﻿VALLEY 
  OF 
  THE 
  ARDECHE 
  — 
  LA 
  BEAUME. 
  9 
  

  

  heat 
  being 
  gradually 
  spent, 
  the 
  currents 
  have 
  lost 
  their 
  mobility, 
  and 
  do 
  not 
  at 
  

   all 
  extend 
  themselves 
  into 
  the 
  plains. 
  When 
  we 
  trace 
  these 
  lava 
  currents 
  to 
  

   their 
  sources, 
  the 
  result 
  is 
  uniformly 
  the 
  discovery 
  of 
  a 
  crater, 
  often 
  formed 
  in 
  

   the 
  breast 
  of 
  a 
  mound 
  of 
  cinders, 
  whose 
  fiery-red 
  colour 
  will 
  bear 
  a 
  comparison, 
  

   in 
  point 
  of 
  apparent 
  freshness, 
  with 
  any 
  of 
  those 
  which 
  stud 
  the 
  flanks 
  of 
  Vesu- 
  

   vius, 
  or 
  the 
  more 
  prolific 
  Etna 
  ; 
  and, 
  in 
  very 
  many 
  instances, 
  the 
  precise 
  point 
  of 
  

   ejection 
  of 
  the 
  lava 
  may 
  be 
  ascertained 
  with 
  the 
  most 
  extreme 
  nicety, 
  and 
  all 
  

   the 
  accidents 
  of 
  its 
  subsequent 
  course 
  chronologically 
  traced. 
  Thus, 
  every 
  indi- 
  

   vidual 
  eruption 
  has 
  written, 
  as 
  it 
  were, 
  its 
  own 
  history, 
  although 
  the 
  relative 
  

   dates 
  cannot 
  always 
  be 
  determined. 
  It 
  is 
  an 
  inquiry 
  not 
  a 
  little 
  interesting 
  (at 
  

   least 
  upon 
  the 
  spot) 
  to 
  collect 
  these 
  rude 
  hieroglyphics, 
  which 
  form 
  a 
  chapter 
  of 
  

   the 
  ancient 
  records 
  of 
  our 
  globe, 
  and 
  register 
  events 
  amongst 
  the 
  most 
  recent 
  of 
  

   geological 
  change, 
  yet 
  of 
  which 
  no 
  trace 
  or 
  tradition 
  is 
  to 
  be 
  found 
  amongst 
  the 
  

   histories 
  of 
  the 
  Gallic 
  nations. 
  

  

  The 
  hamlet 
  of 
  La 
  Beaume 
  lies 
  on 
  the 
  right 
  bank 
  of 
  the 
  Ardeche, 
  almost 
  

   under 
  the 
  shadow 
  of 
  a 
  basaltic 
  colonnade, 
  which 
  stretches 
  parallel 
  to 
  flie 
  course 
  

   of 
  the 
  river, 
  but 
  leaves 
  a 
  level 
  space 
  between 
  the 
  foot 
  of 
  the 
  cliff 
  and 
  the 
  

   water, 
  along 
  which 
  the 
  public 
  road 
  passes. 
  The 
  section 
  (Plate 
  II., 
  fig. 
  3) 
  is 
  suffi- 
  

   ciently 
  remarkable 
  to 
  have 
  attracted 
  attention 
  ever 
  since 
  the 
  days 
  of 
  Faujas 
  St 
  

   Fond, 
  who 
  has 
  given 
  a 
  view 
  of 
  it, 
  but 
  with 
  great 
  inaccuracy 
  and 
  exaggeration. 
  

   Our 
  figure 
  shews 
  the 
  lava 
  stream 
  {a) 
  invested 
  with 
  a 
  coating 
  of 
  soil, 
  on 
  which 
  is 
  

   abundant 
  vegetation. 
  The 
  lava 
  rests 
  on 
  a 
  mass 
  of 
  scoriae 
  b, 
  which 
  again 
  reposes 
  

   upon 
  the 
  debris 
  and 
  vegetable 
  mould 
  c, 
  thus 
  marking 
  strongly 
  the 
  comparative 
  

   recency 
  of 
  the 
  eruption 
  which 
  produced 
  the 
  lava, 
  and 
  the 
  perfectly 
  natural 
  and 
  

   modern 
  condition 
  of 
  the 
  valley 
  into 
  which 
  it 
  flowed. 
  The 
  debris 
  and 
  soil 
  rest 
  

   upon 
  the 
  primitive 
  rock 
  (granite 
  or 
  gneiss) 
  which 
  is 
  exposed 
  in 
  the 
  bed 
  of 
  the 
  

   river 
  Ardeche. 
  

  

  The 
  contact 
  of 
  the 
  lava 
  and 
  scoriae 
  (beds 
  a 
  and 
  b) 
  presents 
  some 
  interesting 
  

   considerations 
  ; 
  and, 
  first, 
  to 
  account 
  for 
  the 
  so 
  frequent 
  phenomenon 
  of 
  the 
  

   superposition 
  of 
  lava 
  to 
  the 
  scoriae, 
  which, 
  being 
  its 
  scum 
  and 
  refuse, 
  we 
  should 
  

   rather 
  expect 
  to 
  find 
  upon 
  its 
  surface, 
  we 
  must 
  recall 
  the 
  peculiar 
  manner 
  

   of 
  progression 
  of 
  those 
  highly 
  viscid 
  lavas, 
  which 
  most 
  abound 
  in 
  scoriae 
  (for, 
  

   whilst 
  very 
  fluid, 
  there 
  is 
  little 
  or 
  no 
  scoria 
  deposited). 
  The 
  progression 
  is 
  ex- 
  

   ceedingly 
  slow, 
  and, 
  according 
  to 
  the 
  usual 
  laws 
  of 
  a 
  tenacious 
  fluid, 
  moving 
  

   over 
  a 
  rough 
  surface 
  with 
  great 
  friction, 
  the 
  surface 
  moves 
  faster 
  than 
  the 
  bottom 
  

   of 
  the 
  stream, 
  and 
  the 
  front 
  of 
  the 
  wave 
  of 
  lava 
  (that 
  which 
  would 
  be 
  presented 
  

   to 
  a 
  spectator 
  towards 
  whom 
  it 
  is 
  in 
  the 
  act 
  of 
  descending) 
  being 
  hard 
  and 
  scori- 
  

   aceous, 
  in 
  consequence 
  of 
  long 
  exposure 
  to 
  the 
  cooling 
  action 
  of 
  the 
  air, 
  is 
  con- 
  

   tinually 
  thrust 
  under 
  the 
  liquid 
  as 
  it 
  slowly 
  struggles 
  on, 
  and 
  its 
  place 
  is 
  supplied 
  

   by 
  freshly 
  floating 
  scum 
  from 
  the 
  surface, 
  which 
  finally 
  descends 
  the 
  front 
  of 
  

   VOL. 
  xx. 
  part 
  i. 
  c 
  

  

  