five to ten times as rich.

Another feature showing the unity of the system is the symmetry of
the heavens on the two sides of the galactic belt Let us return to
our supposition of such a position of the celestial sphere, with
respect to the horizon, that the latter coincides with the central
line of this belt, one galactic pole being near our zenith. The
celestial hemisphere which, being above our horizon, is visible to
us, is the one to which we have hitherto directed our attention in
describing the distribution of the stars. But below our horizon is
another hemisphere, that of our antipodes, which is the
counterpart of ours. The stars which it contains are in a
different part of the universe from those which we see, and,
without unity of plan, would not be subject to the same law. But
the most accurate counts of stars that have been made fail to show
any difference in their general arrangement in the two
hemispheres. They are just as thick around the south galactic
poles as around the north one. They show the same tendency to
crowd towards the Milky Way in the hemisphere invisible to us as
in the hemisphere which we see. Slight differences and
irregularities, are, indeed, found in the enumeration, but they
are no greater than must necessarily arise from the difficulty of
stopping our count at a perfectly fixed magnitude. The aim of
star-counts is not to estimate the total number of stars, for this
is beyond our power, but the number visible with a given
telescope. In such work different observers have explored
different parts of the sky, and in a count of the same region by
two observers we shall find that, although they attempt to stop at
the same magnitude, each will include a great number of stars
which the other omits. There is, therefore, room for considerable