﻿OF 
  THE 
  HORIZONTAL 
  NEEDLE. 
  

  

  noon 
  to 
  midnight 
  of 
  the 
  30th 
  of 
  August 
  are 
  in 
  one 
  column; 
  and 
  in 
  

   the 
  parallel 
  column, 
  those 
  from 
  midnight 
  to 
  noon 
  of 
  the 
  31st. 
  

  

  TABLE 
  II. 
  

  

  Hour. 
  

  

  Variation. 
  

   N. 
  Pole 
  W. 
  

  

  Temp. 
  

  

  Remarks. 
  

  

  Hour. 
  

  

  Variation. 
  

   N. 
  Pole 
  W. 
  

  

  Temp. 
  

  

  Remarks. 
  

  

  

  Deg 
  

  

  . 
  Min. 
  

  

  Deg. 
  

  

  

  

  

  Deg 
  

  

  •. 
  Min. 
  

  

  Deg. 
  

  

  

  12 
  M. 
  

  

  3 
  

  

  26.2 
  

  

  7S| 
  

  

  Aug. 
  30. 
  Clear. 
  

   C 
  Sun 
  under 
  cloud. 
  

  

  12 
  

  

  m. 
  

  

  3 
  

  

  26.9 
  

  

  71| 
  

  

  Aug. 
  31. 
  Fog. 
  

   fFog. 
  Thermom. 
  

   hung 
  near 
  needle 
  

  

  1 
  P.M. 
  

  

  3 
  

  

  25.8 
  

  

  80| 
  

  

  < 
  Sky 
  generally 
  

   { 
  clear. 
  

  

  1 
  

  

  A.M. 
  

  

  3 
  

  

  25.4 
  

  

  70f 
  

  

  <{ 
  box. 
  Temp, 
  the 
  

   same 
  as 
  before 
  

   (^ 
  removal. 
  

  

  2 
  P.M. 
  

  

  3 
  

  

  25.8 
  

  

  79* 
  

  

  Clear. 
  

  

  2 
  

  

  A.M. 
  

  

  3 
  

  

  23.8 
  

  

  711 
  

  

  

  3 
  P.M. 
  

  

  3 
  

  

  27.0 
  

  

  80 
  

  

  Clear. 
  

  

  3 
  

  

  A.M. 
  

  

  3 
  

  

  22.2 
  

  

  71f 
  

  

  

  41 
  P.M. 
  

  

  3 
  

  

  23.9 
  

  

  811 
  

  

  Clear. 
  

  

  4 
  

   5 
  

  

  A.M. 
  

   A.M. 
  

  

  3 
  

   3 
  

  

  22.2 
  

   21.0 
  

  

  711 
  

   71# 
  

  

  

  51 
  P.M. 
  

  

  3 
  

  

  23.9 
  

  

  79^ 
  

  

  Clear. 
  

  

  5i 
  

  

  6 
  

  

  A.M. 
  

   A.M. 
  

  

  3 
  

   3 
  

  

  20.3 
  

   20.7 
  

  

  724 
  

   721 
  

  

  Hazy. 
  

  

  61 
  P.M. 
  

  

  3 
  

  

  21.9 
  

  

  751 
  

  

  8 
  

  

  Clear. 
  

  

  61 
  

  

  A.M. 
  

  

  3 
  

  

  19.9 
  

  

  72 
  

  

  Mist. 
  

  

  7 
  P.M. 
  

  

  3 
  

  

  19.9 
  

  

  73| 
  

  

  Clear. 
  

  

  71 
  

  

  A.M. 
  

  

  3 
  

  

  18.7 
  

  

  721 
  

  

  

  8 
  P.M. 
  

  

  3 
  

  

  26.2 
  

  

  73 
  

  

  Sky 
  cloudless. 
  

  

  8 
  

  

  A.M. 
  

  

  3 
  

  

  19.1 
  

  

  

  

  9 
  P.M. 
  

  

  3 
  

  

  28.5 
  

  

  71| 
  

  

  Sky 
  cloudless. 
  

  

  9 
  

  

  A.M. 
  

  

  3 
  

  

  18.7 
  

  

  77f 
  

  

  C 
  Sun 
  gleams 
  out. 
  

  

  10 
  P.M. 
  

  

  3 
  

  

  28.5 
  

  

  701 
  

  

  Sky 
  cloudless. 
  

   C 
  Stars 
  not 
  visible 
  

  

  10 
  

  

  A.M. 
  

  

  3 
  

  

  19.9 
  

  

  771 
  

  

  <j 
  Therm, 
  remov- 
  

   £ 
  ed 
  to 
  house. 
  

   C 
  Sun 
  out. 
  Cumu- 
  

   i 
  lus. 
  

  

  C 
  Variation 
  greater 
  

   I 
  than 
  at 
  11. 
  

  

  11 
  P.M. 
  

  

  n 
  

   O 
  

  

  26.9 
  

  

  70§ 
  

  

  < 
  through 
  fog. 
  

  

  11 
  

  

  A.M. 
  

  

  3 
  

  

  23.8 
  

  

  80f 
  

  

  m 
  P.M. 
  

  

  3 
  

  

  26.9 
  

  

  711 
  

  

  £ 
  Wind 
  variable. 
  

  

  111 
  

  

  A.M. 
  

  

  

  

  

  12 
  m. 
  

  

  3 
  

  

  26.9 
  

  

  711 
  

  

  

  12 
  

  

  M. 
  

  

  3 
  

  

  26.3 
  

  

  811 
  

  

  c 
  Cumulus. 
  Sky 
  

   I 
  generally 
  clear. 
  

  

  The 
  curves 
  in 
  No. 
  2, 
  Plate 
  I.*, 
  are 
  those 
  of 
  the 
  variation 
  and 
  tem- 
  

   perature 
  from 
  the 
  table 
  just 
  given. 
  We 
  see 
  that 
  the 
  general 
  features 
  are 
  

   the 
  same, 
  but 
  the 
  details 
  vary 
  very 
  much. 
  We 
  may 
  trace 
  the 
  causes 
  

   of 
  these 
  variations 
  in 
  the 
  curves 
  of 
  temperature, 
  though 
  the 
  knowledge 
  

   which 
  we 
  possess 
  on 
  the 
  subject 
  of 
  the 
  variation 
  of 
  the 
  needle 
  does 
  not 
  

   permit 
  us 
  to 
  do 
  so 
  for 
  it. 
  Both 
  days 
  were 
  clear 
  about 
  noon, 
  with 
  flying 
  

   clouds 
  (cumulus) 
  ; 
  the 
  second 
  was 
  a 
  day 
  of 
  settled 
  weather 
  succeeding 
  

   the 
  first, 
  and 
  the 
  maximum 
  temperature 
  was 
  higher 
  ; 
  but 
  about 
  noon 
  

   in 
  No. 
  2, 
  the 
  sun 
  was 
  frequently 
  obscured 
  by 
  clouds, 
  and 
  the 
  hour 
  

   of 
  maximum 
  was 
  removed 
  to 
  between 
  4 
  and 
  5 
  P.M. 
  No. 
  1 
  was 
  de- 
  

  

  