t delicate balance that science has yet invented, even
show the attraction of the greatest known star. So far as we know, the
two swiftest-moving stars are, first, Arcturus, and, second, one known
in astronomy as 1830 Groombridge, the latter so called because it was
first observed by the astronomer Groombridge, and is numbered 1830 in
his catalogue of stars. If our determinations of the distances of these
bodies are to be relied on, the velocity of their motion cannot be much
less than two hundred miles a second. They would make the circuit of
the earth every two or three minutes. A body massive enough to control
this motion would throw a large part of the universe into disorder.
Thus the problem where these stars came from and where they are going
is for us insoluble, and is all the more so from the fact that the
swiftly moving stars are moving in different directions and seem to
have no connection with each other or with any known star.

It must not be supposed that these enormous velocities seem so to us.
Not one of them, even the greatest, would be visible to the naked eye
until after years of watching. On our finger-ring scale, 1830
Groombridge would be some ten miles and Arcturus thirty or forty miles
away. Either of them would be moving only two or three feet in a year.
To the oldest Assyrian priests Lyra looked much as it does to us
to-day. Among the bright and well-known stars Arcturus has the most
rapid apparent motion, yet Job himself would not to-day see that its
position had changed, unless he had noted it with more exactness than
any astronomer of his time.

Another unsolved problem among the greatest which present themselves to
the astronomer is that of the size of the universe of stars. We know
that several thousand of these bodies are visible to the naked eye;
moderate telescopes show us millions; our giant telescopes of the
present time, when used as cameras to photograph the heavens, show a
number past count, perhaps one hundred millions. Are all these stars
only those few which happen to be near us in a universe extending out
without end, or do they form a collection of stars outside of which is
empty infinite space? In other words, has the universe a boundary?
Taken in its widest scope this question must always remain unanswered
by us mortals because, even if we should discover a boundary within
which all the stars and clusters we ever can know are contained, and
outside of which is empty space, st