﻿250 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  nition 
  here, 
  the 
  one 
  based 
  on 
  the 
  view 
  that 
  the 
  earth 
  started 
  as 
  a 
  

   molten 
  globe, 
  the 
  other 
  that 
  it 
  grew 
  up 
  slowly 
  by 
  the 
  accession 
  of 
  

   solid 
  particles. 
  For 
  the 
  purposes 
  of 
  the 
  present 
  question 
  it 
  is 
  not 
  

   radically 
  material 
  how 
  the 
  molten 
  globe 
  arose, 
  on 
  the 
  one 
  hand, 
  nor 
  

   by 
  what 
  celestial 
  mechanism 
  the 
  accretion 
  took 
  place, 
  on 
  the 
  other, 
  

   beyond 
  the 
  fact 
  that 
  the 
  material 
  of 
  the 
  ocean 
  was 
  supposed 
  to 
  be 
  

   assembled 
  as 
  a 
  vapor 
  about 
  a 
  hot 
  earth, 
  in 
  the 
  one 
  case, 
  ready 
  to 
  begin 
  

   work 
  in 
  full 
  volume 
  when 
  cooling 
  took 
  place, 
  while 
  in 
  the 
  other 
  case 
  

   the 
  waters 
  came 
  into 
  action 
  very 
  gradually. 
  Out 
  of 
  these 
  basal 
  dif- 
  

   ferences, 
  however, 
  there 
  arise 
  some 
  important 
  contrasts 
  in 
  the 
  modes 
  

   of 
  later 
  action 
  that 
  are 
  almost 
  equally 
  radical 
  in 
  their 
  bearings 
  on 
  the 
  

   evolution 
  of 
  the 
  ocean, 
  so 
  that 
  both 
  the 
  original 
  and 
  derivative 
  differ- 
  

   ences 
  need 
  to 
  be 
  sharply 
  in 
  mind 
  in 
  considering 
  the 
  question 
  of 
  the 
  

   earth's 
  age. 
  

  

  1. 
  On 
  the 
  one 
  hand, 
  it 
  is 
  assumed 
  that 
  the 
  ocean 
  was 
  essentially 
  

   uniform 
  in 
  volume 
  throughout 
  all 
  the 
  ages, 
  and 
  that 
  the 
  disintegra- 
  

   tion 
  of 
  the 
  surface 
  rocks, 
  the 
  inflow 
  of 
  solutions, 
  and 
  the 
  content 
  they 
  

   carried 
  were 
  also 
  essentially 
  uniform. 
  If 
  these 
  assumptions 
  are 
  cor- 
  

   rect, 
  or 
  if 
  they 
  hold 
  true 
  of 
  a 
  single 
  leading 
  element, 
  as 
  sodium, 
  the 
  

   present 
  rate 
  and 
  content 
  of 
  inflow 
  may 
  be 
  used 
  as 
  a 
  divisor 
  to 
  ascer- 
  

   tain 
  the 
  total 
  time 
  of 
  inflow. 
  This, 
  however, 
  is 
  subject 
  to 
  the 
  condi- 
  

   tion 
  that 
  there 
  is 
  no 
  important 
  reversal 
  of 
  action, 
  or 
  at 
  least 
  none 
  that 
  

   can 
  not 
  be 
  adequately 
  measured 
  and 
  discounted. 
  

  

  The 
  alternative 
  view 
  assumes 
  that 
  the 
  ocean 
  grew 
  to 
  its 
  present 
  

   volume 
  very 
  slowly 
  from 
  a 
  small 
  beginning, 
  that 
  the 
  solutions 
  came 
  

   from 
  three 
  sources 
  and 
  were 
  variable 
  from 
  the 
  start, 
  so 
  that 
  the 
  whole 
  

   history 
  was 
  very 
  different 
  from 
  the 
  preceding. 
  The 
  three 
  sources 
  of 
  

   solutions 
  were 
  (1) 
  the 
  internal 
  metamorphic 
  action 
  of 
  waters 
  en- 
  

   trapped 
  in 
  the 
  growing 
  accessions, 
  (2) 
  surficial 
  action 
  by 
  the 
  atmos- 
  

   phere 
  and 
  hydrosphere 
  acting 
  on 
  the 
  shell 
  of 
  the 
  lithosphere, 
  and 
  (3) 
  

   accessions 
  of 
  water-substance 
  from 
  the 
  environing 
  sphere 
  under 
  con- 
  

   trol 
  of 
  the 
  sun 
  — 
  particularly 
  accessions 
  through 
  the 
  system 
  of 
  ex- 
  

   change 
  between 
  the 
  ultra-atmosphere 
  of 
  the 
  sun 
  and 
  the 
  ultra-atmos- 
  

  

  system. 
  In 
  other 
  words, 
  the 
  earth 
  and 
  its 
  family 
  have 
  dynamic 
  peculiarities 
  that 
  make 
  

   the 
  question 
  of 
  their 
  origin 
  a 
  special 
  one. 
  These 
  hereditary 
  peculiarities 
  point 
  the 
  ioay 
  

   to 
  their 
  interpretation. 
  The 
  planetesimal 
  hypothesis 
  is 
  simply 
  the 
  result 
  of 
  an 
  attempt 
  

   to 
  follow 
  these 
  hereditary 
  traits 
  back 
  to 
  their 
  parentage. 
  It 
  is 
  as 
  little 
  as 
  possible 
  

   speculative, 
  for 
  it 
  starts 
  with 
  mechanical 
  properties 
  which 
  are 
  rigorously 
  determinate 
  and 
  

   which 
  must 
  be 
  met 
  by 
  any 
  hypothesis 
  of 
  genesis 
  worthy 
  of 
  serious 
  consideration. 
  It 
  

   follows 
  these 
  back 
  to 
  their 
  probable 
  origin 
  in 
  other 
  known 
  properties 
  and 
  natural 
  actions 
  

   so 
  related 
  to 
  them 
  as 
  to 
  be 
  their 
  probable 
  sources. 
  The 
  method 
  followed 
  was 
  only 
  a 
  

   phase 
  of 
  the 
  standard 
  practice 
  of 
  geologists 
  in 
  following 
  the 
  vestiges 
  of 
  a 
  recorded 
  event 
  

   back 
  to 
  their 
  most 
  probable 
  sources. 
  If 
  peculiar 
  at 
  all, 
  it 
  is 
  merely 
  in 
  that 
  the 
  vestiges 
  

   are 
  dynamic. 
  It 
  ill 
  becomes 
  us 
  to 
  be 
  squeamish 
  about 
  historical 
  deductions 
  from 
  his- 
  

   torical 
  vestiges, 
  for 
  there 
  are 
  plenty 
  of 
  people 
  who 
  regard 
  geology 
  as 
  a 
  speculation 
  from 
  

   beginning 
  to 
  end 
  and 
  there 
  is 
  no 
  present 
  help 
  for 
  it. 
  

  

  