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MAGNETISM, TERRESTRIAL

TABLE II.-Recent Values of the Magnetic Elements and their Rate of Secular Change.

Geographical position. Absolute Values of Elements. Secular change (mean per annum). -T Place' Interval Latitude Longitude. Year. D. I. H. V. inyearg D. I. H. V. O I O I U I O I I I Pavlovsk 59 41N 30 29E 1906 1 4-2E 70 36-6N ~16528 -46963 5 -4-5 +0-1 - 6 — I4 Sitka (Alaska) 57 3N 135 20W 1906 30 3-3E 74 41~7N -15502 -56646 4 -3-0 -1-6 +18 -38 Ekiixtariliiburg 56 49N 60 381-3 1906 IO 31-0E 70 49'5N -17664 ~50796 5 ~-4-5 +1-7 -23 +18 u e S ov 5 (Copenhagen) 55 51N 12 27E 1908 9 43-3W 68 45N -17406 -44759 Stonyhurst 53 51N 2 28W 1909 17 28-6W 68 42-SN -17424 -44722 5 -5-9 -1-1 + 6 -25 Hamburg 53 33N 9 SQE 1903 II 1o-2W 67 23-5N °18126 '43527 Wilhelmshaven 53 32N 8 9E 1909 II 46-8W °18129 5 -5-2 - 7 Potsdam .... 52 23N 13 4E 1909 9 10-6W 66 20-oN '18834 '4297I 5 -5-8 +0-1 - 9 -19 Irkutsk .... 52 16N 104 16E 1905 1 58-1E 70 25-oN -20011 -56250 5 +0~6 +2-0 -24 +39 de Bilt 52 5N 5 IIE 1907 13 19-0W 66 49-9N -18559 -43368 5 -4-7 -0-6 + 2 -16 Valencia. SI 56N IO 15W IQOQ 20 50-3W 68 15-1N -17877 '448I2 5 -5-0 -I'2 + 7 -25 Kew . .. 51 28N 0 19W 1909 16 10-8W 66 59-7N ~18506 -43588 5 -5-4 -1-1 + 2 -35 Greenwich SI 28N 0 0 1909 15 47-6W 66 53-9N -18526 ~43432 5 -5-5 -0-7 + 1 -20 Uccle 50 48N 4 21E 1908 13 36-7W 66 1-6N ~1906I -42867 4 »-5-3 -0-8 — 3 -35 Falmouth 50 9N 5 5W 909 17 48~4W 66 30-6N 'ISSOZ -43266 5 -4-7 -1-4 + 9 -30 Prague 50 5N 14 25E 1908 8 20-9W 5 -6-5 Cracow 50 4N 19 58E IQOQ 5 35-IW 64 18N 3 -7-3 5t Helier 49 12N 2 5W 1907 16 27~4W 65 34-5N 5 -5-3 -1-2 Val joyeux 48 49N 2 1E 1909 14 32-9W 64 43'9N »19727 -41792 5 -5-4 -1-7 + 1 ~51 Vienna 48 15N 16 ZIE 1898 8 24~1W Munich 48 9N II 37E 1906 9 59-5W 63 10-oN 20657 -40835 5 -4-8 -1-3 + 4 -31 O'Gyalla 47 53N 18 IZE 1909 6 43'9W 21094 5 -5-0 -10 Odessa .. 46 26N 30 46E 1899 4 36-7W 62 I8-2N 21869 -41660 Pola . 44 52N 15 51E IQOS 8 43-2W 60 6-8N 22207 -38640 5 -5-5 -0-6 - 4 -23 Agmcourt (Toronto) 43 47N 79 16W 1906 5 45-3W 74 35-6N 16397 ~59502 4 +3-4 +0-9 -23 -24 Nice ... 43 43N 7 16E 1899 12 4-0W 60 11-7N 22390 -39087 Toulouse 43 37N 1 28E 1905 13 56-3W 60 49-1N °22025 '39439 5 -4-5 -1-5 + 2 - 2 Perpignan 42 42N 2 53E 1907 13 4-4W 7 -4-7 Tiflis . . 41 43N 44 48E 1905 2 41-6E 56 2-8N -25451 '37799 7 -5~2 +1-7 -26 + 2 Capo di Monte. 40 52N 14 15E 1906 8 40-3W 56 13-5N 5 -5-1 -1-5 Madrid . 40 25N 3 40W 1901 15 35~6W Coimbra . .. 40 12N 8 25W 1908 16 46~2W 58 57-3N 22946 -38120 5 -4-6 -2-9 +17 -45 Baldwin (Kansas) 38 47N 95 10W 1906 8 30-IE 68 45'IN 21807 -56081 4 -1-7 +1-8 -36 - 8 Cheltenham (Maryland) 38 44N 76 50W 1906 5 22-0W 70 27-3N ~20035 -56436 4 +3-8 +1-2 -38 -45 Lisbon .. 38 43N 9 9W 1900 17 18-0W 57 54-8N '235I6 -37484 Athens . . 37 58N 2I 23E 1908 4 52-9W 52 11-7N -26197 -33613 5 -5-5 5an Fernando 36 28N 6 12W 1908 15 25-6W 54 48'4N -24829 -35206 5 -4-6 -2-8 +26 -24 Tpkyo; - ~ - 35 41N 139 4515 1901 435'1W 49 0'0N 29954 '34459 Z1-ka-wel 31 I2N 121 26E 1906 2 32'OW 45 35-3N 33040 -33726 5 +1-5 -1-3 +30 + 6 Dehra Dun 30 19N 78 3E 1907 2 38-3E 43 36-1N 33324 -31736 4 +0-8 +5-5 -26 +77 Helwan 29 52N 31 2IE 1909 2 49-2W 40 40-4N 30031 -25804 5 -5-7 +I'2 - 6 +13 Havana . 