﻿212 
  

  

  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Mar. 
  9, 
  

  

  M. 
  Hebert* 
  also 
  points 
  out 
  in 
  a 
  striking 
  manner 
  the 
  variable 
  

   nature 
  of 
  the 
  Jurassic 
  rocks 
  of 
  France, 
  from 
  the 
  frequent 
  oscillations 
  

   then 
  affecting 
  the 
  north 
  of 
  that 
  empire. 
  In 
  the 
  Grindelwaldt 
  

   (Switzerland), 
  and 
  in 
  large 
  areas 
  around, 
  M. 
  Escher 
  von 
  der 
  Linth 
  

   found 
  Jurassic 
  beds 
  superposed 
  directly 
  on 
  granite 
  and 
  subcrystal- 
  

   line 
  rocks. 
  In 
  the 
  Valley 
  of 
  St. 
  Ortee 
  Mannee, 
  and 
  at 
  Perdas 
  de 
  

   Fogue 
  (Isle 
  of 
  Sardinia), 
  a 
  magnesian 
  limestone 
  (Jurassic) 
  covers 
  

   horizontally 
  carbonaceous 
  shales, 
  which, 
  in 
  their 
  turn, 
  rest 
  on 
  

   Lower 
  Silurian, 
  and 
  thus 
  indicate 
  two 
  separate 
  and 
  large 
  blanks. 
  

   We 
  miss 
  Lias, 
  Trias, 
  Permian, 
  Devonian, 
  &c. 
  J 
  ; 
  and 
  I 
  infer, 
  among 
  

   other 
  things, 
  that 
  a 
  Carboniferous 
  basin 
  laid 
  long 
  bare 
  to 
  the 
  sky 
  ; 
  

   but 
  not 
  without 
  effect, 
  as 
  we 
  shall 
  see. 
  

  

  In 
  the 
  South 
  of 
  France, 
  M. 
  Fournet§ 
  met 
  with 
  Oxford 
  Clay 
  

   resting 
  on 
  Trias, 
  near 
  Valence, 
  and 
  likewise 
  near 
  St. 
  Ambroux. 
  

  

  In 
  Poland, 
  Oolite 
  is 
  incumbent 
  on 
  Muschelkalk, 
  and 
  the 
  sand- 
  

   stone 
  of 
  its 
  third 
  stage 
  on 
  both 
  porphyry 
  and 
  melaphyr 
  || 
  ; 
  Ox- 
  

   fordian 
  also 
  rests 
  on 
  Muschelkalk 
  in 
  the 
  Himalayas 
  4". 
  The 
  Ju- 
  

   rassic 
  series 
  is 
  in 
  two 
  places 
  on 
  Carboniferous 
  shales 
  in 
  Sardinia 
  **, 
  

   and 
  once 
  in 
  Poland 
  f 
  f. 
  In 
  the 
  latter 
  country 
  we 
  find 
  it 
  on 
  Carbo- 
  

   niferous 
  sandstones, 
  as 
  well 
  as 
  in 
  France. 
  

  

  Fig. 
  7. 
  — 
  Section 
  at 
  Rochebelle, 
  near 
  Alais 
  (after 
  Dufrenoy 
  and 
  

  

  De 
  Beaumont). 
  

  

  Metamorphic 
  rocks. 
  

   a. 
  Alluvium. 
  

  

  Coal-measures. 
  

  

  b. 
  Jurassic 
  limestone. 
  

  

  c. 
  Lower 
  Chalk. 
  

  

  In 
  Russia 
  we 
  have 
  seen 
  that 
  the 
  Oxfordian 
  always 
  rests 
  either 
  

   on 
  Permian 
  or 
  Carboniferous 
  (Murchison, 
  ^>assm), 
  and 
  in 
  the 
  

   Mendip 
  Hills 
  %% 
  (Gloucestershire) 
  on 
  the 
  latter. 
  In 
  the 
  Napoleon 
  

   Quarry 
  §§ 
  of 
  the 
  Bas 
  Boulonnais 
  this 
  formation 
  is 
  met 
  with 
  on 
  

   Lower 
  Silurian, 
  with, 
  of 
  course, 
  the 
  omission 
  of 
  many 
  great 
  epochs. 
  

  

  I 
  have 
  now 
  shown 
  how 
  variable 
  in 
  quantity 
  and 
  constitution 
  is 
  

  

  * 
  Comptes 
  Rendus, 
  vol. 
  xliii. 
  p. 
  853. 
  

  

  t 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  vii. 
  p. 
  553. 
  

  

  t 
  Delia 
  Marmora, 
  ' 
  Voyage 
  en 
  Sardaigne,' 
  vol. 
  i. 
  p. 
  1 
  11 
  . 
  

  

  § 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  viii. 
  p. 
  193. 
  

  

  || 
  Ibid. 
  vol. 
  vii. 
  p. 
  553. 
  

  

  •jf 
  Strachy, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  vii. 
  p. 
  306. 
  

  

  ** 
  Delia 
  Marmora, 
  'Sardaigne,' 
  vol. 
  i. 
  p. 
  111. 
  

  

  ft 
  D'Archiac. 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  vii. 
  p. 
  553. 
  

  

  XX 
  Ramsay, 
  Mem. 
  Geol. 
  Surv. 
  Great 
  Britain, 
  vol. 
  i. 
  p. 
  320. 
  

  

  §§ 
  Dufrenoy 
  and 
  De 
  Beaumont, 
  'Explication 
  Carte 
  Geol.' 
  vol. 
  ii. 
  p. 
  155. 
  

  

  