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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  THE 
  TESTIMONY 
  OF 
  THE 
  SEDIMENTS. 
  

  

  In 
  considering 
  possible 
  modifications 
  of 
  the 
  foregoing 
  estimates 
  

   five 
  questions 
  arise: 
  (1) 
  How 
  far 
  do 
  recent 
  investigations 
  tend 
  to 
  

   lengthen 
  or 
  to 
  shorten 
  the 
  older 
  estimates? 
  (2) 
  To 
  what 
  extent 
  has 
  

   human 
  action 
  made 
  the 
  present 
  rate 
  of 
  wash 
  and 
  deposit 
  faster 
  than 
  

   the 
  mean 
  pre-human 
  rate? 
  (3) 
  How 
  far 
  does 
  the 
  present 
  state 
  of 
  

   elevation 
  make 
  the 
  present 
  rate 
  faster 
  or 
  slower 
  than 
  the 
  mean 
  rate 
  

   of 
  the 
  past? 
  (4) 
  How 
  does 
  the 
  present 
  area 
  of 
  erosion 
  compare 
  

   with 
  the 
  mean 
  area? 
  And, 
  finally, 
  (5) 
  does 
  the 
  lower 
  end 
  of 
  the 
  

   geologic 
  column 
  give 
  us 
  the 
  point 
  from 
  which 
  the 
  accumulation 
  of 
  

   the 
  sediments 
  began? 
  I 
  can 
  try 
  to 
  answer 
  these 
  questions 
  only 
  very 
  

   briefly 
  and 
  inadequately. 
  

  

  1. 
  The 
  effect 
  of 
  intensive 
  studies 
  on 
  earlier 
  time 
  estimates. 
  — 
  

   A 
  strictly 
  accurate 
  chronology 
  reaching 
  back 
  from 
  the 
  present 
  for 
  

   several 
  thousands 
  of 
  years 
  is 
  now 
  being 
  worked 
  out 
  by 
  De 
  Geer. 
  7 
  

   He 
  has 
  succeeded 
  in 
  identifying 
  the 
  yearly 
  deposits 
  of 
  glacial 
  waters 
  

   and 
  in 
  correlating 
  them 
  with 
  annual 
  moraines. 
  In 
  addition 
  to 
  this 
  

   he 
  has 
  been 
  able 
  to 
  match 
  sections 
  at 
  distant 
  points 
  by 
  comparing 
  

   the 
  succession 
  of 
  peculiarities 
  in 
  the 
  annual 
  " 
  varve 
  " 
  layers. 
  While 
  

   this 
  is 
  a 
  quite 
  special 
  method 
  and 
  has 
  only 
  limited 
  application, 
  it 
  is 
  

   important 
  to 
  general 
  time 
  estimates, 
  because 
  it 
  gives 
  a 
  means 
  of 
  

   checking 
  up 
  other 
  criteria 
  that 
  indicate 
  glacial 
  time, 
  and 
  these 
  help 
  

   check 
  up 
  certain 
  nonglacial 
  criteria. 
  As 
  is 
  well 
  known, 
  the 
  duration 
  

   of 
  the 
  recent 
  Ice 
  Age 
  was 
  for 
  a 
  time 
  a 
  sharply 
  battled 
  question, 
  and 
  

   the 
  old 
  views 
  pitted 
  against 
  the 
  new 
  views 
  came 
  to 
  be 
  well 
  defined. 
  

   Though 
  not 
  yet 
  ready 
  for 
  precise 
  announcement, 
  it 
  is 
  already 
  fore- 
  

   shadowed 
  that 
  the 
  De 
  Geer 
  method 
  of 
  measurement, 
  when 
  it 
  shall 
  

   have 
  fully 
  covered 
  the 
  retreatal 
  stage 
  of 
  the 
  last 
  glacial 
  epoch, 
  will 
  

   show 
  that 
  stage 
  to 
  be 
  about 
  three 
  times 
  as 
  long 
  as 
  it 
  was 
  made 
  by 
  

   the 
  most 
  representative 
  of 
  the 
  old 
  estimates. 
  The 
  main 
  differences 
  

   of 
  opinion 
  as 
  to 
  the 
  duration 
  of 
  the 
  glacial 
  period, 
  however, 
  grew 
  out 
  

   of 
  the 
  evidence 
  that 
  instead 
  of 
  one 
  simple 
  short 
  epoch 
  there 
  were 
  

   several 
  epochs 
  of 
  glaciation 
  separated 
  by 
  rather 
  long 
  interglacial 
  

   intervals. 
  Now, 
  by 
  using 
  the 
  De 
  Geer 
  method 
  to 
  correct 
  the 
  criteria 
  

   on 
  which 
  time 
  estimates 
  of 
  these 
  glacial 
  and 
  interglacial 
  epochs 
  have 
  

   been 
  based, 
  a 
  glacial 
  period 
  at 
  least 
  twenty 
  times 
  as 
  long 
  as 
  that 
  

   assigned 
  by 
  the 
  old 
  estimate 
  seems 
  to 
  be 
  foreshadowed. 
  Very 
  likely 
  

   this 
  degree 
  of 
  extension 
  of 
  an 
  old-time 
  estimate 
  by 
  a 
  new 
  one 
  is 
  ex- 
  

   ceptional; 
  at 
  any 
  rate, 
  the 
  glacial 
  formations 
  are 
  exceptional 
  de- 
  

   posits 
  and 
  make 
  up 
  only 
  a 
  small 
  part 
  of 
  the 
  geologic 
  column. 
  

  

  7 
  Gerald 
  De 
  Geer, 
  "A 
  geochronology 
  of 
  the 
  last 
  12,000 
  years," 
  Proc. 
  Int. 
  Congr., 
  Stock- 
  

   holm, 
  1910, 
  p. 
  241 
  ; 
  " 
  Kontinentale 
  Niveauveranderungen 
  in 
  Norden 
  Europas," 
  ibid.. 
  

   p. 
  849 
  ; 
  Spitsbergen, 
  ibid., 
  p. 
  1205 
  ; 
  " 
  Phenonienes 
  Quaternaires 
  de 
  Stockholm," 
  ibid., 
  

   p. 
  1290 
  ; 
  " 
  Quaternary 
  phenomena 
  in 
  the 
  southern 
  part 
  of 
  Sweden," 
  ibid., 
  p. 
  1339. 
  

  

  