time, which he had inherited from his predecessors. This is seen
not only in the general course of thought through the opening
chapters of his work, but among his introductory propositions. The
first of these is that the universe--mundus--as well as the earth,
is spherical in form. His arguments for the sphericity of the
earth, as derived from observation, are little more than a
repetition of those of Ptolemy, and therefore not of special
interest. His proposition that the universe is spherical is,
however, not based on observation, but on considerations of the
perfection of the spherical form, the general tendency of bodies--
a drop of water, for example--to assume this form, and the
sphericity of the sun and moon. The idea retained its place in his
mind, although the fundamental conception of his system did away
with the idea of the universe having any well-defined form.

The question as attacked by modern astronomy is this: we see
scattered through space in every direction many millions of stars
of various orders of brightness and at distances so great as to
defy exact measurement, except in the case of a few of the
nearest. Has this collection of stars any well-defined boundary,
or is what we see merely that part of an infinite mass which
chances to lie within the range of our telescopes? If we were
transported to the most distant star of which we have knowledge,
should we there find ourselves still surrounded by stars on all
sides, or would the space beyond be void? Granting that, in any or
every direction, there is a limit to the universe, and that the
space beyond is therefore void, what is the form of the whole
system and the distance of its boundaries? Preliminary in some
sort to these questions are the more approachable ones: Of what
sort of matter is the universe formed? and into what sort of