﻿J. 
  W. 
  JUDD 
  ON 
  THE 
  SECONDARY 
  ROCKS 
  OE 
  SCOTLAND. 
  273 
  

  

  three 
  epochs 
  of 
  intense 
  volcanic 
  activity. 
  This 
  is 
  evidenced 
  by 
  the 
  

   unconformable 
  relations 
  which 
  the 
  rock-masses 
  produced 
  during 
  the 
  

   three 
  periods 
  of 
  eruption 
  bear 
  to 
  one 
  another. 
  

  

  The 
  proofs 
  of 
  extensive 
  denudation 
  having 
  taken 
  place 
  in 
  the 
  in- 
  

   terval 
  between 
  the 
  outflow 
  of 
  the 
  great 
  masses 
  of 
  felspathic 
  and 
  

   basaltic 
  lavas 
  appear 
  to 
  be 
  of 
  a 
  very 
  decisive 
  character. 
  

  

  (1) 
  The 
  basaltic 
  lavas 
  and 
  their 
  accompanying 
  piles 
  of 
  scoriae, 
  rest 
  

   directly 
  in 
  many 
  cases, 
  as 
  is 
  so 
  well 
  seen 
  in 
  both 
  Rum 
  and 
  Mull, 
  not 
  on 
  

   the 
  lavas 
  and 
  ashes 
  which 
  must 
  have 
  constituted 
  the 
  outer 
  portions 
  of 
  

   the 
  earlier 
  volcanoes, 
  but 
  on 
  the 
  intrusive 
  felsites 
  and 
  granites 
  which 
  

   could 
  only 
  have 
  formed 
  their 
  interior 
  and 
  deeply 
  seated 
  portions. 
  

  

  (2) 
  The 
  felspathic 
  lavas, 
  &c, 
  are 
  seen 
  in 
  Mull 
  to 
  have 
  undergone 
  

   considerable 
  movements 
  and 
  to 
  have 
  suffered 
  largely 
  from 
  denudation, 
  

   before 
  they 
  were 
  buried 
  under 
  the 
  overwhelming 
  products 
  of 
  the 
  

   period 
  of 
  basaltic 
  eruptions. 
  

  

  (3) 
  It 
  appears 
  also 
  that 
  the 
  basaltic 
  streams 
  frequently 
  lie 
  in 
  

   hollows 
  eroded 
  in 
  the 
  preexisting 
  felstones. 
  This 
  fact 
  is 
  not 
  so 
  

   easily 
  made 
  out 
  as 
  those 
  before 
  noticed; 
  but 
  I 
  believe 
  there 
  are 
  

   distinct 
  proofs 
  of 
  it 
  in 
  Ardnamurchan. 
  

  

  The 
  evidences 
  of 
  erosion 
  on 
  a 
  very 
  extensive 
  scale 
  having 
  taken 
  

   place 
  between 
  the 
  period 
  of 
  the 
  eruptions 
  of 
  basic 
  rocks 
  and 
  that 
  of 
  

   the 
  formation 
  of 
  the 
  " 
  puys 
  " 
  are 
  not 
  so 
  easily 
  traced 
  as 
  those 
  of 
  the 
  

   former 
  inter-volcanic 
  period, 
  owing 
  to 
  the 
  almost 
  complete 
  removal 
  

   of 
  the 
  latest-formed 
  volcanic 
  deposits 
  of 
  the 
  district 
  by 
  denuda- 
  

   tion. 
  But 
  in 
  the 
  case 
  of 
  the 
  Scur 
  of 
  Eigg, 
  as 
  so 
  clearly 
  explained 
  

   by 
  Prof. 
  Geikie, 
  and 
  in 
  that 
  of 
  Beinn 
  Shiant, 
  which 
  has 
  been 
  de- 
  

   scribed 
  in 
  this 
  paper, 
  the 
  proofs 
  of 
  unconformity 
  between 
  the 
  lavas 
  

   of 
  the 
  two 
  series 
  are 
  sufficiently 
  distinct 
  and 
  striking. 
  

  

  Lastly, 
  of 
  the 
  enormous 
  changes 
  which 
  have 
  taken 
  place 
  since 
  the 
  

   period 
  of 
  the 
  formation 
  of 
  the 
  " 
  puys," 
  we 
  have 
  the 
  clearest 
  proofs 
  

   in 
  the 
  total 
  removal, 
  with 
  rare 
  exceptions, 
  of 
  the 
  volcanic 
  piles 
  which 
  

   doubtless 
  once 
  surmounted 
  those 
  igneous 
  protrusions, 
  which 
  now 
  

   alone 
  mark 
  the 
  sites 
  of 
  the 
  latest 
  series 
  of 
  eruptions 
  in 
  the 
  district. 
  

  

  In 
  the 
  almost 
  total 
  absence 
  of 
  palaeontological 
  evidence, 
  it 
  cannot, 
  

   of 
  course, 
  be 
  absolutely 
  demonstrated 
  that 
  the 
  three 
  series 
  of 
  volcanic 
  

   outbursts 
  which 
  we 
  have 
  described 
  were 
  in 
  the 
  case 
  of 
  the 
  different 
  

   centres 
  strictly 
  synchronous 
  ; 
  but 
  the 
  remarkable 
  uniformity 
  of 
  cha- 
  

   racters, 
  in 
  the 
  succession 
  of 
  products 
  in 
  all 
  the 
  different 
  cases, 
  leads 
  

   to 
  the 
  very 
  strongest 
  presumptions 
  in 
  favour 
  of 
  a 
  connexion 
  having 
  

   existed 
  between 
  these 
  different 
  foci, 
  and 
  of 
  the 
  contemporaneity 
  be- 
  

   tween 
  the 
  several 
  analogous 
  phenomena 
  manifested 
  at 
  each 
  of 
  them. 
  

  

  Our 
  means 
  of 
  correlating 
  these 
  three 
  epochs 
  of 
  volanic 
  activity 
  

   during 
  the 
  Tertiary 
  period, 
  with 
  the 
  divisions 
  of 
  the 
  same 
  era 
  founded 
  

   on 
  the 
  relations 
  which 
  its 
  successive 
  faunas 
  bear 
  to 
  one 
  another 
  and 
  

   to 
  the 
  existing 
  creation, 
  must 
  be 
  confessed 
  to 
  be 
  small 
  ; 
  and 
  hence 
  

   the 
  results 
  attainable 
  by 
  us 
  on 
  this 
  subject 
  are 
  to 
  a 
  certain 
  extent 
  

   indecisive 
  ; 
  nevertheless 
  it 
  will 
  be 
  well 
  in 
  this 
  place 
  to 
  bring 
  together 
  

   the 
  whole 
  mass 
  of 
  evidence 
  as 
  yet 
  obtained 
  which 
  bears 
  upon 
  the 
  

   question. 
  

  

  The 
  beds 
  intercalated 
  with 
  the 
  earliest 
  series, 
  that 
  of 
  the 
  fel- 
  

  

  