﻿38 
  Dr. 
  W. 
  M. 
  Hicks 
  on 
  the 
  Michel 
  son-Morley 
  

  

  These 
  results 
  are 
  represented 
  graphically 
  on 
  Plate 
  L 
  

   All 
  the 
  curves 
  give 
  distinct 
  evidence 
  of 
  a 
  cos 
  2a 
  effect, 
  

   except 
  noon 
  of 
  July 
  8, 
  and 
  possibly 
  of 
  6 
  p.m. 
  of 
  July 
  8 
  ; 
  the 
  

   latter 
  certainly 
  if 
  the 
  supposition 
  of 
  the 
  footnote 
  is 
  correct. 
  

   Moreover, 
  the 
  curves 
  clearly 
  show 
  that 
  the 
  observations 
  of 
  

   July 
  9, 
  11, 
  12 
  belong 
  to 
  one 
  type 
  (B 
  or 
  A), 
  and 
  those 
  of 
  

   July 
  8 
  to 
  the 
  other 
  (A 
  or 
  B). 
  The 
  last 
  curve 
  represents 
  the 
  

   average 
  of 
  all, 
  on 
  this 
  supposition. 
  That 
  is 
  the 
  value 
  of 
  the 
  

   ordinates 
  are 
  one-third 
  of 
  July 
  9 
  + 
  July 
  11— 
  July 
  8 
  and 
  

   July 
  9 
  + 
  July 
  12 
  -July 
  8. 
  

  

  . 
  The 
  evidence 
  is 
  also 
  strengthened 
  by 
  comparison 
  of 
  the 
  

   noon 
  and 
  p.m. 
  curves. 
  The 
  drift 
  at 
  6 
  p.m 
  would 
  be 
  at 
  right- 
  

   angles 
  to 
  that 
  at 
  noon, 
  consequently 
  we 
  should 
  expect 
  the 
  

   curve 
  to 
  be 
  shifted 
  half 
  a 
  period 
  (i. 
  e. 
  90°) 
  with 
  reference 
  to 
  

   the 
  first. 
  Now 
  in 
  the 
  p.m. 
  observations, 
  the 
  rotation 
  of 
  the 
  

   apparatus 
  was 
  in 
  the 
  opposite 
  direction 
  to 
  that 
  at 
  noon. 
  

   Consequently, 
  in 
  order 
  to 
  compare 
  the 
  curves, 
  the 
  numbers 
  for 
  

   the 
  p.m. 
  curves 
  should 
  be 
  read 
  backwards. 
  This 
  is 
  done 
  in 
  

   the 
  dotted 
  curves 
  in 
  PI. 
  I. 
  A 
  glance 
  at 
  the 
  curves 
  renders 
  

   evident 
  the 
  fact 
  that 
  the 
  shift 
  shown 
  is 
  of 
  the 
  right 
  character. 
  

   The 
  amplitude 
  of 
  the 
  p.m. 
  curve 
  should 
  be 
  less 
  than 
  that 
  of 
  

   the 
  noon 
  in 
  the 
  ratio 
  sin 
  2 
  X* 
  where 
  X 
  is 
  the 
  latitude. 
  

  

  The 
  preceding 
  attempt 
  to 
  get 
  rid 
  of 
  the 
  temperature 
  effect 
  

   is 
  not 
  proposed 
  as 
  one 
  which 
  gives 
  an 
  accurate 
  result. 
  The 
  

   object 
  is 
  to 
  show 
  that 
  the 
  observations 
  of 
  Michelson 
  and 
  Morley 
  

   do 
  give 
  an 
  affirmative 
  answer 
  to 
  the 
  question 
  " 
  Is 
  there 
  a 
  

   drift 
  of 
  sether 
  past 
  the 
  earth 
  ? 
  " 
  The 
  argument 
  is 
  sufficient 
  

   to 
  show 
  that 
  the 
  experiments 
  should 
  be 
  repeated 
  with 
  extreme 
  

   care 
  to 
  eliminate 
  temperature 
  errors, 
  and 
  if 
  possible 
  in 
  vacuo. 
  

   If 
  possible 
  the 
  absence 
  of 
  observers 
  would 
  be 
  desirable, 
  and, 
  

   for 
  the 
  reason 
  stated 
  in 
  § 
  15, 
  also 
  the 
  absence 
  of 
  reading- 
  

   telescopes. 
  We 
  have 
  seen 
  that 
  if 
  a 
  slit 
  is 
  used 
  for 
  the 
  light 
  

   source, 
  fringes 
  are 
  formed 
  on 
  a 
  screen 
  placed 
  in 
  any 
  position. 
  

   This 
  points 
  to 
  a 
  method 
  in 
  which 
  a 
  photographic 
  film 
  on 
  a 
  

   rotating 
  drum 
  is 
  exposed 
  automatically. 
  

  

  The 
  FitzGerald-Lorentz 
  Effect. 
  

  

  19. 
  Amongst 
  the 
  various 
  explanations 
  advanced 
  to 
  account 
  

   for 
  the 
  supposed 
  null 
  result 
  of 
  Michelson 
  and 
  Morley's 
  experi- 
  

   ment, 
  the 
  best 
  known 
  and 
  accepted 
  is 
  that 
  first 
  proposed, 
  I 
  

   believe, 
  by 
  G. 
  F. 
  Fitz 
  Gerald, 
  viz., 
  that 
  the 
  very 
  motion 
  of 
  a 
  

  

  * 
  That 
  is 
  supposing 
  the 
  component 
  of 
  the 
  drift 
  perpendicular 
  to 
  the 
  

   plane 
  of 
  the 
  apparatus 
  to 
  produce 
  no 
  effect. 
  It 
  probably 
  does 
  produce 
  

   an 
  effect, 
  however. 
  

  

  