The Sphere of Johannes de Sacrobosco

DE SACROBOSCO CAP. I.

has the glorious and sublime God arranged them. And these are called the four elements, which in turn are altered, corrupted, and generated from themselves.

Elements are simple bodies that cannot be divided into parts of different forms: from their mixture, the diverse species of generated things are made. Any one of these three surrounds the earth in a circular manner on all sides, except where the dryness of the earth opposes the moisture of the water, for the preservation of the life of living creatures. Everything besides the earth is mobile: the earth, as the center of the world, by its own weight, fleeing the great motion of the extremes equally on all sides, occupies the middle of the round sphere.

Around the elemental region, the ethereal region, luminous and immune from all variation due to its immutable essence, proceeds with continuous circular motion, 8 and this is called by philosophers the quinta essentia fifth essence/quintessence. Of this there are nine spheres, as was treated in the previous section: namely, those of the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, the fixed stars, and the ultimate heaven. Any one of these spheres spherically surrounds the one inferior to it: of which there are two motions. One is that of the ultimate heaven upon the two extremities of the axis, namely the arctic pole and the antarctic pole, returning from the east through the west back to the east, which the equinoctial circle divides through the middle. There is also another motion of the inferior spheres through an oblique path opposite to this one, upon their poles 9 distant from the first by twenty-three degrees