﻿NODULAK 
  FELSTONES 
  OF 
  THE 
  LLEYN. 
  269 
  

  

  might 
  be 
  to 
  form 
  the 
  shadowy 
  devitrification-granules, 
  which 
  some- 
  

   times 
  coexist 
  with 
  the 
  radial 
  arrangement 
  of 
  fibres. 
  

  

  I 
  have 
  ventured 
  to 
  think 
  that 
  the 
  formations 
  here 
  indicated 
  may 
  

   be 
  of 
  interest, 
  as 
  affording 
  some 
  additional 
  illustrations 
  of 
  structures 
  

   described 
  in 
  the 
  various 
  papers 
  quoted. 
  Throughout 
  my 
  attempt 
  I 
  

   have 
  received 
  from 
  Prof. 
  Bonney 
  much 
  continuous 
  help, 
  the 
  value 
  

   of 
  which 
  I 
  need 
  not 
  specify. 
  It 
  has 
  included 
  advice 
  and 
  assistance 
  

   in 
  many 
  difficulties, 
  as 
  well 
  as 
  the 
  opportunity 
  afforded 
  me 
  of 
  

   examining 
  rocks 
  and 
  rock-sections 
  from 
  various 
  localities. 
  Exam- 
  

   ples 
  from 
  Jersey 
  were 
  of 
  special 
  interest, 
  and 
  the 
  gift 
  of 
  some 
  of 
  

   these 
  specimens, 
  which 
  was 
  made 
  the 
  more 
  valuable 
  by 
  notes 
  on 
  

   the 
  general 
  character 
  of 
  the 
  rocks, 
  enabled 
  me 
  to 
  compare 
  their 
  

   microscopic 
  structure 
  and 
  to 
  find 
  in 
  it 
  some 
  confirmatory 
  evidence. 
  

  

  Discussion-. 
  

  

  Mr. 
  Cole 
  remarked 
  that 
  some 
  features 
  connected 
  with 
  the 
  sphe- 
  

   rulites 
  appeared 
  to 
  bear 
  out 
  his 
  views. 
  A 
  complete 
  illustration 
  of 
  

   the 
  phenomena 
  of 
  the 
  Lleyn 
  felsites 
  is 
  furnished 
  by 
  the 
  Permian 
  

   pitehstone 
  of 
  Zwickau. 
  

  

  In 
  one 
  of 
  Miss 
  Paisin's 
  specimens 
  a 
  small 
  film 
  with 
  beautiful 
  

   spherulitic 
  structure 
  projected 
  into 
  the 
  central 
  quartz-mass, 
  appa- 
  

   rently 
  pointing 
  to 
  the 
  destruction 
  of 
  the 
  central 
  portion. 
  In 
  

   Mr. 
  Iddings's 
  specimens 
  the 
  cavity, 
  when 
  existent, 
  is 
  comparatively 
  

   small, 
  and 
  the 
  typical 
  hollow 
  spherulites 
  of 
  Wales 
  cannot 
  be 
  

   explained 
  even 
  by 
  comparison 
  with 
  lithophysso. 
  

  

  Dr. 
  Hicks 
  believed 
  that 
  the 
  hollows 
  in 
  the 
  nodules 
  had 
  been 
  sub- 
  

   sequently 
  filled 
  in 
  with 
  secondary 
  silica, 
  but 
  that 
  the 
  cavities, 
  in 
  the 
  

   majority 
  of 
  cases, 
  originally 
  existed 
  in 
  the 
  rock. 
  

  

  Prof. 
  Bonnet 
  commented 
  on 
  the 
  too 
  close 
  comparison 
  between 
  

   small 
  things 
  and 
  great. 
  He 
  still 
  remained 
  sceptical 
  as 
  to 
  Mr. 
  Cole's 
  

   explanation. 
  The 
  vesicles 
  became 
  more 
  irregular 
  in 
  outline 
  in 
  the 
  

   more 
  acid 
  rocks, 
  and 
  the 
  proposed 
  interpretation 
  of 
  sections 
  might 
  

   thus 
  be 
  erroneous. 
  The 
  Boulay 
  Bay 
  specimens 
  seemed 
  to 
  show 
  

   that 
  the 
  spherulites 
  were 
  the 
  least 
  decomposed 
  part 
  of 
  the 
  rock, 
  

   and 
  there 
  was 
  evidence 
  that, 
  in 
  a 
  non-spherulitic 
  part 
  of 
  the 
  mass, 
  the 
  

   cavities 
  had 
  existed 
  from 
  the 
  first. 
  He 
  had 
  not 
  gathered 
  from 
  

   Mr. 
  Iddings's 
  description 
  that 
  either 
  the 
  spherulites 
  or 
  the 
  cavities 
  

   in 
  the 
  Yellowstone 
  rocks 
  were 
  so 
  small. 
  These 
  rocks 
  were 
  beauti- 
  

   fully 
  fresh, 
  so 
  that 
  Mr. 
  Cole's 
  explanation 
  could 
  not 
  be 
  applied 
  to 
  

   them. 
  

  

  