﻿1864.] 
  BIGSBY 
  MISSING 
  SEDIMENTARY 
  FORMATIONS. 
  209 
  

  

  all 
  these 
  deposits 
  being 
  horizontal 
  and 
  undisturbed 
  in 
  one 
  place, 
  

   but 
  fractured, 
  faulted, 
  displaced, 
  and 
  folded 
  in 
  another, 
  makes 
  the 
  

   study 
  of 
  the 
  Alpine 
  Jurassic 
  strata 
  extremely 
  difficult. 
  This 
  poly- 
  

   morphism 
  of 
  the 
  Jurassic 
  rocks 
  of 
  the 
  north 
  slope 
  of 
  the 
  Alps 
  we 
  

   find 
  represented 
  in 
  all 
  the 
  chains 
  of 
  complex 
  mountains, 
  that 
  is, 
  of 
  

   those 
  which 
  owe 
  their 
  existence 
  to 
  a 
  repetition 
  on 
  the 
  same 
  spot 
  of 
  

   the 
  phenomena 
  of 
  fracture 
  and 
  upheaval. 
  

  

  On 
  the 
  south 
  flank 
  of 
  the 
  Maritime 
  Alps*, 
  and 
  of 
  Piedmont 
  gene- 
  

   .rally, 
  there 
  are, 
  as 
  far 
  as 
  we 
  know, 
  only 
  two 
  great 
  Oolitic 
  horizons, 
  

   those 
  of 
  the 
  Oxford 
  Clay 
  and 
  the 
  Lias, 
  and 
  these 
  without 
  any 
  dis- 
  

   tinct 
  subdivisions. 
  Over 
  large 
  spaces, 
  as 
  on 
  Monte 
  .Rosa 
  f, 
  Monte 
  

   Cervino, 
  the 
  Gries 
  Pass, 
  in 
  the 
  Formazza 
  Valley, 
  and 
  at 
  Andermatt 
  

   (Switzerland), 
  the 
  Jurassic 
  strata, 
  by 
  metamorphism, 
  become 
  gneiss, 
  

   and 
  repose 
  on 
  another 
  and 
  older 
  form 
  of 
  that 
  rock. 
  On 
  the 
  

   south 
  slope 
  of 
  the 
  Italian 
  Alps 
  J, 
  as 
  well 
  as 
  in 
  Tuscany 
  and 
  in 
  the 
  

   Central 
  Apennines, 
  observers 
  are 
  agreed 
  that 
  the 
  upper 
  group 
  of 
  

   the 
  Jurassic 
  formation 
  is 
  wanting, 
  and 
  that 
  the 
  middle 
  and 
  lower 
  

   groups 
  are 
  very 
  poor, 
  and 
  represented 
  rather 
  by 
  some 
  species 
  of 
  fossils 
  

   than 
  by 
  distinct 
  beds; 
  that 
  the 
  Lias 
  is 
  greatly 
  developed 
  to 
  the 
  

   exclusion 
  of 
  the 
  rest 
  of 
  the 
  series 
  ; 
  and 
  that 
  the 
  distribution 
  of 
  the 
  

   fossils 
  of 
  these 
  different 
  stages 
  does 
  not 
  constitute 
  distinct 
  faunas 
  as 
  

   in 
  Western 
  and 
  Central 
  Europe. 
  

  

  As 
  to 
  Italy, 
  the 
  Jurassic 
  rocks, 
  in 
  the 
  two 
  districts 
  in 
  which 
  they 
  

   occur, 
  have 
  little 
  thickness, 
  and 
  are 
  defective 
  in 
  other 
  respects. 
  

  

  In 
  every 
  direction 
  from 
  the 
  Jura 
  Mountains, 
  and 
  not 
  southward 
  

   only, 
  this 
  formation 
  diminishes 
  in 
  completeness 
  §, 
  and 
  becomes 
  gra- 
  

   dually 
  simpler; 
  for 
  instance, 
  as 
  we 
  advance 
  eastward 
  through 
  

   "Wurtemberg, 
  Moravia, 
  and 
  Silesia, 
  until 
  we 
  arrive 
  on 
  the 
  frontier 
  

   of 
  Europe 
  and 
  Asia, 
  where 
  it 
  is 
  found 
  to 
  consist 
  of 
  only 
  a 
  single 
  

   term 
  of 
  the 
  series. 
  In 
  these 
  various 
  countries 
  the 
  second 
  group 
  of 
  

   Jurassic 
  rocks 
  is 
  the 
  sole 
  representative 
  of 
  the 
  epoch 
  ; 
  and 
  it 
  is 
  im- 
  

   portant 
  to 
  note 
  that 
  in 
  Germany 
  ||, 
  in 
  the 
  broad 
  interval 
  between 
  the 
  

   Rliine 
  and 
  Vienna, 
  the 
  petrographical 
  characters 
  of 
  the 
  Jurassic 
  

   beds, 
  their 
  local 
  divisions, 
  stratification, 
  and 
  fauna, 
  all 
  become 
  in- 
  

   capable 
  of 
  detailed 
  comparison 
  with 
  the 
  type 
  of 
  the 
  Jura 
  chain, 
  so 
  

   great 
  and 
  multiplied 
  have 
  been 
  the 
  changes 
  in 
  the 
  constitution 
  of 
  

   this 
  formation 
  from 
  movements 
  of 
  oscillation 
  of 
  level. 
  

  

  In 
  the 
  South 
  of 
  Erance 
  %, 
  and 
  in 
  various 
  other 
  parts 
  of 
  that 
  

   empire, 
  the 
  Oolite 
  presents 
  numerous 
  irregularities 
  in 
  the 
  deposi- 
  

   tion 
  of 
  its 
  stages 
  and 
  groups 
  ; 
  and 
  there 
  are 
  many 
  blanks, 
  as 
  in 
  the 
  

   Departments 
  of 
  Calais, 
  the 
  Var, 
  and 
  the 
  Gard. 
  The 
  Upper 
  Oolite 
  

   is 
  wanting 
  on 
  the 
  east 
  flank 
  of 
  the 
  Beaujolais 
  Mountains 
  and 
  on 
  the 
  

   south 
  side 
  of 
  the 
  Cote 
  d'Or, 
  while 
  in 
  the 
  Valleys 
  of 
  the 
  Isere, 
  of 
  the 
  

   Drac, 
  and 
  in 
  the 
  Drome 
  the 
  lower 
  group 
  is 
  lost 
  **. 
  

  

  * 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  vii. 
  p. 
  281. 
  

   t 
  Ibid. 
  (Sismonda) 
  vol. 
  vii. 
  p. 
  226. 
  J 
  Ibid. 
  vol. 
  vii. 
  p. 
  337. 
  

  

  § 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  vii. 
  p. 
  677. 
  || 
  Ibid. 
  vol. 
  vii. 
  p. 
  703. 
  

   •ff 
  Dufrenoy 
  and 
  De 
  Beaumont, 
  ' 
  Explication 
  Carte 
  Geol. 
  de 
  France,' 
  vol. 
  ii. 
  

   p. 
  555. 
  

   ** 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres,' 
  vol. 
  vi. 
  p. 
  559, 
  vol. 
  viii. 
  p. 
  193. 
  

  

  