on the Intensity of Magnetic Forces , 148 
time at which the observations concluded was noted. The tempe- 
rature of the water in the pans was now increased or diminished, 
according to circumstances, by the addition of other water, and 
the pans covered over, to prevent any rapid changes of tempe- 
rature during the observations. After allowing a short time 
for the magnets to acquire the temperature of the water, the 
observations were repeated. The scale made use of for the 
temperature was in all cases that of Fahrenheit.” 
From the results of the observations given in the tables de- 
scribed in the paragraph last quoted, we extract the following : 
“ Table of the Magnetic Intensities corresponding to different 
Temperatures of the Magnets. 6th June 1823. 
Mean Temp, 
of the Mag- 
nets. 
Diff. of Temp, 
in successive 
observations. 
Magnetic In- 
tensity orVa- 
F 
lues of — • 
M 
Variation of 
jjjfor l°Fahr. 
F 
° rA ‘M 
62.05 
212.5620 
59.05 
— 3.00 
212.9423 
0.1268 
77-65 
+ 18.60 
210.6228 
0.1247 
74.00 
_ 3.65 
210.9892 
0.1004 
70.65 
— 3.35 
211.4178 
0.1279 
67.15 
— 3.50 
211.8353 
0.1193 
63.80 
— 3.35 
212.2167 
0.1138 
62.05 
— 1.75 
212.4640 
0.1413 
Some anomalies observed by Mr Barlow between the daily 
changes in the direction of a needle, when placed in the house 
and when in the open air *, which Mr Christie also noticed, and 
stated, in a former paper, his opinion that they had arisen from 
the difference in the changes of temperature in the magnets in 
the two situations, are next investigated in the memoir before 
us ; observations on the temperature of the magnets having 
been made in the open air, corresponding to those made in- 
doors. 
We select the subjoined table from among the results of this 
branch of Mr Christie’s inquiry. 
* These anomalies are described by Mr Barlow in his paper on the daily 
variation of the horizontal and dipping needles under a reduced directive 
power. 
