﻿298 
  J. 
  W. 
  JUDD 
  ON 
  THE 
  SECONDABY 
  BOCKS 
  OE 
  SCOTLAND. 
  

  

  between 
  two 
  epochs 
  of 
  the 
  most 
  violent 
  volcanic 
  activity, 
  the 
  

   Mesozoic 
  era 
  may 
  well 
  be 
  supposed 
  to 
  have 
  been 
  characterized 
  by 
  

   the 
  subdued 
  efforts 
  of 
  those 
  imprisoned 
  forces 
  which 
  were 
  unequal 
  

   to 
  the 
  task 
  of 
  opening 
  " 
  safety-valves 
  " 
  for 
  their 
  violence 
  at 
  the 
  

   surface. 
  I 
  shall 
  show 
  in 
  the 
  sequel 
  that 
  many 
  of 
  the 
  anomalous 
  

   characters 
  of 
  tbe 
  Secondary 
  rocks 
  in 
  this 
  district 
  can 
  only 
  be 
  ex- 
  

   plained 
  on 
  the 
  supposition 
  that 
  during 
  the 
  period 
  of 
  their 
  deposition 
  

   the 
  area 
  was 
  subject 
  to 
  frequent 
  and 
  great 
  oscillations 
  of 
  level. 
  

  

  (3) 
  It 
  is 
  to 
  the 
  [overwhelming 
  masses 
  of 
  matter 
  poured 
  out 
  by 
  

   the 
  Tertiary 
  volcanoes 
  that 
  the 
  preservation 
  even 
  of 
  such 
  small 
  

   vestiges 
  of 
  the 
  Secondary 
  rocks 
  as 
  remain 
  to 
  us 
  is 
  wholly 
  due. 
  In 
  the 
  

   case 
  of 
  each 
  of 
  the 
  patches 
  of 
  these 
  strata 
  which 
  we 
  are 
  called 
  upon 
  

   to 
  study 
  on 
  the 
  west 
  coast 
  of 
  Scotland, 
  the 
  positions 
  and 
  relations 
  

   of 
  its 
  beds, 
  and 
  the 
  nature 
  and 
  extent 
  of 
  its 
  metamorphism, 
  are 
  the 
  

   result 
  of 
  that 
  complicated 
  series 
  of 
  volcanic 
  phenomena 
  which 
  

   followed 
  their 
  deposition. 
  

  

  3. 
  The 
  " 
  Geological 
  Record" 
  in 
  the 
  Scottish 
  Highlands. 
  — 
  The 
  

   purposes 
  which 
  the 
  Alps 
  have 
  served 
  to 
  continental 
  geologists, 
  have 
  

   been 
  to 
  a 
  great 
  extent 
  fulfilled 
  in 
  the 
  case 
  of 
  British 
  observers 
  by 
  

   the 
  Scottish 
  Highlands 
  ; 
  and 
  in 
  either 
  of 
  these 
  districts 
  the 
  materials 
  

   for 
  the 
  solution 
  of 
  some 
  of 
  the 
  most 
  important 
  problems 
  of 
  physical 
  

   geology 
  have 
  been 
  not 
  unsuccessfully 
  sought 
  for. 
  It 
  was 
  not 
  unnatural 
  

   that, 
  in 
  the 
  case 
  of 
  both 
  these 
  mountain-groups, 
  the 
  greatly 
  altered 
  

   and 
  highly 
  crystalline 
  character 
  of 
  the 
  rocks 
  which 
  compose 
  them 
  

   should 
  have 
  been 
  looked 
  upon 
  by 
  the 
  older 
  geologists 
  as 
  proofs 
  of 
  their 
  

   great 
  antiquity. 
  But 
  the 
  discovery 
  of 
  fossils 
  in 
  some 
  of 
  the 
  less- 
  

   altered 
  portions 
  of 
  the 
  Alpine 
  rocks 
  has 
  quite 
  revolutionized 
  the 
  

   views 
  of 
  geologists 
  upon 
  the 
  subject 
  of 
  their 
  age 
  ; 
  and, 
  similarly, 
  the 
  

   results 
  of 
  recent 
  researches 
  in 
  the 
  Scottish 
  Highlands 
  enable 
  us 
  to 
  

   refer 
  their 
  great 
  crystalline 
  masses 
  to 
  well-known, 
  and 
  in 
  some 
  

   cases 
  very 
  recent, 
  geological 
  periods. 
  

  

  Should 
  any 
  one 
  still 
  cling 
  to 
  the 
  old 
  view 
  that 
  highly 
  crystalline 
  

   characters 
  in 
  rocks 
  may 
  be 
  regarded 
  as 
  a 
  criterion 
  of 
  antiquity, 
  I 
  

   would 
  point 
  to 
  the 
  Cuchullin 
  Hills 
  of 
  Skye, 
  which 
  have 
  been 
  

   regarded 
  as 
  of 
  Laurentian 
  age, 
  but 
  which, 
  from 
  the 
  clearest 
  evi- 
  

   dence, 
  we 
  have 
  shown 
  to 
  belong 
  to 
  the 
  Miocene 
  period. 
  

  

  The 
  early 
  maps 
  of 
  the 
  Scottish 
  Highlands 
  were 
  of 
  necessity 
  

   purely 
  miner 
  alogical. 
  The 
  first 
  attempt 
  at 
  the 
  production 
  of 
  a 
  

   geological 
  map, 
  that 
  is 
  of 
  one 
  in 
  which 
  the 
  classification 
  of 
  the 
  rocks 
  

   adopted 
  is 
  based 
  upon 
  the 
  periods 
  of 
  their 
  formation, 
  is 
  the 
  Sketch 
  

   Map 
  of 
  Murchison 
  and 
  Geikie, 
  published 
  in 
  1861. 
  The 
  production 
  of 
  

   this 
  was 
  rendered 
  possible 
  by 
  Peach's 
  important 
  discovery 
  of 
  Lower 
  

   Silurian 
  fossils 
  in 
  the 
  limestone 
  of 
  Durness. 
  We 
  are 
  now, 
  however, 
  

   in 
  a 
  position 
  to 
  show 
  that 
  the 
  rocks 
  of 
  the 
  Highlands, 
  far 
  from 
  being 
  

   of 
  great 
  and 
  unknown 
  antiquity, 
  include 
  representatives 
  of 
  a 
  great 
  

   variety 
  of 
  geological 
  periods. 
  The 
  rocks 
  of 
  Lower 
  Silurian 
  age 
  are 
  of 
  

   great 
  thickness, 
  and 
  cover 
  a 
  vast 
  extent 
  of 
  country; 
  and 
  beneath 
  them 
  

   we 
  find 
  two 
  older 
  series 
  of 
  strata 
  which 
  may, 
  possibly, 
  represent 
  the 
  

   Cambrian 
  and 
  the 
  Laurentian. 
  Of 
  the 
  existence 
  of 
  Upper 
  Silurian 
  

   rocks 
  in 
  the 
  Highlands 
  we 
  have 
  as 
  yet 
  no 
  certain 
  evidence 
  ; 
  but 
  the 
  

  

  