﻿VALLEY 
  OF 
  THE 
  ARDECHE 
  — 
  NEYRAC 
  — 
  THUEZ. 
  17 
  

  

  occur 
  there, 
  as 
  well 
  as 
  of 
  the 
  valley 
  of 
  Thuez. 
  It 
  has 
  a 
  distinct, 
  though 
  degraded 
  

   crater, 
  which 
  has 
  given 
  way 
  on 
  the 
  south-eastern 
  side. 
  The 
  sides 
  of 
  the 
  ridge 
  

   are 
  wooded 
  ; 
  but 
  I 
  traced 
  two 
  distinct 
  streams, 
  though 
  of 
  no 
  great 
  dimensions, 
  

   into 
  the 
  valley 
  of 
  the 
  Ardeche, 
  which 
  evidently 
  came 
  from 
  the 
  crater 
  of 
  Neyrac. 
  

   They 
  include 
  between 
  them 
  the 
  hamlet 
  which 
  bears 
  that 
  name 
  ; 
  and 
  one 
  at 
  

   least 
  of 
  them 
  (the 
  most 
  westerly) 
  may 
  be 
  traced 
  down 
  the 
  bed 
  of 
  an 
  insignificant 
  

   watercourse 
  in 
  the 
  granite, 
  down 
  to 
  the 
  valley, 
  where 
  it 
  has 
  formed 
  columnar 
  

   basalt 
  for 
  a 
  short 
  distance. 
  The 
  other 
  patches 
  of 
  basalt, 
  between 
  this 
  point 
  and 
  

   the 
  junction 
  of 
  the 
  Alignon, 
  are 
  probably 
  due 
  to 
  this 
  stream. 
  

  

  Opposite 
  to 
  the 
  village 
  of 
  Neyrac, 
  the 
  following 
  section 
  occurs 
  (Plate 
  III., 
  fig. 
  1), 
  

   which 
  attracted 
  my 
  attention 
  from 
  the 
  complete 
  state 
  of 
  aggregation 
  of 
  the 
  sand 
  

   and 
  gravel 
  intervening 
  between 
  the 
  basalt 
  and 
  the 
  granite 
  soil. 
  It 
  is 
  evidently 
  

   formed 
  by 
  the 
  concreting 
  action 
  of 
  calcareous 
  matter, 
  held 
  in 
  solution 
  by 
  the 
  

   carbonic 
  acid 
  which 
  occurs 
  abundantly 
  in 
  the 
  neighbourhood 
  upon 
  the 
  detritus 
  

   of 
  the 
  valley, 
  which 
  it 
  has 
  compacted 
  to 
  such 
  a 
  degree 
  as 
  to 
  form 
  a 
  kind 
  of 
  sand- 
  

   stone. 
  The 
  carbonic 
  acid 
  occurs 
  in 
  a 
  spring 
  rising 
  in 
  a 
  neighbouring 
  meadow, 
  

   and 
  having 
  a 
  temperature 
  of 
  no 
  less 
  than 
  78 
  0, 
  5, 
  whilst 
  a 
  small 
  spring, 
  between 
  it 
  

   and 
  the 
  river, 
  marked 
  only 
  51°. 
  The 
  elevation 
  of 
  the 
  mineral 
  spring 
  above 
  

   the 
  sea 
  is 
  1359 
  feet. 
  In 
  the 
  side 
  of 
  a 
  granite 
  hill, 
  close 
  to 
  the 
  hamlet 
  of 
  Neyrac, 
  

   is 
  a 
  dry 
  discharge 
  of 
  carbonic 
  acid 
  gas, 
  producing 
  a 
  suffocating 
  atmosphere, 
  

   similar 
  to 
  that 
  of 
  the 
  Grotto 
  del 
  Cane 
  near 
  Naples, 
  the 
  effects 
  of 
  which 
  have 
  been 
  

   elaborately 
  described 
  by 
  Faujas 
  and 
  other 
  older 
  writers 
  on 
  the 
  Vivarais. 
  

  

  Continuing 
  to 
  ascend 
  the 
  valley 
  from 
  Neyrac, 
  either 
  by 
  the 
  road 
  or 
  by 
  the 
  

   river, 
  objects 
  of 
  interest 
  multiply. 
  The 
  slopes 
  on 
  the 
  right 
  are 
  occupied 
  by 
  an 
  im- 
  

   mense 
  mass 
  of 
  red 
  cinders, 
  and 
  slaggy 
  lava 
  and 
  ejected 
  bombs, 
  indicating 
  the 
  

   close 
  proximity 
  of 
  a 
  crater, 
  round 
  the 
  outside 
  of 
  which, 
  indeed, 
  the 
  road 
  winds 
  

   for 
  some 
  distance, 
  — 
  whilst 
  the 
  valley 
  seems 
  absolutely 
  barred 
  in 
  advance 
  by 
  im- 
  

   mense 
  cliffs 
  of 
  basalt, 
  which 
  tower 
  over 
  rugged 
  rocks 
  of 
  granite, 
  amongst 
  which 
  

   the 
  river 
  struggles. 
  Across 
  it 
  has 
  been 
  thrown 
  an 
  extremely 
  slender 
  and 
  elegant 
  

   arch, 
  which 
  bears 
  the 
  name 
  of 
  Pont 
  du 
  Diable, 
  or 
  Pont 
  d'Enfer. 
  The 
  basaltic 
  cliffs 
  

   rise 
  to 
  a 
  height 
  of 
  nearly 
  300 
  feet 
  above 
  the 
  level 
  of 
  the 
  stream, 
  and 
  upon 
  the 
  

   plateau 
  which 
  they 
  form 
  is 
  the 
  mean 
  but 
  charmingly-situated 
  village 
  of 
  Thuez. 
  

   For 
  variety 
  of 
  outline, 
  luxuriance 
  of 
  vegetation, 
  rich 
  colouring, 
  and 
  romantic 
  

   forms 
  of 
  ground, 
  few 
  spots 
  can 
  be 
  compared 
  to 
  it 
  ; 
  and, 
  on 
  my 
  last 
  visit, 
  disre- 
  

   garding 
  the 
  very 
  indifferent 
  accommodation 
  which 
  it 
  affords, 
  I 
  made 
  it 
  the 
  prin- 
  

   cipal 
  centre 
  of 
  my 
  excursions. 
  A 
  short 
  description 
  will, 
  I 
  hope, 
  tend 
  to 
  give 
  a 
  

   distinct 
  idea 
  of 
  its 
  situation, 
  and 
  the 
  chief 
  points 
  of 
  picturesque 
  as 
  well 
  as 
  of 
  

   geological 
  interest. 
  

  

  The 
  reader 
  must 
  imagine 
  the 
  bed 
  of 
  a 
  rapid 
  stream 
  (the 
  Ardeche) 
  to 
  have 
  

   been 
  worked 
  out 
  through 
  the 
  lapse 
  of 
  ages, 
  by 
  natural 
  operations, 
  to 
  a 
  great 
  

   depth 
  in 
  a 
  soil 
  of 
  granite, 
  — 
  that 
  near 
  the 
  junction 
  with 
  a 
  tributary 
  stream 
  on 
  the 
  

   left, 
  a 
  powerful 
  volcano 
  suddenly 
  opened, 
  emitting 
  a 
  torrent 
  of 
  lava 
  which 
  filled 
  

  

  VOL. 
  XX. 
  PART 
  I. 
  E 
  

  

  