CHANGE IN DIRECTION OP EARTHS MAGNETIC FIELD. 
281 
Lat. 12° 04 / S. CALLAO, PERU. Long. 77° 08' W. 
Year. 
Magnetic 
declina¬ 
tion. 
Authority. 
Observer. 
Where recorded. 
1709.9 .... 
o 
— 6.25 
Feuillee.. 
Hansteen’s Magnetismus der Erde, Christiana, 
1819. 
1802 
— 9.83 
Becquerel’s Traitb du Magnetisme. 
1823........ 
— 9.50 
1 
1827 
—10.66 
!». 
Voyages of the Adventure and Beagle, 1826—1836, 
1835........ 
—10.60 
1 
London, 1839. 
1836.. 
—10.40 
1838. 
—10.50 
}. 
Phil. Trans. Royal Society, 1877. 
1858 . 
—10.66 
Friesach. 
Phil. Trans. Royal Society, Part II, 1877. 
1866. 
—10.50 
Phil. Trans. Royal Society, 1877. 
1883.... 
— 9.97 
Ensign Favereau, 
, Fr. N.... 
Annales Hydrographiques, 2d series, 1884. 
1892. 
—10.00 
Lieut. W. P. Conway,U.S.N. 
Hydrographic information from U.S.S. Yorktown. 
1893.... 
—10.00 
Lieut. L. 
Mottez,' 
Fr. N . 
Annales Hydrographiques, 2d vol., 1893. 
1 
Year. 
Observed. 
Computed. 
O-C. 
-2 
O-C . 
1709.9 .... 
o 
— 6.25 
o 
— 6.32 
+0.07 
0.0049 
1802 . 
— 9.83 
— 9.52 
—0.31 
0.0961 
1823 . . 
— 9.50 
—10.21 
+0.71 
0.5041 
1827.. . 
— 10.66 
—10.31 
—0.35 
0.1225 
1835. . 
— 10.60 
—10.47 
—0.13 
0.0169 
1836.. . 
—10.40 
—10.49 
+0.09 
0.0081 
Probable error of a single observation = ± 12.25'. 
1838. 
—10.50 
—10.59 
+0.01 
0.0001 
Period = 300 years. 
1858. 
—10.66 
—10.60 
—0.06 
0.0036 
1866. 
—10.50 
—10.53 
+0.03 
0.0009 
1883. 
— 9.97 
—10.19 
+0.22 
0.0484 
1892... 
—10.00 
— 9.91 
—0.09 
0.0081 
1893. 
-10.00 
— 9.87 
—0.13 
0.0169 
i 
0.8306 
Empirical equation for finding the declination for any year: v — — 8°.45 — 0.105 
sin 1.2 (t — 1850) — 2.16 cos 1.2 (t — 1850). 
