ARISTOTLE AND THE EARLIER PERIPATETICS vol.I by Eduard Zeller, B.F.C.Costelloe 1897

a;
:
PHYSICS 487
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Furthermore, the shape of the universe is determined
by the nature of the five simple bodies. Since
circular motion is proper to one of them, and rectilinear
motion to the rest, we obtain in the first place the
distinction, touched upon above, between the two chief
regions of the world—that in which circular motion
rules, and that in which the opposite movements up
and down hold sway : i.e. that which is full of asther, and
that which contains the four elements. In both of
them the materials lie in spherical layers one above
the other.
For since similar materials uniformly strive
to reach their natural localities,
which in turn are determined
by their distance from the centre of the world,
it follows that the materials of each sort are conglobated
in spheres which are at all points equidistant from the
centre. In the middle of the whole lies the earth—
solid sphere, 1
the world. 2
but in extent a relatively small portion of
Its fixture in this locality proceeds partly
1
Besides theargumentquoted 2 In proof of this statement
in the text, Aristotle proves the Aristotle, Meteor, i. 3, 339, b, 6,
rotundity of the earth (De Casio, 340, a, 6, refers generally to the
ii. 14, 297, a, 6 sqq.) from the a.a