50 
Mr. Christie on the effects of temperature on 
To obtain from these corrected observations the diurnal 
variation of the terrestrial magnetic intensity, I take half the 
sum of the mean easterly and westerly arcs at different hours 
during the day as the mean azimuths of the points of equi- 
librium at those hours, and substituting these azimuths suc- 
cessively for (p in the equation (a), 
M — F (.004690814 + 000829329 cos.^ (p) = 0 , 
1 obtain the values of M in terms of F at those hours : 
dividing each of these values by the minimum value of M, 
which in every case appears to happen at about lo*' so"” in 
the morning, 1 obtain the relative terrestrial magnetic in- 
tensities at the times of observation. These results are con- 
tained in the following table. 
13 , Table of the mean Terrestrial Magnetic Intensities at different 
hours during the day, deduced from the preceding observations. 
Note. The observations were made within doors. 
14.1 0 
o-S 
u 5 * 
Mean of the Observations of 
May 22 , 23 , 24 , 25 , 26 . 
Mean of the Observations of 
May 27,28, 2 Q, 30 , 31 . 
Mean of the two 
sets. 
6 £ 
Azimuth of 
Terrestrial 
Azimuth of 
Terrestrial 
Terrestrial 
0 
the Points of 
Magnetic 
the Points of 
Magnetic 
Magneric 
Equilibrium. 
Intensity. 
Equilibrium. 
Intensity. 
Intensity. 
h. m. 
6 00 
o / 
8l 27.3 
1 .00175 
0 ' 
81 56.9 
I .00170 
I .00173 
7 30 
82 19.9 
I .00100 
82 27.4 
I .00128 
I .001 14 
9 00 
83 J 3‘9 
I .00031 
83 33-6 
I . 00046 
I .00039 
10 30 
83 40.5 
I .00000 
84 16.2 
I .00000 
I .00000 
Noon. 
82 22.8 
I .00096 
83 40*3 
r .00038 
1 .00067 
I 30 
81 43 -S 
I .00151 
82 39.5 
I .00112 
1 .00132 
3 00 
81 29.1 
I. 00173 
81 57.2 
I .00170 
I .00172 
4 30 
81 11.5 
I .00199 
82 10.8 
1 .00151 
I .00175 
6 00 
81 17.7 
I .00190 
81 41.7 
1 .00192 
I .00191 
7 30 
81 00.9 
I .00216 
81 20.5 
I .00224 
1 .00220 
9 30 
80 52.6 
1 .00229 
81 14.5 
1.00233 
1.00231 
1 1 20 
81 19.7 
I .00225 
I .00225 
