386 Mr. Christie on the diurnal deviations of the 
the evening was cold, the needle did not return to within 
24° and 2 3 0 of its situations in the morning. When the sun 
was hottest, a thermometer exposed to its rays stood at 
97 ° Fahrenheit, so that the change in the temperature of 
the magnets could not exceed 50°. 
On the day following, a thermometer being placed on the 
table with the bulb exposed close to the side of one of the 
magnets, I observed as follows : 
Time. 
Ther. 
Points of Equilibrium. 
N. W. 
N. E. 
h 
O 
0 / 
0 / 
5 ° 58 
3 P.M. 
73 
50 28 
9 P.M. 
5 M 
54 52 
55 08 
Here, although the magnets experienced a change of tem- 
perature of 2i°,5, yet the changes of direction were only 
4 ° 30' and 4 0 io / . 
The observations with the other compass were of the same 
character on the 18th of May as those with No. I. : they 
were as follow : 
Compass No. II, May 18. 
Time. 
Points of Equilibrium. 
Remarks. 
h. m. 
N. W. 
0 , 
N. E. 
0 / 
S. E. 
0 / 
5 10 
26 25 
28 40 
3 i 5 
Clear sky. 
6 00 
19 40 
23 15 
4 55 
7 00 
19 30 
24 20 
5 °5 
8 00 
1 7 45 
22 5s 
6 00 
1 Clear sun, striking hot upon the 
9 00 
no point 
13 00 
no point 
> magnets. Therm, in shade 63° ; 
10 00 
no point 
5 »5 
no point 
j exposed to the sun 97 0 . 
Finding the deviations so much increased and the magnets 
hot, I covered them over with porous earthen pans, pouring 
