256 
SECOND REPORT — 1832 . 
obscured bright stars," for the auroral arches which I have 
observed, generally allowed even minute stars to be seen through 
their mass ; but this I admit to be a question of degree. Very 
recently an interesting article by Prof, Jameson has been pub¬ 
lished in the new edition of the Encyclopaedia Britannic a, in 
which the views of Mr. Farquharson cn this point are strongly 
supported*. 
In the paper just alluded to, Mr. Farquharson justly ob¬ 
serves, that the motion of the auroral arches is from north to 
south, or rather N.W. to S.E. : he adds, that he never heard 
of an arch observed whilst low in the north, and traced in its 
course up to the zenith, and thence southward. I beg to refer 
to some circumstantial details of an arch observed by myself, 
21st January, 1826f, traced almost from its origin in the north 
till it disappeared close to the southern horizon- This arch 
had also the peculiarity of moving, not in the direction of the 
magnetic meridian, but from N.E. to S.W., and diametrically 
against the wind. 
o 
Mr. Potter has recently given some interesting views re¬ 
garding the height of the aurora, and pointed out a method by 
which (certain postulates being admitted,) its height may be 
calculated from observations at one station 1. His results co- 
t 
incide generally with those of Mr. Dalton. 
The influence of the aurora upon the magnetic needle has 
for some years afforded a fertile subject for discussion ; and it is 
to be regretted that no continued series of observations has 
been undertaken in Britain, adequate to the solution of the 
question, or indeed materially contributing to our knowledge 
of the state of the earth’s magnetism. M. Arago of Paris 
gave an account, some years ago, of the connexion, which 
his observations established, between the phenomenon of the 
aurora and the irregular motions of the variation and dipping 
needles §. Prof. Hansteen coincided in the truth of this re¬ 
sult ; and added the observed anomalies of the magnetic in¬ 
tensity under the same circumstances ||. M. Arago then re¬ 
marked, that this variation of the horizontal intensity might 
only arise from the irregularity occasioned in the dip, of which 
the former is a function^. Meanwhile, M. Arago’s general 
conclusions were warmly opposed by Dr. Brewster, who con¬ 
sidered the fact as not sufficiently established by such obser- 
* Encyc. Brit., Art. Aurora Borealis. 
f Edinburgh Journal of Science, ix. 129. J Ibid. N. S. v. 23. 
§ Annates de Chimie, 1825. |) Jahrbuch der Cliemie und Physik, xviii. 353. 
Annates de Chimie , 1827. 
