CHANGE IN DIRECTION OF /EARTH S MAGNETIC FIELD. 
291 
Lat. 14° 36' N. MANILA. Long. 120° 58 / E. 
Year. 
Magnetic 
declina¬ 
tion. 
Authority. 
Observer. 
Where recorded. 
17C6. 
1792.6 .... 
1829.5 .... 
1836. 
1844. 
1887. 
1887 *. 
1890. 
o 
+0.25 
—0.29 
—0.58 
—0.50 
-0.30 
—0.83 
—1.00 
—0.80 
Le Gentil. 
( Lutke, 1829, 0°.17. 
j Laplace, 1830, 1°. 
Belcher. 
Observatory. 
U. S. S. Essex. 
Observatory. 
Hansteen’s Magnetismus der Erde, Christiana, 
1819. • 
Brewster’s Treatise on Magnetism, Edinburg, 
1834. 
>Phil. Trans. Royal Society, Part I, 1875. 
Voyage de la Bonite, Paris, 1842. 
Phil. Trans. Royal Society, Part I, 1875. 
El Magnetismo Terrestre en Filipinas por P. 
Ricardo Cirera, S. J. 
Hydrographic Office archives document. 
Report of Observatorio Meteorologico de Manila, 
1890. 
Year. 
Observed. 
Computed. 
O-C. 
o-c 2 . 
1766. 
1792.6 .... 
1829.5 .... 
1836. 
1844. 
1887. 
1890. 
o 
+0.25 
—0.29 
—0.58 
—0.50 
—0.30 
—0.83 
—0.80 
o 
+0.13 
—0.11 
—0.47 
—0.53 
—0.60 
—0.80 
—0.80 
+0.12 
—0.18 
—0.11 
+0.03 
+0.30 
—0.03 
+0.00 
Wts. 
0.0144 1 0.0144 
0.0324 1 0.0324 
0.0121 2 0.0242 
0.0009 2 0.0018 
0.0900 1 0.0900 
0.0009 3 0.0027 
0.0000 3 0.0000 
Probable error of a single observa¬ 
tion = ± 08.3'. 
Period = 360 years. 
0.1655 
* Omitted in investigation. 
Empirical equation for determining the declination for any year: v = — 0°.223 
— 0.399 sin {t — 1850) — 0.418 cos (t — 1850). 
