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  BIGSBY 
  MISSING 
  SEDIMENTARY 
  FORMATIONS. 
  

  

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  VOL. 
  XX. 
  PART 
  I. 
  

  

  by 
  steps. 
  The 
  general 
  idea 
  of 
  any 
  advance 
  

   arrives 
  first, 
  and 
  may 
  perhaps 
  lie 
  dormant 
  

   for 
  years, 
  when 
  follows 
  its 
  development 
  by 
  

   another 
  workman, 
  and 
  perhaps 
  in 
  another 
  

   country 
  ; 
  just 
  as 
  Vicomte 
  d'Archiac, 
  in 
  

   1848, 
  sketched 
  in 
  unmistakeable 
  language 
  

   the 
  principal 
  features 
  of 
  the 
  great 
  Terripetal 
  

   Theory, 
  which 
  Bronn, 
  in 
  1862, 
  made 
  his 
  

   own 
  by 
  the 
  most 
  masterly 
  elaboration, 
  

   — 
  Ami 
  Boue, 
  in 
  1852, 
  having 
  prepared 
  the 
  

   way 
  by 
  an 
  elaborate 
  article 
  in 
  the 
  ' 
  Bul- 
  

   letin 
  de 
  la 
  Societe 
  Geologique 
  de 
  France,' 
  

   2nd 
  series, 
  vol. 
  ix. 
  p. 
  437. 
  While 
  in 
  their 
  

   vertical 
  order 
  of 
  succession 
  the 
  sedimentary 
  

   rocks 
  never 
  vary, 
  unless 
  disturbed, 
  they 
  differ 
  

   greatly 
  in 
  thickness 
  and 
  extent 
  — 
  far 
  stretch- 
  

   ing 
  out 
  and 
  thin 
  in 
  plains, 
  thick 
  and 
  limited 
  

   in 
  area 
  among 
  mountains, 
  as 
  we 
  see 
  

   abundantly 
  verified 
  in 
  the 
  Americas, 
  India, 
  

   Russia, 
  &c. 
  But 
  they 
  have 
  also 
  been 
  from 
  

   the 
  very 
  earliest 
  periods 
  largely, 
  and 
  fre- 
  

   quently, 
  absent 
  from 
  their 
  normal 
  situa- 
  

   tions, 
  and 
  much 
  more 
  so 
  than 
  appears 
  in 
  

   systematic 
  works; 
  and 
  it 
  is 
  easy 
  to 
  see, 
  

   from 
  the 
  vast 
  and 
  universal 
  prevalence 
  of 
  

   these 
  suspensions 
  and 
  removals 
  of 
  deposits, 
  

   that 
  it 
  will 
  be 
  one 
  day 
  proved 
  that 
  the 
  

   emerged 
  tracts 
  were 
  at 
  all 
  periods 
  so 
  ex- 
  

   tensive 
  and 
  so 
  united 
  as 
  to 
  constitute 
  from 
  

   one-fifth 
  to 
  one-third 
  of 
  the 
  whole 
  surface 
  

   of 
  the 
  globe. 
  

  

  While 
  any 
  given 
  district 
  was 
  in 
  a 
  state 
  of 
  

   emergence, 
  various 
  sediments 
  were 
  being 
  

   deposited 
  in 
  the 
  neighbouring 
  sea, 
  which 
  

   was 
  at 
  the 
  same 
  time 
  tenanted 
  by 
  a 
  fauna 
  

   so 
  balanced 
  and 
  harmonized 
  that 
  the 
  indi- 
  

   viduals 
  could 
  thrive 
  and 
  follow 
  the 
  prompt- 
  

   ings 
  of 
  their 
  instincts 
  — 
  whole 
  races 
  dying 
  

   out, 
  we 
  may 
  safely 
  suppose. 
  Now, 
  if 
  only 
  

   one 
  such 
  epoch 
  commence, 
  become 
  mature, 
  

   and 
  decline, 
  we 
  see 
  that 
  the 
  raised 
  land 
  must 
  

   have 
  remained 
  as 
  such 
  for 
  an 
  immensely 
  

   long 
  period. 
  What 
  then 
  must 
  have 
  been 
  

   the 
  length 
  of 
  that 
  period 
  of 
  time 
  during 
  

   which 
  an 
  emerged 
  tract 
  remained 
  through 
  

   ten 
  or 
  twenty 
  epochs 
  above 
  water, 
  as 
  has 
  

   frequently 
  occurred?* 
  Missing 
  formations, 
  

   then, 
  hold 
  a 
  high 
  and 
  important 
  place 
  as 
  a 
  

   result 
  of 
  one 
  of 
  the 
  constructive 
  processes 
  of 
  

  

  * 
  Canada, 
  Hudson's 
  Bay, 
  Germany, 
  &c. 
  &c. 
  

  

  P 
  

  

  