work.[8] He says:--

Copernicus, as we have already remarked, did not attack the
principle of the epicyclical theory: he merely sought to make it
more simple by placing the centre of the earth's orbit in the centre
of the universe. This was the point to which the motions of the
planets were referred, for the planes of their orbits were made to
pass through it, and their points of least and greatest velocities
were also determined with reference to it. By this arrangement the
sun was situate mathematically near the centre of the planetary
system, but he did not appear to have any physical connexion with
the planets as the centre of their motions.

According to Copernicus' sixth book, the planes of the planetary
orbits do not pass through the sun, and the lines of apses do not pass
through to the sun.

Such was the theory advanced by Copernicus: The earth moves in an
epicycle, on a deferent whose centre is a little distance from the
sun. The planets move in a similar way on epicycles, but their
deferents have no geometrical or physical relation to the sun. The
moon moves on an epicycle centred on a second epicycle, itself centred
on a deferent, excentric to the earth. The earth's axis rotates about
the pole of the ecliptic, making one revolution and a twenty-six
thousandth part of a revolution in the sidereal year, in the opposite
direction to its orbital motion.

In view of this fanciful structure it must be noted, in fairness to
Copernicus, that he repeatedly states that the reader is not obliged
to accept his system as showing the real motions; that it does not