﻿OF 
  THE 
  WEST!. 
  EX 
  ISLES 
  OF 
  SCOT 
  TAN 
  D. 
  215 
  

  

  In 
  several 
  other 
  passages 
  of 
  the 
  same 
  Report 
  Captain 
  Dutton 
  clearly 
  

   intimates 
  that 
  his 
  belief 
  in 
  " 
  fissure 
  -eruptions 
  " 
  was 
  most 
  seriously 
  

   shaken 
  by 
  what 
  he 
  saw 
  in 
  the 
  Sandwich 
  Islands. 
  

  

  VI. 
  Conclusion. 
  

  

  But 
  even 
  if 
  it 
  were 
  conclusively 
  demonstrated 
  that 
  the 
  basalts 
  of 
  

   the 
  Snake-River 
  area, 
  of 
  the 
  Uinkaret 
  plateau, 
  of 
  the 
  Highlands 
  of 
  

   Utah, 
  and 
  of 
  the 
  plains 
  of 
  New 
  Mexico, 
  could 
  only 
  have 
  originated 
  

   in 
  " 
  fissure-eruptions," 
  I 
  fail 
  to 
  see 
  how 
  this 
  affects 
  the 
  question 
  of 
  

   the 
  existence 
  of 
  great 
  volcanoes 
  in 
  the 
  Western 
  Isles 
  of 
  Scotland. 
  

   It 
  would 
  seem 
  that 
  districts 
  which 
  have 
  only 
  been 
  hastily 
  traversed 
  

   are 
  scarcelj 
  r 
  likely 
  to 
  afford 
  evidence 
  that 
  can 
  be 
  placed 
  in 
  comparison 
  

   with 
  the 
  clear 
  and 
  unmistakable 
  indications 
  found 
  in 
  a 
  district 
  

   which 
  has 
  been 
  made 
  the 
  scene 
  of 
  careful 
  and 
  searching 
  investigation. 
  

  

  It 
  is 
  very 
  difficult 
  to 
  understand 
  what 
  idea 
  the 
  advocates 
  of 
  

   " 
  fissnre-eruptions 
  " 
  wish 
  to 
  convey 
  by 
  their 
  favourite 
  phrase. 
  If 
  by 
  

   using 
  it 
  they 
  intend 
  to 
  imply 
  that 
  volcanic 
  action 
  takes 
  place 
  along 
  

   lines 
  of 
  fissure, 
  I 
  know 
  of 
  no 
  vulcanologist 
  who 
  has 
  ever 
  denied 
  it. 
  

   In 
  that 
  sense 
  all 
  volcanic 
  outbursts 
  are 
  " 
  fissure-eruptions." 
  If 
  it 
  be 
  

   meant 
  to 
  indicate 
  that 
  the 
  outflow 
  of 
  lava 
  from 
  a 
  vent 
  may 
  take 
  

   place 
  with 
  little 
  or 
  no 
  explosive 
  action, 
  this 
  is 
  equally 
  a 
  part 
  of 
  the 
  

   creed 
  of 
  all 
  vulcanologists. 
  

  

  But 
  if, 
  on 
  the 
  other 
  hand, 
  it 
  be 
  intended 
  to 
  assert 
  that, 
  either 
  

   during 
  the 
  Tertiarj 
  7 
  or 
  any 
  earlier 
  geological 
  period, 
  there 
  is 
  evidence 
  

   that 
  lavas 
  were 
  extruded 
  upon 
  the 
  earth's 
  surface 
  under 
  wholly 
  

   different 
  conditions 
  from 
  those 
  which 
  prevail 
  in 
  the 
  volcanic 
  areas 
  of 
  

   the 
  present 
  day, 
  this 
  is 
  a 
  proposition 
  which 
  I 
  utterly 
  deny 
  : 
  — 
  and 
  

   I 
  challenge 
  the 
  supporters 
  of 
  "fissure-eruptions" 
  to 
  bring 
  forward 
  

   a 
  particle 
  of 
  evidence 
  in 
  its 
  support 
  *. 
  

  

  The 
  study 
  of 
  the 
  Hawaian 
  volcanoes 
  has 
  long 
  ago 
  shown 
  how 
  

   remarkably 
  the 
  effusive 
  action, 
  resulting 
  in 
  the 
  outwelling 
  of 
  suc- 
  

   cessive 
  sheets 
  of 
  lava, 
  may 
  preponderate 
  over 
  explosive 
  action 
  at 
  

   certain 
  volcanic 
  vents. 
  

  

  Captain 
  Dutton 
  very 
  justly 
  remarks 
  that 
  "the 
  long 
  and 
  gentle 
  

   slopes 
  of 
  Mauna 
  Loa 
  are 
  merely 
  the 
  surface 
  of 
  a 
  mass 
  of 
  lavas 
  which 
  

   have 
  been' 
  piled 
  over 
  each 
  other 
  in 
  the 
  form 
  of 
  lava-streams, 
  poured 
  

   out 
  at 
  intervals 
  throughout 
  an 
  epoch 
  of 
  vast 
  but 
  unknown 
  duration. 
  

   These 
  great 
  lava-floods 
  burst 
  out 
  seemingly 
  in 
  a 
  most 
  capricious 
  

   manner, 
  here 
  there 
  and 
  everywhere. 
  They 
  break 
  out 
  far 
  more 
  fre- 
  

   quently 
  at 
  or 
  near 
  the 
  summit 
  than 
  upon 
  the 
  lower 
  flanks 
  of 
  the 
  

   mountain, 
  and 
  so 
  vast 
  is 
  the 
  amount 
  of 
  lava 
  outpoured 
  at 
  each 
  

   eruption, 
  that 
  the 
  streams 
  often 
  reach 
  literally 
  from 
  the 
  summit 
  to 
  

  

  [ 
  * 
  My 
  difficulty 
  in 
  understanding 
  what 
  is 
  meant 
  by 
  a 
  " 
  fissure-eruption 
  " 
  

   has 
  been 
  only 
  increased 
  by 
  the 
  explanations 
  offered 
  after 
  the 
  reading 
  of 
  the 
  

   present 
  memoir 
  (see 
  page 
  219). 
  It 
  is 
  said 
  that 
  the 
  lavas 
  have 
  not 
  flowed 
  out 
  

   " 
  directly 
  from 
  long 
  open 
  fissures, 
  but 
  that 
  vents 
  were 
  established 
  on 
  such 
  

   fissures, 
  sometimes 
  of 
  considerable 
  size, 
  with 
  the 
  usual 
  accompaniment 
  of 
  vol- 
  

   canic 
  eruptions." 
  I 
  presume, 
  then, 
  that 
  when 
  an 
  outburst 
  occurs 
  at 
  the 
  summit- 
  

   crater 
  of 
  Etna, 
  it 
  must 
  be 
  called 
  a 
  volcanic 
  eruption, 
  but 
  when 
  it 
  takes 
  place 
  

   on 
  the 
  flanks 
  of 
  the 
  mountain, 
  like 
  that 
  of 
  1874, 
  so 
  well 
  described 
  by 
  Silvestri, 
  

   it 
  is 
  a^z'ss^e-eruption 
  !] 
  

  

  