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  ON 
  THE 
  RELATIVE 
  HORIZONTAL 
  INTENSITIES 
  

  

  times 
  of 
  vibration 
  resulting 
  from 
  differences 
  of 
  arc 
  are 
  entirely 
  in- 
  

   sensible. 
  

  

  We 
  proceed 
  now 
  to 
  give 
  the 
  observations 
  and 
  calculations 
  for 
  the 
  

   magnetic 
  intensity 
  at 
  the 
  several 
  places 
  named 
  in 
  the 
  title 
  of 
  our 
  me- 
  

   moir. 
  

  

  RELATIVE 
  HORIZONTAL 
  INTENSITIES 
  AT 
  PHILADELPHIA 
  AND 
  

  

  WEST 
  POINT. 
  

  

  Before 
  giving 
  the 
  tables 
  of 
  observations 
  at 
  these 
  two 
  places, 
  we 
  pro- 
  

   pose 
  to 
  state 
  the 
  different 
  occasions 
  on 
  which 
  the 
  observations 
  were 
  

   made. 
  

  

  First 
  Series. 
  

  

  The 
  first 
  observations 
  were 
  made 
  at 
  West 
  Point 
  on 
  the 
  21st 
  of 
  

   April 
  1834, 
  with 
  needle 
  No. 
  1. 
  This 
  needle 
  was 
  then 
  taken 
  to 
  

   Philadelphia, 
  its 
  rate 
  ascertained 
  (May 
  16th 
  and 
  20th), 
  and 
  the 
  needle 
  

   returned 
  to 
  West 
  Point, 
  where 
  it 
  was 
  observed, 
  at 
  intervals, 
  during 
  

   five 
  weeks 
  (from 
  June 
  2d 
  to 
  July 
  8th). 
  In 
  this 
  last 
  period 
  3558 
  os- 
  

   cillations 
  were 
  observed. 
  The 
  same 
  needle 
  was 
  oscillated 
  at 
  Philadel- 
  

   phia 
  on 
  the 
  5th 
  of 
  August, 
  at 
  West 
  Point 
  on 
  the 
  13th, 
  and 
  again 
  at 
  

   Philadelphia 
  on 
  the 
  20th 
  of 
  the 
  same 
  month. 
  These 
  repeated 
  trans- 
  

   fers 
  completely 
  guard 
  against 
  the 
  effect 
  of 
  change 
  of 
  rate 
  in 
  the 
  needle. 
  

  

  No. 
  3 
  was 
  first 
  oscillated 
  at 
  West 
  Point 
  on 
  the 
  23d 
  of 
  April, 
  and 
  

   again 
  between 
  the 
  28th 
  of 
  May 
  and 
  9th 
  of 
  June. 
  It 
  was 
  then 
  trans- 
  

   ferred 
  to 
  Philadelphia, 
  where 
  it 
  was 
  observed 
  on 
  the 
  26th 
  of 
  June 
  and 
  

   12th 
  of 
  July. 
  It 
  was 
  taken 
  to 
  West 
  Point 
  and 
  oscillated 
  on 
  the 
  7th 
  

   and 
  8th 
  of 
  August, 
  and 
  finally 
  observed 
  at 
  Philadelphia 
  on 
  the 
  20th 
  

   and 
  25th 
  of 
  August. 
  

  

  This 
  series 
  comprises 
  6478 
  oscillations 
  at 
  West 
  Point, 
  and 
  7069 
  at 
  

   Philadelphia. 
  

  

  The 
  observations 
  at 
  Philadelphia 
  were 
  made 
  at 
  two 
  different 
  places 
  

   in 
  the 
  city. 
  In 
  part 
  of 
  the 
  series 
  the 
  apparatus 
  was 
  placed 
  in 
  the 
  

   open 
  air 
  upon 
  a 
  marble 
  column, 
  and 
  in 
  the 
  other 
  part, 
  in 
  a 
  small 
  ob- 
  

   servatory 
  ; 
  both 
  in 
  the 
  yard 
  attached 
  to 
  professor 
  Bache's 
  dwelling. 
  

  

  The 
  observations 
  at 
  West 
  Point 
  were 
  made 
  upon 
  a 
  small 
  brick 
  

   column, 
  north 
  of 
  professor 
  Courtenay's 
  house. 
  

  

  