CHANGE IN DIRECTION OF EARTH’S MAGNETIC FIELD. 285 
Lat. 29° 57' S. COQUIMBO. Long. 71° 22' W. 
Year. 
Magnetic 
declina¬ 
tion. 
Authority. 
Observer. 
Where recorded. 
1700........ 
o 
— 8.53 
—10.00 
—11.77 
—14.00 
—14.40 
—14.40 
—14.59 
—14.67 
—14.35 
—13.70 
—13.59 
—13.63 
Feuillee. 
Hansteen’s Magnetismus der Erde, Christiana, 
1819. 
Brewster’s Treatise on Magnetism, Edinburg, 
1834. 
Becquerel’s Traite du Magnetisme. 
Phil. Trans. Royal Society, Part II, 1877. 
Voyages of Adventure and Beagle, London, 1839. 
French Chart No. 1746. 
Annales Hydrographiques, 2d series, 1884. 
Naval Professional Papers, No. 19. 
Chilean Hydrographic Notices, No. 12, 1890. 
Contributions to Terrestrial Magnetism, Hydro¬ 
graphic Office Publication, No. 109. 
1712.... 
1791.3 .... 
1821. 
}. 
B. Hall... 
1828. 
1834. 
Fit?: R.ov... 
1853. 
1870.... 
1882.;. 
1883. 
1889. 
}. 
Ensign Favereau, 
Lieut. F. Hanford, 
Chilean astronome 
Lieut. J. F. Moser, 
U. S. S. San Fran 
Fr. N. 
U. S. N... 
rs. 
1891. 
U. S. N., 
cisco. 
Year. 
Observed. 
Computed. 
O-C. 
0+3. 
- 
1700. 
o 
— 8.53 
o 
— 8.97 
+0.44 
0.1936 
1712. 
—10.00 
— 9.27 
—0.77 
0.5929 
1791.3 .... 
—11.77 
—12.77 
+1.00 
1.0000 
1821.. 
—14.00 
—13.88 
—0.12 
0.0144 
1828. 
—14.40 
—14.06 
—0.34 
0.1156 
1834.. 
—14.40 
—14.18 
—0.22 
0.0484 
Probable error of a single observation = ± 21.3'. 
1853. 
—14.59 
—14.39 
—0.20 
0.0400 
Period = 360 years. 
1870. 
—14.67 
—14.30 
—0.37 
0.1369 
1882. 
—14.35 
—14.09 
—0.26 
0.0676 
1883. 
—13.70 
—14.06 
+0.36 
0.1296 
1889. 
—13.59 
—13.92 
+0.33 
0.1089 
1891. 
—13.63 
—13.86 
+0.23 
0.0529 
2.5008 
Empirical formula for determining the declination for any year: v — —11°.55 
— 0.281 sin (t — 1850) — 2.82 cos (t— 1850). 
42-Bull. Phil. Soc., Wash., Vol. 13. 
