n: MAP NO. 16.]

There are three constellations represented on map No. 16 to which we
shall pay brief visits. First Aquila demands attention. Its doubles may
be summarized as follows: 11, magnitudes five and nine, distance 17.4",
p. 252 deg.; pi, magnitudes six and seven, distance 1.6", p. 122 deg.; 23,
magnitudes six and ten, distance 3.4", p. 12 deg.--requires the five-inch
and good seeing; 57, magnitudes five and six, distance 36", p. 170 deg.;
Sigma 2654, magnitudes six and eight, distance 12", p. 234 deg.; Sigma 2644,
magnitudes six and seven, distance 3.6", p. 208 deg..

The star eta is an interesting variable between magnitudes three and a
half and 4.7; period, seven days, four hours, fourteen minutes. The
small red variable R changes from magnitude six to magnitude seven and a
half and back again in a period of three hundred and fifty-one days.

Star cluster No. 4440 is a striking object, its stars ranging from the
ninth down to the twelfth magnitude.

Just north of Aquila is the little constellation Sagitta, containing
several interesting doubles and many fine star fields, which may be
discovered by sweeping over it with a low-power eyepiece. The star zeta
is double, magnitudes five and nine, distance 8.6", p. 312 deg.. The larger
star is itself double, but far too close to be split, except with very
large telescopes. In theta we find three components of magnitudes seven,
nine, and eight respectively, distances 11.4", p. 327 deg., and 70", p.
227 deg.. A wide double is epsilon, magnitudes six and eight, distance 92",
p. 81 deg.. Nebula No. 4572 is planetary.

Turning to Delphinus, we find a very beautiful double in gamma,
magnitudes four and five, distance 11", p. 273 deg., colors golden and
emerald. The leader alpha, which is not as bright as its neighbor beta,
and which is believed to be irregularly variable, is of magnitude four,
and has a companion of nine and a half magnitude at the distance 35", p.
278 deg.. At a similar distance, 35", p. 335 deg., beta has an
eleventh-magnitude companion, and the main star is also double, but
excessively close, and much beyond our reach. It is believed to be a
swiftly moving binary, whose stars are never separated widely enough to
be distinguished with common telescopes.

CHAPTER VI

FROM LYRA TO ERIDANUS

"This Orpheus struck when with his wondrous song
He charmed the woods and drew the rocks along."--MANILIUS.

[Illustration: MAP NO. 17.]

We resume