﻿606 
  F 
  A. 
  Ferret 
  — 
  The 
  Ascent 
  of 
  Lava. 
  

  

  In 
  seeking 
  to 
  explain 
  these 
  anomalies 
  we 
  may 
  safely 
  assume 
  

   two 
  things, 
  viz., 
  some 
  guiding 
  principle 
  or 
  directive 
  force, 
  

   which 
  determines 
  and 
  maintains 
  the 
  upward 
  direction 
  of 
  prog- 
  

   ress 
  as 
  a 
  compass 
  points 
  to 
  the 
  north 
  ; 
  and, 
  second, 
  some 
  mode 
  of 
  

   action, 
  — 
  some 
  excavating 
  agent 
  other 
  than 
  simple 
  heat 
  and 
  

   pressure, 
  — 
  which 
  has 
  not 
  yet 
  been 
  considered. 
  

  

  Beginning 
  with 
  the 
  latter, 
  we 
  may 
  ask 
  ourselves 
  if 
  there 
  is 
  

   anything 
  at 
  the 
  upper 
  level, 
  where 
  the 
  progression 
  takes 
  place, 
  

   which 
  is 
  not 
  to 
  be 
  found 
  at 
  the 
  other 
  contact 
  surfaces 
  ? 
  The 
  

   answer 
  is 
  — 
  gas. 
  

  

  We 
  have 
  here 
  another 
  demonstration, 
  and 
  a 
  notable 
  one, 
  of 
  

   the 
  importance 
  of 
  the 
  gaseous 
  element 
  in 
  the 
  dynamics 
  of 
  vol- 
  

  

  Fig. 
  1. 
  

  

  

  _\\\\\\\n\\\^§^ 
  

  

  Fig. 
  1. 
  Lava 
  column 
  with 
  compressed 
  gaseous 
  head, 
  fluxing 
  its 
  way- 
  

   upward 
  through 
  solid 
  strata. 
  

  

  canic 
  action. 
  If 
  the 
  lava 
  were 
  a 
  simple 
  liquid 
  and 
  its 
  function 
  

   purely 
  hydrostatic, 
  as 
  has 
  sometimes 
  been 
  contended, 
  the 
  up- 
  

   ward 
  progression, 
  as 
  observed, 
  could 
  not 
  occur. 
  It 
  is 
  the 
  escape 
  

   of 
  free 
  gas 
  which 
  results, 
  as 
  we 
  shall 
  see, 
  in 
  the 
  formation 
  of 
  

   the 
  tunnel, 
  but 
  before 
  taking 
  up 
  that 
  phase 
  of 
  the 
  subject, 
  we 
  

   may 
  realize 
  that 
  we 
  have 
  also 
  discovered 
  the 
  guiding 
  principle 
  

   — 
  the 
  directive 
  force 
  which 
  determines 
  and 
  maintains 
  the 
  up- 
  

   ward 
  way. 
  This 
  lies 
  in 
  the 
  gravitative 
  adjustment 
  of 
  gas 
  and 
  

   lava, 
  — 
  the 
  gas, 
  by 
  its 
  lightness, 
  places 
  itself 
  above 
  the 
  lava 
  and, 
  

   constituting, 
  as 
  it 
  does, 
  the 
  active 
  boring 
  agent, 
  the 
  direction 
  

   of 
  progression 
  will 
  and 
  must 
  be 
  upward 
  ; 
  nothing 
  could 
  be 
  

   simpler. 
  

  

  As 
  to 
  the 
  modus 
  operandi 
  of 
  this 
  trepanning 
  by 
  the 
  gas- 
  

   headed 
  lava, 
  it 
  is 
  obvious 
  that 
  we 
  must 
  consider 
  the 
  nature 
  of 
  

   the 
  material 
  to 
  be 
  perforated. 
  If 
  this 
  consists 
  of 
  strata 
  of 
  solid 
  

   rock 
  the 
  gases 
  will 
  be 
  largely 
  retained 
  above 
  the 
  lava 
  column 
  

  

  