﻿218 
  PROF. 
  J. 
  W. 
  JTJDD 
  OX 
  THE 
  TERTIARY 
  VOLCANOES 
  

  

  formation 
  of 
  lines 
  of 
  scoria-cones 
  similar 
  to 
  those 
  so 
  constantly 
  formed 
  

   when 
  an 
  eruption 
  takes 
  place 
  on 
  the 
  flanks 
  of 
  Etna. 
  

  

  It 
  is 
  very 
  necessary 
  that 
  the 
  true 
  nature 
  of 
  the 
  phenomena 
  dis- 
  

   played 
  at 
  Krakatoa 
  and 
  at 
  Maun 
  a 
  Loa 
  respectively 
  should 
  be 
  correctly 
  

   appreciated, 
  and 
  that 
  the 
  manner 
  in 
  which, 
  at 
  all 
  volcanic 
  centres, 
  

   the 
  two 
  kinds 
  of 
  activity- 
  — 
  of 
  which 
  these 
  are 
  the 
  extreme 
  types 
  — 
  

   may 
  be 
  found 
  in 
  ever 
  varying 
  combinations 
  should 
  be 
  clearly 
  under- 
  

   stood. 
  When 
  this 
  result 
  is 
  arrived 
  at, 
  I 
  am 
  convinced 
  that 
  the 
  

   hypothesis 
  of 
  " 
  fissure-eruptions 
  " 
  will 
  soon 
  sink 
  into 
  that 
  same 
  

   oblivion 
  which 
  has 
  already 
  overtaken 
  its 
  predecessor 
  and 
  parent 
  " 
  the 
  

   theory 
  of 
  the 
  trap-rocks." 
  

  

  Drscussiox. 
  

  

  Dr. 
  Geikie, 
  alluding 
  to 
  the 
  fact 
  that 
  his 
  memoir, 
  which 
  had 
  been 
  

   reviewed 
  by 
  Professor 
  Judd, 
  had 
  probably 
  not 
  yet 
  been 
  seen 
  by 
  

   many 
  of 
  those 
  present, 
  who 
  were 
  therefore 
  unacquainted 
  with 
  the 
  

   mass 
  of 
  detailed 
  observations 
  on 
  which 
  his 
  conclusions 
  were 
  based, 
  

   proceeded 
  to 
  give 
  a 
  history 
  of 
  his 
  researches 
  in 
  the 
  volcanic 
  rocks 
  of 
  

   the 
  West 
  of 
  Scotland. 
  He 
  had 
  first 
  broken 
  ground 
  among 
  them 
  

   more 
  than 
  30 
  years 
  before, 
  and 
  after 
  publishing 
  various 
  papers 
  on 
  

   the 
  subject, 
  had 
  presented 
  to 
  the 
  Society 
  in 
  1871 
  what 
  he 
  intended 
  

   to 
  be 
  the 
  first 
  of 
  a 
  series 
  of 
  papers 
  on 
  the 
  Tertiary 
  volcanic 
  rocks 
  of 
  

   the 
  British 
  Isles. 
  Before 
  the 
  second 
  paper 
  of 
  the 
  series 
  was 
  ready, 
  

   Professor 
  Judd 
  entered 
  the 
  field, 
  and 
  by 
  his 
  paper 
  of 
  187-1 
  covered 
  

   most 
  of 
  the 
  ground 
  that 
  he 
  himself 
  had 
  been 
  working 
  over. 
  He 
  

   laid 
  aside 
  the 
  subject 
  for 
  a 
  few 
  years, 
  but 
  an 
  excursion 
  into 
  Western 
  

   America 
  in 
  1879 
  gave 
  him 
  new 
  insight 
  into 
  the 
  volcanic 
  history 
  of 
  

   Western 
  Scotland, 
  and 
  he 
  then 
  resumed 
  his 
  researches, 
  and 
  con- 
  

   tinued 
  them 
  until 
  he 
  was 
  able 
  to 
  publish, 
  last 
  May, 
  the 
  large 
  memoir 
  

   which 
  had 
  been 
  criticized 
  by 
  Professor 
  Judd 
  *. 
  He 
  had 
  not 
  been 
  

   able 
  to 
  confirm 
  his 
  critic's 
  conclusion 
  as 
  to 
  the 
  order 
  of 
  succession 
  

   among 
  the 
  volcanic 
  rocks, 
  which 
  he 
  found 
  to 
  have 
  been 
  the 
  reverse 
  

   of 
  what 
  had 
  been 
  stated. 
  But 
  with 
  a 
  strong 
  dislike 
  of 
  controversy, 
  

   he 
  had 
  refrained 
  from 
  emphasizing 
  the 
  differences 
  of 
  opinion 
  

   between 
  Professor 
  Judd 
  and 
  himself, 
  and 
  after 
  stating 
  generally 
  

   his 
  disagreement, 
  had 
  abstained 
  from 
  pointing 
  out 
  what 
  he 
  

   believed 
  to 
  be 
  serious 
  errors 
  of 
  observation, 
  and 
  preferred 
  to 
  quote 
  

   from 
  the 
  paper 
  of 
  1874 
  when 
  he 
  agreed 
  with 
  it. 
  He 
  wished 
  em- 
  

   phatically 
  to 
  declare 
  that 
  his 
  Memoir 
  was 
  not 
  official 
  work 
  of 
  the 
  

   Geological 
  Survey, 
  but 
  that 
  for 
  any 
  demerits 
  it 
  might 
  contain 
  he 
  

   was 
  himself 
  solely 
  responsible. 
  Exhibiting 
  on 
  the 
  wall 
  an 
  enlarged 
  

   copy 
  of 
  Professor 
  Judd's 
  map 
  of 
  Mull, 
  he 
  showed 
  also 
  a 
  rough 
  

   enlargement 
  of 
  his 
  own 
  map 
  of 
  the 
  same 
  island, 
  which, 
  out 
  of 
  

   deference 
  to 
  Professor 
  Judd, 
  whose 
  work 
  it 
  contradicted, 
  he 
  had 
  

   refrained 
  from 
  publishing 
  in 
  his 
  paper, 
  but 
  which 
  he 
  now 
  felt 
  com- 
  

   pelled 
  to 
  produce. 
  He 
  pointed 
  out 
  what 
  he 
  considered 
  to 
  be 
  the 
  

   grave 
  errors 
  in 
  the 
  former 
  map. 
  

  

  There 
  was 
  in 
  reality 
  no 
  central 
  core 
  of 
  granite 
  with 
  a 
  ring 
  of 
  

  

  * 
  Trans. 
  Eoy. 
  Soc. 
  Edinb. 
  vol. 
  xxxv. 
  pp. 
  21-184. 
  

  

  