﻿296 
  J. 
  W. 
  JTJDD 
  ON 
  THE 
  SECONDARY 
  EOCKS 
  OF 
  SCOTLAND. 
  

  

  by 
  Prof. 
  Geikie 
  and 
  other 
  authors. 
  These 
  unconformities 
  do 
  not 
  

   appear, 
  however, 
  to 
  have 
  the 
  same 
  significance 
  which 
  we 
  naturally 
  

   attribute 
  to 
  phenomena 
  of 
  the 
  same 
  kind 
  when 
  exhibited 
  by 
  rocks 
  

   which 
  have 
  been 
  formed 
  under 
  less 
  violent 
  conditions. 
  

  

  "We 
  have 
  seen 
  that, 
  during 
  the 
  later 
  portions 
  of 
  the 
  Tertiary 
  

   epoch, 
  the 
  eruptions 
  from 
  the 
  great 
  centres 
  of 
  volcanic 
  activity 
  were 
  

   succeeded 
  by 
  a 
  series 
  of 
  sporadic 
  eruptions, 
  resulting 
  in 
  the 
  formation 
  

   of 
  numerous 
  small 
  cones 
  or 
  "puys;" 
  and 
  in 
  this 
  we 
  find 
  a 
  close 
  

   analogy 
  with 
  what 
  has 
  taken 
  place 
  in 
  the 
  case 
  of 
  many 
  modern 
  

   volcanoes. 
  The 
  great 
  volcanoes 
  of 
  the 
  Grampians, 
  which 
  were 
  in 
  

   activity 
  during 
  the 
  Newer 
  Palaeozoic 
  periods, 
  also 
  appear 
  on 
  their 
  

   extinction 
  to 
  have 
  been 
  succeeded 
  by 
  the 
  outburst 
  of 
  numerous 
  

   " 
  puys.'' 
  " 
  The 
  area 
  of 
  the 
  Lothians 
  and 
  Fife," 
  says 
  Prof. 
  Geikie, 
  

   " 
  appears 
  to 
  have 
  been 
  dotted 
  over 
  with 
  innumerable 
  volcanic 
  

   vents 
  ; 
  " 
  and 
  these 
  sporadic 
  eruptions 
  seem 
  to 
  have 
  continued 
  

   during 
  a 
  great 
  part 
  of 
  the 
  Carboniferous 
  and 
  Permian 
  periods. 
  

   These 
  latest 
  eruptions 
  of 
  the 
  Palaeozoic 
  epoch 
  consisted 
  of 
  materials 
  

   of 
  more 
  or 
  less 
  basic 
  character 
  ; 
  and 
  the 
  wide-spreading 
  sheets 
  of 
  

   melaphyre 
  and 
  similar 
  rocks 
  connected 
  with 
  them, 
  and 
  intruded 
  

   between 
  the 
  older 
  strata, 
  have 
  given 
  rise 
  to 
  those 
  numerous 
  " 
  crags 
  " 
  

   which, 
  often 
  crowned 
  by 
  old 
  castles, 
  form 
  such 
  a 
  striking 
  feature 
  in 
  

   Lowland 
  scenery. 
  The 
  most 
  familiar 
  type 
  of 
  these 
  later 
  palaeozoic 
  

   " 
  puys 
  " 
  is 
  the 
  well-known 
  Arthur's 
  Seat, 
  near 
  Edinburgh, 
  the 
  

   origin 
  of 
  which 
  has 
  been 
  so 
  well 
  illustrated 
  by 
  Maclaren, 
  Edward 
  

   Forbes, 
  and 
  Prof. 
  Geikie 
  ; 
  but 
  innumerable 
  other 
  beautiful 
  examples 
  

   of 
  the 
  same 
  kind 
  occur, 
  some 
  of 
  which 
  are 
  described 
  in 
  the 
  publica- 
  

   tions 
  of 
  the 
  Geological 
  Survey. 
  

  

  IV. 
  Conclusion. 
  

  

  1. 
  Comparison 
  of 
  the 
  two 
  Great 
  Periods 
  of 
  Volcanic 
  Activity 
  in 
  

   Scotland. 
  — 
  From 
  the 
  facts 
  described 
  in 
  the 
  present 
  paper 
  it 
  appears 
  

   that 
  the 
  British 
  archipelago, 
  in 
  common 
  with 
  the 
  surrounding 
  

   districts, 
  has 
  been 
  the 
  theatre 
  at 
  two 
  distinct 
  periods, 
  since 
  the 
  

   deposition 
  of 
  the 
  Silurian 
  rocks, 
  of 
  exhibitions 
  of 
  volcanic 
  pheno- 
  

   mena 
  upon 
  the 
  very 
  grandest 
  scale. 
  The 
  first 
  of 
  these 
  epochs 
  of 
  

   violent 
  igneous 
  activity 
  appears 
  to 
  have 
  lasted 
  from 
  the 
  commence- 
  

   ment 
  of 
  the 
  Old-Eed-Sandstone 
  period 
  down 
  to 
  the 
  close 
  of 
  the 
  

   Palaeozoic 
  era 
  ; 
  the 
  second, 
  during 
  nearly 
  the 
  whole 
  of 
  the 
  Tertiary 
  

   epoch. 
  The 
  interval 
  between 
  these 
  two 
  grand 
  displays 
  of 
  igneous 
  

   forces, 
  namely 
  that 
  during 
  which 
  the 
  Mesozoic 
  strata 
  were 
  de- 
  

   posited, 
  appears 
  to 
  have 
  been 
  one 
  of 
  comparative, 
  perhaps 
  of 
  

   complete, 
  quiescence 
  of 
  volcanic 
  action. 
  Bearing 
  in 
  mind 
  the 
  

   arguments 
  of 
  Mr. 
  Darwin 
  in 
  support 
  of 
  " 
  the 
  identity 
  of 
  the 
  force 
  

   which 
  elevates 
  continents 
  with 
  that 
  which 
  occasions 
  volcanic 
  

   outbursts," 
  it 
  is 
  not 
  a 
  little 
  interesting 
  to 
  find 
  that 
  the 
  periods 
  of 
  

   maximum 
  volcanic 
  activity, 
  namely 
  the 
  Old-Red-Sandstone 
  and 
  the 
  

   Miocene, 
  appear 
  to 
  have 
  coincided 
  with 
  those 
  during 
  which 
  (as 
  

   hown 
  from 
  various 
  considerations 
  by 
  Professor 
  Ramsay) 
  a 
  great 
  

   extent 
  of 
  continental 
  land 
  prevailed 
  in 
  the 
  same 
  areas. 
  

  

  