23 8N 82 25W 1905 2 25-0E 52 57-4N 30531 -40452 Barrackpore 22 46N 88 22E 1907 1 9-9E 30 30-2N 37288 ~21967 3 +4-2 +3-4 +21 +62 Hong-Kong. 22 18N 114 1oE 1908 0 3-9E 31 2-5N 37047 -22292 5 +1-9 -1-8 +43 - 1 Honolulu 21 19N 158 4W 1906 9 21-7E 40 1-SN 29220 -24545 4 -0-9 -3-2 -19 -62 Kolaba 18 54N 72 49E 1905 0 I4°OE 2I 58-5N 37382 -15084 5 +2-1 +7-2 -11 +86 Alibagh . 18 39N 72 52E IQ09 1 0-3E 23 29'ON 36845 -16008 3 +I- +6-8 -I0 +82 Vieques (Porto Rico) 18 9N 65 26W 1906 1 33-2W 49 47-7N 28927 -34224 2 +7- +6-8 -49 +66 Manila ... 14 35N 120 59E 1904 0 51-4E 16 0-2N 38215 -10960 5 +0-1 -3-9 +47 —34 Kodaikanal IO 14N 77 28E 1907 0 40-7W 3 27-2N 37431 -02259 4 +4- +5-5 +16 +61 Batavia 6 115 106 49E 1906 0 54-IE 30 48-55 36708 -21889 4 +2- -7-7 - 2 +110 Dar es Salaam 6 495 39 18E 1903 7 35-2W, Mauritius 20 65 57 33E 1908 9 14-3W 53 44-95 ' ~23415 -31932 5 -0-3 +2'9 -53 -131 Rio de Janeiro 22 555 43 11W 1906 8 55-3W 13 57-15 -24772 'O6164 5 +9-1 -6-8 -42 +44 Santiago (Chile) 33 275 70 42W 1906 14 18-7E 30 11-85 3 +6-1 +9-9 Melbourne 37 505 144 58E 1901 8 26-7E 67 25-05 -23305 -56024 Christchurch, N.Z. 43 325 172 37E 1903 16 18-4E 67 42-35 -22657 -55259 west lasting for about sixty years. Further west the period shortens. At Pueblo (Colorado) it is about forty years, at Salt Lake under thirty years, at Prescott (Arizona) about twenty years. Considering how fast the area throughout which the secular change is easterly has extended to the east since 1885, one would be tempted to infer that at no distant date it will include the whole of the United States. In the extreme north-east, however, the movement of the needle to the west, which had slackened perceptibly after 1860 or 1870, is once more accelerating. Thus the auspices do not all point one way, and the future is as uncertain as it is interesting. § 12. Table VII. gives particulars of the secular change of horizontal force and northerly inclination at London. Prior to the middle of the 19th century information as to the value of H is of uncertain value. The earlier inclination data” are due to Norman, Gilbert, Bond, Graham, Heberden and Gilpin. The data from 1857 onwards, both for H and I, refer to Kew. “London " is rather a vague term, but the differences between the values of H and I at Kew and Greenwich-in the extreme west and eastare almost nil. For some time after its discovery by Robert Norman inclination at London increased. The earlier observations are not sufficient to admit of the date of the maximum inclination or its absolute value being determined with precision. Probably the date was near 1723. This view is supported by the fact that at Paris the inclination fell from 72° 15' in 1754 to 71° 48” in 1780. The TABLE III.-Declination at London. O I 0 I 1580 1622 1634 1657 1665 1672 1692 1723 1748 2 6 14 17 1 E 1773 1787 1795 1802 1805 1817 1818 1819 1820 22W 30 0 17 40 21 23 23 24 24 24 24 24 8 36 38 36 24 34 9W 19 57 6 Date. Declination. Date. Declination. O I II 5 6 0 4 6 0 0 1 1860 1865 1870 1875 ISSO 1885 1890 1895 1900 IQOS 2I 20 20 19 18 I Date. Declination. I8 17 17 16 16 38'9W 53-7 18-3 35'6 52-1 19-2 50-6 16-8 52'7 32"9