of the Magnetic Poles of the Earth. 175 
cording to former experiments, but in spite of philosophical 
misgivings has been removed by Ciérsted’s discovery. It is 
possible that the various illumination and heating of the earth 
during the period of one revolution on its axis, may produce 
a magnetic tension, as well as it produces the electrical powers, 
and that the altered position of the magnetic axes may be 
explained from an altered position of the terrestrial axis to- 
wards its orbit. Let it however be understood, that I ad- 
vance these positions merely as suppositions. 
It is proved then that the earth has two magnetic axes; 
and, consequently, four magnetic poles, of which the two 
northern turn from west to east, and the two southern from 
east to west, but with great difference in their motion. Let 
us see whether the variation in the declination may be ex- 
plained from this. In the beginning of the 17th century the 
declination throughout all Europe was eastward; then it de- 
creased, and disappeared a short time after the middle of that 
century; then became westward, increasing till within the late 
years, when it began to become invariable, and even to de- 
crease.—Thus the declination in Paris was in 
1541 = 7° O'E. 1667 = 0°15' W. 
1550 8 O 167a. dap 
1580 11 30 1680 2 40 
1603 8-45 1683 _ 3 50 
1630 4 30 1700 7 40 
1640 3 0 1800 22 12 
1659 2 0 1807 22.34 
1664 0 40 1814 22 54 
1666 0 0 1894 22 931% 
From the motions of the two northern magnetic poles found 
before, it appears that in the year 1580 the Siberian pole 4, 
was about 40° E. of Greenwich, z.e. north of the White Sea; 
whilst the American B, was in about 224° E. from Greenwich, 
and thus somewhat above 30° east from Behring’s Straits. 
Thus the former lay much nearer Europe than now; and the 
latter was further off:—thence the effect of the former was 
greater in Europe than that of the latter, and the needle 
turned towards the east. In the mean time the first removed 
towards the Siberian Ocean; and as the second approached 
Europe, although rather slowly, its effect became stronger, 
and the needle turned westward, till it has now attained its 
greatest declination, and will probably again approach the 
* I have added this declination from the Annales de Chimie, tom. xxvii. 
p. 436.—K. ea 
meridian, 
