OBSERVATIONS ON THE AURORA BOREALIS.

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liant as during its absence. I have every reason to think that not only the varioustints that are sometimes seen in the Aurora, but also some other of its characteristics,are the effects of refraction and reflection of the original auroral light; or, in otherwords, that they are secondary effects. W. S.

Note.— The dates of the preceding displays of the Aurora Borealis, are those givenin the heading of each individual case. The dates of the several descriptions of themwill be found in the Abstracts, Section II.

A DESCRIPTION OF SEVERAL EXTRAORDINARY DISPLAYS OF THE AURORABOREALIS, AS OBSERVED AT PRESTWICK* DURING THE WINTER OF1848-1849 ; WITH THEORETICAL REMARKS.

(Read at the Royal Institution, Manchester, March 28th, 1849, and originally published in the Edinburgh

New Philosophical Journal.)

Having had opportunities of observing several fine displays of the Aurora Borealissince the commencement of last autumn, some of which presented phenomena of veryrare occurrence, a description of them as they appeared at this place can hardly failto be interesting to philosophical inquirers; more especially as data are still wantingto establish a foundation for a true theory of the meteor—a physical problem of longstanding, and hitherto without any satisfactory solution.

The first grand display of the Aurora Borealis, in this list, occurred on Wednesdayevening, October 18th, 1848. It began with the close of the day, and lasted, withvarious degrees of brilliancy, till ten o’clock, or probably later ; for, labouring underthe effects of a severe cold, I could not watch it closely out of doors. It consisted ofan extensive arch of light, which crossed the magnetic meridian at nearly right angles(which, however, was not its invariable position, but that which it assumed duringthe greater part of the display), and immense floods of lambent streamers, which occa-sionally flowed gently upwards and downwards, from various parts of the arch. Theaverage colour of the light was that of a candle flame, though in parts, and especiallytowards the eastern extremity, the colour was red, inclining to violet. I observednothing extraordinary in these streamers, nor in the general aspect of the Aurora ;but, for reasons already stated, I could not make a minute survey.

For several days previous to this Aurora, the atmosphere had been highly chargedwith the electric fluid. On the preceding Saturday I had the electrical kite elevatedabout 400 yards, from the string of which a small jar was rapidly and frequentlycharged: a steel needle was magnetized, and its poles reversed several times, by the

* Prestwich is a village at the distance of four miles from Manchester, in a north-west direction, on the New road to Bury,from which it is also four miles distant.