80 
ME. C. CHAMBEES ON THE DIRECTION AND INTENSITY 
Table IX. 
Month. 
Mean Monthly Declination reduced to Mean 
Monthly Reading of thelarge 
Declination Magnetometer. 
Mean Monthly Reading of large Declination 
Magnetometer. 
1867. 
1868. 
1869. 1 
1870. 
1871. 
1872. 
1873. 
1867. 
1868. 
1869. 
1870. 
1871. 
1872. 
1873. 
January 
' 
* 
44 
8 
45 
55 
48 
27 
49 
52 
52 
26 
53 
51 
35-23 
35- 
50 
35-89 
36-24 
36-48 
36-61 
February 
43 
54 
47 
0 
48 
14 
50 
26 
52 
43 
53 
43 
35-28 
35 
55 
35-90 
36-28 
36-53 
36-60 
March 
44 
52 
47 
15 
48 
33 
50 
46 
52 
52 
53 
49 
35-31 
35 
59 
35-95 
36-31 
36-51 
36-65 
April 
May 
45 
14 
47 
30 
48 
55 
51 
3 
52 
52 
53 
55 
35-40 
35 
63 
35-98 
36-31 
36-51 
36-63 
44 
26 
47 
37 
48 
51 
50 
53 
52 
40 
53 
51 
35 41 
35 
70 
35-94 
36-26 
36-49 
36-57 
June 
44 
43 
47 
49 
48 
57 
50 
44 
52 
48 
54 
2 
35-41 
35 
70 
35-93 
36-23 
36-49 
36-61 
July 
43 
16 
44 
38 
47 
23 
49 
16 
51 
3 
52 
38 
54 
14 
35- 
11 
35-43 
35 
■68 
35-95 
36-28 
36-46 
36-61 
August 
43 
6 
45 
38 
47 
47 
49 
39 
51 
37 
53 
13 
54 
36 
35- 
07 
35-50 
35 
•75 
3605 
36-33 
365*2 
36-65 
September 
43 
35 
45 
31 
47 
38 
50 
35 
51 
22 
53 
12 
54 
12 
35- 
11 
35-58 
35 
■81 
3617 
36-34 
36-51 
36-65 
October 
43 
56 
46 
1 
47 
47 
50 
37 
52 
1 
53 
43 
54 
0 
35' 
16 
35-64 
35 
■81 
36-22 
36-38 
3661 
36-65 
November 
44 
19 
45 
56 
47 
50 
50 
7 
52 
28 
53 
45 
53 
56 
35' 
18 
35-57 
35 
•82 
36-22 
36-45 
36-61 
36-65 
December 
43 
58 
45 
42 
48 
20 
50 
8 
52 
21 
53 
47 
53 
48 
35' 
19 
35-46 
35 
■83 
3621 
36-44 
36-60 
36-67 
11. Annual Mean Values and Secular Change . — Table X. shows the Absolute Decli- 
nation, both as observed and corrected as in Table IX., for each year from 1867 to 1873, 
and also the respective annual increments of declination and the mean annual increment 
for the period of six and a half years. 
Table X. 
1 
Year. 
Absolute Declination and Annual Increments. 
As observed. 
Corrected to Mean 
Reading of large 
Declination Magnetometer. 
Declination. 
Annual 
Increment. 
Declination. 
Annual 
Increment. 
1867, July to December 
1868, July to December 
1868, January to December 
1869, January to December 
1870, January to December 
1871, January to December 
1872, January to December 
1873, January to December 
1 
42 20 
44 20 
43 57 
46 8 
47 47 
49 38 
51 34 
52 38 
[+2 0] 
+2 11 
+ 1 39 
+ 1 51 
+ 1 56 
+1 4 
43 42 
45 34 
45 4 
47 29 
49 21 
51 13 
53 3 
54 0 
[+1 52] 
+2 25 
+ 1 52 
+ 1 52 
+1 50 
+0 57 
Mean for 6J years 
48 8 
+ 1 46 
49 32 
+ 1 48 
The values 48' 8'' and 49' 32" of absolute easterly declination, as observed and as 
corrected, correspond to the mean epoch October 1, 1870 ; the annual increase of decli- 
nation (1' 46" or 1' 48") differs by a scarcely appreciable amount, whether it is derived 
directly from the observations or from the observations corrected. In calculating the 
means, only half weight has been given to the values in brackets, which are derived 
from only half as many observations as the other values. 
12. Annual Variation . — The means for the period of six and a half years of easterly 
declination in each month are shown below, both as observed and corrected ; the cor- 
