﻿474 
  G. 
  C. 
  Comstock 
  — 
  The 
  Secular 
  Variation 
  of 
  Latitudes. 
  

  

  with 
  the 
  prime 
  vertical 
  transit 
  by 
  botli 
  06m 
  and 
  Nyren, 
  the 
  

   epochs 
  of 
  their 
  respective 
  observations 
  being 
  in 
  the 
  mean 
  1862 
  

   and 
  1881. 
  Auwers 
  has 
  published 
  proper 
  motions 
  for 
  all 
  of 
  

   these 
  stars 
  save 
  one 
  for 
  which 
  I 
  adopt 
  Nyren's 
  value 
  and 
  com- 
  

   paring 
  the 
  declinations 
  observed 
  at 
  the 
  two 
  epochs 
  I 
  find 
  for 
  

   the 
  variation 
  of 
  the 
  latitude 
  between 
  1862 
  and 
  1881 
  -0"*12, 
  or 
  

   Annual 
  Variation 
  -0 
  //- 
  006, 
  agreeing 
  exactly 
  with 
  the 
  result 
  

   furnished 
  by 
  the 
  vertical 
  circle. 
  I 
  very 
  much 
  regret 
  that 
  I 
  

   have 
  not 
  had 
  access 
  to 
  the 
  results 
  of 
  observations 
  made 
  with 
  

   the 
  prime 
  vertical 
  transit 
  during 
  the 
  years 
  1840-1860 
  by 
  W. 
  

   Struve. 
  I 
  have, 
  however, 
  compared 
  the 
  declinations 
  of 
  the 
  

   three 
  stars 
  most 
  frequently 
  observed 
  during 
  this 
  period, 
  which 
  

   are 
  discussed 
  in 
  Nyren's 
  paper 
  Bestimrmong 
  der 
  Nutation 
  der 
  

   Erdachse, 
  with 
  Nyren's 
  observations 
  with 
  the 
  same 
  instrument. 
  

   From 
  375 
  observations 
  of 
  these 
  stars 
  at 
  the 
  mean 
  epoch. 
  1846 
  

   combined 
  with 
  113 
  observations 
  at 
  the 
  epoch 
  1881 
  using 
  

   Auwers' 
  proper 
  motions 
  I 
  find 
  

  

  Annual 
  variation 
  of 
  latitude, 
  -0 
  //, 
  094. 
  

  

  Each 
  star 
  shows 
  a 
  diminution 
  of 
  the 
  latitude. 
  These 
  results 
  

   derived 
  from 
  two 
  different 
  instruments 
  and 
  from 
  different 
  

   series 
  of 
  observations 
  with 
  these 
  instruments 
  seem 
  to 
  me 
  in- 
  

   explicable 
  on 
  any 
  other 
  hypothesis 
  than 
  that 
  of 
  a 
  change 
  of 
  

   latitude 
  and 
  I 
  adopt 
  as 
  the 
  rate 
  of 
  variation 
  at 
  Pulkowa 
  -0 
  //, 
  006 
  

   per 
  annum. 
  

  

  I 
  know 
  of 
  no 
  other 
  European 
  observatory 
  at 
  which 
  a 
  varia- 
  

   tion 
  of 
  latitude 
  can 
  be 
  established 
  in 
  an 
  equally 
  satisfactory 
  

   manner 
  and 
  the 
  only 
  one 
  to 
  which 
  reference 
  seems 
  required 
  is 
  

   Konigsberg. 
  Two 
  careful 
  determinations 
  of 
  the 
  latitude 
  of 
  

   the 
  E-epsold 
  meridian 
  circle 
  have 
  been 
  made 
  with 
  the 
  follow- 
  

   ing 
  results 
  : 
  

  

  Date. 
  

  

  Observer. 
  

  

  Latitude. 
  

  

  843-5 
  

  

  Bessel. 
  

  

  54° 
  42' 
  50"-56 
  = 
  h0"'03 
  

  

  SSY'O 
  

  

  Rahts. 
  

  

  50-43 
  dc 
  '04 
  

  

  No 
  investigation 
  of 
  a 
  possible 
  change 
  in 
  the 
  amount 
  of 
  the 
  

   refraction 
  between 
  the 
  two 
  epochs 
  appears 
  to 
  have 
  been 
  made, 
  

   but 
  in 
  spite 
  of 
  this 
  defect 
  the 
  precision 
  of 
  the 
  observations 
  and 
  

   the 
  care 
  with 
  which 
  the 
  instrumental 
  errors 
  were 
  investigated 
  

   together 
  with 
  the 
  Pulkowa 
  results 
  in 
  regard 
  to 
  the 
  refraction 
  

   seem 
  to 
  entitle 
  these 
  determinations 
  to 
  some 
  consideration. 
  I 
  

   therefore 
  adopt 
  for 
  Konigsberg 
  

  

  Annual 
  variation 
  of 
  latitude 
  , 
  -0"*003. 
  

  

  Turning 
  now 
  from 
  European 
  to 
  American 
  observatories 
  we 
  

   find 
  a 
  very 
  different 
  set 
  of 
  values. 
  I 
  shall 
  first 
  consider 
  the 
  

   latitude 
  of 
  the 
  Washburn 
  Observatory 
  at 
  Madison, 
  Wis., 
  as 
  

  

  