﻿452 
  

  

  ON 
  THE 
  RELATIVE 
  HORIZONTAL 
  INTENSITIES 
  

  

  RELATIVE 
  INTENSITIES 
  AT 
  NEW 
  YORK 
  AND 
  PHILADELPHIA. 
  

  

  The 
  observations 
  to 
  be 
  presented 
  belong 
  to 
  both 
  series. 
  Those 
  

   of 
  the 
  first 
  are 
  retained 
  as 
  second 
  in 
  number 
  to 
  the 
  Philadelphia 
  and 
  

   West 
  Point 
  observations 
  of 
  the 
  same 
  series. 
  The 
  observations 
  of 
  the 
  

   first 
  series 
  were 
  made 
  in 
  April 
  and 
  in 
  August 
  1834. 
  In 
  the 
  first 
  set 
  

   I 
  had 
  the 
  kind 
  assistance 
  of 
  professor 
  Renwick; 
  the 
  times 
  were 
  ob- 
  

   served 
  with 
  a 
  pocket 
  chronometer 
  belonging 
  to 
  him, 
  the 
  rate 
  of 
  which 
  

   was 
  ascertained, 
  but 
  was 
  not 
  such 
  as 
  to 
  affect 
  the 
  results 
  sensibly. 
  At 
  

   his 
  suggestion 
  the 
  observations 
  made 
  at 
  Columbia 
  College 
  green 
  were 
  

   checked 
  by 
  a 
  set 
  made 
  near 
  Belle 
  vue. 
  Another 
  set 
  was 
  made 
  in 
  the 
  

   north 
  part 
  of 
  the 
  city, 
  but 
  there 
  appeared 
  no 
  difference 
  of 
  local 
  attrac- 
  

   tion 
  in 
  the 
  three 
  places. 
  The 
  pocket 
  chronometer 
  used 
  in 
  the 
  Au- 
  

   gust 
  observations 
  was 
  of 
  good 
  character. 
  

  

  TABLE 
  No. 
  X. 
  

  

  Observations 
  at 
  New 
  York. 
  — 
  First 
  Series. 
  

  

  o 
  

   s 
  . 
  

  

  •ate 
  

  

  OS 
  

   0) 
  

  

  Q 
  

  

  > 
  

   M 
  

   GJ 
  

  

  ta 
  

  

  og 
  

  

  t« 
  • 
  -3 
  

   O 
  *^ 
  

  

  o 
  

   Q 
  

  

  o 
  .5 
  

  

  B.S 
  

  

  n 
  

  

  CfH 
  

  

  o 
  

   p 
  

  

  fai 
  CU 
  

   O 
  0) 
  

  

  1* 
  

  

  GJ 
  

  

  J} 
  

   '3 
  

  

  GO 
  

  

  ? 
  CO 
  

  

  cu 
  w 
  

  

  Q 
  

   3 
  

  

  z, 
  

  

  Arc 
  at 
  Begin- 
  

   ning 
  and 
  End. 
  

  

  Observed 
  Time 
  

   of 
  Ten 
  Vibra- 
  

   tions. 
  

   Time 
  of 
  Ten 
  

   Vibrations 
  cor- 
  

   rected 
  for 
  Arc 
  

   and 
  Tempera- 
  

   ture. 
  

  

  Weather, 
  &.c. 
  

  

  Observers 
  and 
  Places 
  of 
  

   Observation. 
  

  

  Hours. 
  

  

  Fah.° 
  

  

  Degs. 
  Sees. 
  

  

  Sees. 
  

  

  No. 
  1. 
  

  

  U 
  

  

  a 
  

  

  1834. 
  

   April 
  25 
  

   u 
  ti 
  

   ii 
  a 
  

   « 
  24 
  

  

  A.M. 
  8.0 
  

   " 
  8.5 
  

  

  P.M. 
  12.6 
  

   " 
  6.1 
  

  

  42 
  

  

  i< 
  

  

  44.5 
  

   50 
  

  

  330 
  

   320 
  

   350 
  

   280 
  

  

  25 
  a 
  5 
  

  

  it 
  

   ii 
  

   u 
  

  

  46.03 
  

   46.05 
  

   46.20 
  

   46.24 
  

  

  46.24 
  

   46.26 
  

   46.36 
  

   46.28 
  

  

  Wind 
  N. 
  W. 
  

   Nimb. 
  & 
  Snow. 
  

   Slight 
  Rain. 
  

   W'dhighN.W. 
  

  

  Prof. 
  Bache 
  & 
  Renwick. 
  

  

  Col. 
  College 
  Green. 
  

   Bache. 
  Rose 
  hill. 
  

   Bache. 
  No. 
  31. 
  5th 
  St. 
  

  

  a 
  

  

  August 
  7 
  A. 
  M. 
  6.2 
  

  

  76 
  

  

  548 
  

  

  20 
  a 
  3 
  

  

  46.98 
  

  

  46.56 
  

  

  Clear. 
  N. 
  W. 
  

  

  Bache. 
  Colum. 
  College 
  

   Green. 
  

  

  Needle 
  No. 
  1 
  ; 
  No. 
  of 
  Vibrations 
  1823; 
  Time 
  of 
  10 
  Vibrations 
  at 
  60°, 
  reduced 
  for 
  Arc, 
  4G.340 
  Sees. 
  

  

  Comparing 
  this 
  result 
  with 
  the 
  mean 
  time 
  of 
  No. 
  1 
  at 
  Philadel- 
  

   phia, 
  we 
  have 
  the 
  relative 
  horizontal 
  intensity 
  at 
  New 
  York, 
  .97202. 
  

   The 
  time 
  of 
  ten 
  oscillations 
  as 
  observed 
  in 
  August, 
  indicates 
  a 
  real 
  

   diminution 
  of 
  intensity 
  in 
  the 
  magnetism 
  of 
  the 
  needle 
  or 
  of 
  the 
  earth. 
  

   The 
  observations 
  at 
  Philadelphia 
  do 
  not 
  indicate 
  a 
  change 
  in 
  the 
  mag- 
  

   netism 
  of 
  the 
  needle, 
  we 
  have 
  therefore 
  retained 
  this 
  result, 
  and 
  used 
  

   it 
  in 
  obtaining 
  the 
  mean. 
  

  

  