﻿BicKEETON. 
  — 
  On 
  Par'Jal 
  finpaci, 
  12^ 
  

  

  is 
  a 
  well-known 
  fact, 
  that 
  if 
  a 
  projectile 
  revolves 
  on 
  one 
  axis 
  at 
  right 
  

   angles 
  to 
  the 
  line 
  of 
  motion, 
  there 
  is 
  a 
  tendency 
  to 
  move 
  in 
  a 
  curve. 
  

   (The 
  fall 
  discussion 
  of 
  this 
  phenomenon 
  would 
  occupy 
  much 
  time.) 
  Ifc 
  is 
  

   possible 
  to 
  show 
  that 
  this 
  force 
  afc 
  first 
  would 
  have 
  considerable 
  effect 
  in 
  

   rendering 
  the 
  orbits 
  circular, 
  but 
  finally 
  with 
  the 
  planets 
  near 
  the 
  sun 
  its 
  

   effect 
  may 
  he 
  to 
  render 
  the 
  orbits 
  more 
  elliptical. 
  All 
  these 
  forces, 
  there- 
  

   fore, 
  tend 
  to 
  render 
  the 
  orbits 
  more 
  circular, 
  hut 
  not 
  as 
  an 
  average 
  result 
  

   to 
  alter 
  their 
  mean 
  distance 
  from 
  the 
  sun. 
  The 
  larger 
  masses 
  would 
  

   suffer 
  less 
  resistance 
  in 
  proportion 
  than 
  the 
  smaller 
  ones, 
  and 
  the 
  general 
  

   result 
  would 
  be, 
  that 
  if 
  all 
  started 
  at 
  the 
  same 
  distance 
  the 
  smaller 
  bodies 
  

   would 
  be 
  brought 
  nearer 
  the 
  sun. 
  It 
  is 
  easy 
  to 
  see 
  that 
  the 
  centrifugal 
  

   force 
  and 
  the 
  attraction 
  of 
  nebulous 
  mass 
  would 
  cause 
  all 
  the 
  planets 
  to 
  

   travel 
  approximately 
  in 
  the 
  plane 
  of 
  the 
  ecliptic, 
  also 
  why 
  the 
  sun's 
  equator 
  

   so 
  nearly 
  approaches 
  it, 
  and 
  generally, 
  why 
  the 
  rotations 
  of 
  the 
  planets 
  on 
  

   their 
  axes 
  should 
  be 
  in 
  the 
  same 
  direction. 
  On 
  the 
  other 
  hand, 
  the 
  pressure 
  

   due 
  to 
  heat, 
  the 
  extreme 
  want 
  of 
  symmetry 
  of 
  such 
  a 
  case 
  of 
  partial 
  impact, 
  

   combined 
  with 
  the 
  original 
  motion 
  of 
  rotation 
  of 
  the 
  colliding 
  bodies, 
  if 
  they 
  

   had 
  any, 
  must 
  all 
  tell 
  in 
  the 
  ultimate 
  resultant 
  motion, 
  both 
  orbital 
  and 
  

   axial. 
  Almost 
  certainly 
  these 
  forces 
  would 
  produce 
  slightly 
  inclined 
  orbital 
  

   planes, 
  inclination 
  of 
  polar 
  axes 
  to 
  these 
  planes, 
  and 
  may 
  as 
  an 
  extreme 
  

   case 
  produce 
  a 
  retrograde 
  motion. 
  It 
  is 
  also 
  easy 
  to 
  see 
  that 
  the 
  enormous 
  

   atmospheres 
  of 
  those 
  early 
  days 
  would 
  effectually 
  clear 
  the 
  bodies 
  of 
  all 
  hut 
  

   very 
  large 
  masses 
  of 
  cosmical 
  dust. 
  

  

  llie 
  Asteroids. 
  

   This 
  fact 
  appears 
  of 
  itself 
  sufficient 
  to 
  show 
  that 
  the 
  production 
  of 
  the 
  

   asteroids 
  must 
  have 
  heen 
  a 
  subsequent 
  event 
  to 
  the 
  formation 
  of 
  the 
  solar 
  

   system. 
  With 
  respect 
  to 
  the 
  asteroids, 
  it 
  is 
  conceivable 
  that 
  the 
  destruction 
  

   of 
  the 
  planet 
  which 
  formed 
  them 
  may 
  have 
  been 
  produced 
  by 
  a 
  large 
  

   meteoric 
  visitant, 
  with 
  a 
  high 
  velocity. 
  This 
  hypothesis 
  shows 
  that 
  such 
  

   bodies 
  may 
  exist 
  in 
  considerable 
  numbers. 
  Such 
  a 
  mass 
  might 
  conceivably 
  

   bury 
  itself 
  in 
  another 
  body, 
  and 
  when 
  its 
  motion 
  of 
  mass 
  was 
  stopped, 
  its 
  

   heat 
  might 
  be 
  sufficient 
  to 
  produce 
  a 
  pressure 
  of 
  many 
  thousand 
  atmo- 
  

   spheres. 
  Such 
  an 
  explosion 
  of 
  developed 
  gas 
  might 
  reasonably 
  be 
  expected 
  

   to 
  blow 
  the 
  body 
  to 
  pieces. 
  It 
  is 
  generally 
  considered 
  that 
  if 
  the 
  asteroids 
  

   had 
  been 
  produced 
  by 
  the 
  destruction 
  of 
  a 
  planet, 
  the 
  fragments 
  Avould 
  

   have 
  the 
  same 
  mean 
  distance 
  from 
  the 
  sun, 
  and 
  would 
  pass 
  the 
  same 
  points 
  

   in 
  their 
  orbits 
  where 
  the 
  destruction 
  occurred 
  ; 
  which 
  is 
  contrary 
  to 
  the 
  

   observed 
  motions 
  of 
  these 
  bodies. 
  The 
  hypothesis 
  that 
  they 
  are 
  pieces 
  of 
  a 
  

   planet 
  is 
  therefore 
  not 
  generallj^ 
  accepted 
  ; 
  but 
  these 
  assumptions 
  are 
  only 
  

   true 
  if 
  the 
  velocity 
  remain 
  the 
  same, 
  the 
  eccentricity 
  of 
  the 
  orbit 
  the 
  same, 
  

   and 
  there 
  is 
  no 
  resisting 
  atmosphere. 
  The 
  first 
  of 
  these 
  assumptions 
  is 
  

  

  