152 
LAST VOYAGE OF CAPT. ROSS. 
In the arch described by Capt. Parry, the lower part only was 
well defined, the space under it appearing* dark as if a black 
cloud had been there, which however was not the case, as the 
stars were seen in it unobscured except by the light of the 
aurora. The revolution of an arch from north to south, occupies 
at different periods a space of time varying from twenty minutes 
to two hours, and sometimes it appears stationary for several 
hours together. 
Innumerable streams of white or yellowish light, appear 
sometimes to occupy the greater portion of the heavens to the 
south of the zenith. Some of these streams of light are in soft 
lines like rays, others crooked and waving in all sorts of irregular 
figures, and moving with great rapidity in various directions; 
among these might frequently be observed the shorter collections 
or bundles of rays, which moving with greater velocity than the 
rest, have acquired the name of Merry Dancers. 
Total darkness would sometimes ensue from the sudden dis¬ 
appearance of the aurora, and then it would as suddenly re-appear 
in forms altogether different from those which preceded, over¬ 
spreading the sky with sheets of silvery light, wafted quickly 
along, like thin strata of clouds before the wind. Sometimes 
narrow streaks of flame shot forth with extreme velocity, travers¬ 
ing in a few seconds the entire concave of the heavens, and dis¬ 
appearing beneath the south eastern horizon. Occasional broad 
masses of light suddenly appeared in the zenith, and descended 
towards the earth in the form of beautiful continuous radiated 
circles. 
Speaking generally, the lustre of the polar lights may be 
described as varying in kind as well as in intensity; sometimes 
it is pearly, sometimes imperfectly vitreous, and sometimes almost 
metallic. Its degree of intensity varies from a very faint 
radiance, to a light nearly equal to that of the moon. 
The colours of the Aurora Borealis are of various tints, and do 
not seem to depend on the presence of any luminary, but to be 
generated by the motion of the beams; the rays or beams are 
steel grey, yellowish grey, pea green, celandine green, gold 
yellow, violet blue and purple; sometimes rose red, crimson red, 
