DiUKNAL VaEIATIONS FOE THE MAGNETIC DECLINATION. 
XXV 
Throughout the year, therefore, the effect of disturbance in increasing the westerly declination is greatest be- 
tween 8^ A.M. and 2*^ p.m. ; being near the latter hour for the months about mid-summer and mid-winter, and 
near the former hour for the intermediate months. 
2d, That the greatest effect of disturbance in decreasing the westerly declination occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 8h P.M. 12^^ P.M. P.M. ll^^P-M. 11^ P.M. 121" P.M. 9^^ P.M. 10'' P.M. 8'^ P.M. 11'^ P.M. 
Sd, That the effect on the hourly mean westerly declination is zero 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 5^^ A.M. and p.m. 4^ a.m. and 6^ p.m. 5"^ a.m. and 6^^ p.m. 4"^ a.m. and 5^^^ p.m. 4^*' a.m. and 5^** p.m. 
Diurnal Variation of frequency of Positive and Negative Excursions from the Hourly Mean Position. — The 
number of observations which were to the west of the hourly mean for each month in 1844 and 1845 having 
been obtained, the following Table was formed, containing the numbers per cent, for quarterly groups of months. 
Table 16. — Numbers of Excursions of the Declination Magnet in 100 which were to the West ; 
1st, of the Hourly Means, as deduced from all the Hourly Observations in each Month of 1844 
and 1845 ; and, 2d, of those deduced from the Selected Days. 
Mak. 
With reference to Mean of all. 
With 
reference to Mean of Selected Days. 
Mean 
Nov. 
Feb. 
May. 
Aug. 
Nov. 
Feb. 
May. 
Aug. 
Time. 
Dec. 
March. 
June. 
Sept. 
Year. 
Dec. 
March. 
June. 
Sept. 
Year. 
Jan. 
April. 
July. 
Oct. 
Jan. 
April. 
July. 
Oct. 
h. m. 
12 10 
63-9 
66-7 
551 
60- 1 
61-4 
39-9 
47-1 
36-1 
32-3 
38-8 
13 10 
67-7 
63-4 
60-8 
59-5 
62-8 
43-7 
49-0 
31-0 
31-6 
38-8 
14 10 
57-6 
60-8 
57-6 
53-8 
57-4 
46-2 
51-0 
40-5 
42-4 
45-0 
15 10 
58-9 
59-5 
47-5 
48-7 
53-6 
53-8 
51-0 
44-9 
42-4 
48-0 
16 10 
50-6 
50-3 
44-3 
50-0 
48-8 
46-8 
53-6 
36-1 
38-0 
43-5 
17 10 
53-2 
49-7 
42-4 
35-4 
45-1 
46-2 
55-6 
43-0 
47-5 
48-0 
18 10 
34-8 
45-8 
43-7 
26-6 
37-6 
58-2 
66-7 
50-6 
56-2 
57-7 
19 10 
37-3 
45-1 
42-4 
32-9 
39-4 
66-5 
65-4 
47-5 
58-2 
59-3 
20 10 
33-5 
39-9 
4M 
36- 1 
37-6 
67-7 
59-5 
56-3 
62-0 
61-4 
21 10 
36-7 
42-5 
43-7 
37-3 
400 
71-5 
70-6 
65-2 
61-4 
67-1 
22 10 
36-7 
34-6 
47-5 
43-7 
40-7 
70-9 
64-7 
69-6 
58-2 
65-9 
23 10 
40-5 
42-5 
46-8 
45-6 
43-9 
60-8 
62-1 
61-4 
66-5 
62-7 
0 10 
38-6 
39-2 
45-6 
45-6 
42-3 
67-7 
65-4 
65-2 
68-4 
66-7 
1 10 
40-5 
43-1 
44-3 
47-5 
43-9 
63-3 
68-0 
58-2 
65-8 
63-8 
2 10 
36-1 
43-1 
44-9 
41-8 
41-5 
64-6 
64-7 
63-3 
64-1 
64-1 
3 10 
46-2 
39-2 
47-5 
45-0 
44-5 
65-8 
66-7 
58-2 
53-8 
6M 
4 10 
43-7 
41-8 
49-4 
45-6 
45-1 
62-0 
70-6 
56-3 
57-0 
61-4 
5 10 
53-8 
53-6 
48-7 
50-6 
51-7 
59-5 
52-3 
41-8 
53-2 
51-7 
6 10 
65-2 
68-6 
47-5 
63-3 
6M 
58-2 
49-0 
43-0 
53-8 
51-0 
7 10 
70-9 
69-3 
57-6 
63-9 
65-4 
48-7 
47-1 
38-6 
50-6 
46-3 
8 10 
72-8 
68-6 
61-4 
63-9 
66-7 
38-0 
45-1 
34-2 
38-6 
38-9 
9 10 
69-6 
65-4 
67-1 
690 
67-8 
54-4 
44-4 
40-5 
34-2 
43-4 
10 10 
69-0 
63-4 
61-4 
67-7 
65-4 
39-2 
44-4 
38-6 
29-1 
37-8 
11 10 
67-1 
60-8 
63-3 
67-7 
64-8 
36-7 
47-1 
35-5 
41-1 
40-0 
40. The following are the epochs of maximum and minimum frequency of the positive or westerly excursions. 
N^ov. Dec. Jan. 
?eb. March, April. 
'»Iay, June, July, 
^ug. Sept. Oct. 
From the Means of all the Observations. 
Min. 
a.m. 
10'' A.M. 
P.M. 
6^ A.M. P.M. 
Max. 
8'^ P.M. 
61h P.M. 
9^ 
From the Means of the Undisturbed Days 
Min. Max. 
11^^ P.M. 
9^ P.M. 
8^ P.M. 1'' A.M. 
lO*' P.M. 1^ A.M. 
91h A.M. 
9'^ A.M.— 
10^ A.M. 
0'^ Noon. 
.4h 
