﻿Experiment 
  relating 
  to 
  the 
  Drift 
  of 
  the 
  jiEtlier. 
  37 
  

  

  •errors. 
  I 
  have 
  applied 
  this 
  correction 
  to 
  the 
  published 
  

   means. 
  The 
  result 
  is 
  the 
  same 
  as 
  if: 
  the 
  correction 
  had 
  first 
  

   been 
  applied 
  to 
  each 
  series 
  and 
  the 
  results 
  then 
  averaged. 
  

   This 
  would 
  have 
  been 
  preferable 
  if 
  possible, 
  as 
  a 
  comparison 
  

   of 
  each 
  set 
  with 
  the 
  average 
  would 
  have 
  given 
  data 
  for 
  a 
  

   measure 
  of 
  the 
  probable 
  error. 
  

  

  To 
  illustrate 
  the 
  method 
  of 
  applying 
  this 
  correction, 
  I 
  give 
  

   here 
  the 
  working 
  of 
  the 
  6 
  p.m. 
  observations 
  on 
  July 
  8 
  : 
  — 
  

  

  I. 
  61-2, 
  63-3, 
  63-3*, 
  68-2, 
  67-7, 
  69-3, 
  70-3, 
  698, 
  69-0 
  

   II. 
  61-2, 
  62-1, 
  630, 
  639, 
  648, 
  657, 
  66'6, 
  67'5, 
  684 
  

  

  III. 
  

  

  I. 
  

   II. 
  

  

  II] 
  

  

  IV. 
  

  

  

  

  + 
  1-2 
  

  

  +'3 
  

  

  +4-3 
  

  

  -4-2-9 
  

  

  4-3-6 
  

  

  4-3-7 
  

  

  +2-3 
  

  

  4- 
  '6 
  

  

  69-0, 
  

   68-4, 
  

  

  71-3, 
  

   69-3, 
  

  

  71-3, 
  

   70-2, 
  

  

  70-5, 
  

   71-1, 
  

  

  71-2, 
  

   72-0, 
  

  

  71-2, 
  

   72-9, 
  

  

  70-5, 
  

  

  73-8, 
  

  

  72-5, 
  

   74-7, 
  

  

  75-7 
  

   75-7 
  

  

  +•6 
  

  

  

  

  +2-0 
  

   +1-2 
  

  

  + 
  11 
  

  

  + 
  •3 
  

  

  - 
  -6 
  

  

  +4'3 
  

  

  -•8 
  

   +2-9 
  

  

  -1-7 
  

  

  +3-6 
  

  

  -3-3 
  

  

  4-3-7 
  

  

  — 
  2*2 
  

  

  +2-3 
  

  

  4-0 
  

   +•6 
  

  

  •6 
  

  

  +3-2 
  

  

  +1-4 
  

  

  +3-7 
  

  

  +2-1 
  

  

  + 
  1-9 
  

  

  4- 
  -4 
  

  

  4-1 
  

  

  + 
  '6 
  

  

  Deduct! 
  v 
  _ 
  1#1 
  +1 
  . 
  5 
  _. 
  3 
  +2 
  . 
  Q 
  + 
  , 
  4 
  + 
  . 
  2 
  _ 
  1 
  . 
  ;3 
  _ 
  1>( 
  . 
  _ 
  vl 
  

  

  In 
  the 
  above, 
  line 
  I. 
  gives 
  the 
  published 
  observations. 
  

   Line 
  II. 
  gives 
  a 
  series 
  of 
  numbers, 
  increasing 
  by 
  equal 
  steps 
  

   from 
  61*2 
  to 
  75*7. 
  Line 
  III. 
  gives 
  the 
  differences 
  of 
  I. 
  & 
  II., 
  

   and 
  therefore, 
  according 
  to 
  our 
  supposition, 
  freed 
  from 
  the 
  

   temperature 
  errors. 
  Line 
  IV. 
  gives 
  the 
  mean 
  of 
  the 
  first 
  

   eight 
  and 
  the 
  last 
  eight, 
  and 
  therefore 
  eliminates 
  effects 
  

   depending 
  on 
  cos 
  a 
  (see 
  § 
  15). 
  Line 
  V. 
  is 
  the 
  result 
  obtained 
  

   by 
  deducting 
  1*7 
  from 
  each, 
  so 
  as 
  to 
  reduce 
  readings 
  to 
  give 
  

   deviations 
  from 
  the 
  mean, 
  1*7= 
  sum/8. 
  

  

  The 
  other 
  sets 
  are 
  treated 
  in 
  the 
  same 
  way. 
  The 
  results 
  

   are 
  as 
  follows 
  : 
  — 
  

  

  Noon 
  Observations. 
  

  

  July 
  8. 
  -l-0 
  + 
  0*2+i-2 
  + 
  0-7-r-2-8— 
  1-1 
  +0-2 
  +2-6- 
  1-0 
  

   July 
  9. 
  — 
  1-7-1-8— 
  0-2+0-3+0-4+1-1 
  + 
  2-2— 
  1-4-1-7 
  

   July 
  11. 
  0-9-2-2-2-1-2-7+0-3+2-0 
  + 
  1-9 
  + 
  1-7 
  + 
  0-9 
  

  

  p.m. 
  Observations. 
  

  

  July 
  8. 
  -M 
  + 
  l-5-0-3 
  + 
  2-0 
  + 
  0-4+0-2-1-3 
  — 
  1-6— 
  1-1 
  

   July 
  9. 
  -1-3-0-74-0-1-0-54-M 
  + 
  1-64-0-3-O6-1-3 
  

   July 
  12. 
  0-4-1-0-2-2-1-6-2-0-f 
  1-4+3-3+1-5 
  + 
  0-4 
  

  

  * 
  If 
  this 
  were 
  a 
  MS. 
  misreading 
  for 
  65-3, 
  the 
  correct 
  numbers 
  in 
  

   lines 
  III., 
  IV., 
  and 
  V. 
  would 
  be 
  2-3, 
  3-4, 
  and 
  1-7, 
  which, 
  as 
  a 
  glance 
  at 
  

   the 
  curve 
  in 
  Plate 
  I. 
  will 
  show, 
  would 
  make 
  the 
  curve 
  regular. 
  

  

  