11. Towards the year 140 of the Christian Era, Ptolemy, one of the most illustrious men of the Alexandrian school, combining his own ideas with common beliefs, and a few of the more recent astronomical discoveries, composed a system, which one can call a compound of beliefs, which took his name, and during a period of nearly fifteen centuries was solely adopted in the civilized world.
According to the theory of Ptolemy, the Earth is a sphere in the center of the universe, and is composed of four elements, — earth, water, air, and fire. This is the first region, called “elementary.” The second, called “the ethereal,” comprised eleven heavens, or concentric spheres, turning around the Earth; viz., that of the moon, those of Mercury, Venus, of the sun, Mars, Jupiter, Saturn, of the fixed stars, of the first crystalline heaven (a solid transparent sphere), of the second crystalline sphere, and at last of the outer circle, of primitive mobility, which, by its motion, was supposed to carry around all those within it, causing them to make a revolution every twenty-four hours. Beyond these eleven spheres was the Empyrean, or highest sphere, “abode of the blessed,” thus named from the Greek pyr or pur, which signifies “fire,” because they believed this region to be resplendent with light like fire.
The belief in many superposed heavens or spheres has prevailed for a long time; but they varied in regards to number. The seventh was generally regarded as the highest, whence the expression, “to be carried to the seventh heaven.” St. Paul said that he had been elevated to the third heaven.
Independent of the general motion, the stars had, according to Ptolemy, some particular movements of their own, greater or less according to their distance from the center. The fixed stars made a revolution in 25,816 years. This last computation denotes knowledge of the precession of the equinoxes, which is actually accomplished in about 25,868 years.