﻿212 
  

  

  ON 
  THE 
  MAGNETIC 
  DIP 
  

  

  MAGNETIC 
  DIP 
  AT 
  NEW 
  YORK. 
  

  

  The 
  dip 
  was 
  observed 
  on 
  the 
  green 
  in 
  front 
  of 
  Columbia 
  College 
  

   nearly 
  in 
  the 
  position 
  in 
  which 
  the 
  observations 
  of 
  Captain 
  Sabine 
  were 
  

   made 
  in 
  December 
  1822. 
  The 
  kindness 
  of 
  Professor 
  Renwick 
  fur- 
  

   nished 
  the 
  means 
  of 
  rendering 
  the 
  observations 
  effective, 
  and 
  pointed 
  

   out 
  the 
  locality 
  where 
  those 
  of 
  Captain 
  Sabine 
  were 
  made. 
  

  

  The 
  latitude 
  of 
  New 
  York, 
  as 
  given 
  by 
  Mr 
  Paine, 
  is 
  40° 
  42' 
  40" 
  N. 
  

   and 
  the 
  longitude 
  74° 
  01 
  ; 
  08" 
  W. 
  

  

  Needle. 
  

  

  Observed 
  Dip. 
  

  

  Temp. 
  

  

  Date 
  of 
  Observation. 
  

  

  Observer. 
  

  

  Weather. 
  

  

  No. 
  1, 
  

  

  No. 
  2, 
  

  

  72° 
  48'.4 
  

   72 
  55 
  .0 
  

  

  80° 
  Fahr. 
  

  

  August 
  7, 
  1834, 
  

   H 
  A.M. 
  

  

  A. 
  D. 
  Bache. 
  

  

  Clear. 
  

   Wind 
  N. 
  W. 
  

  

  Mean, 
  

  

  72 
  51 
  .7 
  

  

  | 
  

  

  i 
  

  

  

  The 
  dip 
  observed 
  by 
  Captain 
  Sabine 
  was 
  73° 
  00'.5. 
  A 
  comparison 
  of 
  

   the 
  result 
  just 
  given 
  with 
  this, 
  shows 
  a 
  difference 
  of 
  8'.8, 
  which, 
  if 
  

   we 
  were 
  certain 
  that 
  the 
  decrease 
  had 
  been 
  progressive, 
  would 
  indicate 
  

   a 
  diminution 
  of 
  about 
  nine 
  minutes 
  in 
  the 
  interval 
  of 
  twelve 
  years. 
  

   This 
  seems, 
  however, 
  from 
  the 
  results 
  obtained 
  at 
  West 
  Point, 
  and 
  next 
  

   to 
  be 
  given, 
  not 
  to 
  have 
  been 
  the 
  case, 
  observations 
  there, 
  indicating 
  a 
  

   slight 
  increase 
  from 
  April 
  to 
  July 
  1834. 
  The 
  decision 
  of 
  this 
  ques- 
  

   tion 
  must 
  be 
  left 
  to 
  future 
  observations. 
  

  

  MAGNETIC 
  DIP 
  AT 
  WEST 
  POINT, 
  NEW 
  YORK. 
  

  

  The 
  greatest 
  number 
  of 
  observations 
  made 
  at 
  any 
  one 
  of 
  the 
  places 
  

   at 
  which 
  we 
  have 
  observed, 
  were 
  made 
  at 
  West 
  Point, 
  latitude 
  41° 
  23' 
  

   35" 
  X., 
  and 
  longitude 
  74° 
  01' 
  W. 
  The 
  first 
  set 
  of 
  observations 
  was 
  

   taken 
  under 
  the 
  shelter 
  of 
  a 
  tent, 
  about 
  the 
  middle 
  of 
  the 
  plain 
  on 
  

   which 
  the 
  buildings 
  of 
  the 
  Military 
  Academy 
  are 
  situated 
  ; 
  the 
  others 
  

   on 
  a 
  brick 
  column, 
  raised 
  for 
  these 
  and 
  similar 
  observations, 
  to 
  the 
  

   north 
  of 
  the 
  residence 
  of 
  Professor 
  Courtenay. 
  

  

  The 
  following 
  table 
  contains 
  results 
  obtained 
  between 
  the 
  15th 
  of 
  

   April 
  1833, 
  and 
  July 
  14th, 
  1834. 
  It 
  seems 
  to 
  indicate 
  a 
  gradual 
  

  

  