XX1l GENERAL RESULTS OF THE MAGNETICAL OBSERVATIONS. 
If the corrections recorded in the preceding Table be applied to the observa- 
tions, we obtain the monthly means as follows :— 
TaBLE 2.—Monthly and Yearly Means of Declination. 


1847. 1848. 1849, 1850. 1851. 1852. 1853. 1854, 
Ones ¥ | pAe. 24° 4 24° 4. QA° 4. 24° + 24° + 24°4 
January, .| 62°69 | 55-88 | 47:90 | 42-09 | 34°31 | 27-10 | 21:12 | 15-35 
February, .| 62°54 | 54-67 | 47-66 | 42-41 | 33-65 | 27-85 | 20°95 | 15-32 
March, . .| 62°60 | 54-66 | 47-35 | 41:88 | 33-41 | 27-16 | 2050 | 14-22 
April, . .| 62:07 | 58:58 | 46-30 | 40-41 | 32:18 | 27-61 | 19-92 |... 
May,. . .| 60°60 | 5316 | 46-20 | 40-45 | 32-29 | 96-51 | 18-99 
June, . .| 59:69 | 51-43 | 45:85 | 40-10 | 39-35 | 25-53 | 20-95 | 
July,. . .| 59°52 | 51-44 | 4413 | 89-15 | 31-26 | 24-93 | 19:93 | 
August, . .| 59:11 | 50:56 | 43-72 | 37-33 | 30-21 | 23-49 | 16-96 
September, .| 57:20 | 49-10 | 42°75 | 37:02 | 30°56 | 23-92 | 17-19 | 10-10 
October,. .| 56°62 | 49°33 | 43°33 | 36°47 | 29°24 | 23-58 | 16:02 8:00 
November, .| 56°79 | 48°83 | 43°65 | 34:88 | 28-21 | 22°73 | 15-77 cis 
December, .| 55°90 | 49:22 | 43:73 | 35°35 | 28°37 | 22:00 | 16:72 8°45 

Mean } 
WMeckabion. 59°61 | 51°82 | 45°21 | 38°96 | 31:34 | 25:20 | 18°69 |[11:82]| [5:25] 
If we examine the change of the declination from year to year, we shall find 
that this increases from 1841 to 1855. 
The secular change is not therefore strictly constant. 
Let us suppose that it may be represented by the following formula :— 
Yearly secular change =x + ny 
Where z denotes the most probable secular change between 1841 and 1842, and 
y its yearly increase, so that z+y denotes the change between 1842 and 1843; 
z+2y that between 1843 and 1844, and so on. 
Also let d denote the most probable value of the declination for 1841, then 
we have, by well-known methods, 
d=25° 33-78 
a= —5:'525 
y= —0133 

