402 
ME. J. A. BROUN ON THE VARIATIONS OE THE 
Table V. — Moon’s Positions in Declination and in Latitude in each case. 
No. of 
case. 
Days from Moon furthest north. 
Diminution commencing 
Moon’s mean latitude. 
Greater than 3 o- 0. 
Less than 3°‘0. 
-9 
to 
+ 11 . 
—2 
to 
+ 2 . 
+3 
to 
+5. 
Other 
days. 
South. 
I North. 
South. 
North. 
a 
a 
a 
a 
i. 
+ 3 
— 3-0 to -4-5 
2 , 
+ 4 
—3-8 „ —4-5 
3. 
+ 2 
-2-8 „ -4-4 
4. 
— 4 
+ 3*8 to +2*9 
5. 
— 8 
+ 5-1 „ +4-9 
6 . 
0 
— DO to — 2-0 
7. 
— 8 
+ 5-0 to +4-0 
8 . 
2 
+ 1-3 to +6*3 
9. 
— 9 
+ 4.5 to +5*2 
10 . 
— 7 
+ 4-9 „ +3-7 
11 . 
+ 4 
— 4‘5 to —5+ 
12 . 
-10 
+ 3-7 „ +5-0 
13. 
- i 
+ 0-1 to — 1-9 
14. 
+ 5 
-4-7 to -5-0 
15. 
+ i 
-2-6 „ -4-2 
16 . 
+ 5 
-5-2 „ — 5“0 
17. 
— 5 
+ 3-4 „ +2-4 
18. 
+ 2 
— 3*5 to — 4-9 
19. 
+ 1 
-2-6 „ -3-5 
20 . 
+ 4 
— 4-6 „ —4-9 
21. 
+ 2 
-4-2 „ -4*7 
22. 
-10 
+ 4*4 to +5-2 
23. 
+ 1 
-3*3 to —4-1 
24. 
+ ii 
— 1*5 to + 1-1 
25. 
0 
-2-0 to -4-5 
26. 
+ 12 
-07 „ +1-8 
27. 
-10 
+ 5*2 to + 5-2 
28. 
2 
-0*6 to -2-7 
1 
1 

the more northerly cases were the more frequent. In the same way it is found that of 
the 6 cases for which the moon was south of the equator, in 4 the mean declination was 
more than 15° (=15° - 6) and in 2 less (=10 o- 8). There were thus only 2 cases remaining 
for which the mean declination of the moon was within the limits 10°*2 N. and 10°*8 S., 
a space covering half the moon’s whole path. 
It would appear, then, that the exact recurrence of the greater diminutions of terrestrial 
magnetic force for certain days happens only in the solar period, but that their frequency 
depends on the position of the moon relatively to the equator. It may also be remarked 
for the cases Nos. 18, 19, 20, 21, 23, 25, and 28, for which the disturbance commenced 
near the solar meridian -j- 8, the moon was within two days of her greatest northerly 
declination (except one case, for which her mean declination was 15° N.). 
It has been supposed that this apparent action of the moon is due to her position 
relatively to the equator ; but as the nodical period differs only 0T1 day from the tropical, 
it is possible that it is her position relatively to the ecliptic which is in question. I have 
in consequence examined the cases with regard to the moon’s latitude, with the following 
