certain conclusions as to their origin, which give us quite light which seemed to have a tendency to meet together 
i a new conception of the whole phenomenon of aurore. | in the zenith of the inclination-needle. The beams of 
is It is well known that aurore are of two different kinds. | light continually changed their place, increasing in 
= The most usual ones in that part of the northern hemi- | number and size, and finally there appeared the well- 
____ sphere which is more or less inhabited, and therefore the | known beautiful “draperies” of rays, 
¢ best known, show us a luminous arc which consists of! But besides this kind of aurorz there was sometimes 
rays and beams of light perpendicular to its lower edge. | observed another, consisting simply of a luminous halo- 
These beams flow towards the zenith, and sometimes they | like arc, not distributed into rays, and characterised by 
meet together and accumulate in the neighbourhood of | its feeble brilliancy, as well as by the remarkable quiet- 
_ this point in the shape of a crown; sometimes they are ness of the whole phenomenon. Such were, with one 
dissolved into light and bright clouds, or in regular strata | single exception, all the aurorze observed during the 
of light. The most characteristic feature of these aurorz | wintering of the Vega at Kolutchin Bay (67° 5’ N. Jat., 
is the restless motion of light and their continuous and 186° 37’ E. long.) “Only once,’ Nordenskjéld says, 
changes. Those observed by the Swedish Spitzbergen | “on March 29 to 30, did we see some beams of light ; 
Expedition in 1872-73, at Mussel Bay, belong to the same | but nearly always, as soon as the sky was bright and the 
kind of aurorz, but with the difference from the European | faint light of the aurora was not dimmed by sun- or moon- 
part of the sky. They usually began in the shape of an) horizon an arc of equally spread light, the summit of 
~~ arched band of light at a small height above the southern | which was 5° to 12° above the horizon. Usually it 
part of the horizon; soon it rose higher, became less | reached about 10°, and then it spread with a regular 
- regular and more brilliant, and divided into bundles of | curvature for about 45° on both sides of its summit, which 
Fic, 1.—Vhe common aurora-arc at the Vega's winter quarters. 
was situated toward north-north-east (see Fig. 1). Hour rarely, it happened also that rays of light were cast to a 
after hour, day after day, this arc remained unchanged, height of 20° or 30°, or even to the zenith. 
varying but insignificantly as to its height, extension, and The “common arc’? was often accompanied by one, 
bearing. Indeed, one might ask if it could not be pho- or several exterior arcs from which it was separated by a 
tographed by an ‘exposure’ for fifteen minutes.” This dark strip, sometimes crossed by rays of light flowing 
arc soon received from the Vega’s crew the name of the from one arc to the other. The exterior edge of the 
“common aurora-arc,”’ which name Nordenskjéld main-  aurora-arc was not well defined, as its brilliancy dimi- 
tains in his description. At Mussel Bay the members of | nished towards the upper edge, spreading a noticeable 
the Swedish expedition also had seen such arcs with | light on the sky above it. On the contrary the separa- 
regularly spread light, and they had thought that they | tion line between light and darkness was more definite on 
originated in rays being directed towards the observer. | the lower edge, so as to convey the impression that the 
But now Nordenskjéld doubts whether on any occasion | luminous arc reposed on a dark cloud-like basis—the so- 
the avrora-arc could consist of rays of light. If this called ‘‘dark segment.” The true name for it would, 
explanation were true the arc ought to be more brilliant however, be “the unlighted segment,’’ as it remained 
than the separate rays, but the contrary is the case. Be- | dark whilst the sky above the arc was as if covered with 
sides, the arcs observed at Mussel Bay were of a far less | a feeble luminous veil. In reality there is no ‘dark 
regular shape and more changeable as to the brilliancy | segment” at all. Whilst zswad//y the stars were visible 
of their different parts, than those observed at the Vega’s | through the “dark segment” without any loss of bril- 
wintering place. In these last there were sometimes ob- | liancy, that was not always the case. In the latter case 
served also streams of light like pulsations which move | the “dark segment” was in reality a true cloud which 
from one part of the arc to another; and sometimes, but | simply seemed to have the shape of the aurora-are; it 
[ Feb, 2, 1882 
ones that they appeared in the southern or south-eastern | light, we have seen on the north-eastern part of the - 
a eee ee ee ee 
