POLAR LIGHT. L57 



of the equinoxes. To the northern lights which have been 

 seen in Peru, and to the southern lights which have been 

 visible in Scotland, we may add a coloured Aurora, which 

 was observed for more than two hours continuously by 

 Lafond in the Candide, on the 14th of January, 1831, south 

 of New Holland, in latitude 45. 16 



The accompaniment of sound in the Aurora has been as 

 definitely denied by the French physicists and Siljestrom at 

 Bossekop 16 as by Thienemann, Parry, Franklin, Richardson, 

 Wrangel, and A.njou. Bravais estimated the altitude of the 

 phenomenon to be fully 51307 toises (or 52 geographical 

 miles), whilst an otherwise very careful observer, Farquhar- 

 son, considers that it scarcely amounts to 4000 feet. The 

 data on which all these determinations are based are very 

 uncertain, and are rendered less trustworthy by optical illu- 

 sions, as well as by erroneous conjectures regarding the posi- 

 tive identity of the luminous arch seen simultaneously at two 

 remote points. There is, however, no doubt whatever of tli 

 influence of the northern light on declination, inclination, 

 horizontal and total intensity, and consequently on all the 

 elements of terrestrial magnetism, although this influence 

 is exerted very unequally in the different phases of this great 

 phenomenon, and on the different elements of the force. 

 The most complete investigations of the subject were those 

 made in Lapland by the able physicists Siljestrom and 

 Bravais 17 (in 1838 1839), and the Canadian observations at 

 Toronto (1840 1841), which have been most ably dis- 

 cussed by Sabine. 18 In the preconcerted simultaneous ob- 

 servations which were made by us at Berlin (in the Men- 

 delssohn-Bartholdy Garden), at Freiberg below the surface 

 of the earth, at St. Petersburgh, Kasan and Nikolajew, we 

 found that the magnetic variation was affected at all these 

 places by the Aurora boreal is, which was visible at Alford in 

 Aberdeenshire (57 15' N. lat.) on the night of the 19-20th 

 of December, 1829. At some of these stations, at which 



15 Comptes rendus de PAcad. des Sciences, t. iv, 1837, p. 589. 

 6 Voyages en Scandinavie, en Laponie, etc., (Awores boreales,) p. 559 ; 

 and Martin's Trad, de la Meteorologie de Kaemtz, p. 460. In reference 

 to the conjectured elevation of the northern light, see Bravais, Op. cit. 

 pp. 549, 559. 



V Op. cit. p. 462. 



18 Sabine, Unusual Mcynet. Disturbances, pt. i, pp. xviii, xxii, 3, 54. 



