﻿590 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  multiple 
  hypotheses 
  controlled. 
  Their 
  objective 
  was 
  a 
  tenable 
  hypoth- 
  

   esis 
  of 
  the 
  origin 
  of 
  the 
  planetary 
  system. 
  They 
  examined 
  all 
  the 
  

   hypotheses 
  that 
  occupied 
  the 
  field 
  and 
  devised 
  many 
  others, 
  both 
  

   comprehensive 
  and 
  subsidiary. 
  Chamberlin's 
  constructive 
  mind 
  

   grouped 
  facts, 
  originated 
  explanations, 
  suggested 
  tests. 
  He 
  reasoned 
  

   by 
  "naturalistic 
  logic." 
  Moul 
  ton's 
  analytical 
  genius 
  checked 
  Cham- 
  

   berlin's 
  concepts 
  against 
  the 
  principles 
  of 
  celestial 
  mechanics, 
  and 
  

   applied 
  critical 
  mathematical 
  tests 
  to 
  the 
  dynamical 
  consequences. 
  In 
  

   their 
  discussions 
  each 
  always 
  maintained 
  independence 
  of 
  judgment. 
  

   When 
  agreements 
  were 
  reached 
  it 
  was 
  only 
  on 
  convincing 
  proof. 
  

  

  Even 
  so, 
  agreement 
  between 
  Chamberlin 
  and 
  Moulton 
  was 
  not 
  

   regarded 
  by 
  them 
  as 
  demonstration. 
  An 
  hypothesis 
  was 
  abandoned 
  

   only 
  when 
  it 
  was 
  clearly 
  inconsistent 
  with 
  known 
  facts 
  or 
  laws. 
  

   All 
  hypotheses 
  that 
  withstood 
  the 
  tests 
  of 
  the 
  realities 
  were 
  carried 
  on 
  

   as 
  possible 
  working 
  material. 
  Yet 
  after 
  25 
  years 
  of 
  research 
  only 
  one 
  

   hypothesis 
  of 
  planetary 
  genesis, 
  the 
  planetesimal, 
  survived. 
  

  

  The 
  gaseous 
  group 
  of 
  genetic 
  hypotheses 
  represented 
  by 
  the 
  theory 
  

   of 
  Laplace 
  failed 
  because 
  the 
  kinetic 
  energy 
  of 
  gases 
  would 
  not 
  permit 
  

   the 
  assembling 
  of 
  the 
  actual 
  planets 
  by 
  gravitation, 
  as 
  postulated, 
  

   and 
  the 
  observed 
  moments 
  of 
  momentum 
  of 
  revolution 
  could 
  not 
  have 
  

   been 
  attained. 
  The 
  meteoritic 
  hypotheses 
  failed 
  similarly 
  to 
  with- 
  

   stand 
  Moulton's 
  incisive 
  studies 
  of 
  their 
  dynamical 
  implications. 
  

  

  Having 
  failed 
  to 
  find 
  a 
  solution 
  of 
  their 
  problem 
  in 
  the 
  general 
  con- 
  

   cepts 
  relating 
  to 
  the 
  movements 
  and 
  attractions 
  of 
  stellar 
  bodies, 
  

   Chamberlin 
  and 
  Moulton 
  turned 
  their 
  attention 
  to 
  the 
  specific 
  

   peculiarities 
  of 
  the 
  solar 
  system, 
  in 
  the 
  hope 
  of 
  finding 
  in 
  them 
  a 
  

   suggestion 
  of 
  the 
  conditions 
  to 
  which 
  they 
  owed 
  their 
  evolution. 
  

   The 
  orderly 
  arrangement 
  of 
  the 
  planets 
  nearly 
  in 
  a 
  common 
  plane 
  of 
  

   orbits, 
  the 
  distribution 
  of 
  masses, 
  which 
  contrasts 
  extraordinarily 
  

   with 
  the 
  distribution 
  of 
  moments 
  of 
  momentum, 
  the 
  directions 
  of 
  

   rotation 
  of 
  the 
  planets, 
  and 
  many 
  minor 
  peculiarities 
  were 
  critically 
  

   studied. 
  They 
  suggested 
  that 
  two 
  bodies 
  had 
  been 
  concerned 
  in 
  the 
  

   birth 
  of 
  the 
  planets 
  from 
  the 
  sun 
  — 
  the 
  sun 
  itself 
  and 
  a 
  visiting 
  star. 
  

   This 
  hint 
  was 
  developed 
  constructively 
  by 
  Chamberlin 
  and 
  mathe- 
  

   matically 
  by 
  Moulton, 
  until 
  the 
  possibilities 
  of 
  a 
  dynamical 
  encounter 
  

   had 
  been 
  traversed 
  and 
  that 
  which 
  seemed 
  b^st 
  to 
  suit 
  the 
  actual 
  

   facts 
  of 
  the 
  solar 
  system 
  had 
  been 
  isolated 
  from 
  the 
  general 
  possibili- 
  

   ties. 
  This 
  conception 
  and 
  demonstration 
  belong 
  entirely 
  to 
  Chamber- 
  

   lin 
  and 
  Moulton; 
  they 
  constitute 
  a 
  great 
  original 
  contribution 
  in 
  the 
  

   field 
  of 
  celestial 
  mechanics. 
  

  

  Directing 
  his 
  atte^ition 
  specifically 
  to 
  the 
  evolution 
  of 
  the 
  earth 
  

   Chamberlin 
  postulated 
  the 
  eruption 
  of 
  its 
  mass 
  from 
  the 
  sun 
  as 
  a 
  

   result 
  of 
  the 
  enormous 
  expulsive 
  activities 
  of 
  the 
  sun, 
  stimulated 
  by 
  

   the 
  attraction 
  of 
  the 
  passing 
  star. 
  This 
  concept 
  he 
  has 
  described 
  as 
  

   "the 
  soul 
  of 
  the 
  planetesimal 
  theory." 
  

  

  