40 
THE VOYAGE OF THE VEGA. 
[chap. 
height, extent, and position from which I believe I may draw the 
following inferences : that our globe even during a minimum 
aurora year is adorned with an almost constant, single, double, or 
multiple luminous crown, whose inner edge is situated at a height 
of about 200 kilometres or. 0'03 radius of the earth above its 
surface, whose centre, “ the aurora-pole,” lies somewhat under the 
earth’s surface, a little north of the magnetic-pole, and which, 
with a diameter of 2,000 kilometres or 0'3 radius of the earth, 
extends in a plane perpendicular to the radius of the earth, which 
touches the centre of the circle. 
I have named this luminous crown the aurora glory on account 
of its form and its resemblance to the crown of rays round the 
head of a saint. It stands in the same relation to the ray and 
drapery auroras of Scandinavia as the trade and monsoon winds 
in the south to the irregular winds and storms of the north. The 
light of the crown itself is never distributed into rays, but re¬ 
sembles the light which passes through obscured glass. When 
the aurora is stronger, the extent of the light-crown is altered: 
double or multiple arcs are seen, generally lying in about the 
same plane and with a common centre, and rays are cast between 
the different arcs. Arcs are seldom seen which lie irregularly to 
or cross each other. 
The area in which the common arc is visible is bounded by 
two circles dravm upon the earth’s surface, with the aurora-pole 
for a centre and radii of 8° and 28° measured on the circumference 
of the globe. It touches only to a limited extent countries 
inhabited by races of European origin (the northernmost part of 
Scandinavia, Iceland, Danish Greenland), and even in the middle 
of this area there is a belt passing over middle Greenland, South 
Spitzbergen, and Franz Josef Land, where the common arc forms 
only a faint, very widely extended, luminous veil in the zenith, 
which perhaps is only perceptible by the winter darkness being 
there considerably diminished. This belt divides the regions 
where these luminous arcs are seen principally to the south from 
