﻿1875.] 
  

  

  Transit 
  of 
  Venus 
  across 
  the 
  Sun. 
  

  

  381 
  

  

  There 
  is, 
  however, 
  an 
  incongruity 
  in 
  (4) 
  • 
  for 
  in 
  this 
  reduction 
  the 
  longi- 
  

   tude 
  of 
  Yenus 
  Station 
  is 
  taken 
  east 
  of 
  Greenwich 
  by 
  5 
  h 
  12 
  m 
  12 
  S 
  -2=H, 
  

   the 
  origin 
  for 
  Indian 
  longitude 
  being 
  adopted 
  at 
  5 
  h 
  20 
  m 
  57 
  s, 
  3 
  E. 
  for 
  

   Madras 
  Observatory. 
  Id 
  realit} 
  r 
  , 
  however, 
  H 
  refers 
  not 
  to 
  the 
  local 
  

   meridian 
  necessarily 
  adopted 
  in 
  (2), 
  but 
  to 
  a 
  concluded 
  meridian 
  of 
  origin 
  

   adopted 
  for 
  the 
  principal 
  triangulation 
  of 
  the 
  Great 
  Trigonometrical 
  

   Survey 
  at 
  Kalianpur, 
  whereas 
  the 
  times 
  (2) 
  refer 
  to 
  the 
  local 
  meridian, 
  

   as 
  alread} 
  r 
  stated. 
  Denoting 
  the 
  value 
  of 
  H 
  corresponding 
  to 
  the 
  local 
  

   meridian 
  by 
  H 
  15 
  we 
  may 
  find 
  (nearly) 
  H 
  x 
  — 
  H=7i 
  s 
  thus 
  : 
  — 
  Let 
  A 
  denote 
  

   the 
  azimuth 
  of 
  a 
  terrestrial 
  point 
  P 
  as 
  determined 
  by 
  observations 
  to 
  a 
  

   circumpolar 
  star 
  about 
  its 
  elongation, 
  and 
  A 
  c 
  the 
  corresponding 
  value 
  as 
  

   brought 
  up 
  by 
  the 
  triangulation 
  from 
  the 
  concluded 
  meridian 
  of 
  origin 
  ; 
  

   also 
  let 
  A 
  — 
  A 
  c 
  =a", 
  and 
  let 
  X 
  stand 
  for 
  the 
  latitude 
  of 
  P 
  ; 
  then 
  it 
  can 
  be 
  

   seen 
  that, 
  as 
  a 
  correction 
  to 
  (4), 
  

  

  h 
  s 
  =Z^L 
  cosec 
  A. 
  

   15 
  

  

  Now 
  a" 
  is 
  not 
  known 
  at 
  Venus 
  Station; 
  but. 
  at 
  Banog 
  Station, 
  distant 
  

   2-9 
  miles 
  W.N.W., 
  a" 
  = 
  — 
  14"-54. 
  Adopting 
  this 
  value, 
  we 
  find 
  h 
  s 
  = 
  + 
  l 
  s 
  -9, 
  

   and 
  the 
  true 
  Greenwich 
  mean 
  times 
  of 
  contact 
  become 
  

  

  h 
  m 
  s 
  

  

  1st 
  internal 
  contact 
  14 
  17 
  9 
  ^ 
  

  

  2nd 
  „ 
  „ 
  18 
  5 
  32-6 
  L 
  .... 
  (5) 
  

  

  2nd 
  external 
  „ 
  18 
  32 
  49-6 
  J 
  

  

  The 
  results 
  (5) 
  are 
  given 
  in 
  supercession 
  of 
  (4). 
  

   Dehra 
  Doon, 
  17th 
  Dec,, 
  1874. 
  

  

  [The 
  " 
  better 
  sketch 
  " 
  referred 
  to 
  in 
  the 
  author's 
  footnote 
  to 
  Note 
  No. 
  I. 
  

   (p. 
  256) 
  arrived 
  in 
  time 
  to 
  appear 
  in 
  that 
  Note, 
  and 
  is, 
  in 
  fact, 
  the 
  sketch 
  

   from 
  which 
  the 
  woodcut 
  on 
  p. 
  257 
  was 
  copied. 
  — 
  G. 
  G. 
  S.] 
  

  

  " 
  Appendix 
  to 
  Notes 
  on 
  Transit 
  of 
  Venus 
  across 
  the 
  Sun." 
  

   Received 
  January 
  11, 
  1875. 
  

  

  After 
  posting 
  my 
  Note 
  No. 
  I., 
  describing 
  the 
  phenomena 
  I 
  had 
  ob- 
  

   served 
  at 
  Mussoorie, 
  I 
  received, 
  on 
  12th 
  December, 
  1874, 
  a 
  communica- 
  

   tion 
  from 
  my 
  friend 
  the 
  Rev. 
  H. 
  D. 
  James, 
  M.A., 
  describing 
  briefly 
  what 
  

   he 
  had 
  seen 
  at 
  his 
  station 
  of 
  observation. 
  In 
  reply 
  I 
  made 
  inquiry 
  on 
  

   some 
  additional 
  points, 
  to 
  which 
  he 
  replied 
  on 
  14th 
  inst., 
  so 
  that 
  his 
  

   letter 
  has 
  just 
  reached 
  me. 
  Mr. 
  James 
  was 
  located 
  at 
  Chakrata, 
  on 
  the 
  

   Himalaya 
  Mountains, 
  at 
  a 
  height 
  of 
  7300 
  feet 
  above 
  the 
  sea, 
  in 
  lat. 
  N. 
  

   30° 
  43', 
  long. 
  E. 
  77° 
  54'. 
  His 
  station 
  is 
  distinctly 
  visible 
  from 
  Mussoorie 
  

   on 
  a 
  clear 
  day. 
  The 
  following 
  facts 
  are 
  taken 
  from 
  his 
  letters 
  above 
  

   mentioned, 
  and 
  appear 
  to 
  deserve 
  being 
  recorded, 
  more 
  particularly 
  from 
  

  

  