﻿1864.] 
  BIGSBY— 
  MISSING 
  SEDIMENTARY 
  FORMATIONS. 
  201 
  

  

  an 
  immense 
  gap 
  in 
  the 
  series 
  of 
  formations. 
  Of 
  the 
  condition 
  of 
  the 
  

   ancient 
  surfaces 
  we 
  have 
  no 
  evidences 
  ; 
  but 
  we 
  now 
  see 
  it 
  covered 
  

   with 
  stratified 
  drift 
  of 
  sand 
  and 
  clay, 
  sometimes 
  1000 
  feet 
  above 
  the 
  

   present 
  level 
  of 
  the 
  lake." 
  * 
  

  

  In 
  Nova 
  Scotia 
  there 
  is, 
  according 
  to 
  Dr. 
  Dawson 
  f, 
  no 
  formation 
  

   between 
  the 
  Drift 
  and 
  the 
  Upper 
  Trias. 
  

  

  An 
  important 
  section, 
  running 
  550 
  miles 
  due 
  east 
  through 
  the 
  States 
  

   of 
  Mississippi, 
  Alabama, 
  and 
  Georgia, 
  from 
  Yicksburg 
  on 
  the 
  Missis- 
  

   sippi 
  to 
  the 
  Atlantic, 
  has 
  been 
  pointed 
  out 
  by 
  Sir 
  Charles 
  Lyell^l. 
  It 
  

   gives 
  successively 
  Loess, 
  Eocene, 
  Chalk, 
  Coal, 
  and 
  Granite, 
  and 
  again, 
  

   on 
  the 
  other 
  side 
  of 
  the 
  range, 
  Coal, 
  Chalk, 
  Eocene, 
  and 
  Loess 
  ; 
  and 
  

   thus 
  tells 
  of 
  four 
  blanks 
  or 
  gaps 
  on 
  opposite 
  sides 
  of 
  the 
  central 
  

   mountains 
  (granitic 
  and 
  metamorphic) 
  , 
  each 
  showing 
  the 
  absence 
  

   of 
  several 
  assemblages 
  of 
  strata. 
  In 
  South 
  America, 
  the 
  two 
  Guianas, 
  

   Brazil, 
  and 
  Chili 
  present 
  large 
  surfaces 
  of 
  Palaeozoic 
  and 
  other 
  rocks 
  

   covered 
  by 
  Quaternary 
  beds 
  §. 
  

  

  Large 
  portions 
  of 
  the 
  Ural 
  Mountains, 
  and 
  especially 
  their 
  eastern 
  

   flank, 
  have 
  no 
  deposits 
  between 
  the 
  Drift 
  and 
  the 
  Carboniferous 
  

   rocks 
  ; 
  and 
  the 
  same 
  may 
  be 
  said 
  of 
  Siberia, 
  showing 
  that 
  it 
  was 
  

   for 
  a 
  long 
  time 
  a 
  subaerial 
  continent, 
  although 
  in 
  parts 
  not 
  without 
  

   newer 
  sediments 
  ||. 
  

  

  The 
  Quaternary 
  beds 
  on 
  which 
  the 
  town 
  of 
  St. 
  Girons 
  (France) 
  

   stands 
  most 
  probably 
  conceal 
  the 
  Lias, 
  as 
  is 
  certainly 
  the 
  case 
  at 
  

   Audinac, 
  close 
  by 
  %. 
  

  

  At 
  Maubert 
  Fontaine, 
  in 
  the 
  Ardennes, 
  loose 
  Quaternary 
  beds 
  

   repose 
  on 
  Silurian 
  schists**; 
  and 
  Delia 
  Marmora 
  ft 
  reports 
  several 
  

   similar 
  cases 
  in 
  Sardinia. 
  

  

  It 
  is 
  an 
  old 
  observation 
  of 
  the 
  late 
  Mr. 
  "Warburton, 
  and 
  quoted 
  by 
  

   Sir 
  Henry 
  De 
  la 
  Beche 
  XX, 
  that 
  the 
  alluvial 
  beds 
  in 
  which 
  the 
  bones 
  

   of 
  Elephants 
  are 
  found, 
  in 
  consequence 
  of 
  previous 
  denudation, 
  are 
  

   discovered 
  resting 
  on 
  the 
  blue 
  clay 
  of 
  London, 
  Oxford 
  Clay, 
  or 
  any 
  

   other 
  bed. 
  

  

  These 
  few 
  examples 
  have 
  their 
  analogues 
  abundantly 
  in 
  other 
  

   countries, 
  and 
  they 
  form 
  no 
  insignificant 
  part 
  of 
  the 
  earth's 
  surface, 
  

   especially 
  when 
  we 
  take 
  into 
  consideration 
  other 
  gaps 
  commencing 
  

   with 
  lower 
  epochs. 
  

  

  2. 
  With 
  a 
  Tertiary 
  Roof. 
  — 
  Sir 
  Roderick 
  Murchison§§ 
  found 
  on 
  the 
  

   River 
  Yaga, 
  in 
  northern 
  Russia, 
  a 
  beautiful 
  section 
  of 
  Pleistocene 
  

   strata 
  resting 
  conformably 
  on 
  horizontal 
  Permian 
  beds. 
  It 
  there- 
  

   fore 
  indicates 
  the 
  prolonged 
  rest 
  of 
  that 
  country. 
  In 
  like 
  manner 
  

  

  * 
  Geol. 
  Surv. 
  of 
  Lake 
  Superior 
  Land 
  Districts, 
  

   t 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xii. 
  p. 
  103. 
  

   \ 
  Second 
  Visit 
  to 
  the 
  L 
  T 
  nited 
  States, 
  vol. 
  ii. 
  p. 
  279. 
  

  

  § 
  D'Orbigny, 
  ' 
  Voyage 
  dans 
  1' 
  Amerique 
  Meridionale,' 
  vol. 
  iii. 
  3 
  e 
  partie, 
  pp. 
  210, 
  

   222, 
  &c. 
  

  

  || 
  Murchison, 
  ' 
  Geology 
  of 
  Russia,' 
  vol. 
  i. 
  pp. 
  352-391. 
  

  

  •![ 
  D'Archiac, 
  ' 
  Histoire 
  des 
  Progres 
  de 
  la 
  Geologie,' 
  vol. 
  vi. 
  p. 
  550. 
  

  

  ** 
  Gosselet, 
  Bull. 
  Soc. 
  Geol. 
  de 
  France, 
  2 
  e 
  serie, 
  vol. 
  xviii. 
  p. 
  5. 
  

  

  tt 
  Voyage 
  en 
  Sardaigne, 
  vol. 
  i. 
  p. 
  414. 
  

  

  X\ 
  Mem. 
  Geol. 
  Survey 
  of 
  Great 
  Britain, 
  vol. 
  i. 
  p. 
  239. 
  

  

  §§ 
  Geology 
  of 
  Russia, 
  vol. 
  i. 
  p. 
  331. 
  

  

  p2 
  

  

  