CHANGE IN DIRECTION OF EARTHS MAGNETIC FIELD. 
297 
Lat. 53° 10' S. PUNTA ARENAS. Long. 70° 54' W. 
Year. 
Magnetic 
deelina- 
Authority. 
tion. 
Observer. 
Where recorded. 
o 
( 22.50. Wallis. 1766 
I Voyage of the Adventure and Beagle, 1826-36, 
1766*. 
—22.43 
) 22.36. Carteret,. 1766..... 
f London, 1839. 
182S* 
—23.33 
—22.83 
TCim*_ 
J 
Becquerel’s Trait6 du Magnetisme. 
Voyage of Adventure and Beagle, London, 1839. 
Smithsonian Contributions to Knowledge, No. 
1831*. 
Fitz Rev. 
1866. 
—21.87 
Harkness 
239, 1873. 
1872*. 
—21.83 
British Admiralty Chart, No. 547. 
British Admiralty Chart, No. 545. 
Ann. de l’Obso. Imp. de Rio de Janeiro. 
f 20.75. 
1883........ 
—20.97 
i 21.18, Brazilian Transit of 
Venus Commission. 
1893.3 .... 
—20.17 
! Lieut. L. 
I 
Mottez, 
Fr. N. 
Annales Hydrographiques, 2d vol., 1893. 
Year. 
Observed. 
Computed. 
O-C. 
CM] 2 . 
* 
1766. 
o 
—22.43 
o 
—21.82 
—0.61 
0.3721 
1 
1828. 
—23.33 
—23.73 
+0.40 
0.1600 
1831. 
1866. 
—22.83 
—23.67 
—0.84 
0.7056 
i Probable error of a single observation = ± 19.3'. 
—21.87 
—22.12 
+0.25 
0.0625 
Period = 360 years. 
1872. 
-21.83 
—21.69 
—0.14 
0.0196 
1883. 
—20.97 
—20.85 
—0.12 
0.0144 
1893.3 .... 
—20.17 
-19.99 
—0.18 
0.0324 
1.3666 
* Taken at Port Famine. 
Empirical equation for determining the declination for any year: v = — 18°.68 
+ 2.71 sin (f — 1850) — 4.35 cos (l — 1850). 
