That stars should change color is most natural.  Many causes would produce this effect.  The ancients said Sirius was red.  It is now white.  The change that would most naturally follow mere age and cooling would be from white, through various colors, to red.  We are charmed with the variegated flowers of our gardens of earth, but he who makes the fields blush with flowers under the warm kisses of the sun has planted his wider gardens of space with colored stars.  “The rainbow flowers of the footstool, and the starry flowers of the throne,” proclaim one being as the author of them all.

Clusters of Stars.

From double and multiple we naturally 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.