﻿302 
  J. 
  W. 
  JT7DD 
  ON 
  THE 
  SECONDARY 
  ROCKS 
  OE 
  SCOTLAND. 
  

  

  of 
  one 
  and 
  the 
  same 
  origin. 
  He 
  suggested 
  a 
  doubt 
  whether 
  the 
  

   older 
  granites 
  belonged 
  to 
  so 
  recent 
  a 
  period 
  as 
  that 
  assigned 
  to 
  

   them 
  by 
  the 
  author. 
  

  

  Prof. 
  Maseeltne 
  considered 
  that 
  this 
  paper 
  would 
  go 
  far 
  towards 
  

   settling 
  the 
  question 
  between 
  one 
  half 
  of 
  the 
  penologists 
  of 
  the 
  

   present 
  time 
  and 
  the 
  other 
  half. 
  He 
  accepted 
  the 
  author's 
  view 
  as 
  

   to 
  the 
  Tertiary 
  origin 
  of 
  the 
  granite, 
  inconsistent 
  though 
  it 
  was 
  

   with 
  the 
  view 
  of 
  the 
  age 
  of 
  granite 
  maintained 
  by 
  the 
  school 
  of 
  

   Eichthofen. 
  This 
  paper 
  exemplified 
  the 
  necessity 
  of 
  combining 
  the 
  

   observations 
  of 
  the 
  geologist 
  in 
  the 
  field 
  with 
  those 
  of 
  the 
  mine- 
  

   ralogist 
  in 
  his 
  laboratory. 
  

  

  Mr. 
  Seelet 
  remarked 
  on 
  the 
  importance 
  of 
  this 
  paper 
  as 
  furnish- 
  

   ing 
  lines 
  of 
  departure 
  for 
  investigating 
  the 
  early 
  physical 
  history 
  of 
  

   the 
  earth. 
  He 
  had 
  ascertained 
  that 
  the 
  old 
  lines 
  of 
  volcanic 
  activity 
  

   corresponded 
  with 
  the 
  agonic 
  lines 
  of 
  magnetism 
  ; 
  and 
  the 
  paper 
  

   afforded 
  data 
  which 
  would 
  assist 
  in 
  drawing 
  conclusions 
  as 
  to 
  the 
  

   changes 
  in 
  the 
  position 
  of 
  the 
  earth's 
  axis 
  by 
  a 
  comparison 
  of 
  these 
  

   lines 
  with 
  those 
  of 
  the 
  magnetic 
  currents. 
  

  

  Mr. 
  W. 
  "W. 
  Smxth 
  congratulated 
  himself 
  on 
  again 
  hearing 
  of 
  

   intrusive 
  granitic 
  dykes 
  such 
  as 
  recalled 
  the 
  earlier 
  days 
  of 
  the 
  

   Society, 
  and 
  tended 
  to 
  dispel 
  some 
  accepted 
  ideas 
  as 
  to 
  metamor- 
  

   phism. 
  He 
  adduced 
  the 
  recent 
  deposits 
  of 
  Etna 
  and 
  Vesuvius 
  in 
  

   illustration 
  of 
  the 
  specimens 
  exhibited 
  by 
  the 
  author. 
  

  

  Mr. 
  Blaneord 
  suggested 
  that 
  there 
  might 
  be 
  in 
  this 
  case 
  only 
  one 
  

   form 
  of 
  the 
  existence 
  of 
  granite. 
  When 
  the 
  gradual 
  passage 
  from 
  

   schists 
  into 
  granite 
  could 
  be 
  traced, 
  there 
  could 
  be 
  little 
  doubt 
  of 
  its 
  

   origin 
  ; 
  and 
  even 
  in 
  its 
  eruptive 
  form 
  the 
  granite 
  might 
  be 
  only 
  the 
  

   result 
  of 
  a 
  very 
  complete 
  metamorphism. 
  He 
  agreed 
  with 
  the 
  author 
  

   as 
  to 
  the 
  probability 
  of 
  the 
  great 
  horizontal 
  outflows 
  of 
  basalt 
  being 
  

   subaerial, 
  and 
  not 
  subaqueous, 
  and 
  instanced 
  analogous 
  examples 
  in 
  

   India. 
  

  

  Mr. 
  Tiddeman, 
  referring 
  to 
  the 
  great 
  length 
  of 
  time 
  alluded 
  to 
  by 
  

   the 
  author 
  as 
  represented 
  in 
  the 
  volcanic 
  rocks 
  of 
  Scotland, 
  wished 
  

   to 
  call 
  attention 
  to 
  the 
  rocks 
  in 
  the 
  neighbourhood 
  of 
  Seuir-na- 
  

   Gillean 
  in 
  Skye, 
  which 
  consisted 
  partly 
  of 
  basaltic 
  lavas 
  of 
  Miocene 
  

   age. 
  These 
  appeared 
  to 
  be 
  tilted 
  by 
  the 
  syenite 
  of 
  Marscou 
  &c. 
  ; 
  

   and 
  upon 
  both 
  rested 
  unconformably 
  a 
  great 
  thickness 
  of 
  hyper- 
  

   sthene. 
  But 
  furthermore, 
  the 
  base 
  of 
  this 
  latest 
  rock 
  appeared 
  to 
  

   be 
  thrown 
  down 
  by 
  a 
  fault 
  with 
  a 
  displacement 
  of 
  some 
  thousands 
  

   of 
  feet. 
  

  

  Mr. 
  Jedd, 
  though 
  admitting 
  there 
  were 
  two 
  sides 
  to 
  the 
  question 
  

   as 
  to 
  the 
  origin 
  of 
  granite, 
  could 
  not 
  regard 
  intrusive 
  masses 
  of 
  

   granite 
  passing 
  through 
  rocks 
  of 
  different 
  mineral 
  constitution 
  as 
  

   the 
  metamorphosed 
  representatives 
  of 
  each. 
  He 
  briefly 
  replied 
  to 
  

   the 
  other 
  points 
  raised 
  in 
  the 
  discussion. 
  

  

  