De la Rive on the Aurora Borealis. 353 
Arr. XXXVII.—On the Cause of the Aurora Borealis; by 
Prof. * . 
. A. pe ua Rive 
Wuen in June 1836, 1 published in the Bibliotheque Univer- 
selle a note on the origin of hail and ‘atmospheric electricity, I 
already foresaw that the same cause would explain the aurora 
borealis, and the irregular and diurnal variations of the magnetic 
needle. As I had not then seen an aurora, I withheld at that time 
this application of the principles. Since then I have witnessed 
fine auroras, and the appearances observed, especially during 
that of November 17, 1848, have confirmed my view of the na- 
ture of the phenomena, while they also accord with the observa- 
tions of others, especially with those of Hansteen, Bravais an 
Lottin, and also with the many interesting details in Humboldt’s 
osmos. My subsequent electrical experiments throw additional 
_ light on the origin of the aurora. 
_ This last statement indicates that I regard the cause as electri- 
cal. This view has often been presented before, and was brought 
forward by Arago at the time of CErsted’s discovery. Yet no 
one, to my knowledge, has explained the mode of action and 
production of the electricity, or the attendant phenomena result- 
ing from this cause. 
Without going into any historical details, I will briefly describe 
the Aurora. Borealis itself and its effects, and then pass to my 
own theory, the accordance of which with facts I shall endeavor 
to point out. 
1. Description of the Aurora and its accompanying effects. 
I cite the following details principally from the Cosmos.’ They 
are derived mostly from the descriptions of Hansteen, Bravais, 
Lottin, and other travellers, who have been in favorable places 
for observing the aurora. The learned author of Cosmos has 
grouped the facts with great skill, presenting in an admirable 
manner the prominent points, and seems with scientific tact to 
teach towards the true theory of the phenomena which he de- 
Scribes 
An aurora borealis is always preceded by the formation in the 
horizon of a kind of nebulous veil, which rises slowly to a height 
of four to six or eight, or even ten degrees about the mag- 
netic meridian ; the sky though before pure, becomes darkened, 
and over this obscure segment, whose color varies from brown 
to violet, the stars are seen as through a thick e. n arc 
of light, first white, and afterwards yellow, borders the dark seg- 
Ment. Sometimes this luminous are is agitated for hours by a 
a Mem, Soe. de Phys. et Hist. Nat. de Genéve, xiii, and Bib. Univ., xxiv, 337, Dec. 
53. 
Seconp Serms, Vol. XVIII, No. 54—Nov., 1854. _ 45 
