he latter
representing helium, a constituent of the sun and of some of the stars,
which, until its recent discovery in a few rare minerals was not known
to exist on the earth) are bright, but they vary in visibility.
Moreover, dark lines due to hydrogen also appear in its spectrum
simultaneously with the bright lines of that element. Then, too, the
bright lines are sometimes seen double. Professor Pickering's
explanation is that beta Lyrae probably consists of two stars, which,
like the two composing beta Aurigae, are too close to be separated with
any telescope now existing, and that the body which gives the bright
lines is revolving in a circle in a period of about twelve days and
twenty-two hours around the body which gives the dark lines. He has also
suggested that the appearances could be accounted for by supposing a
body like our sun to be rotating in twelve days and twenty-two hours,
and having attached to it an enormous protuberance extending over more
than one hundred and eighty degrees of longitude, so that when one end
of it was approaching us with the rotation of the star the other end
would be receding, and a splitting of the spectral lines at certain
periods would be the consequence. "The variation in light," he adds,
"may be caused by the visibility of a larger or smaller portion of this
protuberance."

Unfortunate star, doomed to carry its parasitical burden of hydrogen and
helium, like Sindbad in the clasp of the Old Man of the Sea! Surely, the
human imagination is never so wonderful as when it bears an astronomer
on its wings. Yet it must be admitted that the facts in this case are
well calculated to summon the genius of hypothesis. And the puzzle is
hardly simplified by Belopolsky's observation that the body in beta Lyrae
giving dark hydrogen lines shows those lines also split at certain
times. It has been calculated, from a study of the phenomena noted
above, that the bright-line star in beta Lyrae is situated at a distance
of about fifteen million miles from the center of gravity of the
curiously complicated system of which it forms a part.

We have not yet exhausted the wonders of Lyra. On a line from beta to
gamma, and about one third of the distance from the former to the
latter, is the celebrated Ring Nebula, indicated on the map by the
number 4447. We need all the light we can get to see this object well,
and so, although the three-inch will show it, we shall use the
five-inch. Beginning with