19): one of fifth and a half and
sixth magnitudes, at a distance of 2.4", the other of sixth and
seventh, 3.2" distant. The distance between the two pairs is 207".

[Illustration: FIG. 19.--Quadruple star [epsilon] of the Lyre.]

In speaking of Orion, we referred to the marvelous star [theta] situated
in the no less famous Nebula, below the Belt; this star forms a
dazzling sextuple system, in the very heart of the nebula (Fig. 20). How
different to our Sun, sailing through Space in modest isolation!

Be it noted that all these stars are animated by prodigious motions that
impel them in every direction.

[Illustration: FIG. 20.--Sextuple star [theta] in the Nebula of Orion.]

There are no fixed stars. On every side throughout Infinity, the burning
suns--enormous globes, blazing centers of light and heat--are flying at
giddy speed toward an unknown goal, traversing millions of miles each
day, crossing century by century such vast spaces as are inconceivable
to the human intellect.

If the stars appear motionless to us, it is because they are so remote,
their secular movements being only manifested on the celestial sphere by
imperceptible displacements. But in reality these suns are in perpetual
commotion in the abysses of the Heavens, which they quicken with an
extraordinary animation.

These perpetual and cumulative motions must eventually modify the aspect
of the Constellations: but these changes will only take effect very
slowly; and for thousands and thousands of years longer the heroes and
heroines of mythology will keep their respective places in the Heavens,
and reign undisturbed beneath the starry vault.

Examination of these star motions reveals the fact that our Sun is
plunging with all his system (the Earth included) toward the
Constellation of Hercules. We are changing our position every moment: in
an hour we shall be 70,000 kilometers (43,500 miles) farther than we are
at present. The Sun and the Earth will never again traverse the space
they have just left, and which they have deserted forever.

And here let us pause for an instant to consider the _variable stars_.
Our Sun, which is constant and uniform in its light, does not set the
type of all the stars. A great number of them are variable--either
periodically, in regular cycles--or irregularly.

We are already acquainted with the variations of Algol, in Perseus, due
to its partial eclipse by a dark globe gravitating in the line of our
vision. T