1 54 COSMOS. 



advancing towards the zenith, parallel to one another ; while 

 in other cases they are altogether absent. The bundles of 

 rays and columns of light assume the most varied forms, ap- 

 pearing either in the shape of curves, wreathed festoons and 

 hooks, or resembling waving pennants or sails. 9 



In the higher latitudes, " the prevailing colour of the polar 

 light is usually white, while it presents a milky hue when the 

 Aurora is of faint intensity. When the colours brighten, 

 they assume a yellow tinge ; the middle of the broad ray be- 

 comes golden yellow, while both the edges are marked by 

 separate bands of red and green. When the radiation ex- 

 tends in narrow bands, the red is seen above the green. 

 When the Aurora moves sideways from left to right, or from 

 right to left, the red appears invariably in the direction to- 

 wards which the ray is advancing, and the green remains 

 behind it." It is only in very rare cases that either one of 

 the complementary colours, green or red, has been seen alone. 

 Blue is never seen, while dark red, such as is presented by 

 the reflection of a great fire, is so rarely observed in the 

 north that Siljestrom noticed it only on one occasion. 10 The 

 luminous, intensity of the Aurora never even in Finmark 

 quite equals that of the full moon. 



The probable connection which, according to my views, 

 exists between the polar light and the formation of very 

 small and delicate fleecy clouds (whose parallel and equivalent 

 rows follow the direction of the magnetic meridian), has met 

 with many advocates in recent times. It still remains a doubt- 

 ful question, however, 11 whether, as the northern travellers, 

 Thienemann and Admiral Wrangel believe, these parallel 

 fleecy clouds are the substratum of the polar light, or whether 



9 Op. cit. pp. 35, 37, 45, 67, 481 ("Draperie ondulante, flamme d"un 

 navire de guerre deployce horizontalement et agttee par le vent, crochets, 

 fragments d'arcs et de guirlandes)." M. Bevalet, the distinguished artist 

 to the expedition, has given an interesting collection of the many varied 

 forms assumed by this phenomenon. 



10 See Voy. en Scandinavie (Aur. boreal.), pp. 523528, 557. 



11 Cosmos, vol i, p. 194 ; see also, Franklin, Narrative of a Journey to 

 the Shores of the Polar Sea in 18191822, p. 597; and Kiimtz, Lehr- 

 buch der Meteorologie, Bd. iii (1836), s. 488490. The earliest conjec- 

 tures advanced in relation to the connection between the northern 

 light and the formation of clouds are probably those of Frobesius. (Sea 

 Auroras borealis spectacula, Helrnst, 1739, p. 139). 



