166 METEOROLOGY [TERRESTRIAL MAGNETISM. at other stations ; and, although these changes are not strictly simultaneous at the various stations, they have yet been sufficiently general and near together in point of time to indicate that some TABLE I. Secular Change of Variation in Great Britain. Observer. Date. Declination. Mean Annual Westward Change. Burroughs 1580 11 15 E G unter 1622 6 OE. 7 5 Gellibraud 1634 4 6E 9-5 Bond 1657 OE. 10-6 Gellibrand . 1665 1 22 W 10-2 Halley 1672 2 SOW 9 7 Halley 1692 6 W. 10-5 Graham 1723 14 17 W 16 Graham 1748 17 40 W 8-1 Heberden 1773 21 9 W. 8 4 Gilpin 1787 23 19 W 9-3 Gilpin. . 1795 23 57 W 47 Gilpin 1802 24 6 W 1-2 Gilpin 1805 24 8W 07 change has probably taken place in the movement of one set of the magnetic foci of force. 33. Halley sought to explain the four-pole theory and to account TABLE II. Changes of Declination in England, at Buslicy Heath for 1817-20, and at Kewfrom 1858. Declination West. Declination West. 1817 24 36 4 1869 // 20 26 24 1818 24 38 25 1870 20 18 52 1819 24 36 14 1871 20 10 31 1820 24 34 30 1872 20 31 1858 21 54 8 1873 19 57 44 1859 21 47 22 1874 19 51 58 1860 21 39 51 1875 19 41 14 1861 21 31 36 1876 19 31 53 1862 21 23 32 1877 19 22 22 1863 21 13 16 1878 19 13 50 1864 21 3 35 1879 19 6 10 1865 20 59 3 1880 18 57 59 1866 20 51 10 1881 18 50 30 1867 20 40 26 1882 18 44 47 1868 20 33 9 TABLE III. Exhibiting certain Years Values of Declination at Various Places. Toronto Makerstoun. Trevandrum. Cape of Good Hope. Hobart Town. Declination Declination. Declination. Declination. Declination. 1841 1 14-3W. 1841 25 337 W. 1854 25-896 E. 1605 30-0 E. 1843 9 53-32 E. 1842 1 19-1 W. 1842 25 28-4 W. 1855 26-026 E. 1609 12-0 W 1844 9 54-93 E. 1845 1 29-1 W. 1843 25 22-9 W. 1856 26-400 E. 1622 2 0-0 W 1845 9 56-47 E. 1846 1 30-8 W. 1844 25 17-1 W. 1857 27-278 E. 1675 8 14-0 W 1846 9 58-42 E. 1847 1 33-2 W. 1845 25 11-3 W. 1858 28-769 E. 1691 11 0-0 W. 1847 9 59-28 E. 1848 1 35-4 W. 1846 25 6-OW. 1859 30-406 E. 1751 19 15-0 W. 1848 9 60-61 E. 1849 1 36-9 W. 1847 24 59-6 W. 1860 32-034 E. 1775 21 14-0 W. 1850 1 38-6 W. 1848 24 51 -8 W. 1861 34-318 E. 1788 24 4-0 W. 1851 1 40-9 W. 1849 24 45-2 W. 1862 36-654 E. 1792 24 31-0 W. 1856 1 56-3 W. 1850 24 39-0 W. 1863 39-123 E. 1818 26 31 -0 W. 1857 2 0-5 W. 1851 24 31-3 W. 1864 41 603 E. 1836 28 30-0 W. 1858 2 4-5 W. 1852 24 25-2 W. 1865 44-007 E. 1839 29 9-0 W. 1859 2 7 4 W. 1853 24 187 W. 1866 46-310 E 1841 29 6-2 W. 1860 : 2 10-6 W. 1854 24 11-8 W. 1867 47-590 E. 1842 29 5-9W. 1861 2 14-4 W. 1855 24 5-3 W. 1868 48-687 E. 1843 29 6-0 W. 1862 2 157 W. 1869 49735 E. 1844 29 6-2 W. 1863 2 19-1 W. 1845 29 7-4 W. 1864 2 21-9 W. 1846 29 87 W. 1865 2 24-8 W. 1847 29 12-4 W. 1866 2 27-6 W. 1848 29 14-0 W. 1867 2 29-8 W. 1849 29 16-2 W. 1868 2 33-2 W. 1850 29 18-8 W 1869 2 37-1 W. 1870 2 41-9 W. 1871 2 47 9 W. i TABLE IV. Exhibiting certain Years Values of Dip and Horizontal Force at Various Places. The years in this Table are from April to April thus 1845 means the year from, 1st April 1845 to 31st March 1846. London or Kew. Toronto. Hobart Town. Cape of Good Hope. Dip. Hor. Force. Dip. Hor. Force. Dip. Hor. Force. Dip. 1857 68 24-87 1857 37899 1845 75 15-50 1845 3-5476 1842 70 42-2 1846 4-5054 1841 53 9-1 1858 68 22-56 1858 3-7950 1846 75 14-58 1846 3-5419 1843 70 38-2 1847 4-5001 1842 53 15-3 1859 68 21-41 1859 3-8007 1847 75 15-30 1847 3-5384 1844 70 33-3 1848 4-4991 1843 53 20-2 1860 68 19-29 1860 3-8063 1848 75 18-32 1848 3-5339 1845 70 32-0 1849 4-4997 1844 53 29-4 1861 68 17-42 1861 3-8121 1849 75 18-94 1849 3-5367 1846 70 33-0 1850 4-4998 1845 53 29-3 1862 68 14-89 1862 3-8165 1850 75 19-98 1850 3-5322 1847 70 34-5 1863 68 11-71 1863 3-8216 1851 75 20-42 1851 3-5299 1848 70 357 1864 68 9-31 1864 3-8284 1852 75 20-52 1852 3-5154 1865 68 8-50 1865 3-8306 1866 68 5-44 1866 3-8391 1867 68 2-62 1867 3-8467 1868 68 2-13 1868 3-8493 1869 68 0-41 1869 3-8551 1870 67 57-98 1870 3-8585 1871 67 56-12 1871 3-8640 1872 67 53-60 1872 3-8712 1873 67 51-19 1873 3-8777 1874 67 49-64 1874
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