﻿250 
  J. 
  W. 
  JTJDD 
  ON 
  THE 
  SECONDARY 
  BOOKS 
  OP 
  SCOTLAND. 
  

  

  materials 
  of 
  the 
  basic 
  class 
  among 
  the 
  products 
  of 
  this 
  volcano. 
  

   The 
  liquefied 
  materials 
  of 
  this 
  period 
  were 
  forced 
  through 
  the 
  

   older 
  igneous 
  rocks, 
  Assuring 
  them 
  in 
  every 
  direction 
  : 
  those 
  fissures 
  

   ■which 
  did 
  not 
  reach 
  the 
  surface 
  would 
  be 
  filled 
  by 
  the 
  consolidating 
  

   rock 
  and 
  form 
  dykes 
  ; 
  but, 
  doubtless, 
  many 
  of 
  these 
  great 
  rents 
  

   extended 
  to 
  the 
  surface 
  and 
  then 
  gave 
  rise 
  to 
  those 
  eruptions 
  pro- 
  

   ducing 
  the 
  " 
  parasitic 
  cones 
  " 
  so 
  common 
  on 
  the 
  flanks 
  of 
  many 
  great 
  

   volcanoes. 
  The 
  lavas 
  of 
  this 
  period 
  being 
  possessed 
  of 
  so 
  much 
  

   greater 
  fluidity, 
  instead 
  of 
  being 
  confined, 
  like 
  those 
  of 
  older 
  date, 
  

   to 
  the 
  neighbourhood 
  of 
  the 
  volcano, 
  flowed 
  to 
  enormous 
  distances 
  ; 
  

   and 
  so 
  vast 
  were 
  the 
  volumes 
  of 
  material 
  discharged 
  from 
  the 
  

   volcano, 
  that 
  the 
  lava 
  streams 
  accumulated 
  to 
  a 
  thickness 
  of 
  2000 
  

   feet. 
  That 
  the 
  formation 
  of 
  deposits 
  of 
  such 
  vast 
  thickness 
  occu- 
  

   pied 
  periods 
  of 
  enormous 
  duration 
  we 
  may 
  reasonably 
  infer 
  ; 
  and 
  

   the 
  conclusion 
  is 
  confirmed 
  by 
  the 
  proofs 
  of 
  intereruptive 
  denuda- 
  

   tion 
  among 
  these 
  old 
  lavas, 
  and 
  by 
  the 
  existence 
  of 
  old 
  soils, 
  forest- 
  

   growths, 
  river-gravels, 
  and 
  lacustrine 
  deposits 
  between 
  them. 
  

  

  At 
  the 
  close 
  of 
  this 
  second 
  period 
  of 
  eruption 
  the 
  volcano 
  of 
  Mull 
  

   became 
  extinct, 
  and 
  has 
  gradually 
  fallen 
  into 
  that 
  state 
  of 
  decay 
  and 
  

   ruin 
  which 
  it 
  now 
  presents. 
  But, 
  as 
  we 
  shall 
  hereafter 
  show, 
  

   Volcanic 
  activity 
  in 
  the 
  district 
  did 
  not 
  cease 
  with 
  the 
  extinction 
  of 
  

   this 
  and 
  the 
  other 
  similar 
  great 
  volcanic 
  mountains 
  of 
  the 
  period. 
  

  

  Having 
  demonstrated 
  the 
  real 
  nature 
  of 
  the 
  central 
  mountain- 
  

   group 
  in 
  the 
  island 
  of 
  Mull 
  (namely, 
  that 
  it 
  constitutes 
  the 
  basal 
  

   wreck 
  of 
  a 
  great 
  volcanic 
  pile), 
  I 
  shall 
  proceed 
  to 
  show 
  that, 
  at 
  a 
  

   number 
  of 
  other 
  points 
  in 
  the 
  same 
  district, 
  there 
  occur 
  similar 
  

   masses 
  of 
  eruptive 
  rocks 
  associated 
  with 
  volcanic 
  agglomerates 
  and 
  

   breccias, 
  and 
  that 
  these 
  are 
  the 
  relics 
  of 
  other 
  volcanoes, 
  similar 
  to, 
  

   and 
  contemporaneous 
  with, 
  that 
  of 
  Mull. 
  After 
  the 
  details 
  into 
  

   which 
  I 
  have 
  entered 
  with 
  regard 
  to 
  this 
  last-mentioned 
  example, 
  

   it 
  will 
  not 
  be 
  necessary 
  for 
  me 
  to 
  do 
  more, 
  in 
  describing 
  the 
  other 
  

   similar 
  instances, 
  than 
  to 
  point 
  out 
  in 
  a 
  general 
  manner 
  the 
  

   analogies 
  and 
  variations 
  of 
  their 
  structure 
  as 
  compared 
  with 
  that 
  

   which 
  Ave 
  have 
  chosen 
  as 
  the 
  type. 
  

  

  6. 
  The 
  Volcano 
  of 
  Ardnamurclian. 
  — 
  Immediately 
  to 
  the 
  iiorth- 
  

   ward 
  of 
  the 
  island 
  of 
  Mull 
  stretches 
  the 
  peninsula 
  of 
  Ardnamurchan, 
  

   which 
  forms 
  the 
  most 
  western 
  portion 
  of 
  the 
  mainland 
  of 
  Scotland. 
  

   In 
  this 
  district 
  we 
  have 
  exhibited 
  to 
  us, 
  though 
  in 
  a 
  much 
  more 
  

   fragmentary 
  condition, 
  a 
  precisely 
  similar 
  series 
  of 
  rocks, 
  presenting 
  

   relations 
  with 
  one 
  another 
  identical 
  with 
  those 
  described 
  in 
  the 
  

   island 
  of 
  Mull. 
  

  

  Constituting 
  the 
  peak 
  of 
  Meal-nan-con 
  and 
  a 
  number 
  of 
  adjoining 
  

   heights, 
  which 
  stretch 
  in 
  a 
  belt 
  south-westward 
  to 
  near 
  Kilchoan, 
  

   we 
  find 
  great 
  masses 
  of 
  intrusive, 
  felsite 
  presenting 
  many 
  local 
  

   variations, 
  but 
  as 
  a 
  whole 
  exhibiting 
  a 
  striking 
  identity 
  with 
  the 
  

   great 
  felsitic 
  rocks 
  of 
  Mull, 
  like 
  which 
  they, 
  in 
  places, 
  assume 
  a 
  

   distinctly 
  granitic 
  character. 
  Lying 
  upon 
  the 
  eastern 
  and 
  southern 
  

   flanks 
  of 
  these 
  felsites 
  and 
  penetrated 
  by 
  numerous 
  veins 
  which 
  

   proceed 
  from 
  them 
  are 
  numerous 
  sheets 
  of 
  felstone, 
  often 
  of 
  

   amygdaloidal 
  structure. 
  These 
  are 
  interstratified 
  with 
  beds 
  of 
  ash 
  

  

  