DECLINATION. XXiil 
In the following Table the observed declinations are compared with those 
calculated according to this formula, and the differences are exhibited :— 
TABLE 3.—Observed and Calculated Declinations compared together. 






Declination. 
Observed 
Year. Minus 
Observed. Calculated. Cale taed 
1841 95 33-68 25 33-78 —0-10 
1842 25 28-45 25 26:25 + 0:20 
1843 25 22°85 25 22:60 + 0:25 
1844 25 17:06 25 16-80 40:26 
1845 25 11°32 25 10-88 40-44 
1846 25 05-97 25 04-82 4115 
1847 24 59-61 24 58°63 +098 
1848 24 51°82 24 52:30 — 0-48 
1849 24 45:21 24 45-84 ~— 0°63 
1850 24 38:96 24 39-25 — 0-29 
1851 24 31:34 24 32-53 ~1:19 
1852 24 25-20 24 25-67 — 0-47 
1853 24 18°69 24 18°68 + 0-06 | 
1854 24 11°82 24 11°55 + 0:27 
1855 24 05-25 24 04:29 +0:96 
* Mr Chambers, to whom I am indebted for the calculation of the most probable 
values of declination given above, has remarked that the residual differences of 
the last column exhibit some indications of a period in their value. 

Having thus obtained the most probable value of the secular change for any year, 
we may find the annual variation of the declination for a given hour of the day in 
the following manner :— 
From one year’s monthly means of declination for that hour eliminate the 
secular change. 
Having thus obtained monthly means for a given hour for that year free from 
secular change, the annual variation of declination for that hour and year is easily 
found. Ifthere are several years during which observations at that hour were 
taken, we may then, in the usual manner, obtain the mean annual variation for 
these years of declination at the given hour. 
The following Table exhibits the annual variation of the declination for the dif- 
ferent hours :— 
MAG. AND MET. ops. 1847 To 1855. i 
