, but while the velocities given by the bright F line
are positive after the principal minimum of the star's light, those
given by the dark line are negative. Therefore, during the principal
minimum it is a star giving the dark line which is eclipsed, and during
the secondary minimum another star giving the bright line is eclipsed.
This wonderful variable will, however, require more observatioens before
the problem of its constitution is finally solved, and the same may be
said of several variable stars, _e.g._ e Aquilae and d Cephei,
in which a want of harmony has been found between the changes of
velocity and the fluctuations of the light.

There are some striking analogies between the complicated spectrum of
b Lyrae and the spectra of temporary stars. The first "new star"
which could be spectroscopically examined was that which appeared in
Corona Borealis in 1866, and which was studied by Sir W. Huggins. It
showed a continuous spectrum with dark absorption lines, and also the
bright lines of hydrogen; practically the same spectrum as the stars of
Type II.b. This was also the case with Schmidt's star of 1876, which
showed the helium line (D3) and the principal nebula line in addition
to the lines of hydrogen; but in the autumn of 1877, when the star had
fallen to the tenth magnitude, Dr. Copeland was surprised to find that
only one line was visible, the principal nebula line, in which almost
the whole light of the star was concentrated, the continuous spectrum
being hardly traceable. It seemed, in fact, that the star had been
transformed into a planetary nebula, but later the spectrum seems to
have lost this peculiar monochromatic character, the nebula line having
disappeared and a faint continuous spectrum alone being visible, which
is also the case with the star of 1866 since it sank down to the tenth
magnitude. A continuous spectrum was all that could be seen of the new
star which broke out in the nebula of Andromeda in 1885, much the same
as the spectrum of the nebula itself.

When the new star in Auriga was announced, in February, 1892,
astronomers were better prepared to observe it spectroscopically, as it
was now possible by means of photography to study the ultra-violet part
of the spectrum which to the eye is invisible. The visible spectrum was
very like that of Nova Cygni of 1876, but when the wave-lengths of all
the bright lines seen and photographed at the Lick Observatory and at
Potsdam were measured, a