|
Narrative of an Expedition |
|
The general characteristics of the Aurora Borealis are so well known that it is
unnecessary to describe them here; I will therefore confine myself to the following
particulars which appear to deserve a special notice.
1. When the streamers rise high and approach the full moon, a luminous circle of from 20° to 30° is frequently formed round it; the circle continues for a time, and then disappears. 2. When the streamers extend to the zenith, or nearly so, they sometimes resolve themselves into small, faintly luminous, and cloudlike patches, of a milk-white colour, and which, not unfrequently continue to be visible on the following day, in the shape of white wave-like clouds. 3. We often saw on the northern horizon, below the auroral light, dark blue clouds, which bear a great resemblance in colour and form, to the vapours which usually rise from a sudden break in the ice of sea. 4. Even during the most brilliant Auroras, we could never perceive any considerable noise, but in such cases we did hear a slight hissing sound, as when the wind blows on a flame. 5. The Auroras seen from Nishne Kolvmsk usually commence in the north-eastern quarter of the heavens; and the middle of the space which they occupy in the northern horizon, is generally 10° or 20° East of true North. The magnetic variation at this place is about 10° E. 6. Auroras are more frequent and more brilliant on the sea-coast than at a distance from it. The latitude of the place does not otherwise influence them. Thus for example, it would seem from the accounts of the Tschuktschi, that in Koliutschin Island, (in 67° 26 minutes latitude,) Auroras are much more frequent and more brilliant than at Nishne Kolymsk, in latitude 68° 32 minutes. On the coast we often saw the streamers shoot up to the zenith; whereas, this was rarely the case at Nishne Kolymsk; nor was the light nearly so brilliant at the latter place. 7. The inhabitants of the coast affirm, that after a brilliant Aurora they always have a strong gale from the quarter in which it appeared; we did not observe this to be the case at Nishne Kolymsk. The difference, however, may proceed from local circumstances, which often either prevent the sea-winds from reaching so far in land, or alter their direction; for example, it often happens that there is a strong northerly wind at Pochodsk, seventy wersts north of Kolymsk, whilst at the latter place the wind is southerly. 8. The finest Auroras always appear at the beginning of strong gales in November and January; when the cold is most intense, they are more rare. 9. A remarkable phenomenon which I often witnessed deserves to be recorded, i.e. when shooting stars fell near the lower portion of an auroral arch, fresh kindled streamers instantly appeared, and shot up from the spot where the star fell. From some of the above remarks it may be inferred that the freezing of the sea may be connected the appearance of Auroras. Perhaps a great quantity of electricity may be produced by the suddenly rising vapours, or by the friction of large masses of ice against each other. The Aurora does not always occupy the higher regions of the atmosphere; it is usually nearer the surface of the earth, and this is shown by the visible influence of the lower current of the atmosphere, on the beams of the Aurora; we have frequently seen the effect of the wind on the streamers as obvious as it is on clouds; and it is almost always the wind which is blowing at the surface of the earth. |