CHANGE IN DIRECTION OF EARTH’S MAGNETIC FIELD. 329 
Lat. 53° 10' S. PUNTA ARENAS. Long. 70° 54' W. 
Year. 
Magnetic 
dip or in¬ 
clination. 
Authority. 
Observer. 
Where recorded. 
1760 . 
o 
*—65.00 
Cook. 
Hansteen’s Maernetismus der Frde. 1819. 
1769.. . 
*—68.85 
.do. 
Do. 
1852. 
—57.42 
“ T/'Flno-Anip. ” . ... 
Annalen der Hydrographie, 1877. 
1866. 
—54.95 
TTarknoss 
Smithsonian Contributions to Knowledge, 1873. 
1876. 
—53.06 
H. M. S. Challenger . 
Voyage of H. M. S. Challenger. 
1883 . 
—52.77 
Brazilian Transit of Venus 
Ann. de l’Obs. Imp. de Rio de Janeiro. 
Commission.. 
1893.3 .... 
—51.33 
Lieutenant Mottez, Fr. N.... 
Annales Hydrographiques, 2d vol., 1893. 
Year. 
Observed. 
Computed. 
O-C. 
O-C . 
1760 . 
o 
—65.00 
o 
—66.87 
+1.87 
3.4969 
1769 . 
—68.85 
—66.77 
—2.08 
4.3264 
1852 . 
—57.42 
— 57.56 
+0.14 
0.0196 
Probable error of a single observation = ± 59'. 
1866 . 
— 54.95 
—55.22 
+0.27 
0.0729 
Period = 400 years. 
1876 . 
-53.06 
—53.58 
+0.52 
0.2704 
1883 . 
—52.77 
—52.47 
—0.30 
0.0900 
1893.3 .... 
—51.33 
—50.91 
—0.42 
0.1764 
8.4526 
* Observed at Good Success Bay, Tierra del Fuego. 
Empirical equation for determining the inclination for any year: I - — 56°.23 
+ 10.51 sin 0.9 (t — 1850) — 1.66 cos 0.9 {t — 1850). 
