﻿G. 
  C. 
  Comstock 
  — 
  The 
  Secular 
  Variation 
  of 
  Latitudes. 
  477 
  

  

  agreeing 
  more 
  closely 
  than 
  could 
  be 
  expected 
  with 
  the 
  varia- 
  

   tion 
  indicated 
  by 
  the 
  meridian 
  circle, 
  while 
  the 
  several 
  latitudes 
  

   from 
  which 
  the 
  annual 
  variation 
  is 
  derived 
  show 
  the 
  following 
  

   astonishingly 
  close 
  agreement 
  when 
  reduced 
  by 
  it 
  to 
  a 
  common 
  

   epoch 
  : 
  

  

  Date. 
  

  

  Latitude. 
  1890-0. 
  

  

  Weight. 
  

  

  v. 
  

  

  73-6 
  

  

  43° 
  4' 
  37"'10 
  

  

  4-0 
  

  

  — 
  0"-03 
  

  

  81-6 
  

  

  37-11 
  

  

  0-6 
  

  

  — 
  '02 
  

  

  84-5 
  

  

  37*19 
  

  

  1-6 
  

  

  + 
  -06 
  

  

  89-3 
  

  

  37-16 
  

  

  0-5 
  

  

  + 
  '03 
  

  

  90-5 
  

  

  37-12 
  

  

  1-2 
  

  

  — 
  -01 
  

  

  91-5 
  

  

  37-13 
  

  

  2-8 
  

  

  •00 
  

  

  Since 
  these 
  two 
  independent 
  and 
  dissimilar 
  series 
  of 
  observa- 
  

   tions 
  indicate 
  the 
  same 
  variation 
  of 
  the 
  latitude 
  I 
  conclude 
  

   that 
  this 
  variation 
  is 
  real 
  and 
  I 
  adopt 
  for 
  Madison 
  

  

  Annual 
  variation 
  of 
  latitude 
  = 
  + 
  0"-043 
  

  

  If 
  such 
  a 
  variation 
  as 
  this 
  is 
  actually 
  in 
  progress 
  it 
  must 
  

   affect 
  other 
  latitudes 
  and 
  it 
  should 
  be 
  recognized 
  at 
  every 
  

   American 
  observatory 
  at 
  which 
  there 
  is 
  a 
  series 
  of 
  latitude 
  

   determinations 
  extending 
  over 
  a 
  considerable 
  number 
  of 
  years. 
  

   Unfortunately 
  very 
  few 
  such 
  series 
  of 
  observations 
  have 
  been 
  

   published, 
  the 
  Naval 
  Observatory 
  at 
  Washington 
  being 
  almost 
  

   the 
  only 
  institution 
  from 
  which 
  the 
  requisite 
  data 
  can 
  be 
  ob- 
  

   tained. 
  The 
  observations 
  made 
  here 
  with 
  the 
  mural 
  and 
  

   transit 
  circles 
  have 
  been 
  discussed 
  recently 
  by 
  Prof. 
  Hall 
  (A. 
  J., 
  

   No. 
  224) 
  who 
  concludes 
  that 
  "there 
  is 
  no 
  proof 
  of 
  a 
  secular 
  

   change 
  in 
  the 
  latitude." 
  So 
  far 
  as 
  this 
  conclusion 
  relates 
  to 
  the 
  

   meridian 
  instruments 
  of 
  the 
  observatory 
  I 
  concur 
  in 
  it, 
  but 
  

   Prof. 
  Hall 
  includes 
  in 
  his 
  discussion 
  a 
  comparison 
  of 
  the 
  decli- 
  

   nations 
  of 
  a 
  Lyrse 
  determined 
  with 
  the 
  prime 
  vertical 
  transit 
  

   in 
  the 
  years 
  1845, 
  '48 
  and 
  1862-'67, 
  and 
  with 
  reference 
  to 
  these 
  

   observations 
  I 
  dissent 
  from 
  his 
  conclusion 
  and 
  wish 
  to 
  present 
  

   in 
  some 
  detail 
  the 
  evidence 
  furnished 
  by 
  this 
  instrument 
  which 
  

   on 
  account 
  of 
  its 
  extreme 
  precision 
  and 
  its 
  freedom 
  from 
  sys- 
  

   tematic 
  error 
  seems 
  entitled 
  to 
  far 
  more 
  confidence 
  than 
  can 
  

   properly 
  be 
  accorded 
  to 
  the 
  meridian 
  instruments. 
  I 
  must 
  

   here 
  acknowledge 
  my 
  indebtedness 
  to 
  the 
  Superintendent 
  of 
  

   the 
  Naval 
  Observatory, 
  Capt. 
  F. 
  W. 
  McNair, 
  U. 
  S. 
  N., 
  who 
  

   has 
  placed 
  at 
  my 
  disposal 
  the 
  manuscript 
  results 
  of 
  unpublished 
  

   observations 
  made 
  with 
  this 
  instrument 
  in 
  the 
  years 
  1882-'84. 
  

  

  I 
  have 
  collated 
  all 
  the 
  observations 
  of 
  a 
  Lyrse, 
  including 
  

   fifty-eight 
  made 
  in 
  the 
  years 
  1846-'50, 
  but 
  omitted 
  from 
  Prof. 
  

   Hall's 
  data 
  ; 
  have 
  compared 
  them 
  with 
  Auwers' 
  declination 
  of 
  

   the 
  star 
  carried 
  back 
  to 
  the 
  epochs 
  to 
  which 
  the 
  observations 
  

  

  