92 Prof. Hansteen mi the Aurora Borealis. 
dian. 5. The Swedish naturalist Wilcke, has remarked, tha;t, 
during a vivid borealis, the corona sometimes changes its place, 
moving backward and forward several degrees. But since the 
place of the corona is determined by the angle formed by the 
luminous columns with the surface of the earth, it is evident 
that the angle must likewise change. And, in such cases, he 
observed, that the inclination of the needle altered in a similar 
manner, so that moving up and down, it always pointed to the 
centre of the corona. A change in the direction of the earth’s 
magnetism, produces also a change in the direction of the lumi- 
nous columns. 
The perpendicular height of the arch ‘of the aurora borealis 
above the surface of the earth, is to be computed from its height 
above the horizon, observed at two different places, which lie at 
a considerable distance from one another, nearly in the same me- 
ridian. From a number of those arches, the cotemporaneous 
height of which was observed at Borne, Paris, Copenhagen, 
Stockholm, and othei' places, Mr Mairan has found, that the 
ring of the polar lights above the surface of the earth, almost 
always exceeds 100 geographical miles. The luminous co- 
lumns of which the shooting beams consist, have, in all proba- 
bility, the same height Consider now the difficulty of am 
swering the following questions on any other hypothesis than 
what I have suggested : Why do the polar lights spring not 
from the poles of the earth, but from four points at a great dis- 
tance from the poles ? Why do the direction and intensity of 
the earth’s magnetism change so considerably, while the streams 
of this light are issuing forth Why is the direction of the lu- 
minous columns parallel at every place with the direction of the 
magnetism of the earth, or the inclination of the needle ? What 
can that material substance be, which has such powerful influ- 
ence at so great a height over the surface of the earth ? How 
can this, at such a height, produce a certain sound ? From the 
manifold experience we have had of this in the north, it must be 
considered as a fact admitting of no question. Why do the po- 
• When Scoresby talks of the shooting beams appearing to descend to the top- 
masts, this can be considered as nothing else but an optical deception. In the 
Heavens, the eye has no measure of distance. The sun and moon seem equally 
near us, though the first is more than 400 times farther distant than the last. 
