﻿OF 
  TERRESTRIAL 
  MAGNETISM 
  AT 
  SEVERAL 
  PLACES, 
  ETC. 
  447 
  

  

  It 
  is 
  certain, 
  that 
  considerable 
  differences 
  in 
  local 
  attraction 
  exist 
  at 
  

   different 
  positions 
  of 
  this 
  highland 
  station. 
  The 
  place 
  of 
  observation 
  

   is 
  at 
  the 
  base 
  of 
  the 
  hills 
  which 
  inclose, 
  on 
  the 
  west, 
  the 
  table 
  laud 
  

   upon 
  which 
  the 
  buildings 
  of 
  the 
  Military 
  Academy 
  are 
  situated. 
  

  

  The 
  series 
  embracing 
  observations 
  at 
  different 
  hours 
  of 
  the 
  day, 
  with 
  

   different 
  states 
  of 
  weather, 
  &c, 
  are 
  the 
  more 
  valuable, 
  as 
  presenting 
  a 
  

   nearer 
  approximation 
  to 
  the 
  mean 
  intensity. 
  In 
  all 
  the 
  remarks 
  and 
  

   calculations 
  which 
  follow, 
  the 
  intensity 
  is 
  assumed 
  to 
  be 
  constant. 
  

  

  The 
  times, 
  at 
  West 
  Point, 
  were 
  observed 
  by 
  a 
  chronometer 
  by 
  Par- 
  

   kins 
  and 
  Frodsham, 
  of 
  excellent 
  character 
  : 
  those 
  at 
  Philadelphia 
  by 
  

   a 
  pocket 
  chronometer 
  by 
  Barraud, 
  and 
  by 
  one 
  by 
  French, 
  both 
  of 
  good 
  

   character. 
  The 
  daily 
  rates 
  were 
  too 
  small 
  to 
  produce 
  any 
  sensible 
  

   difference 
  by 
  correcting 
  the 
  observations 
  for 
  them. 
  

  

  In 
  the 
  following 
  table, 
  No. 
  VI., 
  the 
  first 
  column 
  contains 
  the 
  number 
  

   of 
  the 
  observation 
  ; 
  the 
  second, 
  the 
  designation 
  of 
  the 
  needle 
  ; 
  the 
  third, 
  

   the 
  date 
  of 
  observation 
  : 
  the 
  fourth, 
  the 
  time 
  of 
  beginning 
  ; 
  the 
  fifth, 
  

   the 
  duration 
  of 
  the 
  experiment 
  ; 
  the 
  sixth, 
  the 
  number 
  of 
  vibrations 
  ; 
  

   the 
  seventh, 
  the 
  mean 
  temperature 
  ; 
  the 
  eighth, 
  the 
  arcs 
  at 
  beginning 
  

   and 
  ending; 
  the 
  ninth, 
  the 
  duration 
  of 
  experiment 
  corrected 
  for 
  arc; 
  

   the 
  tenth, 
  the 
  duration 
  corrected 
  for 
  arc 
  and 
  temperature 
  ; 
  the 
  ele- 
  

   venth, 
  the 
  time 
  of 
  ten 
  vibrations 
  corrected 
  for 
  arc 
  and 
  temperature 
  ; 
  

   the 
  twelfth, 
  the 
  state 
  of 
  the 
  weather 
  ; 
  and 
  the 
  thirteenth, 
  the 
  names 
  

   of 
  the 
  observers. 
  

  

  The 
  table 
  of 
  observations 
  at 
  West 
  Point, 
  No. 
  VII., 
  is 
  arranged 
  in 
  a 
  

   very 
  similar 
  manner 
  to 
  that 
  just 
  described. 
  

  

  The 
  temperature 
  to 
  which 
  the 
  results 
  are 
  reduced 
  is 
  60° 
  Fab. 
  

  

  vol. 
  v. 
  — 
  5 
  P 
  

  

  