CHANGE IN DIRECTION OF EARTH S MAGNETIC FIELD, 
315 
Lat. 36° 42' S. 
CONCEPCION. 
Long. 73° 07 / W. 
Year. 
Magnetic 
dip or in¬ 
clination. 
Authority. 
Observer. 
Where recorded. 
1710.. . 
1768.. . 
1794.. . 
1823.. . 
1827.. . 
1829.. . 
1835.. . 
1882.7 
1893.2 
o 
—55.50 
—55.50 
—52.18 
—44.70 
—45.55 
—45.18 
—43.25 
—37.97 
—36.67 
Feuill6e..... 
Malaspina.. 
Duperrey ... 
Liitke. 
King. 
Fitz Roy... 
Lieutenants Barnaud and 
Barnadieres, Fr. N. 
Lieut. Mottez, Fr. N. 
Hansteen’s Magnetismus der Erde, Christiania, 
1819. 
Wilcke’s Magnetic Chart. 
Berliner Astronomisches Jahrbuch, 1828. 
Phil. Trans. Royal Society, 1877. 
Do. 
Do. 
Do. 
Annales Hydrographiques, 1884. 
Annales Hydrographiques, vol. II, 1893. 
_2 
Year. 
Observed. 
Computed. 
O-C. 
O-C. 
o 
o 
1710. 
—55.50 
—56.01 
+0.51 
0.2601 
1 
1768........ 
—55.50 
—54.73 
—0.77 
0.5929 
1794. 
—52.18 
—51.12 
—1.06 
1.1236 
1823. 
1827.. 
—44.70 
—46.17 
+1.47 
2.1609 
Probable error of a single observation == ± 38'. 
—45.55 
—45.49 
—0.06 
0.0036 
1829. 
Period = 400 years. 
—45.18 
—45.15 
—0.03 
0.0009 
1835... 
—43.25 
—44.10 
+0.85 
0.7225 
1882.7 .... 
—37.97 
—37.32 
—0.65 
0.4225 
1893.2 .... 
—36.67 
t—36.38 
—0.29 
0.0841 
5.3711 
Empirical equation for determining the inclination for any year: I 
+ 10.05 sin 0.9 (t — 1850) + 4.80 cos 0.9 (t — 1850). 
46°.42 
