35 2 Afr. Christie on the diurnal deviations of the 
From these I derive the following 
Table of the greatest Easterly and Westerly Deviations, their times, 
the times of Zero , and the total daily changes in the direction of a 
Magnetic Needle , whose directive force was diminished in the 
ratio of l to .034, by the action of two bar Magnets placed in the 
line of the Dip : the N. end of the Needle pointing North. 
April. 
Max. E. or minus. 
Time of 
Zero. 
Morning. 
Max. W. or plus. 
Time of 
Zero. 
Afternoon. 
Total 
change. 
Value. 
Time. 
Value. 
Time. 
O / 
h. m. 
h. m. 
O i 
h. m. 
h. m. 
0 / 
*5 
— 3 00 
9 OO 
9 44 
+ 6 40 
0 55 
6 10 
9 40 
16 
— O 40 
7 CO 
7 5° 
+ 814 
I 30 
8 54 
17 
— 3 10 
7 40 
10 30 
+ 4 34 
O 05 
4 4° 
7 44 
18 
— 5 4° 
7 3° 
9 36 
+ 6 30 
O 15 
12 10 
19 
— 3 4° 
7 10 
9 00 
+ 9 2 4 
0 50 
6 15 
13 °4 
Mean 
— 3 M 
7 3 6 
9 20 
+ 7 04 
0 43 
5 02 
10 18 
Comparing these mean results with those in the preceding 
table of maxima, we find the times in general earlier : the 
observations are however much too limited to point out a 
very correct mean in either case. 
After having made these observations I entirely removed 
the magnets, and found that the needle made thirty-eight 
vibrations in one hundred seconds, so that its directive power 
continued nearly the same as at the commencement. 
For the purpose of exhibiting at one view the facts pointed 
out by these observations, I have, in the following diagram, 
QP1. XXIV.]] placed the deviations as ordinate^ to a curve, the 
distances between them representing the intervals of time. 
The axis of the curve corresponding to zero, the westerly, or 
plus deviations, are measured to the right, and the easterly, 
or minus deviations, to the left. The days on which the obser- 
vations were made are placed over the respective curves, and 
