﻿TERTIARY 
  VOLCANOES 
  OP 
  THE 
  WESTERN 
  ISLES 
  OF 
  SCOTLAND. 
  187 
  

  

  12. 
  The 
  Tertiary 
  Volcanoes 
  of 
  the 
  Western 
  Isles 
  of 
  Scotland. 
  

  

  By 
  Professor 
  John 
  W. 
  Judd, 
  F.R.S., 
  F.G.S. 
  (Eead 
  January 
  9, 
  

  

  1889.) 
  

  

  Contents. 
  Page 
  

  

  I. 
  Introduction 
  187 
  

  

  II. 
  Views 
  WHICH 
  WERE 
  maintained 
  previous 
  to 
  1874 
  188 
  

  

  III. 
  Conclusions 
  announced 
  in 
  1874, 
  which 
  have 
  been 
  confirmed 
  by 
  

  

  subsequent 
  Observations 
  190 
  

  

  A. 
  The 
  Relations 
  between 
  the 
  Plutonic 
  and 
  the 
  Volcanic 
  Rocks 
  of 
  

  

  the 
  Western 
  Isles 
  of 
  Scotland 
  191 
  

  

  B. 
  The 
  Existence 
  of 
  five 
  Great 
  Centres 
  of 
  Eruption, 
  with 
  many 
  minor 
  

  

  and 
  scattered 
  Vents 
  in 
  the 
  Western 
  Isles 
  of 
  Scotland 
  192 
  

  

  C. 
  The 
  Subaerial 
  Origin 
  of 
  the 
  Lavas 
  and 
  Tuffs, 
  and 
  the 
  Tertiary 
  Age 
  

  

  of 
  both 
  the 
  Plutonic 
  and 
  the 
  Volcanic 
  Rocks 
  194 
  

  

  IV. 
  Conclusions 
  announced 
  in 
  ] 
  874, 
  which 
  are 
  Disputed 
  in 
  a 
  recent 
  

  

  Memoir 
  by 
  Dr. 
  A. 
  G-eikie 
  196 
  

  

  A. 
  The 
  General 
  Order 
  in 
  which 
  the 
  several 
  Varieties 
  of 
  Igneous 
  Rocks 
  

  

  were 
  erupted 
  in 
  the 
  District 
  196 
  

  

  B. 
  The 
  Existence 
  in 
  the 
  District 
  of 
  great 
  Volcanoes, 
  which 
  have 
  

  

  been 
  dissected 
  by 
  Denudation 
  201 
  

  

  V. 
  The 
  Alternative 
  Theory 
  op 
  " 
  Fissure-Eruptions 
  " 
  206 
  

  

  A. 
  Can 
  great 
  Basaltic 
  Plateaux 
  be 
  formed 
  by 
  ordinary 
  Volcanic 
  

  

  Action? 
  ;. 
  206 
  

  

  B. 
  The 
  Age 
  of 
  the 
  Basic 
  Dykes 
  of 
  North 
  Britain 
  209 
  

  

  C. 
  Insufficiency 
  of 
  these 
  Dyke-fissures 
  as 
  Sources 
  of 
  the 
  Plateau-basalts 
  210 
  

  

  D. 
  Arguments 
  drawn 
  from 
  the 
  Lava-fields 
  of 
  the 
  Western 
  Territories 
  

  

  of 
  the 
  United 
  States 
  212 
  

  

  VI. 
  Conclusion 
  215 
  

  

  I. 
  Introduction. 
  

  

  In 
  the 
  year 
  1874 
  I 
  communicated 
  to 
  this 
  Society 
  the 
  results 
  of 
  

   my 
  studies 
  concerning 
  the 
  Tertiary 
  and 
  Older 
  Volcanic 
  rocks 
  of 
  

   Western 
  Scotland, 
  and 
  their 
  relations 
  to 
  the 
  Secondary 
  strata 
  with 
  

   which 
  they 
  are 
  so 
  intimately 
  associated 
  *. 
  The 
  very 
  generous 
  

   manner 
  in 
  which 
  the 
  memoir 
  dealing 
  with 
  those 
  subjects 
  was 
  

   received 
  by 
  this 
  Society 
  — 
  and 
  especially 
  by 
  those 
  who 
  were 
  at 
  that 
  

   time 
  the 
  leaders 
  of 
  geological 
  thought 
  in 
  this 
  country 
  — 
  can 
  never 
  

   be 
  forgotten 
  by 
  me. 
  Such 
  a 
  reception 
  lays 
  upon 
  the 
  author 
  of 
  a 
  

   memoir 
  certain 
  very 
  obvious 
  responsibilities. 
  In 
  the 
  event 
  of 
  serious 
  

   and 
  fatal 
  errors 
  being 
  indicated 
  in 
  his 
  observations 
  or 
  reasoning, 
  it 
  

   is 
  clearly 
  his 
  duty 
  to 
  come 
  forward 
  and 
  frankly 
  withdraw 
  the 
  state- 
  

   ments 
  to 
  which 
  this 
  Society 
  has 
  given 
  such 
  wide 
  currency. 
  It 
  is 
  

   equally 
  incumbent 
  upon 
  him, 
  should 
  his 
  premises 
  and 
  conclusions 
  

   be 
  openly 
  challenged 
  on 
  what 
  seem 
  to 
  him 
  to 
  be 
  insufficient 
  grounds, 
  

   to 
  undertake 
  the 
  task 
  of 
  re-examining 
  and, 
  if 
  necessary, 
  of 
  defending 
  

   his 
  views. 
  

  

  It 
  may 
  not 
  perhaps 
  be 
  out 
  of 
  place 
  to 
  remark 
  that 
  my 
  work 
  in 
  

   Scotland, 
  to 
  which 
  were 
  devoted 
  .five 
  years 
  of 
  heavy 
  labour 
  and 
  

   careful 
  research, 
  was 
  one 
  that 
  taxed 
  to 
  the 
  full 
  the 
  powers 
  of 
  a 
  

   private 
  individual. 
  It 
  involved 
  the 
  examination 
  of 
  the 
  physical 
  

   relations 
  and 
  the 
  discussion 
  of 
  the 
  palseontological 
  characteristics 
  of 
  

   the 
  whole 
  of 
  the 
  rocks 
  of 
  the 
  Highlands 
  between 
  the 
  Old 
  Red 
  Sand- 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxx. 
  (1874), 
  pp. 
  220-302. 
  

  

  