DiuRNAL VARIATIONS FOR 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. 
About 85 p.m—I12" pm. 62 p.m—ll* p.m. 
May, June. 
11 p.m.—12> p.m. 
July, Aug, 
95 p.m. 102 p.m. 
Sept. Oct. Nov. 
8) p.m.—11" p.m. 
3d, 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 537 a.m.and5}" p.m. 45 a.m.and 55p.m. 5% a.m.and63" p.m. 42 a.m. and53"p.m. 43? a.m. and 53" 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. 
With reference to Mean of all. 
With reference to Mean of Selected Days. 
=. 
Nov. 
Dec. 
Jan. 
39-9 
43-7 
46-2 
53-8 
46-8 
46-2 
58-2 
66-5 
67-7 
71-5 
70-9 
60:8 
67-7 
63:3 
64-6 
65-8 
62-0 
59-5 
58-2 
48:7 
38-0 
54.4 
39-2 
36-7 
Feb. 
March. 
April. 
47-1 
49-0 
51-0 
51-0 
53-6 
55-6 
66-7 
65-4 
59-5 
70-6 
64-7 
62-1 
65-4 
68-0 
64-7 
66-7 
70-6 
52-3 
49-0 
47-1 
45-1 
44.4 
44.4 
May. 
June. 
July. 
36-1 
31-0 
40-5 
44-9 
36-1 
43-0 
50-6 
47-5 
56-3 
65-2 
69-6 
61-4 
65-2 
58-2 
63-3 
58-2 
56-3 
41:8 
43-0 
38-6 
34-2 
40-5 
38-6 
35:5 
Aug. 
Sept. 
Oct. 
32-3 
Year. 
40. The following are the epochs of maximum and minimum frequency of the positive or westerly excursions. 
From the Means of all the Observations. From the Means of the Undisturbed Days. 
Min. Max. Min. Max. 
Nov. Dec. Jan. 8) aM. 8) P.M. 11) p.m. 935 am. 
Feb. March, April. 105 a.m. 63 p.m. 9? P.M. 9® a.m.—4® p.m. 
May, June, July, 635 a.m. 9" pM. 8" p.m.—l1> a.m. 10” a.m. 
Aug. Sept. Oct. 62 a.m. 93 p.m. 10® p.m.—l1* a.m. 0» Noon. 
