﻿194 
  PROF. 
  J. 
  W. 
  JUJDD 
  OX 
  THE 
  TERTIARY 
  VOLCANOES 
  

  

  (ibid. 
  p. 
  134), 
  and 
  of 
  Skye 
  (ibid. 
  pp. 
  97, 
  98, 
  109, 
  &c). 
  Especially 
  

   significant 
  is 
  the 
  admission 
  that 
  in 
  Strath 
  we 
  have 
  evidence 
  of 
  whole 
  

   mountain 
  masses 
  of 
  volcanic 
  agglomerate, 
  and 
  the 
  belief 
  of 
  the 
  author 
  

   of 
  the 
  memoir 
  that 
  these 
  indicate 
  the 
  existence 
  of 
  a 
  great 
  funnel 
  

   or 
  vent, 
  originally 
  filled 
  with 
  these 
  materials, 
  which 
  was 
  no 
  less 
  

   than 
  two 
  miles 
  in 
  diameter 
  (ibid. 
  p. 
  108). 
  These 
  accounts 
  may 
  be 
  

   compared 
  with 
  those 
  which 
  I 
  gave 
  in 
  1874 
  (see 
  Q. 
  J. 
  G. 
  S. 
  1874, 
  

   pp. 
  239-242 
  et 
  seq.). 
  Especially 
  close 
  is 
  the 
  agreement 
  between 
  

   the 
  account 
  given 
  of 
  the 
  volcanic 
  breccias 
  of 
  Eum 
  (compare 
  

   T. 
  It. 
  S, 
  E. 
  1888, 
  p. 
  134, 
  and 
  Q. 
  J. 
  G. 
  S. 
  1874, 
  p. 
  253). 
  It 
  is 
  

   perfectly 
  true, 
  as 
  was 
  pointed 
  out 
  in 
  1874, 
  and 
  insisted 
  upon 
  in 
  the 
  

   recent 
  memoir, 
  that 
  at 
  a 
  distance 
  from 
  the 
  great 
  centres 
  of 
  eruption 
  

   the 
  lava-sheets 
  are 
  usually 
  separated 
  only 
  by 
  thin 
  and 
  unimportant 
  

   layers 
  of 
  tuff. 
  

  

  (3) 
  The 
  great 
  intrusive 
  masses 
  so 
  often 
  presenting 
  a 
  horizontal 
  

   disposition 
  and 
  pseudo-stratification, 
  exhibiting 
  evidence 
  of 
  successive 
  

   extrusion, 
  and 
  the 
  phenomena 
  of 
  segregation 
  or 
  contemporaneous 
  

   veins, 
  were 
  described 
  in 
  1874 
  (see 
  Q. 
  J. 
  G. 
  S. 
  1874, 
  pp. 
  238-252, 
  

   and 
  pi. 
  xxiii. 
  figs. 
  1, 
  3, 
  4, 
  5). 
  All 
  the 
  details 
  are 
  fully 
  confirmed 
  

   in 
  the 
  recentlv 
  published 
  memoir 
  (T. 
  E. 
  S. 
  E. 
  1888, 
  pp. 
  111-143 
  and 
  

   151-164). 
  

  

  (4) 
  In 
  1874 
  Mr. 
  Gilbert 
  had 
  not 
  described 
  the 
  interesting 
  phe- 
  

   nomena 
  to 
  which 
  he 
  proposed 
  to 
  give 
  the 
  name 
  of 
  " 
  laccolites 
  ; 
  " 
  

   but 
  the 
  lenticular 
  form 
  of 
  the 
  great 
  felsitic 
  intrusions 
  was 
  clearly 
  

   pointed 
  out 
  in 
  my 
  paper 
  (Q. 
  J. 
  G. 
  S. 
  1S74. 
  pp. 
  268, 
  269), 
  and 
  the 
  

   concentric 
  structure 
  of 
  some 
  of 
  the 
  more 
  acid 
  rock 
  masses, 
  so 
  closely 
  

   resembling 
  the 
  internal 
  character 
  of 
  the 
  domitic 
  Puys 
  in 
  Auvergne, 
  

   was 
  also 
  indicated 
  (compare 
  Q. 
  J. 
  G. 
  S. 
  1874, 
  p. 
  245 
  (footnote), 
  and 
  

   T. 
  E. 
  S.E. 
  1888, 
  p. 
  162). 
  

  

  (5) 
  The 
  evidences 
  of 
  metamorphism 
  produced 
  in 
  both 
  sedimen- 
  

   tary 
  and 
  volcanic 
  rocks 
  by 
  the 
  great 
  intrusive 
  masses, 
  which 
  was 
  

   pointed 
  out 
  in 
  1874, 
  is 
  verv 
  clearly 
  and 
  fullv 
  described 
  in 
  1888 
  

   (compare 
  Q. 
  I. 
  G. 
  S. 
  1874, 
  pn. 
  251, 
  252, 
  &c, 
  and 
  T. 
  E. 
  S. 
  E. 
  1888, 
  

   pp. 
  101-103, 
  138, 
  165-167, 
  &c). 
  

  

  (6) 
  The 
  very 
  full 
  accounts 
  of 
  later 
  eruptions, 
  like 
  that 
  of 
  S'Airde 
  

   Beinn 
  (Sarsta 
  Beinn) 
  and 
  other 
  smaller 
  outbursts 
  composed 
  of 
  dif- 
  

   ferent 
  kinds 
  of 
  acid 
  and 
  basic 
  rock, 
  and 
  seen 
  bursting 
  through 
  the 
  

   basalt 
  of 
  the 
  great 
  plateaux, 
  as 
  given 
  in 
  the 
  recent 
  memoir, 
  are 
  in 
  

   full 
  accord 
  with 
  the 
  earlier 
  descriptions 
  (compare 
  Q,. 
  J. 
  G. 
  S. 
  1874, 
  

   pp. 
  260-267, 
  and 
  T. 
  E. 
  S. 
  E. 
  1388, 
  pp. 
  101-103, 
  177, 
  178, 
  &c). 
  

  

  C. 
  The 
  Subaerial 
  Origin 
  of 
  the 
  Lavas 
  and 
  Tvffs, 
  and 
  the 
  Tertiary 
  

  

  Age 
  of 
  both 
  the 
  Plutonic 
  and 
  the 
  Volcanic 
  HocJiS. 
  

  

  My 
  conclusions 
  on 
  these 
  subjects 
  may 
  be 
  summarized 
  as 
  fol- 
  

   lows 
  : 
  — 
  

  

  (1) 
  There 
  is 
  a 
  total 
  absence 
  of 
  any 
  contemporaneous 
  marine 
  de- 
  

   posits 
  intercalated 
  among 
  the 
  lavas 
  of 
  the 
  district 
  ; 
  but, 
  on 
  the 
  con- 
  

   trary, 
  we 
  find 
  many 
  unmistakable 
  proofs 
  that 
  the 
  lavas 
  and 
  tuffs 
  

   were 
  ejected 
  under 
  subaerial 
  conditions. 
  These 
  proofs 
  consist 
  in 
  the 
  

  

  