135 
If we multiply the mean horizontal force for each year 
successively by the secant, and the tangent, of the mean dip, 
for the same year we get the following values of the Total 
force and the Vertical force for the four years. 
Mean 
Total Force. 
Annual 
Diminution. 
Mean Verti- 
cal Force, 
Annual 
Diminution. 
1873 
10-4414 
-0126 
9-7670 
•0147 
•0025 
1874 
10-4288 
9 7523 
1875 
10-4275 
-0013 
9-7498 
1876. 
10-4264 
•0011 
9-7469 
•0029 
Means 
10-4360 
•0050 
97540 
•0067 
Table III. 
DECLINATION. 
1874. 
1875. 
1876. 
Mean. 
January 
February 
20° 47' 20" 
20 43 30 
20° 47' 20" 
20 43 30 
March 
20° 51' 10" 
20° 49' 0" 
20 35 20 
20 45 10 
April 
20 48 40 
20 46 0 
20 82 40 
20 42 27 
May 
20 24 30 
20 41 50 
20 36 0 
20 34 7 
June 
20 35 30 
20 40 40 
20 33 0 
20 36 23 
Mean 
20 39 58 
20 44 23 
20 37 58 
20 40 22 
July 
20 
38 
20 
20 
36 
0 
20 
33 
50 
20 
36 
3 
August 
20 
31 
0 
20 
29 
10 
20 
36 
40 
20 
32 
17 
September 
20 
48 
40 
20 
32 
30 
20 
33 
30 
20 
38 
13 
October 
20 
52 
40 
20 
36 
40 
20 
27 
40 
20 
39 
0 
November 
20 
43 
50 
20 
43 
50 
20 
41 
0 
20 
42 
53 
December 
20 
58 
30 
20 
39 
0 
20 
42 
20 
20 
46 
37 
Mean 
20 
45 
30 
20 
36 
12 
20 
35 
50 
1 20 
39 
10 
Annual Mean... 
20 
43 
17 
20 
39 
28 
20 
36 
54 
; 20 
39 
42 
The values of the declination in the above table are not 
to be depended on to within two or possibly three minutes, 
as (1) the observation for the torsion of the suspending 
