﻿366 
  Hubert 
  Anson 
  Newton. 
  

  

  give 
  an 
  orbit, 
  and 
  that 
  the 
  true 
  orbit 
  could 
  be 
  distinguished 
  

   from 
  the 
  other 
  four 
  by 
  the 
  calculation 
  of 
  the 
  secular 
  motion 
  

   of 
  the 
  node. 
  

  

  Professor 
  Adams 
  first 
  calculated 
  the 
  motion 
  of 
  the 
  node 
  due 
  

   to 
  the 
  attractions 
  of 
  Jupiter, 
  Venus, 
  and 
  the 
  Earth 
  for 
  the 
  orbit 
  

   having 
  a 
  period 
  of 
  354-6 
  days. 
  This 
  amounted 
  to 
  a 
  little 
  less 
  

   than 
  12' 
  in 
  33*25 
  years. 
  As 
  Professor 
  Newton 
  had 
  shown 
  that 
  

   the 
  dates 
  of 
  the 
  showers 
  require 
  a 
  motion 
  of 
  29 
  ; 
  in 
  33*25 
  years, 
  

   the 
  period 
  of 
  354*6 
  days 
  must 
  be 
  rejected. 
  The 
  case 
  would 
  be 
  

   nearly 
  the 
  same 
  with 
  a 
  period 
  of 
  376*6 
  days, 
  while 
  a 
  period 
  of 
  

   180 
  or 
  185*4 
  days 
  would 
  give 
  a 
  still 
  smaller 
  motion 
  of 
  the 
  

   node. 
  Hence, 
  of 
  the 
  five 
  possible 
  periods 
  indicated 
  by 
  Pro- 
  

   fessor 
  Newton, 
  four 
  were 
  shown 
  to 
  be 
  entirely 
  incompatible 
  

   with 
  the 
  motion 
  of 
  the 
  node, 
  and 
  it 
  only 
  remained 
  to 
  examine 
  

   whether 
  the 
  fifth 
  period, 
  viz 
  : 
  that 
  of 
  33*25 
  years, 
  would 
  

   give 
  a 
  motion 
  of 
  the 
  node 
  in 
  accordance 
  with 
  the 
  observed 
  

   value. 
  As 
  this 
  period 
  gives 
  a 
  very 
  long 
  ellipse 
  for 
  the 
  orbit, 
  

   extending 
  a 
  little 
  beyond 
  the 
  orbit 
  of 
  Uranus, 
  it 
  was 
  necessary 
  

   to 
  take 
  account 
  of 
  the 
  perturbations 
  due 
  to 
  that 
  planet 
  and 
  to 
  

   Saturn. 
  Professor 
  Adams 
  found 
  28' 
  for 
  the 
  motion 
  of 
  the 
  

   node. 
  As 
  this 
  value 
  must 
  be 
  regarded 
  as 
  sensibly 
  identical 
  

   with 
  Professor 
  Newton's 
  29' 
  of 
  observed 
  motion, 
  no 
  doubt 
  

   was 
  left 
  in 
  regard 
  to 
  the 
  period 
  of 
  revolution 
  or 
  the 
  orbit 
  of 
  

   the 
  meteoroids.* 
  

  

  About 
  this 
  time, 
  M. 
  Schiaparelli 
  was 
  led 
  by 
  a 
  course 
  of 
  rea- 
  

   soning 
  similar 
  to 
  Professor 
  Newton's 
  to 
  the 
  same 
  conclusion, 
  — 
  

   that 
  the 
  mean 
  velocity 
  of 
  the 
  meteoroids 
  is 
  not 
  very 
  different 
  

   from 
  that 
  due 
  to 
  parabolic 
  orbits. 
  In 
  the 
  course 
  of 
  his 
  specu- 
  

   lations 
  in 
  regard 
  to 
  the 
  manner 
  in 
  which 
  such 
  bodies 
  might 
  

   enter 
  the 
  solar 
  system, 
  the 
  questions 
  suggested 
  themselves: 
  

   whether 
  meteoroids 
  and 
  comets 
  may 
  not 
  have 
  a 
  similar 
  origin 
  ; 
  

   whether, 
  in 
  case 
  a 
  swarm 
  of 
  meteoroids 
  should 
  include 
  a 
  body 
  

   of 
  sufficient 
  size, 
  this 
  would 
  not 
  appear 
  as 
  a 
  comet 
  ; 
  and 
  whether 
  

   some 
  of 
  the 
  known 
  comets 
  may 
  not 
  belong 
  to 
  streams 
  of 
  

   meteoroids. 
  Calculating 
  the 
  orbit 
  of 
  the 
  Perseids, 
  or 
  August 
  

   meteoroids, 
  from 
  the 
  radiant 
  point, 
  with 
  the 
  assumption 
  of 
  a 
  

   nearly 
  parabolic 
  velocity, 
  he 
  found 
  an 
  orbit 
  very 
  similar 
  to 
  

   that 
  of 
  the 
  great 
  comet 
  of 
  1862, 
  which 
  may 
  therefore 
  be 
  

   considered 
  as 
  one 
  of 
  the 
  Perseids, 
  — 
  probably 
  the 
  largest 
  of 
  

   them 
  all.f 
  

  

  At 
  that 
  time 
  no 
  known 
  cometic 
  orbit 
  agreed 
  with 
  that 
  of 
  

   the 
  Leonids, 
  but 
  a 
  few 
  months 
  later, 
  as 
  soon 
  as 
  the 
  definitive 
  

   elements 
  of 
  the 
  orbit 
  of 
  the 
  first 
  comet 
  of 
  1866 
  were 
  published, 
  

   their 
  resemblance 
  to 
  those 
  of 
  the 
  Leonids, 
  as 
  calculated 
  for 
  the 
  

   period 
  of 
  33*25 
  years, 
  which 
  had 
  been 
  proved 
  to 
  be 
  the 
  correct 
  

  

  * 
  Monthly 
  Notices 
  Roy. 
  Ast. 
  Soc, 
  vol. 
  xxvii, 
  p. 
  247. 
  

   f 
  Entwurf, 
  etc., 
  pp. 
  49-54. 
  

  

  

  