Note 20 — Chapter II · KNOWLEDGE MAY BE ACQUIRED BY ASTRONOMY TO A CERTAIN EXTENT

The following extract from an old geographical work, framed on the rules of Ptolemy, explains the system on which this action of the æther is made to depend:—

“Chap. 2. The world is divided into two parts, the elemental region and the æthereal. The elemental region is constantly subject to alteration, and comprises the four elements; earth, water, air and fire. The æthereal region, which philosophers call the fifth essence, encompasses, by its concavity, the elemental; its substance remains always unvaried, and consists of ten spheres; of which the greater one always spherically environs the next smaller, and so on in consecutive order. First, therefore, around the sphere of fire, God, the creator of the world, placed the sphere of the Moon, then that of Mercury, then that of Venus, then that of the Sun, and afterwards those of Mars, of Jupiter, and of Saturn. Each of these spheres, however, contains but one star: and these stars, in passing through the zodiac, always struggle against the primum mobile, or the motion of the tenth sphere; they are also entirely luminous. In the next place follows the firmament, which is the eighth or starry sphere, and which trembles or vibrates (trepidat) in two small circles at the beginning of Aries and Libra (as placed in the ninth sphere); this motion is called by astronomers the motion of the access and recess of the fixed stars.” (Probably in order to account for the procession of the equinoxes.) “This is surrounded by the ninth sphere, called the chrystalline or watery heaven, because no star is discovered in it. Lastly, the primum mobile, styled also the tenth sphere, encompasses all the before-mentioned æthereal spheres, and is continually turned upon the poles of the world, by one revolution in twenty-four hours, from the east through the meridian to the west, again coming round to the east. At the same time, it rolls all the inferior spheres round with it, by its own force; and there is no star in it. Against this primum mobile, the motion of the other spheres, running from the west through the meridian to the east, contends. Whatever is beyond this, is fixed and immovable, and the professors of our orthodox faith affirm it to be the empyrean heaven which God inhabits with the elect.”—Cosmographia of Peter Apianus (named Benewitz), dedicated to the Archbishop of Salzburg, edited by Gemma Frisius, and printed at Antwerp 1574.