lly come to groups and clusters.
Allusion has been made to the Hyades, Pleiades, etc. Everyone has
noticed the Milky Way. It seems like two irregular streams of compacted
stars. It is not supposed that they are necessarily nearer together
than the stars in the sparse regions about the pole. But the 18,000,000
suns belonging to our system are arranged within a space represented
by a flattened disk. If one hundred lights, three inches apart,
are arranged on a hoop ten feet in diameter, they would be in a
circle. Add a thousand or two more the same distance apart, filling
up the centre, and [Page 216] extending a few inches on each side of
the inner plane of the hoop: an eye in the centre, looking out
toward the edge, would see a milky way of lights; looking out toward
the sides or poles, would see comparatively few. It would seem as if
this oblate spheroidal arrangement was the result of a revolution of
all the suns composing the system. Jupiter and earth are flattened
at the poles for the same reason.

[Illustration: Fig. 76.--Sprayed Cluster below ae in Hercules.]

[Illustration: Fig. 77.--Globular Cluster.]

In various parts of the heavens there are small globular well-defined
clusters, and clusters very irregular in form, marked with sprays
of stars. There is a cluster of this latter class in Hercules,
just under the S, in Fig. 72. "Probably no one ever saw it with a
good telescope without a shout of wonder." Here is a cluster of the
former class represented in Fig. 77. "The noble globular cluster,
o Centauri is beyond all comparison the richest and largest object
of the kind in the heavens. Its stars are literally innumerable;
and as their total light, when received by the naked eye, affects
it hardly more than a star of the fifth to fourth
[Page 217]
magnitude, the minuteness of each star may be imagined."

There are two possibilities of thought concerning these clusters.
Either that they belong to our stellar system, and hence the stars
must be small and young, or they are another universe of millions
of suns, so far way that the inconceivable distances between the
stars are shrunken to a hand's-breadth, and their unbearable splendor
of innumerable suns can only make a gray haze at the distance at
which we behold them. The latter is the older and grander thought;
the former the newer and better substantiated.

_Nebulae._

The gorgeous clusters we have been considering appear to the eye
or the small telesco