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  Hubert 
  Anson 
  Newton. 
  

  

  The 
  results 
  of 
  these 
  investigations 
  appeared 
  in 
  an 
  elaborate 
  

   memoir 
  " 
  On 
  Snooting 
  Stars," 
  which 
  was 
  read 
  to 
  the 
  National 
  

   Academy 
  in 
  1864, 
  and 
  appeared 
  two 
  years 
  later 
  in 
  the 
  

   Memoirs 
  of 
  the 
  Academy.* 
  An 
  abstract 
  was 
  given 
  in 
  this 
  

   Journal 
  in 
  1865. 
  f 
  The 
  following 
  are 
  some 
  of 
  the 
  subjects 
  

   treated, 
  with 
  some 
  of 
  the 
  more 
  interesting 
  results 
  : 
  

  

  The 
  distribution 
  of 
  the 
  apparent 
  paths 
  of 
  shooting 
  stars 
  in 
  

   azimuth 
  and 
  altitude. 
  

  

  The 
  vertical 
  distribution 
  of 
  the 
  luminous 
  part 
  of 
  the 
  real 
  

   paths. 
  The 
  value 
  found 
  for 
  the 
  mean 
  height 
  of 
  the 
  middle 
  

   point 
  of 
  the 
  luminous 
  path 
  was 
  a 
  trifle 
  less 
  than 
  sixty 
  miles. 
  

  

  The 
  mean 
  length 
  of 
  apparent 
  paths. 
  

  

  The 
  mean 
  distance 
  of 
  paths 
  from 
  the 
  observer. 
  

  

  The 
  mean 
  foreshortening 
  of 
  paths. 
  

  

  The 
  mean 
  length 
  of 
  the 
  visible 
  part 
  of 
  the 
  real 
  paths. 
  

  

  The 
  mean 
  time 
  of 
  flight 
  as 
  estimated 
  by 
  observers. 
  

  

  The 
  distribution 
  of 
  the 
  orbits 
  of 
  meteoroids 
  in 
  the 
  solar 
  

   system. 
  

  

  The 
  daily 
  number 
  of 
  shooting 
  stars, 
  and 
  the 
  density 
  of 
  the 
  

   meteoroides 
  in 
  the 
  space 
  which 
  the 
  earth 
  traverses. 
  The 
  aver- 
  

   age 
  number 
  of 
  shooting 
  stars 
  which 
  enter 
  the 
  atmosphere 
  

   daily, 
  and 
  which 
  are 
  large 
  enough 
  to 
  be 
  visible 
  to 
  the 
  naked 
  

   eye, 
  if 
  the 
  sun, 
  moon 
  and 
  clouds 
  would 
  permit 
  it, 
  is 
  more 
  

   than 
  seven 
  and 
  a 
  half 
  millions. 
  Certain 
  observations 
  with 
  

   instruments 
  seem 
  to 
  indicate 
  that 
  this 
  number 
  should 
  be 
  

   increased 
  to 
  more 
  than 
  four 
  hundred 
  millions, 
  to 
  include 
  tele- 
  

   scopic 
  shooting 
  stars, 
  and 
  there 
  is 
  no 
  reason 
  to 
  doubt 
  that 
  an 
  

   increase 
  of 
  optical 
  power 
  beyond 
  that 
  employed 
  in 
  these 
  obser- 
  

   vations 
  would 
  reveal 
  still 
  larger 
  numbers 
  of 
  these 
  small 
  bodies. 
  

   In 
  each 
  volume 
  of 
  the 
  size 
  of 
  the 
  earth, 
  of 
  the 
  space 
  which 
  

   the 
  earth 
  is 
  traversing 
  in 
  its 
  orbit 
  about 
  the 
  sun, 
  there 
  are 
  as 
  

   many 
  as 
  thirteen 
  thousand 
  small 
  bodies, 
  each 
  of 
  which 
  is 
  such 
  

   as 
  would 
  furnish 
  a 
  shooting 
  star 
  visible 
  under 
  favorable 
  cir- 
  

   cumstances 
  to 
  the 
  naked 
  eye. 
  

  

  These 
  conclusions 
  are 
  certainly 
  of 
  a 
  startling 
  character, 
  but 
  not 
  

   of 
  greater 
  interest 
  than 
  those 
  relating 
  to 
  the 
  velocity 
  of 
  

   meteoroids. 
  There 
  are 
  two 
  velocities 
  to 
  be 
  considered, 
  which 
  

   are 
  evidently 
  connected, 
  the 
  velocity 
  relative 
  to 
  the 
  earth, 
  and 
  

   the 
  velocity 
  of 
  the 
  meteoroids 
  in 
  the 
  solar 
  system. 
  To 
  the 
  lat- 
  

   ter, 
  great 
  interest 
  attaches 
  from 
  the 
  fact 
  that 
  it 
  determines 
  the 
  

   nature 
  of 
  the 
  orbit 
  of 
  the 
  meteoroid. 
  A 
  velocity 
  equal 
  to 
  that 
  

   of 
  the 
  earth, 
  indicates 
  an 
  orbit 
  like 
  that 
  of 
  the 
  earth 
  ; 
  a 
  velocity 
  

   y/2 
  times 
  as 
  great, 
  a 
  parabolic 
  orbit 
  like 
  that 
  of 
  most 
  comets, 
  

   while 
  a 
  velocity 
  greater 
  than 
  this 
  indicates 
  a 
  hyperbolic 
  orbit. 
  

  

  Professor 
  Newton 
  sought 
  to 
  form 
  an 
  estimate 
  of 
  this 
  criti- 
  

   cal 
  quantity 
  in 
  more 
  than 
  one 
  way. 
  That 
  on 
  which 
  he 
  placed 
  

  

  * 
  Yol. 
  i, 
  3d 
  memoir. 
  f 
  II, 
  xxxix, 
  193. 
  

  

  