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  F. 
  A. 
  Ferret— 
  The 
  Ascent 
  of 
  Lava. 
  

  

  flow 
  of 
  gas 
  through 
  the 
  lava 
  column, 
  thus 
  continuously 
  bring- 
  

   ing 
  up 
  heat 
  from 
  below. 
  

  

  In 
  fig. 
  2 
  the 
  lava 
  is 
  represented 
  as 
  eating 
  its 
  way 
  upward 
  

   through 
  the 
  chaotic 
  materials 
  obstructing 
  the 
  conduit 
  of 
  a 
  vol- 
  

   cano 
  as 
  the 
  result 
  of 
  the 
  last 
  eruption 
  — 
  the 
  lava 
  rising 
  to 
  re- 
  

   establish 
  communication 
  with 
  the 
  crater 
  and 
  inaugurate 
  a 
  new 
  

   eruptive 
  phase 
  after 
  a 
  period 
  of 
  repose. 
  The 
  sketch 
  repro- 
  

   duces 
  the 
  actual 
  condition 
  of 
  Vesuvius 
  where, 
  after 
  seven 
  years 
  

   of 
  external 
  repose, 
  during 
  which 
  time 
  the 
  conduit 
  has 
  been 
  

   blocked, 
  the 
  lava 
  has, 
  at 
  last, 
  virtually 
  reached 
  the 
  crater. 
  Its 
  

   gradual 
  approach, 
  by 
  the 
  process 
  here 
  described, 
  has 
  for 
  many 
  

   months 
  been 
  visibly 
  manifested 
  by 
  a 
  progressive 
  increase 
  in 
  

   the 
  temperature 
  and 
  volume 
  of 
  the 
  f 
  umarolic 
  emanations 
  at 
  the 
  

   crater 
  bottom 
  and 
  especially 
  by 
  repeated 
  collapses 
  indicative 
  of 
  

   the 
  subterranean 
  stoping. 
  

  

  We 
  may 
  conclude 
  that 
  the 
  progression 
  of 
  a 
  lava 
  column 
  and 
  

   its 
  direction 
  are 
  determined 
  by 
  the 
  gaseous 
  emanation. 
  

  

  Posillipo, 
  Naples, 
  September, 
  1913. 
  

  

  