NOTES. xlvii 



the direction of the cirrus bands at Bosekop, like the auroral arch, perpendicular 

 to the magnetic meridian (Voyage en Scandinavie; Phenomena de translation 

 dans les pieds de 1'Arc des Auroras bore'ales, p. 534 537), describes, with his 

 usual exactness, the shiftings of position of the true auroral arch, p. 27, 92, 122, 

 and 487. In the southern hemisphere, Sir James Ross also observed similar pro- 

 gressive changes of direction of the aurora australis, changing from W.N.W. 

 E.S.E. to N.N.E. S.S.W. (Voyage in the Southern and Antarctic Regions, 

 vol. i. p. 311.) The absence of colour seems to be very frequent in the aurora 

 australis (vol. i. p. 266; vol. ii. p. 209). On nights without aurora in Lap- 

 land, see Bravais, work before quoted, p. 545. 



( 2H ) p. 157. Kosmos, Bd. i. S. 440, Anm. 43 (English edition, Note 

 173). Auroral arches seen in daylight remind us of the strength of the 

 light in the nuclei and tails of the comets of 1843 and 1847, which were 

 seen in North America, at Parma, and London near, the sun. Kosmos, Bd. i. 

 S. 390, Anm. 13 (English edition, Note 43); Bd. iii. S. 563 (English edition, 

 p. 400). 



( 215 ) p. 157. Comptes rendus de 1'Acad. des Sciences, t. iv. 1837, p. 589. 



( 216 ) p. 157. Voyages en Scandinavie, en Laponie, &c. (aurores bore'ales), 

 p. 559; and Martins, Trad, de la Mete'orol. de Ksemtz, p. 460. On the sup- 

 posed height of the aurora, see Bravais, work above quoted, p. 549 and 559. 



( 217 ) p. 158. Same work, p. 462. 



( 218 ) p. 158. Sabine, Unusual Magnet. Disturbances, Pt. I. p. xviii. xxii. 

 3 and 54. 



( 219 ) p. 158. Dove, in Poggend. Ann. Bd. xx. S. 333 to 341. The unequal 

 effect exercised by an aurora on the declination needle at places situated in very 

 different meridians, may, in many cases, lead to the determination of the place of 

 the acting cause, for the outbreak of the luminous magnetic storm is by no 

 means always to be sought at the magnetic pole itself; and, as Argelander had 

 before said, and Bravais has confirmed, the summit of the luminous arch some- 

 times deviates more than 11 from the magnetic meridian. 



C 220 ) p. 159. " On the 20th December, 1806. Sky azure- blue, without 

 trace of cloud. Towards ten o'clock, there appeared in the N.N.W. a reddish- 

 yellow luminous arch, through which I could distinguish, with the telescope, 

 stars of the 7th magnitude; a lyrse, being almost directly under the highest 

 point of the arch, enabled me to determine the azimuth of that point. It was 

 situated rather to the west of the vertical plane of the magnetic declination. 

 The aurora, which was in the N.N.W., repelled the North pole of the needle; for 

 instead of progressing towards the west, as did the azimuth of the arch, it 

 returned towards the east. The changes of magnetic declination, which amount 



