Tfof. Hatisteen on the Aurora Borealis. B5 
setver sees his own portion. We may give an explanation of 
this by means of the hour-circle on a globe. Suppose a little 
insect creeping round the globe in the 60th parallel, it will only 
see a small part of the ring, as the largest portion of it will be 
concealed by the globe which forms the insect’s horizon. The 
highest part of the arch which in this case it can see will be due 
north. If it approach nearer to " the ring, it wall see' a' larger 
portion of it; and when it is close under its edge, this will ap- 
pear to be in the zenith. If it come nearer the Pole, and within 
the ring, the nearest and highest part of the ring will be seen to 
the south, just as the ring of the Aurora Borealis was seen at 
•Good Hope. Now, were the pole of the earth, or rather a point 
of its lengthened axis, the centre of the ring of the Aurora Bo- 
realis, the highest point of the arch would be 'seen every where 
in the true meridian, or due north. But, as this is not the case, 
-since, with us, the highest point of the arch is seen about 20° 
west of due north, in North America it is seen due north, and 
at Good Hope, in Greenland, to the east, it follows that the 
centre of the ring must lie about from 20° to 30° from the Pole 
of the earth, in a meridian passing through the States of North 
America. And since the arch is sometimes seen in the zenith 
near Iceland, and often stretches so far to the south as to pass 
the zenith, both here, in Christiania and in Copenhagen, and even 
in more southerly regions, it follows that the radius of the ring 
of the aurora borealis may extend from 20° to 40° and above. 
It is easy now to perceive in what manner the arch of the 
aurora borealis will appear in different meridians. If it be 
viewed from a point lying in the same meridian with its centre, 
its highest point will appear due north ; and if this rise so high 
as to pass through the zenith, its extremities will terminate in 
the east and west. If, again, it be viewed from a point lying 
eastward of the meridian of the ring, as with us in Europe, then 
the highest point of the arch wilPmove to the west of the meri- 
dian, and the farther the more you advance to the north, till 
you come to the same latitude with the centre of the ring, be- 
tween 60° and 70°. Here the highest point of the arch will lie 
due west ; and if the ring extend so far as to pass through the 
observer’s zenith, it will go from north to south, that is, it will 
be parallel with the meridian. Such was the case with regard 
to the arch seen by Captain Scoresby on the 15th of April io 
