It was this system of the world which was, thanks to Ptolemy’s authority, to perpetuate itself on the whole until the time of Copernicus. We will here give a broad outline of its essential features, because the eschatological doctrines were to remain for centuries connected with it. The terrestrial globe was held to be suspended, motionless, in the centre of the universe, surrounded by an atmosphere formed of the three other elements and reaching to the moon. That part of the atmosphere which was near the earth was thickened and darkened by heavy vapours rising from the soil and the waters. Above, there moved a purer and lighter air which, as it neared the sky, was warmed by contact with the higher fires. Still higher were ranged the concentric spheres of the seven planets, wrapped in ether, a subtle and ardent fluid—first the moon, which still received and gave back the exhalations of the earth,[79] then Mercury and Venus, the two companions of the sun in his daily course. The fourth place, that is, the middle point of the superimposed heavens, was occupied by the luminary of the day,—here Posidonius forsakes Plato and follows the Chaldeans,—the burning heart of the world, the intelligent light which is the source of our minds.[80] Above the sun moved the three higher planets—Mars, Jupiter and Saturn. And these seven wandering stars were surrounded by the sphere of the fixed stars, which were animated by constant and uniform movement. That sphere marked the world’s boundary: beyond it there was only void or the ether. The universe, as this philosophy imagined it, had therefore well-defined limits: when men raised their eyes to the constellations of the firmament, they thought they perceived its end. The depths of the sky were not then unfathomable; he who sank his gaze in them was not seized with giddiness at the abysses nor bewildered by inconceivable magnitudes, and was not tempted to cry with Pascal:[81] “The eternal silence of these boundless spaces affrights me.” Nor was the universe then a multiplicity of heavenly bodies moving to an unknown goal and perpetually transformed, transitory manifestations of an energy developed for undiscoverable ends. The conception formed of the world was static, not dynamic. It was a machine of which the wheels turned according to immutable laws, an organism of which all the parts were united by reciprocal sympathy as they acted and reacted on each other.