s rapid period, that varies for each system.

One of the most splendid of these _double stars_, and at the same time
one of the easiest to perceive, is [zeta] in the Great Bear, or Mizar,
mentioned above in describing this constellation. It has no contrasting
colors, but exactly resembles twin diamonds of the finest water, which
fascinate the gaze, even through a small objective.

Its components are of the second and fourth magnitudes, their distance =
14"[6]. Some idea of their appearance in a small telescope may be
obtained from the subjoined figure (Fig. 17).

Another very brilliant pair is Castor. Magnitudes second and third.
Distance 5.6"". Very easy to observe. [gamma] in the Virgin resolves
into two splendid diamonds of third magnitude. Distance, 5.0". Another
double star is [gamma] of the Ram, of fourth magnitude. Distance, 8.9".

[Illustration: FIG. 17.--The double star Mizar.]

And here are two that are even more curious by reason of their coloring:
[gamma] in Andromeda, composed of a fine orange star, and one
emerald-green, which again is accompanied by a tiny comrade of the
deepest blue. This group in a good telescope is most attractive.
Magnitudes, second and fifth. Distance, 10".

[beta] of the Swan, or Albireo, referred to in the last chapter, has
been analyzed into two stars: one golden-yellow, the other sapphire.
Magnitudes, third and fifth. Distance, 34". [alpha] of the Greyhounds,
known also as the Heart of Charles II, is golden-yellow and lilac.
Magnitudes, third and fifth. Distance 20".[7]

[alpha] of Hercules revolves a splendid emerald and a ruby in the skies;
[zeta] of the Lyre exhibits a yellow and a green star; Rigel, an
electric sun, and a small sapphire; Antares is ruddy and emerald-green;
[eta] of Perseus resolves into a burning red star, and one smaller that
is deep blue, and so on.

* * * * *

These exquisite double stars revolve in gracious and splendid couples
around one another, as in some majestic valse, marrying their
multi-colored fires in the midst of the starry firmament.

Here, we constantly receive a pure and dazzling white light from our
burning luminary. Its ray, indeed, contains the potentiality of every
conceivable color, but picture the fantastic illumination of the worlds
that gravitate round these multiple and colored suns as they shed floods
of blue and roseate, red, or orange light around them! What a fairy
spectacle must life pr