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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  that 
  in 
  both 
  time 
  and 
  place 
  the 
  foldings 
  are 
  conformable. 
  Then 
  

   there 
  come 
  three 
  great 
  foldings, 
  well 
  recognized 
  in 
  time, 
  place, 
  

   and 
  nature, 
  the 
  Caledonian, 
  tlie 
  Variscian, 
  and 
  the 
  Alpidian. 
  Each 
  

   one 
  of 
  these 
  three 
  is 
  not 
  — 
  as 
  was 
  assumed 
  in 
  the 
  older 
  interpreta- 
  

   tions—geologically 
  speaking, 
  the 
  work 
  of 
  one 
  time; 
  rather 
  each 
  one 
  

   is 
  the 
  result 
  of 
  a 
  great 
  number 
  of 
  different 
  folding 
  phases, 
  which 
  

   among 
  themselves 
  and 
  at 
  different 
  places 
  were 
  of 
  differing 
  intensi- 
  

   ties 
  and 
  were 
  separated 
  by 
  periods 
  of 
  relative 
  rest 
  so 
  far 
  as 
  faulting 
  

   goes. 
  We 
  owe 
  to 
  Stille 
  a 
  striking 
  comparison 
  of 
  the 
  occurrence 
  of 
  

   separate 
  rhythms, 
  the 
  localities 
  of 
  which 
  are 
  very 
  restricted 
  upon 
  

   small 
  mobile 
  zones 
  of 
  the 
  earth's 
  surface; 
  in 
  general 
  these 
  places 
  are 
  

   altered 
  for 
  each 
  rhythm, 
  showing 
  the 
  improbability 
  of 
  a 
  really 
  

   ubiquitous 
  occurrence 
  of 
  the 
  Archaic 
  foldings. 
  

  

  Expressing 
  the 
  times 
  of 
  the 
  occurence 
  of 
  these 
  mountain 
  forma- 
  

   tions 
  in 
  customary 
  geological 
  nomenclature, 
  the 
  youngest, 
  the 
  Alpid- 
  

   ian, 
  lasted 
  with 
  its 
  11 
  or 
  13 
  phases 
  and 
  their 
  subphases, 
  from 
  the 
  be- 
  

   ginning 
  of 
  the 
  Triassic 
  to 
  the 
  end 
  of 
  the 
  Tertiary, 
  through 
  no 
  par- 
  

   ticular 
  length 
  of 
  geological 
  time. 
  There 
  is 
  a 
  strengthening 
  of 
  its 
  

   phases 
  until 
  the 
  older 
  Tertiary 
  and 
  subsequently 
  a 
  decline. 
  In 
  the 
  

   principal 
  phases 
  the 
  folding 
  was 
  extraordinarily 
  strong. 
  The 
  quies- 
  

   cent 
  periods 
  increased 
  in 
  length 
  toward 
  the 
  Tertiary 
  and 
  then 
  de- 
  

   creased 
  in 
  the 
  more 
  recent 
  Tertiary. 
  From 
  its 
  predecessor, 
  the 
  

   Variscian 
  folding, 
  it 
  was 
  separated 
  by 
  the 
  geologically 
  short 
  quiescent 
  

   period 
  of 
  the 
  Triassic 
  and 
  in 
  some 
  places 
  by 
  the 
  upper 
  Dyas 
  and 
  the 
  

   Triassic. 
  

  

  The 
  Variscian 
  folding 
  period, 
  Avith 
  its 
  four 
  or 
  five 
  phases, 
  occurred 
  

   during 
  the 
  Carboniferous 
  age 
  and 
  far 
  into 
  the 
  Dyas, 
  and 
  in 
  certain 
  

   regions, 
  to 
  the 
  eiid 
  'of 
  it. 
  Its 
  phases, 
  varying 
  greatly 
  in 
  intensity 
  in 
  

   different 
  regions, 
  are 
  separated 
  from 
  each 
  other, 
  so 
  far 
  as 
  the 
  sedi- 
  

   mentation 
  indicates, 
  by 
  relatively 
  long 
  periods 
  of 
  rest 
  from 
  faulting. 
  

  

  The 
  Caledonian 
  folding 
  period 
  was 
  separated 
  from 
  the 
  Variscian 
  

   by 
  the 
  Devonian 
  age, 
  which 
  saw 
  no 
  folding 
  of 
  notable 
  intensity. 
  In 
  

   this 
  period 
  there 
  are 
  only 
  two 
  folding 
  phases 
  recognizable, 
  separated 
  

   by 
  almost 
  the 
  whole 
  Silurian. 
  The 
  later, 
  the 
  true 
  Caledonian 
  fold- 
  

   ing, 
  was 
  the 
  stronger 
  and 
  the 
  wider 
  spread. 
  The 
  long 
  period 
  of 
  

   quiescence 
  of 
  the 
  Cambrian 
  and 
  the 
  lower 
  Silurian 
  separates 
  the 
  

   Caledonian 
  folding 
  from 
  those 
  of 
  the 
  pre-Cambrian, 
  the 
  Algonkian 
  

   and 
  the 
  Archaic 
  times, 
  which 
  are 
  to 
  be 
  placed 
  in 
  no 
  definite 
  com- 
  

   parable 
  relation 
  with 
  the 
  three 
  later 
  periods. 
  

  

  No 
  geological 
  evidence 
  known 
  up 
  to 
  the 
  present 
  gives 
  a 
  basis 
  for- 
  

   the 
  assumption 
  that 
  the 
  time 
  intervals 
  between 
  the 
  three 
  periods 
  of 
  

   folding 
  should 
  be 
  increased. 
  The 
  number 
  of 
  folding 
  phases 
  in 
  the 
  

   three 
  periods 
  increases 
  and 
  the 
  intei*vening 
  intervals 
  shorten 
  rather 
  

   than 
  lengthen 
  from 
  period 
  to 
  period. 
  

  

  