﻿358 
  BE. 
  C. 
  CALLAWAY 
  OS 
  THE 
  ORIGIN 
  OF 
  [Aug. 
  1 
  897, 
  

  

  in 
  fluxion. 
  The 
  paper 
  opened 
  up 
  numerous 
  questions 
  of 
  considerable 
  

   importance. 
  

  

  Prof. 
  Bojstney 
  said 
  that 
  for 
  many 
  years 
  he 
  had 
  been 
  working 
  in 
  

   other 
  regions 
  in 
  the 
  hope 
  that 
  he 
  might 
  understand 
  districts 
  like 
  

   Anglesey. 
  There 
  we 
  had 
  to 
  bear 
  in 
  mind 
  that 
  we 
  were 
  dealing 
  

   with 
  rocks 
  which 
  originally 
  had 
  structures 
  of 
  their 
  own, 
  and 
  had 
  

   had 
  structures 
  impressed 
  on 
  them. 
  These 
  he 
  thought 
  the 
  Author 
  

   had 
  not 
  always 
  distinguished. 
  As 
  for 
  the 
  included 
  blocks 
  of 
  diorite 
  

   in 
  the 
  grey 
  gneiss 
  it 
  was 
  difficult 
  to 
  say 
  what 
  was 
  the 
  explanation 
  ; 
  

   for 
  the 
  diagram 
  would 
  bear 
  more 
  than 
  one. 
  He 
  thought 
  it 
  impos- 
  

   sible 
  that 
  the 
  specimens 
  of 
  gneiss 
  exhibited 
  could 
  have 
  been 
  formed 
  

   from 
  a 
  felsite. 
  He 
  doubted 
  whether 
  chlorite 
  could 
  be 
  converted 
  

   into 
  mica 
  except 
  in 
  cases 
  of 
  contact-metamorphism. 
  But 
  no 
  doubt 
  

   many 
  changes 
  had 
  taken 
  place 
  in 
  our 
  views 
  during 
  the 
  last 
  twenty 
  

   years. 
  

  

  The 
  Rev. 
  J. 
  F. 
  Blake 
  was 
  glad 
  on 
  this 
  occasion 
  to 
  agree 
  with 
  

   all 
  the 
  remarks 
  of 
  the 
  last 
  speaker, 
  especially 
  upon 
  the 
  larger 
  

   crystals 
  of 
  the 
  gneisses 
  supposed 
  to 
  be 
  derived 
  from 
  a 
  fine-grained 
  

   felsite. 
  He 
  also 
  agreed 
  with 
  the 
  Author 
  that 
  in 
  the 
  distortions 
  of 
  

   the 
  rocks 
  it 
  was 
  quite 
  possible 
  that 
  rifts 
  might 
  be 
  made 
  that 
  were 
  

   now 
  filled 
  by 
  a 
  different 
  crystalline 
  material 
  from 
  the 
  neighbouring 
  

   rock, 
  or 
  into 
  which 
  felsite 
  was 
  intruded 
  in 
  thin 
  sheets, 
  thus 
  making 
  

   the 
  Author's 
  ' 
  gneisses 
  of 
  primary 
  injection 
  ' 
  ; 
  or 
  where 
  a 
  diorite 
  

   was 
  intrusive, 
  as 
  atLlangaffo 
  cutting, 
  materials 
  from 
  it 
  might 
  easily 
  

   be, 
  and 
  no 
  doubt 
  were, 
  carried 
  by 
  water 
  and 
  deposited 
  between 
  the 
  

   folia 
  of 
  the 
  adjacent 
  gneisses, 
  thus 
  making 
  the 
  Author's 
  ' 
  gneisses 
  

   of 
  secondary 
  injection.' 
  But 
  in 
  both 
  cases 
  the 
  phenomena 
  were 
  

   purely 
  local 
  — 
  limited 
  in 
  fact 
  to 
  a 
  few 
  feet 
  or 
  inches, 
  and 
  threw 
  

   no 
  light 
  upon 
  the 
  general 
  mass 
  of 
  gneiss 
  which 
  covered 
  many 
  square 
  

   miles 
  of 
  country. 
  With 
  regard 
  to 
  the 
  so-called 
  ' 
  diorite-blocks,' 
  

   they 
  were 
  simply 
  the 
  ends 
  of 
  offshoots 
  from 
  some 
  larger 
  mass 
  of 
  

   diorite 
  which 
  had 
  been 
  subsequently 
  distorted. 
  

  

  As 
  to 
  the 
  Author's 
  ' 
  felsite,' 
  the 
  speaker 
  was 
  entirely 
  at 
  variance 
  

   with 
  him. 
  It 
  is 
  true 
  that 
  a 
  microscopic 
  section 
  of 
  it 
  was 
  examined 
  by 
  

   some 
  eminent 
  petrologists 
  at 
  the 
  British 
  Association 
  Meeting 
  in 
  1887, 
  

   and 
  pronounced 
  to 
  be 
  felsite, 
  and 
  this 
  the 
  speaker 
  regretted 
  ; 
  for, 
  as 
  

   it 
  was 
  perfectly 
  clear 
  to 
  him 
  on 
  stratigraphical 
  grounds 
  that 
  the 
  

   rock 
  was 
  not 
  a 
  felsite, 
  he 
  could 
  only 
  conclude 
  that 
  it 
  was 
  impossible, 
  

   by 
  the 
  microscopical 
  examination 
  of 
  a 
  rock-section, 
  to 
  ascertain 
  

   whether 
  or 
  not 
  that 
  rock 
  was 
  a 
  felsite. 
  He 
  showed, 
  however, 
  the 
  

   locality 
  of 
  this 
  supposed 
  felsite 
  to 
  a 
  large 
  number 
  of 
  foreign 
  

   geologists 
  after 
  the 
  International 
  Geological 
  Congress 
  in 
  1888, 
  but 
  

   none 
  of 
  them 
  suggested 
  that 
  the 
  rock 
  was 
  a 
  felsite. 
  It 
  is 
  true 
  that 
  

   the 
  rock 
  referred 
  to 
  by 
  the 
  Author 
  is 
  very 
  fine-grained 
  and 
  resembles 
  

   a 
  felsite 
  — 
  and 
  that 
  it 
  passes 
  by 
  insensible 
  gradations 
  into 
  the 
  ordinary 
  

   grey 
  gneiss 
  : 
  the 
  phenomenon 
  is, 
  however, 
  a 
  purely 
  local 
  one, 
  and 
  

   over 
  many 
  square 
  miles 
  of 
  country 
  there 
  is 
  no 
  sign 
  of 
  such 
  a 
  felsite- 
  

   mimicking 
  rock 
  ; 
  but 
  the 
  folia 
  of 
  the 
  gneiss 
  are 
  clear 
  and 
  parallel. 
  

   The 
  specially 
  compact 
  appearance 
  is 
  limited 
  to 
  the 
  neighbourhood 
  

   of, 
  and 
  is 
  probably 
  due 
  to 
  the 
  pressure 
  from, 
  the 
  largest 
  dioritic 
  

  

  