of the Magitétic Poles of the Earth. 173 
The distance we found above for the year 1773 was 
Distance from the pole = 20° 39 
E. longitude from Greenwich = 136 15 
It is possible that the determinations for the year 1642 may 
not be quite correct, since at that period they had no means 
of giving the exact longitude; nevertheless I do not believe 
that the uncertainty with respect to the longitude of this point 
amounts to one degree. Thus then this magnetic pole has 
moved within 131 years, 10° 14’; or 469 per annum west- 
ward. The situation of the other magnetic pole south of 
the continent, I have fixed for the year 1670, from some ob- 
servations mentioned by Halley in his table of variations of 
the magnetic needle (Philos. Trans. No. 148), as follows: 
Distance from the pole =, 15° 53! 
E. longitude from Greenwich = 265 263 
We have found the situation of this pole for the year 1774: 
Distance from the pole =e ey 
E. longitude from Greenwich = 
Thus this pole has moved within 104 years 28° 43/1, or 
16'°57 annually, westward. 
Whence we see that the two magnetic poles in the northern 
hemisphere move eastward, while those in the southern hemi= 
sphere move westward. 
For the sake of abbreviation we will designate the south- 
eastern pole below New Holland, by A; the south-western 
below Terra del Fuego, by a; the north-westerly in America, 
by B; and the north-easterly in Siberia, by 4. Thus A and 
B are very nearly diametrically opposed to each other: for 
the distance of both from the pole is about 20°; and A lies in 
the meridian 136°, and B in that of 260° E. of Greenwich, 
which makes a difference in longitude of about 125°. The 
case is similar, although with greater deviations, with the points 
a and b; the distance of the former from the antarctic pole 
being 13°, and of the latter from the arctic pole a little above 
4°; and the longitude of the former being = 237°, and that 
of the latter 116°; thus giving a difference in longitude of 
= 121°. Experience, however, teaches us that there are no 
magnets with one or three poles, 7. e. with any odd number 
of poles; a result which might have been found @ priori, 
as the magnetic force only arises from a destruction of the 
equilibrium in the opposite powers; whilst one power prevails 
in one part of the body, the other must be forced into the 
opposite extremity. Therefore a magnet of several poles must 
be considered as an assemblage of magnets each of which has 
its 
