6o 
Mr. Christie on the effects of temperature on 
for the month of May 1820, and about seven o'clock in the 
evening for the month of June. The intensity which, in these 
observations, is taken as unity, is that deduced from an ob- 
servation made during an aurora borealis ; but for the purpose 
of comparison, I have, for the months of May and June, taken 
the intensity deduced from his observations at 10^ 30™ in the 
morning as unity, reduced the intensities, which he gives for 
other times in the day, to this standard, and placed them in 
the following table, with the corresponding intensities de- 
duced from my own observations. 
Intensity deduced from Hansteen’s 
Observations in 1820. 
Intensity deduced from the preceding 
Observations in 1823. 
Time. 
May. 
June. 
Time. 
May. 
June. 
h. m. 
h. m. 
8 00 A. M. 
1.00034 
1.00010 
7 30 A. M. 
1.00114 
1.00061 
10 30 
1.00000 
1.00000 
10 30 
1.00000 
1.00000 
4 00 P. M. 
1.00299 
1.00251 
4 30 P. M. 
1.00175 
1.00223 
7 00 
1.00294 
1.00302 
7 30 
1.00220 
1.00239 
10 30 
1.00191 
1.00267 
9 30 
1.00231 
1.00209 
The principal difference to be observed in the nature of 
the changes of intensity during the day, in the two cases, is, 
that from my observations, the intensity appears to decrease 
more rapidly in the morning, and increase more slowly in 
the afternoon, than it does from those of Professor Han- 
sTEEN ; but the general character of these changes is as nearly 
the same as v/e can expect from methods so different, at dif- 
ferent times, and at places where both the variation and dip of 
the needle are different. My object however was, to point out 
