CHANGE IN DIRECTION OF EARTH’S MAGNETIC FIELD. 
289 
Lat. 21° 18 / N. HONOLULU. Long. 157° 52' W. 
Year. 
Magnetic 
declina¬ 
tion. 
Authority. 
Observer. 
Where recorded. 
1817. 
o 
—10.95 
Kotzebue. 
Coast and Geodetic Survey Report, 1882, Appen¬ 
dix No. 12. 
1819 .... 
—10.40 
Freycinet. 
Do. 
1824.5 .... 
— 9.87 
Byron. 
Phil. Trans. Royal Society, 1875. 
—10.43 
—10.18 
_ 10 33 / 
Do. 
188R 
Voyage de la Bonite, Paris, 1842. 
Voyage de la Venus, Paris, 1841. 
1837. 
110.66 
Beechey.. 
Phil. Trans. Royal Society, 1875. 
1838 . 
—10.65 
Belcher. 
Do. 
1840. 
— 9.28 
Berghaus . 
Coast and Geodetic Survey Report, 1882. 
1852 ... 
— 9.17 
Collinson. 
Phil. Trans. Royal Society, 1875. 
Memoirs of the Imperial Academy of Sciences, 
Vienna, vols. XXIX to XLIV. 
1859.2 .... 
— 9.68 
Friesach. 
1871 ... 
— 9.60 
Lyon. 
Hawaiian Government Survey. 
Do. 
1872. 
— 9.30 
.do. 
1875. 
— 9.27 
Alexander. 
Do. 
1875.5 .... 
— 9.35 
Capts. Nares and Thom¬ 
son, R. N. 
Voyage of H. M. S. Challenger. 
1879. 
— 9.53 
Lyon. 
Coast and Geodetic Survey Report, 1888, Appen¬ 
dix No. 7. 
1881 
— 9.67 
—10.23 
.do. 
Do. 
Do. 
1884 
.do. 
1888.2 .... 
—10.05 
Lieut. J. O. Wilson, 
U. S. N. 
Hydrographic Office archives document. 
1891.2 .... 
— 10.20 
Lyon. 
Communicated in letter to author, Feb. 16,1891. 
1892.5 .... 
—10.27 
E. D. Preston. 
Coast and Geodetic Survey Report for 1893, part 2. 
1894.9 .... 
—10.33 
Lyon. 
Hydrographic Office archives document. 
Year. 
Observed. 
Computed. 
O-C. 
- 2 
O-C . 
o 
o 
1817. 
—10.95 
—10.85 
— 0.10 
0.0100 
1819. 
—10.40 
—10.72 
+0.32 
0.1024 
1824.5 .... 
— 9.87 
—10.40 
+0.53 
0.2809 
1827. 
—10.43 
—10.27 
—0.16 
0.0256 
1836. 
—10.18 
— 9.88 
—0.30 
0.0900 
1837. 
—10.33 
— 9.85 
—0.48 
0.2304 
1838. 
—10.65 
— 9.82 
—0.83 
0.6889 
1840. 
— 9.28 
— 9.75 
+0.47 
0.2209 
1852. 
— 9.17 
— 9.49 
+0.32 
0.1024 
1859.2 .... 
— 9.68 
— 9.43 
—0.25 
0.0625 
\ 
1871. 
— 9.60 
— 9.52 
—0.08 
0.0064 
■Probable error of a single observation = ± 14'. 
1872. 
— 9.30 
— 9.53 
+0.23 
0.0529 
1875. 
— 9.27 
— 9.59 
+0.32 
0.1024 
1875.5 .... 
— 9.35 
— 9.60 
+0.25 
0.0625 
1879. 
— 9.53 
— 9.68 
+0.15 
0.0225 
1881. 
— 9.67 
— 9.74 
+0.07 
0.0049 
1884. 
—10.23 
— 9.83 
—0.40 
0.1600 
1888.2 .... 
—10.05 
— 10.00 
—0.05 
0.0025 
1891.2 .... 
—10.20 
—10.13 
—0.07 
0.0049 
1892,5 .... 
—10.27 
—10.19 
—0.08 
0.0064 
1894.9 .... 
—10.33 
—10.30 
—0.03 
0.0009 
2.2403 
Empirical equation for determining the declination for any year: v = — 9°.52 
f 0.0158 {t — 1850) — 0.00074 {t — 1850) 2 . 
