "granulite 
  " 
  

   at 
  a 
  high 
  angle 
  ends 
  sharply 
  at 
  the 
  " 
  granulite 
  " 
  and 
  does 
  not 
  reappear 
  

   in 
  the 
  serpentine 
  on 
  the 
  other 
  side, 
  which 
  it 
  would 
  surely 
  do 
  if 
  

   the 
  " 
  granulite 
  " 
  had 
  been 
  erupted 
  through 
  the 
  serpentine 
  and 
  its 
  

   contained 
  gabbro. 
  The 
  natural 
  inference 
  is 
  that 
  the 
  gabbro 
  is 
  cut 
  

   off 
  by 
  a 
  fault. 
  

  

  Discussion. 
  

  

  The 
  President 
  noticed 
  the 
  revival 
  of 
  Bischofs 
  views. 
  The 
  

   supposed 
  ash-beds 
  the 
  late 
  David 
  Forbes 
  was 
  perhaps 
  right 
  in 
  

   considering 
  had 
  been 
  produced 
  by 
  lava 
  issuing 
  into 
  water. 
  

  

  Dr. 
  G-eikie 
  would 
  be 
  reluctant 
  to 
  accept 
  the 
  Author's 
  conclusions. 
  

   Though 
  he 
  had 
  not 
  examined 
  the 
  ground, 
  he 
  could 
  not 
  believe 
  that 
  

   the 
  rocks 
  there 
  had 
  escaped 
  from 
  the 
  deformation 
  which 
  was 
  so 
  

   manifest 
  throughout 
  Cornwall. 
  

  

  Mr. 
  Teall 
  commented 
  on 
  the 
  complexity 
  of 
  the 
  subject. 
  The 
  

   district 
  had 
  been 
  examined 
  by 
  Dr. 
  Bonney, 
  and 
  subsequently 
  by 
  

   himself, 
  and 
  although 
  on 
  some 
  points 
  the 
  Author 
  reconciled 
  the 
  

  

  