﻿264 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192*1 
  

  

  throughout 
  all 
  the 
  time 
  of 
  the 
  history 
  of 
  the 
  earth 
  known 
  to 
  us. 
  This 
  

   principle, 
  which 
  has 
  influenced 
  the 
  thoughts 
  of 
  geologists 
  for 
  nearly 
  

   100 
  years, 
  is 
  taken 
  to 
  hold 
  now 
  only 
  in 
  the 
  sense 
  that 
  never 
  upon 
  the 
  

   earth's 
  crust 
  have 
  forces 
  been 
  active 
  other 
  than 
  those 
  which 
  are 
  acting 
  

   at 
  present. 
  

  

  Indeed 
  even 
  the 
  oldest 
  known 
  series 
  of 
  rocks 
  tell 
  us, 
  as 
  do 
  those 
  of 
  

   to-day, 
  of 
  the 
  chemical 
  and 
  physical 
  weathering 
  of 
  the 
  previously 
  

   existing 
  rocks, 
  of 
  the 
  transport 
  of 
  the 
  weathering 
  products 
  by 
  water 
  

   and 
  wind. 
  They 
  tell 
  of 
  the 
  accumulation 
  of 
  these 
  products 
  in 
  the 
  

   lowlands 
  which 
  then 
  existed 
  in 
  opposition 
  to 
  the 
  highlands. 
  They 
  

   indicate 
  an 
  atmosphere 
  and 
  a 
  hydrosphere 
  with 
  their 
  movements 
  

   and 
  as 
  to-day, 
  also, 
  the 
  influence 
  of 
  the 
  cosmical 
  agency 
  in 
  the 
  radia- 
  

   tion 
  from 
  the 
  sun. 
  From 
  the 
  manner 
  of 
  juxtaposition 
  of 
  even 
  the 
  

   oldest 
  known 
  rocks 
  there 
  may 
  be 
  inferred 
  the 
  breaking 
  of 
  the 
  earth's 
  

   crust 
  into 
  huge 
  blocks 
  and 
  mountain 
  building 
  movements 
  of 
  the 
  same 
  

   nature 
  as 
  those 
  of 
  later 
  periods, 
  just 
  as 
  in 
  the 
  more 
  recent 
  periods, 
  

   glowing 
  liquid 
  from 
  the 
  depths 
  was 
  pressed 
  through 
  and 
  out 
  of 
  the 
  

   earth's 
  crust. 
  In 
  one 
  detail 
  only 
  does 
  the 
  evidence 
  of 
  the 
  earth's 
  

   earlier 
  life 
  difl^er 
  from 
  that 
  of 
  the 
  present: 
  The 
  evidence 
  of 
  organic 
  

   life 
  is 
  not 
  handed 
  down 
  to 
  us 
  in 
  the 
  same 
  manner 
  as 
  it 
  is 
  from 
  later 
  

   periods. 
  That 
  organic 
  life 
  did 
  exist 
  in 
  the 
  Archeozoic 
  era 
  the 
  

   presence 
  of 
  lime 
  and 
  carbonaceous 
  deposits 
  demonstrates. 
  But 
  the 
  

   Archaic 
  life 
  was 
  less 
  developed 
  than 
  in 
  subsequent 
  tirnes 
  and 
  conse- 
  

   quently 
  its 
  influence 
  in 
  the 
  building 
  and 
  transformation 
  of 
  rocks 
  

   was 
  of 
  less 
  importance 
  than 
  later. 
  

  

  Always, 
  throughout 
  all 
  time, 
  the 
  same 
  forces, 
  the 
  same 
  manifesta- 
  

   tions 
  of 
  the 
  life 
  of 
  our 
  earth 
  have 
  been 
  at 
  work 
  as 
  to-day. 
  But 
  not 
  

   always 
  have 
  they 
  had 
  the 
  same 
  relative 
  importance. 
  Even 
  to-day 
  

   they 
  do 
  not 
  work 
  the 
  same 
  in 
  all 
  places 
  nor 
  at 
  the 
  same 
  time. 
  

   Weathering 
  and 
  denudation 
  are 
  much 
  greater 
  in 
  mountainous 
  regions, 
  

   in 
  the 
  Alps, 
  for 
  instance, 
  than 
  in 
  the 
  flat 
  lowlands 
  in 
  the 
  north 
  of 
  

   Germany 
  or 
  on 
  the 
  wide 
  plains 
  of 
  central 
  Russia. 
  Weathering 
  and 
  

   denudation 
  work 
  quite 
  differently 
  under 
  different 
  climatic 
  conditions, 
  

   as, 
  for 
  instance, 
  upon 
  the 
  east 
  and 
  west 
  sides 
  of 
  the 
  South 
  American 
  

   Andes. 
  The 
  accumulation 
  and 
  transport 
  of 
  weathered 
  rock 
  is 
  greater 
  

   in 
  mountain 
  valleys 
  and 
  on 
  the 
  declivities 
  of 
  high 
  peaks 
  than 
  upon 
  

   the 
  same 
  base 
  in 
  the 
  plains. 
  The 
  action 
  of 
  glaciers 
  is 
  limited 
  geo- 
  

   graphically, 
  topographically, 
  and 
  by 
  climatic 
  conditions 
  to 
  certain 
  

   regions. 
  The 
  motions 
  of 
  the 
  earth's 
  crust 
  through 
  earthquakes 
  and 
  

   volcanic 
  disturbances 
  occur 
  in 
  some 
  regions 
  very 
  much 
  more 
  than 
  in 
  

   others. 
  In 
  the 
  same 
  places 
  the 
  destructive 
  and 
  constructive 
  forces 
  

   change 
  even 
  now 
  with 
  the 
  season 
  and 
  climatic 
  changes. 
  

  

  The 
  same 
  conditions 
  held 
  in 
  the 
  past. 
  The 
  nature 
  and 
  amounts 
  of 
  

   movements 
  and 
  the 
  results 
  varied 
  at 
  the 
  same 
  time 
  in 
  different 
  re- 
  

  

  