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  ANNUAL 
  KEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1921 
  

  

  Yet 
  what 
  shall 
  we 
  understand 
  as 
  the 
  aging 
  of 
  this 
  earth 
  ? 
  Where 
  

   and 
  how 
  will 
  this 
  aging 
  be 
  expressed? 
  

  

  Shall 
  we 
  carry 
  over 
  to 
  the 
  earth 
  without 
  further 
  qualification 
  

   the 
  physiological 
  ideas 
  and 
  processes 
  of 
  growing 
  old, 
  which 
  in 
  many 
  

   instances 
  are 
  not 
  exactly 
  qualified 
  or 
  known? 
  May 
  we 
  apply 
  such 
  

   ideas 
  to 
  an 
  inorganic 
  body 
  like 
  the 
  earth? 
  

  

  Evidently 
  the 
  earth, 
  in 
  its 
  processes, 
  presents 
  no 
  picture 
  of 
  de- 
  

   velopments 
  equal 
  to 
  organic 
  developments. 
  

  

  The 
  biological 
  changes 
  in 
  the 
  life 
  processes 
  of 
  an 
  organism 
  are 
  

   bound 
  with 
  the 
  wonderful 
  protoplasm 
  through 
  the 
  highly 
  specialized 
  

   phenomena 
  of 
  assimilation, 
  dissimilation, 
  organic 
  growth, 
  and 
  

   reproduction. 
  

  

  The 
  petrologist 
  in 
  discussing 
  the 
  earth's 
  volcanic 
  rocks 
  may 
  in- 
  

   deed 
  speak 
  of 
  magmatic 
  " 
  assimilation 
  " 
  ; 
  but 
  the 
  inorganic 
  " 
  assimila- 
  

   tion 
  " 
  in 
  the 
  earth's 
  crust, 
  in 
  the 
  earth's 
  body, 
  is 
  nothing 
  more 
  than 
  

   a 
  " 
  solution 
  " 
  within 
  the 
  molten 
  mass 
  through 
  the 
  addition 
  of 
  a 
  

   foreign 
  substance 
  within 
  an 
  existing 
  molten 
  substance. 
  Similarly 
  

   magmatic 
  " 
  differentiation 
  " 
  is 
  not 
  to 
  be 
  compared 
  with 
  organic 
  

   " 
  dissimilation." 
  It 
  is 
  nothing 
  more 
  than 
  one 
  of 
  the 
  various 
  reac- 
  

   tions 
  between 
  the 
  components 
  of 
  the 
  magma 
  according 
  to 
  their 
  

   relative 
  quantities 
  and 
  relations 
  to 
  each 
  other 
  and 
  the 
  variations 
  

   in 
  the 
  pressure 
  and 
  temperature 
  of 
  the 
  surroundings. 
  

  

  Though, 
  following 
  the 
  planetesimal 
  theory, 
  we 
  talk 
  of 
  the 
  earth 
  

   growing 
  to 
  its 
  present 
  size, 
  yet 
  tliis 
  growth 
  is 
  not 
  taken 
  in 
  the 
  sense 
  

   of 
  the 
  growth 
  of 
  an 
  organism 
  through 
  the 
  actions 
  and 
  reactions 
  of 
  the 
  

   latter's 
  protoplasm. 
  The 
  growth 
  of 
  the 
  earth 
  is 
  to 
  be 
  taken 
  merely 
  as 
  

   a 
  simple 
  increase 
  in 
  bulk 
  through 
  the 
  accretion 
  of 
  cosmic 
  bodies. 
  

   There 
  was, 
  and 
  is 
  yet 
  to-day, 
  an 
  assimilation 
  of 
  these 
  bodies 
  into 
  

   the 
  earth's 
  substance 
  through 
  weathering 
  and 
  various 
  transforma- 
  

   tions; 
  but 
  there 
  is 
  here 
  only 
  an 
  addition 
  to 
  the 
  earth 
  of 
  matter, 
  

   similar 
  to 
  the 
  substance 
  of 
  the 
  earth, 
  coming 
  to 
  it 
  from 
  outside 
  

   space. 
  

  

  If 
  we 
  might 
  speak 
  of 
  the 
  moon, 
  as 
  W. 
  H. 
  Pickering 
  expresses 
  it, 
  

   as 
  a 
  late-born 
  child 
  of 
  the 
  earth, 
  and 
  if 
  the 
  depths 
  of 
  the 
  Pacific 
  

   Ocean 
  indeed 
  show 
  the 
  womb 
  from 
  which 
  the 
  moon 
  was 
  torn 
  out 
  

   of 
  mother 
  earth's 
  body, 
  this 
  process 
  of 
  the 
  division 
  of 
  a 
  heavenly 
  

   body 
  into 
  two 
  is 
  least 
  of 
  all 
  to 
  be 
  taken 
  as 
  an 
  instance 
  of 
  organic 
  

   reproduction. 
  

  

  In 
  general 
  what 
  then 
  shall 
  we 
  take 
  as 
  an 
  expression 
  of 
  the 
  life 
  

   of 
  the 
  earth 
  that 
  we 
  may 
  measure 
  its 
  growing 
  old? 
  The 
  life 
  of 
  an 
  

   organism 
  is 
  bound 
  up 
  with 
  protoplasm 
  and 
  its 
  motion. 
  With 
  what 
  is 
  

   the 
  life 
  of 
  the 
  earth 
  bound? 
  Neither 
  its 
  existence 
  nor 
  yet 
  its 
  length 
  

   of 
  existence 
  is 
  to 
  be 
  taken 
  as 
  the 
  sense 
  of 
  its 
  life. 
  If 
  we 
  are 
  to 
  draw 
  a 
  

   liarallel 
  from 
  the 
  life 
  of 
  the 
  organic 
  Avorld, 
  then 
  the 
  life 
  of 
  a 
  star 
  

  

  