﻿260 
  J. 
  W. 
  JUDD 
  ON 
  THE 
  SECONDARY 
  ROCKS 
  OE 
  SCOTLAND. 
  

  

  mit 
  of 
  a 
  volcano, 
  and 
  in 
  a 
  few 
  days, 
  weeks, 
  or 
  months 
  a 
  new 
  

   cone 
  of 
  different 
  form 
  and 
  proportions 
  built 
  up. 
  Such 
  changes 
  

   doubtless 
  occurred 
  over 
  and 
  over 
  again 
  in 
  the 
  case 
  of 
  the 
  ancient 
  

   volcanoes 
  of 
  Scotland 
  as 
  well 
  as 
  in 
  those 
  of 
  more 
  recent 
  date. 
  

  

  From 
  the 
  area 
  which 
  its 
  relics 
  occupy, 
  we 
  may 
  conclude 
  that 
  

   the 
  volcano 
  of 
  Skye 
  was 
  not 
  inferior 
  in 
  its 
  dimensions 
  to 
  that 
  of 
  

   Mull 
  ; 
  and 
  on 
  similar 
  grounds 
  we 
  are 
  led 
  to 
  infer 
  that 
  the 
  volcanoes 
  

   of 
  Rum, 
  Ardnamurchan, 
  and 
  St. 
  Kilda, 
  though 
  somewhat 
  smaller 
  

   than 
  these, 
  were 
  nevertheless 
  mountains 
  of 
  great 
  extent 
  and 
  

   elevation. 
  

  

  Thus 
  we 
  are 
  led 
  to 
  the 
  conclusion 
  that 
  during 
  the 
  Tertiary 
  

   epoch 
  there 
  existed 
  in 
  the 
  north-western 
  part 
  of 
  the 
  British 
  

   Islands 
  a 
  range 
  of 
  volcanic 
  mountains 
  which 
  were 
  on 
  the 
  grandest 
  

   scale 
  — 
  a 
  fact 
  which 
  all 
  who 
  consider 
  the 
  wonderful 
  extent 
  and 
  

   thickness 
  of 
  their 
  accumulated 
  lava 
  streams 
  will 
  be 
  fully 
  prepared 
  

   to 
  admit. 
  

  

  12. 
  Series 
  of 
  later 
  Volcanic 
  Eruptions 
  in 
  the 
  Hebrides 
  resulting 
  

   in 
  the 
  formation 
  of 
  "Pays.'" 
  — 
  -I 
  shall 
  now 
  proceed 
  to 
  show 
  that, 
  

   subsequently 
  both 
  to 
  the 
  period 
  of 
  the 
  eruption 
  of 
  the 
  acid 
  lavas 
  and 
  

   to 
  that 
  of 
  the 
  ejection 
  of 
  basic 
  rocks, 
  and 
  at 
  a 
  time 
  when 
  the 
  great 
  

   volcanoes 
  from 
  which 
  these 
  flowed 
  had 
  become 
  extinct 
  and 
  their 
  

   products 
  greatly 
  denuded, 
  another 
  series 
  of 
  volcanic 
  outbursts 
  of 
  a 
  

   sporadic 
  character 
  took 
  place 
  within 
  the 
  district, 
  and 
  gave 
  rise 
  to 
  the 
  

   formation 
  of 
  numerous 
  smaller 
  cones 
  with 
  their 
  accompanying 
  lava 
  

   streams. 
  

