the Milky Way. Such
objects are called star clusters. We find every variety in the clusters;
sometimes the stars are remarkable for their brilliancy, sometimes for
their enormous numbers, and sometimes for the remarkable form in which
they are grouped. Sometimes a star cluster is adorned with
brilliantly-coloured stars; sometimes the luminous points are so close
together that their separate rays cannot he disentangled; sometimes the
stars are so minute or so distant that the cluster is barely
distinguishable from a nebula.

Of the clusters remarkable at once both for richness and brilliancy of
the individual stars, we may mention the cluster in the Sword-handle of
Perseus. The position of this object is marked on Fig. 83, page 415. To
the unaided eye a hazy spot is visible, which in the telescope expands
into two clusters separated by a short distance. In each of them we have
innumerable stars, crowded together so as to fill the field of view of
the telescope. The splendour of this object may be appreciated when we
reflect that each one of these stars is itself a brilliant sun, perhaps
rivalling our own sun in lustre. There are, however, regions in the
heavens near the Southern Cross, of course invisible from northern
latitudes, in which parts of the Milky Way present a richer appearance
even than the cluster in Perseus.

The most striking type of star cluster is well exhibited in the
constellation of Hercules. In this case we have a group of minute stars
apparently in a roughly globular form. Fig. 96 represents this object as
seen in Lord Rosse's great telescope, and it shows three radiating
streaks, in which the stars seem less numerous than elsewhere. It is
estimated that this cluster must contain from 1,000 to 2,000 stars, all
concentrated into an extremely small part of the heavens. Viewed in a
very small telescope, this object resembles a nebula. The position of
the cluster in Hercules is shown in a diagram previously given (Fig. 88,
page 420). We have already referred to this glorious aggregation of
stars as one of the three especially interesting objects in the heavens.

[Illustration: PLATE D.

MILKY WAY NEAR MESSIER II.

_Photographed by E.E. Barnard, 29th June, 1892._]

The Milky Way forms a girdle which, with more or less regularity,
sweeps completely around the heavens; and when viewed with the
telescope, is seen to consist of myriads of minute stars. In some places
the stars are much more numerous