﻿Horizontal 
  Intensity 
  of 
  the 
  Earth's 
  Magnetic 
  Field. 
  11Z 
  

  

  fields, 
  two 
  slightly 
  larger 
  than, 
  and 
  one 
  slightly 
  smaller 
  

   than 
  the 
  earth's 
  field, 
  were 
  made, 
  one 
  o£ 
  which 
  is 
  detailed 
  

   above. 
  The 
  results 
  of 
  the 
  other 
  two 
  calculated 
  exactly 
  as 
  

   above 
  were 
  as 
  follows 
  : 
  — 
  

  

  Time 
  of 
  swing 
  t 
  x 
  =2*7513 
  seconds 
  

   Current 
  giving 
  this 
  = 
  '014492 
  ampere 
  

   H 
  = 
  -17193. 
  

  

  Time 
  of 
  swing 
  t 
  Y 
  =2*7597 
  seconds 
  

  

  Current 
  to 
  produce 
  this 
  = 
  '014416 
  ampere 
  

   H= 
  -17185. 
  

  

  Taking 
  the 
  mean 
  of 
  these 
  three 
  values 
  we 
  get 
  

  

  H 
  = 
  -17188 
  . 
  

  

  Time 
  of 
  second 
  experiment 
  was 
  

  

  1.15 
  A.M.-2.45 
  a.m. 
  April 
  9th, 
  1913. 
  

  

  The 
  magnet 
  used 
  in 
  this 
  experiment 
  was 
  stronger 
  than 
  

   the 
  one 
  used 
  in 
  the 
  last, 
  and 
  the 
  timing 
  of 
  the 
  oscillations 
  

   consequently 
  more 
  reliable. 
  

  

  Time 
  of 
  swing 
  in 
  earth's 
  field 
  =2-5026 
  seconds. 
  

  

  Time 
  of 
  swing 
  t 
  x 
  =2*4912 
  seconds 
  

  

  Current 
  required 
  to 
  produce 
  this 
  = 
  '014541 
  ampere 
  

  

  H= 
  -172U. 
  

  

  Time 
  of 
  swing 
  t 
  x 
  =2*5010 
  seconds 
  

  

  Current 
  required 
  to 
  give 
  this 
  = 
  "0144852 
  ampere 
  

  

  H 
  = 
  - 
  17209. 
  

  

  Time 
  of 
  swing 
  ^ 
  =2' 
  5055 
  seconds 
  

  

  Current 
  required 
  to 
  give 
  this 
  = 
  '014459 
  ampere 
  

  

  H= 
  -17216. 
  

   Giving 
  on 
  the 
  average 
  

  

  H 
  = 
  -17213 
  . 
  

  

  As 
  a 
  check 
  on 
  the 
  values 
  obtained 
  " 
  H 
  " 
  was 
  determined 
  

   by 
  the 
  Kew 
  T 
  magnetometer 
  in 
  the 
  same 
  room 
  and 
  at 
  about 
  

   the 
  same 
  time 
  of 
  the 
  night. 
  An 
  experienced 
  observer, 
  Mr. 
  

   Southern, 
  performed 
  this 
  latter 
  experiment, 
  and 
  he 
  obtained 
  

   the 
  value 
  H 
  = 
  *1726. 
  His 
  work 
  was 
  carried 
  out 
  about 
  the 
  

   end 
  of 
  January, 
  so 
  that 
  coincidence 
  of 
  results 
  could 
  not 
  be 
  

   expected. 
  Apart 
  from 
  the 
  possible 
  actual 
  alteration 
  in 
  H 
  

  

  Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  154. 
  Oct. 
  1913. 
  3 
  F 
  

  

  