It is a great encouragement to the astronomer that, although he
cannot yet set any exact boundary to this universe of ours, he is
gathering faint indications that it has a boundary, which his
successors not many generations hence may locate so that the
astronomer shall include creation itself within his mental grasp.
It can be shown mathematically that an infinitely extended system
of stars would fill the heavens with a blaze of light like that of
the noonday sun. As no such effect is produced, it may be
concluded that the universe has a boundary. But this does not
enable us to locate the boundary, nor to say how many stars may
lie outside the farthest stretches of telescopic vision. Yet by
patient research we are slowly throwing light on these points and
reaching inferences which, not many years ago, would have seemed
forever beyond our powers.

Every one now knows that the Milky Way, that girdle of light which
spans the evening sky, is formed of clouds of stars too minute to
be seen by the unaided vision. It seems to form the base on which
the universe is built and to bind all the stars into a system. It
comprises by far the larger number of stars that the telescope has
shown to exist. Those we see with the naked eye are almost equally
scattered over the sky. But the number which the telescope shows
us become more and more condensed in the Milky Way as telescope
power is increased. The number of new stars brought out with our
greatest power is vastly greater in the Milky Way than in the rest
of the sky, so that the former contains a great majority of the
stars. What is yet more curious, spectroscopic research has shown
that a particular kind of stars, those formed of heated gas, are
yet more condensed in the central circle of this band; if they