﻿OF 
  THE 
  WESTERN 
  ISLES 
  OF 
  SCOTLAND. 
  189 
  

  

  In 
  1851 
  the 
  Duke 
  of 
  Argyll 
  brought 
  forward 
  the 
  evidence 
  of 
  the 
  

   plant-remains 
  of 
  Ardtun, 
  which 
  Professor 
  Edward 
  Forbes 
  correctly 
  

   interpreted 
  as 
  proving 
  the 
  Tertiary 
  age 
  of 
  the 
  basalts 
  with 
  which 
  

   they 
  were 
  intercalated 
  *. 
  

  

  Unfortunately, 
  as 
  the 
  result 
  of 
  a 
  hasty 
  yachting-cruise 
  in 
  the 
  

   Western 
  Isles, 
  Prof. 
  Forbes 
  at 
  the 
  same 
  time 
  suggested, 
  though 
  

   with 
  much 
  reserve, 
  that 
  the 
  basalts 
  of 
  Loch 
  Staffin 
  might 
  possibly 
  be 
  

   contemporaneous 
  with 
  the 
  associated 
  Jurassic 
  strata 
  f. 
  

  

  In 
  the 
  year 
  1858 
  Dr. 
  Archibald 
  Geikie 
  published 
  his 
  first 
  memoir 
  

   dealing 
  with 
  the 
  igneous 
  rocks 
  of 
  the 
  Hebrides 
  £. 
  In 
  this 
  memoir 
  

   the 
  most 
  serious 
  charges 
  were 
  brought 
  against 
  Dr. 
  Macculloch, 
  his 
  

   veracity 
  was 
  impeached, 
  and 
  an 
  attempt 
  was 
  made 
  to 
  throw 
  dis- 
  

   credit 
  upon 
  the 
  whole 
  of 
  his 
  geological 
  observations 
  §. 
  The 
  author, 
  

   as 
  the 
  result 
  of 
  his 
  own 
  studies, 
  maintained 
  that 
  the 
  granitic 
  rocks 
  

   of 
  central 
  Skye 
  belong 
  to 
  two 
  different 
  periods. 
  He 
  noticed 
  the 
  

   peculiar 
  rocks 
  of 
  Cnoc 
  nam 
  Fitheach, 
  but 
  failed 
  to 
  recognize 
  that 
  

   they 
  are 
  masses 
  of 
  volcanic 
  agglomerate. 
  

  

  The 
  same 
  author, 
  in 
  1861, 
  published 
  a 
  paper 
  devoted 
  to 
  the 
  full 
  

   consideration 
  of 
  " 
  the 
  Chronology 
  of 
  the 
  Trap-Rocks 
  of 
  Scotland 
  " 
  ||. 
  

  

  This 
  memoir, 
  which 
  is 
  illustrated 
  by 
  a 
  map 
  and 
  section, 
  aims 
  at 
  

   substituting 
  for 
  the 
  conclusions 
  of 
  Macculloch 
  the 
  following 
  pro- 
  

   positions 
  : 
  — 
  

  

  (1) 
  The 
  gabbros 
  (" 
  hypersthene-rock 
  ") 
  of 
  Syke 
  are 
  of 
  metamor- 
  

   phic 
  origin 
  and 
  of 
  Laurentian 
  age. 
  

  

  (2) 
  The 
  great 
  mass 
  of 
  the 
  igneous 
  rocks 
  of 
  the 
  Western 
  Isles 
  

   are 
  of 
  Oolitic 
  age, 
  and 
  this 
  is 
  also 
  the 
  age 
  of 
  the 
  numerous 
  dykes 
  

   traversing 
  Southern 
  Scotland 
  and 
  the 
  North 
  of 
  England. 
  

  

  (3) 
  In 
  Mull, 
  however, 
  there 
  occur 
  certain 
  basalts 
  which 
  were 
  

   erupted 
  during 
  the 
  Tertiary 
  period. 
  

  

  In 
  1865 
  the 
  same 
  author 
  published 
  a 
  work 
  ^[ 
  in 
  which 
  the 
  Lauren- 
  

   tian 
  age 
  of 
  Skye 
  gabbros, 
  and 
  the 
  Oolitic 
  age 
  of 
  the 
  great 
  mass 
  of 
  

   the 
  basalts 
  of 
  the 
  Western 
  Isles 
  of 
  Scotland, 
  is 
  still 
  maintained. 
  

  

  Two 
  years 
  later 
  appeared 
  a 
  memoir 
  from 
  the 
  same 
  hand, 
  in 
  

   which 
  it 
  is 
  admitted 
  that, 
  so 
  far 
  as 
  Mull 
  is 
  concerned, 
  the 
  reference 
  

   of 
  the 
  great 
  masses 
  of 
  basalts 
  to 
  the 
  Oolitic 
  period 
  was 
  a 
  mistake, 
  

   and 
  that 
  they 
  really 
  belong 
  to 
  the 
  Tertiary 
  **. 
  

  

  Still 
  later, 
  in 
  1871, 
  a 
  very 
  admirable 
  account 
  of 
  the 
  geology 
  of 
  

   the 
  Island 
  of 
  Eigg, 
  by 
  the 
  same 
  author, 
  was 
  preceded 
  by 
  a 
  state- 
  

   ment 
  of 
  his 
  general 
  views 
  concerning 
  the 
  relations 
  and 
  age 
  of 
  the 
  

   igneous 
  rocks 
  of 
  the 
  Western 
  Isles 
  of 
  Scotland. 
  It 
  must 
  be 
  pointed 
  out 
  

   that 
  in 
  this 
  general 
  statement, 
  while 
  the 
  Tertiary 
  age 
  of 
  all 
  the 
  basaltic 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  vii. 
  (1851), 
  pp. 
  89 
  and 
  103. 
  

  

  t 
  Loc. 
  cit. 
  p. 
  108. 
  

  

  \ 
  Ibid. 
  vol. 
  xiv. 
  (1858), 
  pp. 
  1-23. 
  

  

  § 
  Loc. 
  cit. 
  pp. 
  3-4. 
  I 
  have 
  shown 
  on 
  a 
  former 
  occasion 
  that 
  these 
  very 
  grave 
  

   charges 
  against 
  one 
  of 
  the 
  great 
  pioneers 
  in 
  British 
  Geology 
  are 
  entirely 
  ground- 
  

   less. 
  See 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxiv. 
  (1878), 
  p. 
  700 
  (footnote). 
  

  

  || 
  Trans. 
  Koy. 
  Soc. 
  Edinb. 
  vol. 
  xxii. 
  (1861), 
  pp. 
  633-753. 
  

  

  ^[ 
  ' 
  The 
  Scenery 
  of 
  Scotland 
  viewed 
  in 
  connection 
  with 
  its 
  Physical 
  Geology,' 
  

   with 
  a 
  Geological 
  Map 
  (1865). 
  

  

  ** 
  Proc. 
  Hoy. 
  Soc. 
  Edinb. 
  vol/vi. 
  (1867), 
  p. 
  71. 
  

  

  