176 Prof. Hansteen on the Magnetic Poles of the Earth. 
meridian. In the same manner it may be explained why the 
eastern declination was less before the year 1580. 
The changes in the southern hemisphere may also be ex- 
plained from the above-mentioned motions of the magnetic 
poles. Thus, for instance, at the Cape of Good Hope and 
in the different bays of the adjoining sea, the declination, 
during the time of Vasco de Gama was easterly (i.e. the 
northern pole of the needle pointed to the east, the southern 
to the west); but subsequently it became westerly, and that by 
more than 25°. It was in the year 
1605 = 0°30! E. 1724 = 16°27! W. 
1609 OTF Wa OL 75e ro oD 
1614 Ts 1768 19 30 
1667 ye 1775 Q1 14 
1675 8 30 1791 25 40 
1702 12 50 1804 25 4 
But in the year 1605 the position of the South American 
magnetic pole a was 283°3 E. 7. e. nearly south of Terra del 
Fuego; and the New Holland magnetic pole A lay about 150° 
E. from Greenwich. ‘The first point lay therefore much 
nearer the Cape of Good Hope, which is about 18° E. from 
Greenwich, than it does now, whilst the latter was further 
from it. ‘Thence the effect of the former on the needle was 
stronger than at present, whilst that of the latter was weaker ; 
and the southern pole of the needle moved more towards the 
west, and the northern more towards the east. But as the 
American southern point went further off, and that of New 
Holland approached, the southern pole of the needle turned 
more and more towards the latter, whereby the declination 
became westerly. 
The dip also varies on different parts of the surface of the 
earth, increasing in some, and diminishing in others. Thus 
it was in Paris: 
in 1671 = 71° .0 1798 = 69°26! 
1754 7215 1806 69 12 
1780 71 48 1814 68 36 
In eastern Siberia and at Kamtschatka it increases. Both 
are the results of the motion of the Siberian magnetic pole 
towards the east, in which it is removing from Europe, and 
approaching Kamtschatka. In the whole of South America 
the southern dip decreases, and that in consequence of the 
motion of the south-western magnetic pole, towards the west. 
APPEN- 
