370 
NATURE 
[ Fed. 16, 1882 
another are also in the same strata. In this case they 
could not be rectilinear, but must flow upon curves drawn 
by a radius equal to the distance from the crowns to the 
centre of earth; therefore, when seen from the Vega’s 
winter quarters, the rays which were cast 50° or 60° from 
the edge of the luminous arc, would appear only exception- 
ally as straight lines; usually they would show a regular 
curvature of several degrees. But neither at Kolutchin 
Bay nor at other places did Nordenskjéld remark such a 
curvature, and he concludes that the common aurora- 
glory must be produced in a plane perpendicular to the 
earth's radius, which passes through the aurora-pole. 
But it is possible also that the long exterior rays may 
have quite another direction than those which connect 
together aurora-rings; and whilst these last are cast in 
the plane of the aurcra-glory, the former may be launched 
in the direction of the inclination-needle. 
A drapery-aurora was seen but once at the Vega's 
winter-quarters. But sometimes the common arc rose 
more above the horizon, or changed its bearing ; or new 
arcs, quite different from the common one, appeared. 
Sometimes, as, for instance, during the night of March 3 
to 4 (Fig. 3), the bows crossed one another. In general 
the feeble aurorze were quite regular, whilst the more 
intense afforded more or less irregularity. But even these 
latter usually began with the appearance of the common 
faint arc ; this soon increased, divided into pieces by the 
appearance of brilliant knots—not divided, however, into 
rays—and flame-like knots maintained for a long time the 
same position, sometimes in the neighbourhood of the 
arc, but mostly in the north-eastern part of the sky, some- 
times also in the zenith. From these knots were thrown 
flames of equally diffused light (not divided into rays), 
often, as it seemed, perpendicular to the plane of the 
glory, and in such case spreading to a very great height 
above the surface of the ea:th. The aurora of March 3 
to 4 was remarkable for the number of arcs which ap- 
peared; towards 9.30 p.m. they crossed one another at 
their north-western extremities, but disappeared after 
eleven o’clock, so that at midnight only the common arc 
was seen. But about one o'clock another series of arcs 
appeared towards the west, the outer being tangential 
to the common arc near the horizon, much like toa double 
solar halo. 
Another interesting aurora was seen on March 20 to 
21 (Figs. 4,5,and 6). It was remarkable by the extension 
and great size of the arcs, by their elliptic shape, and by 
the circumstance that the short axes of the ellipses were 
not vertical above the horizon, but inclined, sometimes to 
the right (Fig. 5) and sometimes to the left (Fig. 6). It 
seems as if the plane of the glory was slowly oscillating 
for some 4° or 5° on both sides of its usual position. 
On March 30 to 31 there appeared a great number of 
arcs, which were seen all at the same time. Of six arcs, 
only two were in the north-eastern part of the sky, whilst 
the summit of the third was nearly at the zenith, at a 
height of 80° and three others were beyond the zenith, 
their summits being respectively 105°, 125°, and 135° dis- 
tant from the north-eastern horizon. 
It is most important to determine where, and under 
what aspect, the aurora-glory is visible in different parts 
of our globe, and Nordenskjéld gives special attention 
to this subject. The second (outer) ring and its rays can 
be seea over a very great surface of the northern hemi- 
sphere. If the rays which were seen from the Vega as 
flowing from this ring to the zenith were cast in the plane 
of the glory, and if they were cast from all parts of the 
ring, they must have been seen over a circle drawn from 
the aurora-pole by a radius measuring 5000 kilometres on 
the surface of the earth. This circle would include 
North America as far as California, England, France, 
and the northern parts of the Iberian Peninsula, Austria- 
Hungary, Crimea, Siberia, and Northern Sakhalin. But 
the rays often passed beyond the zenith of the Vega, and 
thus the region of their visibility must be still further 
increased, including Mexico, Spain, Morocco, Greece, 
Asia Minor, a part of Turkestan, and Mantchuria ; that 
is, even such tracts where aurorze very rarely occur. But 
Nordenskjéld does not maintain that all aurore observed 
in Europe were due to rays cast from the glory in its 
plane. He thinks it would be too bold an assertion, as it 
would mean that thousands of observers were in error as 
to the idea they got of the direction of rays. But it is 
probable that a certain part of radiant auroras observed in 
Europe are due to rays cast in the plane of the glory, and 
not to rays cast in the direction of the inclination-needle. 
As to the drapery-aurora which was seen once during the 
Vega's wintering, it seemed to have had its seat nearer to 
the surface of the earth. Such aurore are obviously in 
the same relations to the common arc as the irregular 
winds and storms of the north are to the regular trade- 
winds of the south. 
On the contrary, the space where the common ring of 
the glory is visible is very limited. Its projection on the 
earth’s surfacce would be a circle drawn from the aurora 
pole by a radius of 18°, measured on the surface of our 
globe. And if its height above this surface is 0’03 radius 
of the earth, it must be seen above the horizon in a belt 
14° wide on both sides of this projection. But to be ob- 
served its faint arc must have a height of at least 4° 
above the horizon, and so the belt of visibility of the 
common glory-ring is still less. Besides, if the aurora- 
glory is in reality a ring of light of small thickness 
situated 200 kilometres above the surface of our globe, 
it will not be visible in those parts of the earth where it 
appears in the zenith; there it would appear as a too 
faint diffused girdle of light about 60° wide, and most 
probably would not be perceived. 
Therefore we must have five different regions situated 
around the aurora pole, where the glory would appear 
under quite different aspects. These five regions are 
represented on the map, Fig. 7, which is a reduction of 
Nordenskjéld’s map. 
In the first circular region around the aurora-pole (I. 
on our map), inscribed in a circle drawn from the aurora 
pole with a radius measuring 8° on the surface of the 
earth, the glory is visible only as a luminous mist, or as a 
very low bow, in a direction opposite to the aurora-pole. 
As the projection of rays within the common arc seems to 
be very rare, the aurora phenomena is very rarely to be 
seen in this region. Very many Arctic explorers have 
visited this region: Parry, Ross, McClintock, Kennedy, 
Osborn, Saunders, Belcher, Hayes, Kane, Hall, Stephen- 
son, and Nares, have wintered within it ; but among their 
careful and varied observations aurore occupy quite an 
insignificant place—a circumstance very remarkable, as it 
is obvious that aurore cannot be overlooked by Arctic 
travellers, being the only variety during the long Arctic 
nights. Parry saw aurore as a feeble diffused light in 
the south-west ; Hayes saw but three aurora; and Capt. 
Nares says: “Light flashes of aurora wera occasionally 
seen on various bearings, but most commonly passing 
through the zenith. None were of sufficient brilliancy to 
call for notice. The phenomena may be said to have 
been insignificant in the extreme, and, as far as we could 
discover, were totally unconnected with any magnetic or 
electric disturbance.” : 
The second region (II.) is inclosed between two circles 
drawn from the aurora pole by radii 8° and 16° long. The 
common ring of aurora must be seen in this region as 
a luminous bow, the upper part of which is situated in 
a bearing opposite to that of the aurora-pole, that is, 
about the magnetic south. Ross, Parry, McClure, Mac 
Clintock, Koldewey, and Nordenskjéld (1872-73) have 
wintered in this region. Ross, on September 23, 28, and 
29, 1818, saw vertical rays in the southern part of the 
horizon, and Parry, on September 15, 1825, saw a bow 5 
or 6° high, which lasted, nearly unchanged, for two or 
