﻿J. 
  W. 
  JTJDD 
  ON 
  THE 
  SECONDARY 
  ROCKS 
  OF 
  SCOTLAND. 
  295 
  

  

  tion 
  a 
  portion 
  of 
  the 
  lavas 
  and 
  associated 
  beds 
  which 
  formed 
  the 
  

   outskirts 
  of 
  one 
  of 
  the 
  great 
  Newer 
  Palaeozoic 
  volcanoes 
  — 
  the 
  

   lavas 
  of 
  Glencoe 
  lying 
  in 
  part 
  on 
  the 
  disturbed 
  and 
  metamorphosed 
  

   stratified 
  rocks, 
  and 
  in 
  part 
  on 
  the 
  great 
  eruptive 
  masses 
  which 
  

   have 
  produced 
  that 
  disturbance 
  and 
  metamorphism. 
  

  

  Besides 
  Beinn 
  Nevis 
  and 
  Glencoe 
  there 
  are 
  some 
  other 
  points 
  

   which 
  exhibit, 
  though 
  in 
  a 
  less 
  striking 
  manner, 
  relics 
  of 
  these 
  

   doubtless 
  once 
  grandly 
  developed 
  masses 
  of 
  lava 
  and 
  fragmentary 
  

   materials, 
  which 
  during 
  the 
  Newer 
  Palaeozoic 
  periods 
  formed 
  those 
  

   great 
  volcanic 
  cones 
  of 
  which 
  the 
  granitic 
  masses 
  of 
  the 
  Grampians 
  

   constituted 
  the 
  central 
  cores, 
  and 
  which 
  rose 
  above 
  vast 
  pla- 
  

   teaux 
  of 
  the 
  felspathic 
  lavas 
  that 
  issued 
  from 
  them 
  ; 
  of 
  these 
  

   plateaux 
  only 
  small 
  and 
  outlying 
  fragments 
  have, 
  by 
  a 
  combination 
  

   of 
  accidents, 
  escaped 
  destruction 
  by 
  denudation. 
  There 
  is 
  one 
  fact 
  

   which 
  I 
  have 
  not 
  yet 
  noticed, 
  but 
  which 
  is 
  of 
  a 
  sufficiently 
  striking 
  

   character 
  to 
  arrest 
  the 
  attention 
  of 
  every 
  geological 
  observer; 
  I 
  

   allude 
  to 
  the 
  very 
  marked 
  similarity 
  in 
  petrological 
  characters 
  

   between 
  the 
  vestiges 
  of 
  the 
  lava 
  rocks 
  preserved 
  in 
  Beinn 
  Nevis 
  and 
  

   Glencoe 
  on 
  the 
  one 
  hand, 
  and 
  those 
  which 
  make 
  up 
  the 
  larger 
  areas, 
  

   as 
  of 
  Lorn 
  and 
  central 
  Scotland 
  on 
  the 
  other. 
  

  

  10. 
  Physical 
  Features 
  of 
  Northern 
  Scotland 
  during 
  the 
  Neiver 
  

   Palaeozoic 
  periods. 
  — 
  That 
  the 
  different 
  deposits 
  of 
  the 
  Old 
  Ked 
  

   Sandstone 
  were 
  accumulated 
  in 
  lakes, 
  has 
  been 
  suggested 
  by 
  Mr. 
  

   Godwin-Austen, 
  and 
  supported 
  by 
  a 
  variety 
  of 
  arguments 
  by 
  Prof. 
  

   Bamsay. 
  The 
  peculiar 
  characters 
  of 
  the 
  deposits 
  of 
  this 
  age 
  in 
  the 
  

   districts 
  referred 
  to 
  in 
  this 
  paper 
  appear 
  to 
  accord 
  perfectly 
  with 
  

   this 
  hypothesis. 
  

  

  The 
  conditions 
  which 
  prevailed 
  during 
  the 
  earlier 
  part 
  of 
  the 
  

   Newer 
  Palaeozoic 
  periods 
  would 
  appear 
  to 
  have 
  been 
  as 
  follows 
  : 
  — 
  In 
  

   what 
  is 
  now 
  the 
  Scottish 
  Highlands 
  an 
  extensive 
  land 
  area 
  existed, 
  

   with 
  a 
  number 
  of 
  more 
  or 
  less 
  isolated 
  lakes 
  or 
  inland 
  seas. 
  Along 
  

   the 
  line 
  now 
  occupied 
  by 
  the 
  Grampian 
  Mountains 
  rose 
  a 
  range 
  of 
  

   great 
  volcanic 
  cones, 
  while 
  numerous 
  intermittent 
  eruptions 
  took 
  

   place 
  at 
  the 
  bottom 
  of 
  the 
  great 
  sheets 
  of 
  water 
  ; 
  the 
  centres 
  of 
  

   eruption 
  of 
  some, 
  at 
  least, 
  of 
  these 
  have 
  been 
  pointed 
  out 
  by 
  Mr. 
  

   Maclaren 
  and 
  Prof. 
  Geikie. 
  Thus 
  while 
  great 
  masses 
  of 
  lava, 
  with 
  

   agglomerates, 
  tuffs, 
  and 
  ashes, 
  were 
  accumulating 
  round 
  the 
  great 
  

   volcanoes, 
  other 
  enormous 
  deposits 
  were 
  simultaneously 
  formed, 
  con- 
  

   sisting 
  of 
  alternations 
  of 
  similar 
  lavas 
  with 
  stratified 
  rocks 
  — 
  the 
  latter 
  

   being 
  composed 
  in 
  part 
  of 
  the 
  detritus 
  of 
  these 
  lavas, 
  in 
  part 
  of 
  

   fragmentary 
  eruptive 
  materials 
  which 
  fell 
  into 
  the 
  lakes, 
  and 
  in 
  part 
  

   of 
  the 
  materials 
  derived 
  from 
  the 
  older 
  rocks 
  which 
  formed 
  their 
  

   shores. 
  A 
  similar 
  series 
  of 
  operations 
  went 
  on 
  during 
  the 
  next 
  suc- 
  

   ceeding 
  period, 
  that 
  of 
  the 
  Calciferous 
  Sandstone, 
  though, 
  in 
  conse- 
  

   quence 
  of 
  physical 
  changes, 
  lacustrine 
  were 
  exchanged 
  for 
  estuarine 
  

   and 
  terrestrial 
  conditions. 
  

  

  During 
  the 
  whole 
  of 
  these 
  periods 
  much 
  local 
  subsidence 
  must 
  

   have 
  taken 
  place, 
  to 
  permit 
  of 
  the 
  accumulation 
  of 
  such 
  enormous 
  

   thicknesses 
  of 
  rocks 
  ; 
  and 
  the 
  resulting 
  disturbances 
  led 
  to 
  the 
  

   production 
  of 
  those 
  local 
  unconformities 
  which 
  have 
  been 
  noticed 
  

  

  y2 
  

  

  