“The Heaven of Saturn,” he says, “has two properties by which it may be compared to Astrology. The first is the slowness of its movement through the twelve signs; for, according to the writings of Astrologers, its revolution requires twenty-nine years and more. The second is, that it is the highest of all the planets. And these two properties are in Astrology; for in completing its circle, that is, in learning it, a great space of time passes; both on account of its demonstrations, which are more than in any of the above-mentioned sciences, and on account of the experience which is necessary to judge rightly in it.