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  Transactions. 
  — 
  Miscellaneous. 
  

  

  Comets 
  and 
  Solar 
  System. 
  

  

  It 
  is 
  almost 
  certain 
  that 
  the 
  initially 
  irregular 
  shape 
  of 
  the 
  two 
  coalesced 
  

   pieces 
  would 
  canse 
  many 
  smaller 
  masses 
  to 
  fly 
  off 
  into 
  space, 
  producing 
  

   possible 
  visitants 
  to 
  other 
  worlds, 
  but 
  in 
  most 
  cases 
  the 
  heat 
  would 
  be 
  

   sufficient 
  to 
  cause 
  all 
  these 
  masses 
  to 
  be 
  converted 
  into 
  gas. 
  

  

  When 
  two 
  bodies 
  of 
  different 
  size 
  attract 
  each 
  other, 
  the 
  velocity 
  

   acquired 
  by 
  the 
  smaller 
  body 
  will 
  be 
  greater 
  than 
  that 
  of 
  the 
  larger 
  one 
  (as 
  

   an 
  apple 
  falling 
  to 
  the 
  earth 
  does 
  not 
  give 
  the 
  earth 
  the 
  same 
  velocity 
  as 
  

   the 
  apple 
  itself 
  acquires). 
  With 
  unequal 
  bodies 
  therefore, 
  when 
  collision 
  

   occurs, 
  the 
  larger 
  piece 
  will 
  have 
  a 
  smaller 
  velocity 
  than 
  the 
  smaller, 
  hence 
  

   there 
  will 
  be 
  two 
  orders 
  of 
  fragments. 
  First, 
  from 
  the 
  small 
  piece, 
  the 
  high 
  

   velocity 
  of 
  which 
  may 
  make 
  comets 
  and 
  shooting 
  stars 
  of 
  them. 
  

  

  Pkmets. 
  

  

  Secondly, 
  the 
  fragments 
  of 
  the 
  larger 
  piece, 
  whose 
  small 
  velocity 
  may 
  

   not 
  take 
  these 
  bodies 
  away 
  from 
  effective 
  attraction, 
  and 
  they 
  may 
  thus 
  

   become 
  planets. 
  

  

  But 
  the 
  large 
  mass 
  of 
  our 
  sun 
  shows 
  that 
  if 
  the 
  planets 
  of 
  our 
  system 
  

   have 
  been 
  formed 
  in 
  this 
  way, 
  one 
  of 
  two 
  things 
  must 
  have 
  occurred, 
  either 
  

   the 
  original 
  proper 
  motion 
  of 
  the 
  bodies 
  must 
  have 
  been 
  very 
  much 
  greater 
  

   than 
  the 
  average 
  is 
  at 
  present, 
  or 
  the 
  bodies 
  themselves 
  must 
  have 
  been 
  

   very 
  large, 
  so 
  that 
  even 
  at 
  impact 
  the 
  centres 
  were 
  a 
  long 
  distance 
  from 
  

   each 
  other. 
  There 
  is, 
  however, 
  another 
  reason 
  why 
  at 
  impact 
  the 
  centres 
  

   may 
  have 
  been 
  at 
  a 
  distance 
  from 
  each 
  other 
  — 
  namely, 
  the 
  great 
  distortion 
  

   of 
  the 
  bodies 
  which 
  must 
  take 
  place 
  immediately 
  before 
  impact, 
  in 
  conse- 
  

   quence 
  of 
  their 
  mutual 
  attraction. 
  It 
  is 
  impossible 
  to 
  give 
  even 
  an 
  approxi- 
  

   mate 
  idea 
  of 
  how 
  much 
  this 
  may 
  influence 
  the 
  result. 
  Generally, 
  it 
  is 
  easy 
  

   to 
  see 
  that 
  the 
  problems 
  offered 
  by 
  partial 
  impact 
  are 
  of 
  extreme 
  difficulty, 
  

   the 
  data 
  being 
  of 
  necessity 
  of 
  infinite 
  variety. 
  

  

  It 
  is 
  shown 
  further 
  on, 
  that 
  there 
  is 
  another 
  partial 
  impact 
  hypothesis 
  

   which 
  may 
  possibly 
  explain 
  the 
  origin 
  of 
  our 
  system. 
  

  

  All 
  the 
  following 
  remarks 
  apply 
  equally 
  to 
  that 
  hyj^othesis 
  : 
  — 
  

  

  At 
  first 
  the 
  orbits 
  of 
  these 
  bodies 
  would 
  be 
  extraordinarily 
  eccentric 
  ; 
  

   on 
  passing 
  away 
  on 
  this 
  first 
  journey 
  they 
  would 
  be 
  in 
  advance 
  of 
  the 
  

   expelled 
  gas, 
  but 
  would 
  meet 
  it 
  on 
  returning. 
  This 
  would 
  tend 
  to 
  

   neutralise 
  the 
  force 
  of 
  attraction, 
  and 
  the 
  orbit 
  would 
  become 
  much 
  more 
  

   circular. 
  Again, 
  the 
  passage 
  of 
  the 
  planet 
  through 
  the 
  gas 
  would 
  retard 
  it. 
  

   And 
  lastly, 
  on 
  each 
  of 
  its 
  orbits 
  the 
  attraction 
  of 
  gravitation 
  would 
  be 
  

   greater 
  on 
  its 
  outward 
  journey 
  than 
  on 
  its 
  return, 
  in 
  consequence 
  of 
  the 
  

   expelled 
  matter 
  passing 
  outside 
  its 
  orbit 
  into 
  space. 
  This 
  fact 
  would 
  both 
  

   tend 
  to 
  render 
  the 
  orbit 
  more 
  circular, 
  and 
  also 
  tend 
  to 
  neutralise 
  the 
  action 
  

   of 
  the 
  gaseous 
  resistance 
  in 
  causing 
  the 
  body 
  to 
  approach 
  the 
  sun. 
  It 
  

  

  