  

  The 
  researches 
  of 
  Mr. 
  Scrope 
  in 
  Central 
  France, 
  of 
  Mr. 
  Darwin 
  

   in 
  the 
  volcanic 
  islands 
  of 
  the 
  Atlantic, 
  of 
  Hamilton 
  and 
  Strickland 
  

   in 
  Asia 
  Minor, 
  with 
  others 
  that 
  might 
  be 
  cited, 
  have 
  sufficiently 
  

   demonstrated 
  that 
  the 
  extinction 
  of 
  great 
  volcanoes 
  is 
  in 
  many 
  (if 
  

   not 
  in 
  all) 
  cases 
  followed 
  by 
  eruptions 
  on 
  a 
  minor 
  scale, 
  which 
  burst 
  

   out 
  in 
  the 
  plains 
  at 
  their 
  base 
  and 
  give 
  rise 
  to 
  the 
  formation 
  of 
  nu- 
  

   merous 
  small 
  cones, 
  usually 
  arranged 
  along 
  what 
  appear 
  to 
  be 
  lines 
  

   of 
  fissure. 
  It 
  would 
  seem 
  that 
  the 
  volcanic 
  forces 
  having 
  to 
  a 
  

   great 
  extent 
  expended 
  themselves, 
  and 
  being 
  insufficient 
  to 
  raise 
  

   columns 
  of 
  lava 
  to 
  the 
  summits 
  of 
  the 
  mountains 
  which 
  successive 
  

   eruptions 
  have 
  continually 
  elevated, 
  have 
  nevertheless 
  been 
  able, 
  

   before 
  sinking 
  into 
  absolute 
  quiescence, 
  to 
  open 
  new 
  vents 
  at 
  lower 
  

   levels. 
  To 
  the 
  class 
  of 
  smaller 
  volcanoes 
  thus 
  produced 
  it 
  will 
  be 
  

   convenient 
  to 
  apply 
  the 
  general 
  term 
  "puys,"* 
  from 
  the 
  name 
  by 
  

  

  * 
  It 
  is 
  of 
  course 
  impossible 
  to 
  draw 
  any 
  absolute 
  line 
  of 
  demarcation 
  between 
  

   the 
  class 
  of 
  subsidiary 
  or 
  parasitical 
  cones 
  which 
  are 
  so 
  abundant 
  on 
  the 
  flanks 
  

   of 
  many 
  great 
  volcanoes 
  (on 
  Etna 
  there 
  are 
  said 
  to 
  be 
  no 
  less 
  than 
  800 
  of 
  them) 
  

   and 
  that 
  of 
  the 
  " 
  puys," 
  or 
  cones 
  thrown 
  up 
  in 
  the 
  plains 
  in 
  their 
  vicinity. 
  As 
  

   is 
  so 
  well 
  shown 
  by 
  Mr. 
  Scrope, 
  in 
  his 
  work 
  on 
  Central 
  France, 
  the 
  formation 
  

   of 
  such 
  puys 
  in 
  a 
  district 
  may 
  be 
  going 
  on 
  during 
  periods 
  of 
  vast 
  duration, 
  and 
  

   the 
  several 
  eruptions 
  to 
  which 
  they 
  owe 
  their 
  origin 
  may 
  be 
  separated 
  by 
  very 
  

   wide 
  intervals 
  of 
  time. 
  They 
  appear, 
  however, 
  in 
  almost 
  all 
  cases 
  to 
  be 
  of 
  sub- 
  

   sequent 
  date 
  to 
  the 
  extinction 
  of 
  the 
  great 
  central 
  volcanic 
  mountains, 
  and 
  some- 
  

   times, 
  indeed 
  (as 
  in 
  the 
  case 
  of 
  the 
  Puy 
  de 
  Tartaret 
  in 
  the 
  Mont 
  Dore), 
  to 
  have 
  

   been 
  formed 
  in 
  the 
  midst 
  of 
  the 
  ruinous 
  masses 
  of 
  rocks 
  to 
  which 
  such 
  great 
  

   volcanoes 
  have 
  been 
  reduced 
  by 
  denudation. 
  The 
  course 
  of 
  events 
  in 
  connexion 
  

   with 
  the 
  history 
  of 
  the 
  decline 
  and 
  decay 
  of 
  a 
  great 
  volcano 
  would 
  appear 
  to 
  be 
  

  

  