The structure of the Kosmos Diogenes supposed to have been effected by portions of the infinite air, taking upon them new qualities and undergoing various transformations. Some air, becoming cold, dense, and heavy, sunk down to the centre, and there remained stationary as earth and water: while the hotter, rarer, and lighter air ascended and formed the heavens, assuming through the intelligence included in it a rapid rotatory movement round the earth, and shaping itself into sun, moon, and stars, which were light and porous bodies like pumice stone. The heat of this celestial matter acted continually upon the earth and water beneath, so that the earth became comparatively drier, and the water was more and more drawn up as vapour, to serve for nourishment to the heavenly bodies. The stars also acted as breathing-holes to the Kosmos, supplying the heated celestial mass with fresh air from the infinite mass without.[194] Like Anaxagoras, Diogenes conceived the figure of the earth as flat and round, like a drum; and the rotation of the heavens as lateral, with the axis perpendicular to the surface of the earth, and the north pole always at the zenith. This he supposed to have been the original arrangement; but after a certain time, the earth tilted over spontaneously towards the south--the northern half was elevated and the southern half depressed--so that the north pole was no longer at the zenith, and the axis of rotation of the heavens became apparently oblique.[195] He thought, moreover, that the existing Kosmos was only of temporary duration; that it would perish and be succeeded by future analogous systems, generated from the same common substance of the infinite and indestructible air.[196] Respecting animal generation--and to some extent respecting meteorological phenomena[197]--Diogenes also propounded several opinions, which are imperfectly known, but which appear to have resembled those of Anaxagoras.