due to helium,
caught the eye; and they had companions too numerous to be easily
counted. The hydrogen lines were broad and bright; C blazed, as Mr.
Espin said, "like a danger-signal on a dark night"; the sodium pair were
identified at Tulse Hill, and the yellow helium ray was suspected to
lurk close beside them. Fig. 2 in the same plate shows the spectrum as
it was seen and mapped by Lady Huggins, February 2 to 6, together with
the spectra employed to test the nature of the emissions dispersed in
it. One striking feature will be at once remarked. It is that of the
pairing of bright with dark lines. Both in the visible and the
photographic regions this singular peculiarity was unmistakable; and
since the two series plainly owned the same chemical origin, their
separate visibility implied large displacement. Otherwise they would
have been superposed, not juxtaposed. Measurements of the bright rays,
accordingly, showed them to be considerably pushed down towards the red,
while their dark companions were still more pushed up towards the blue
end. Thus the spectrum of Nova Aurigae, like that of Beta Lyrae,
with which it had many points in common, appeared to be really double.
It was supposed to combine the light of two distinct bodies, one, of a
gaseous nature, moving rapidly away from the earth, the other, giving a
more sunlike spectrum, approaching it with even higher speed. The
relative velocity determined at Potsdam for these oppositely flying
masses amounted to 550 miles a second.[1485] And this prodigious rate of
separation was fully maintained during six weeks! It did not then
represent a mere periastral rush-past.[1486] To the bodies exhibiting
its effects, and parting company for ever under its stress, it must have
belonged, with slight diminution, in perpetuity. The luminous outburst
by which they became visible was explained by Sir William Huggins, in a
lecture delivered at the Royal Institution, May 13, 1892, on the tidal
theory of Klinkerfues and Wilsing. Disturbances and deformations due to
the mutual attraction of two bulky globes at a close approach would, he
considered, "give rise to enormous eruptions of the hotter matters from
within, immensely greater, but similar in kind, to solar eruptions; and
accompanied, probably, by large electrical disturbances." The multiple
aspect and somewhat variable character of both bright and dark lines
were plausibly referred to processes of "reversal," such as are nearly