﻿190 
  PROF. 
  J. 
  W. 
  JUDD 
  ON 
  THE 
  TERTIARY 
  VOLCANOES 
  

  

  rocks 
  is 
  maintained, 
  no 
  reference 
  is 
  made, 
  either 
  in 
  the 
  text 
  or 
  in 
  

   the 
  table 
  given, 
  to 
  the 
  gabbros 
  of 
  Skye, 
  which, 
  as 
  we 
  have 
  seen, 
  

   had 
  always 
  been 
  held 
  by 
  the 
  author 
  to 
  be 
  metamorphic 
  rocks 
  of 
  

   Lanrentian 
  age. 
  The 
  gabbros 
  of 
  Mull 
  are 
  doubtfully 
  referred 
  to 
  as 
  

   being 
  basaltic 
  lavas 
  which 
  have 
  undergone 
  metamorphism 
  *. 
  

  

  In 
  the 
  same 
  year, 
  1871, 
  Prof. 
  Zirkel 
  published 
  his 
  admirable 
  

   " 
  Geologische 
  Skizzen 
  von 
  der 
  Westkiiste 
  Schottlands 
  " 
  f, 
  con- 
  

   taining 
  a 
  very 
  excellent 
  account 
  of 
  the 
  petrology 
  of 
  the 
  district. 
  

   In 
  treating 
  of 
  the 
  age 
  and 
  relations 
  of 
  the 
  various 
  rock-masses 
  of 
  

   igneous 
  origin, 
  he 
  unfortunately 
  took 
  Dr. 
  Geikie 
  as 
  his 
  guide 
  rather 
  

   than 
  Dr. 
  Macculloch; 
  and 
  as 
  Zirkel's 
  work 
  has 
  become 
  classical, 
  

   owing 
  to 
  the 
  excellence 
  of 
  his 
  petrographic 
  descriptions, 
  the 
  erro- 
  

   neous 
  representations 
  of 
  the 
  relations 
  and 
  ages 
  of 
  the 
  igneous 
  rocks 
  

   given 
  in 
  it 
  have 
  been 
  extensively 
  copied 
  and 
  very 
  widely 
  circulated. 
  

   Even 
  at 
  the 
  present 
  day 
  most 
  foreign 
  manuals 
  of 
  geology 
  continue 
  

   to 
  reproduce 
  these 
  admittedly 
  erroneous 
  statements 
  concerning 
  the 
  

   age 
  and 
  relations 
  of 
  the 
  igneous 
  rocks 
  of 
  Western 
  Scotland. 
  

  

  Such 
  was 
  the 
  state 
  of 
  information 
  upon 
  the 
  subject 
  when 
  I 
  took 
  

   up 
  the 
  study 
  of 
  the 
  district, 
  and 
  after 
  several 
  years 
  of 
  continuous 
  

   work 
  upon 
  it, 
  published 
  my 
  paper 
  of 
  1874. 
  While 
  acknowledging 
  

   the 
  very 
  great 
  assistance 
  I 
  had 
  derived 
  from 
  the 
  writings 
  of 
  Dr. 
  

   Macculloch 
  and 
  Professor 
  Zirkel, 
  I 
  was 
  compelled 
  to 
  state 
  that 
  my 
  

   observations 
  led 
  to 
  conclusions 
  at 
  utter 
  variance 
  with 
  those 
  arrived 
  

   at 
  by 
  Dr. 
  Geikie, 
  as 
  indicated 
  above 
  J. 
  

  

  After 
  an 
  interval 
  of 
  nearly 
  fifteen 
  years, 
  the 
  last-named 
  author 
  

   has 
  issued 
  a 
  memoir 
  § 
  in 
  which, 
  while 
  abandoning 
  his 
  old 
  views 
  and 
  

   adopting 
  in 
  almost 
  every 
  particular 
  the 
  conclusions 
  I 
  had 
  announced 
  

   in 
  1874, 
  he 
  lays 
  great 
  stress 
  on 
  certain 
  minor 
  points 
  of 
  difference 
  

   between 
  us, 
  and 
  offers 
  a 
  different 
  theoretical 
  explanation 
  of 
  the 
  

   facts 
  from 
  that 
  which 
  I 
  had 
  proposed. 
  

  

  My 
  object, 
  in 
  the 
  present 
  memoir, 
  is 
  to 
  direct 
  attention 
  to 
  the 
  

   following 
  subjects 
  : 
  — 
  

  

  First. 
  The 
  conclusions 
  of 
  my 
  paper 
  of 
  1 
  874 
  which 
  find 
  support 
  in 
  

   the 
  observations 
  since 
  made 
  by 
  Dr. 
  Greikie 
  and 
  other 
  members 
  of 
  

   the 
  Geological 
  Survey 
  — 
  the 
  results 
  of 
  which 
  are 
  given 
  in 
  the 
  memoir 
  

   referred 
  to 
  ; 
  

  

  Secondly. 
  The 
  observations 
  which 
  seem 
  to 
  contradict 
  or 
  qualify 
  

   the 
  conclusions 
  at 
  which 
  I 
  arrived 
  in 
  1874 
  ; 
  and 
  

  

  Thirdly. 
  The 
  alternative 
  theory 
  which 
  has 
  been 
  proposed 
  to 
  

   explain 
  the 
  general 
  relations 
  of 
  the 
  rocks 
  of 
  the 
  district. 
  

  

  III. 
  Conclusions 
  announced 
  in 
  1874, 
  which 
  have 
  been 
  

  

  CONFIRMED 
  BY 
  SUBSEQUENT 
  OBSERVATIONS. 
  

  

  I 
  cannot 
  do 
  better 
  than 
  to 
  state, 
  as 
  succinctly 
  as 
  possible, 
  the 
  chief 
  

   propositions 
  the 
  truth 
  of 
  which 
  I 
  endeavoured 
  to 
  establish 
  in 
  my 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxvii. 
  (1871), 
  pp. 
  282-283. 
  

  

  t 
  Zeitschr. 
  d. 
  d. 
  geol. 
  Gresellsch. 
  Bd. 
  xxiii. 
  (1871), 
  pp. 
  1-124. 
  

   | 
  \ 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxx. 
  (1874), 
  p. 
  223 
  (footnote). 
  

   '" 
  § 
  " 
  The 
  History 
  of 
  Volcanic 
  Action 
  during 
  the 
  Tertiary 
  Period 
  in 
  the 
  British 
  

   Isles," 
  Trans. 
  Roy. 
  Soc. 
  Edinb. 
  vol. 
  xxxv. 
  pt. 
  2, 
  pp. 
  21-184. 
  

  

  